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MuhammadAttiqueKhanS

Role of Radiations in Health and Medical Physics.

Health & Medicine
1 of 353
We Are Learning To What do we know? How do we know? What should be the next?
ACKNOWLEDGEMENTs: To All those who donate me their live, lighten my way by candles, learned me and guided me along with My Mother, Father, Teachers, Brothers, Sisters and Friends . I thank Almighty GOD too much that I could become capable after a lot of effort and constraints that faced by me during my Academic cum Administrative Journey. I Also have full thanks for my M Phil /PhD supervisor (Late) Dr K.Hussain for his Scholastic Guidance suggested ideas and orientations through out my R&D Caliber May God Bless his soul in an Eternal Peace Ameen!. 4
Abstract  Atomic radiation as a phenomenon is as old as the universe itself. It is a normal part of nature and life. At this very moment, thousands of rays are penetrating your body every second. The majority of radiation originates in nature and is totally independent of what man does. Today, our environment also contains a small amount of extra “unnatural” radiation which is caused by the activities of mankind.  The use of radiation has become an integral part of modern life. From the x-ray picture of broken limb to the treatment of cancer, the medical applications of radiation are now accepted as commonplace, and x-ray facilities are available in almost every community hospital.  Radiation contributes in the production of electricity, agriculture, and in other industry.  In my presentation I will try to describe in simple terms, what ionizing radiation to which man is exposed and second to review its sources and then I will shed a light on the applications of radiation in different walks of life, their detection& measurements along with some protective measures.
An Overview :The Presentation covers the following key points. 1. The Atom 2. Atomic Radiation 3. Our Radiation Heritage(Natural Sources of Radiation) 4. Man Made Radiation(Artificial Sources Of Radiation) 5. Application of Atomic/Nuclear Radiation In:  Medicine  Power Production  Weapons  Agriculture  Industry 6. Biological Effects of Radiation 7. Radiation Protection 8. Radiation Detection & Measurements/Dosimetry 9. Summary
Discovery & study of radioactivity 1898 Marie &.Pierre Curie Introduction of quantum concept 1900 Max Planck h Theory of special relativity 1905 Albert Einstein E=m·c2 Quantization of light (photoelectric effect) 1905 Albert Einstein E=h· Discovery of atomic nucleus 1911 Ernest Rutherford Interpretation of atom structure 1913 Nils Bohr Particle waves 1924 Louis de Broglie Wave mechanics 1925 Erwin Schrödinger Uncertainty principle 1927 Werner Heisenberg Discovery of Neutron 1932 James Chadwick Artificial Radioactivity (Reactions) 1934 Frederic Joliot & Irene Curie Discovery of fission 1938 Otto Hahn, Fritz Strassmann Interpretation of fission 1938 Liese Meitner, Otto Frisch Prediction of thermonuclear fusion 1939 C.F. v. Weizsäcker, H. Bethe The Development of Scientific Thought in the 20th Century x·p=ђ
The Basics of Radiation Radioactive materials have an unstable nucleus that release one or more particles or energy Nuclear radiation refers to the released energy and matter. A large part of the radiation you are exposed to comes from background radiation (from the sun – solar and the earth – terrestrial. Radiation is going through you all the time.
Contents/Concepts:  Aiming only at a general introduction  obviously more examples from my own practical experience  important to understand the concepts, not to memorize the details  interrupt and ask if something is not clear!  You do not have the slides  but sometimes it is the Best Practice that you will try to arrive at answers to questions yourselves – don’t cheat by looking at the following slides !
R 1.5R 5R 60° 60°
The Good, The Bad, and the Ugly…
Training/Refresher Course Requirements  In order to work with radioactive material you must be properly trained on the safe use and the minimization of risk associated with each isotopes.  To keep your radiation worker status, you must have radiation safety refresher training once a year
Annual Refresher Training Radiation Safety
17 Describing the hazard We need to know how much of a hazardous substance a worker can breathe without harm This is given by the Occupational Exposure Limit OEL
18 Occupational Exposure Limits The OEL is the concentration in the air to which nearly all workers may be repeatedly exposed day after day without adverse health effects to themselves or their children. Termed Threshold Limit Value TLV by ACGIH (ACGIH is an American organisation for industrial hygiene)
Setting an OEL – how it is calculated LAD (mg/kg/day) * BW OEL = --------------------------------------------------- V*T*SF*a LAD lowest active dose BW body weight (50 kg) V volume inhaled air (10 m3) T time, in days, to reach steady state in plasma SF safety factor a % absorption (assumed = 100%)
20 Acceptable Surface Limits  The ASL is the acceptable mass on a specified surface area (typically 10 x 10 cm, the area of palms of hand)  Often set at 10 times the OEL for an area of 100cm2  Not as frequently used as OEL  Not set by ACGIH for any substance Acceptable Surface Limit OEL
Exposure to different substances or mixtures = rule of cumulative effect = S Cn / GWn < 1 C1/GW1 + C2/GW2 + C3/GW3 + …. < 1 C1 … n = measured concentration of the substance in the air GW1 … n = OEL of the measured substance Cumulative effect
Miracles of the Qur’an Qur’an in Focus Qur’an is not a book of SCIENCE but it is a book of SIGNS. It clearly states a number of scientific truths that were uncovered only with the help of modern technology in the 20th century. Therefore, we will use science as a yardstick to measure the accuracy of the statements in Qur’an. “Science without Religion is lame and Religion without Science is blind”. Albert Einstein – A Physicist & a Noble Price Winner
Oklo, Gabon – A natural fission reactor (Pitchblende)  235U natural abundance is well known: 0.00720 ± 0.00001  Uranium deposit where self- sustained nuclear chain reactions have occurred.  235U abundance 0.00717, about 3 standard deviations below the accepted value.  The only process which can lead to reduction of U is fission by low- energy neutrons.  2 x 109 y, 235U (~3%) reactor moderated by groundwater.  Fission product isotope signatures Nd, Ru Geological Situation in Gabon leading to natural nuclear fission reactors: 1. Nuclear reactor zones 2. Sandstone 3. Ore layer 4. Granite
Fossil Reactor 15, located in Oklo, Gabon. Uranium oxide remains are visible as the yellowish rock. Source: NASA
Oklo Estimations  5 tonnes of 235U were fissioned.  Total energy released 2 x 1030 MeV or 108 MW∙h. A contemporary power reactor can operate at 103 MW.  Average power 0.01 MW, operating for 106 y. Important feature: the fission products are still in place in the reactor zone and have migrated very little. Despite climate changes, no substantial movement of the fission products has taken place over the past 2 x 109 y.
THE SUN(Exposure ,Over/Under Exposure/Low /High B.P)
Flow of Energy
Orphans Radioactive sources or materials or waste that does not have an ‘owner’ Creates a lot of work for RPO RPO has to pay for its legal disposal PLEASE NO ORPHANS X
Vibrations/Rotation/Reflect ion Asymmetric Shape
Introduction  Scientists have studied radiation for over 150 years and we know a great deal about it.  Radiation is part of nature. All living creatures, from the beginning of time, have been, and are still being, exposed to radiation.
Radiation is really everywhere?  Yep, it sure is! We live in a radioactive world, and radiation has always been all around us as a part of our natural environment.  The annual average dose per person from all sources is about 360 mrem, but it is not uncommon for any of us to receive more than that average does in a given year (largely as a result of medical procedures).
Natural Radioactivity  There are small amounts of radioactive minerals in the air, ground, and water  Even in the food you eat!  The radiation you are exposed to from natural sources is called background radiation(Radioactive Equilibrium, Natural Radioactive Series) Tro: Chemistry: A Molecular Approach
 There is a small amount of radiation around us all the time because of radioactive materials in the environment. This is called background radiation.
- Each exposure to radiation carries its own very small risk. So, the third or fourth scan you have carries the exact same risk as the very first. - The benefit of having a correct diagnosis and discovering what is going on in your body outweighs the risk of the exam itself. Risk or Benefit?
Risk Assessment Must be made prior to commencing any new work involving ionising radiation. Identify hazards Who could be harmed Evaluate risks Record findings Review / revise Significant hazard but is it a risk?
Fear of radiation • usually undetectable by human senses • serious consequences – cancers (time-delayed) – contamination long-lasting • unaware of background radiation • media scares - especially after Chernobyl Reactor Accident • secrecy - industrial, military & political interests
We Live (And Have Always Lived) in a “Sea of Radiation”/Human Beings and Auora
42 Nonmedical Uses of Radioactive Isotopes Tro: Chemistry: A Molecular Approach • Smoke detectors  Am–241  smoke blocks ionized air, breaks circuit • Insect control  sterilize males • Food preservation • Radioactive tracers  follow progress of a “tagged” atom in a reaction • Chemical analysis  neutron activation analysis
43 Nonmedical Uses of Radioactive Isotopes Tro: Chemistry: A Molecular Approach • Authenticating art object  many older pigments and ceramics were made from minerals with small amounts of radioisotopes • Crime scene investigation • Measure thickness or condition of industrial materials  corrosion  track flow through process  gauges in high temp processes  weld defects in pipelines  road thickness
Nonmedical Uses of Radioactive Isotopes Tro: Chemistry: A Molecular Approach • Agribusiness  develop disease-resistant crops  trace fertilizer use • Treat computer disks to enhance data integrity • Nonstick pan coatings  initiates polymerization • Photocopiers to help keep paper from jamming • Sterilize cosmetics, hair products and contact lens solutions and other personal hygiene products
Radiation Exposure  We are all exposed to radiation:  Cosmic radiation ○ sun, space  Terrestrial radiation ○ soil, rocks  Internally ○ Food (potassium-40), air  Medical treatment Cosmic Rays Internal Sources Terrestrial Radiation
Radiation Exposure/Over or Under Exposure  We cannot avoid radiation exposure from sources of background radiation (cosmic and terrestrial radiation) or as a result of medical treatment  However, by following safe work habits, we can minimize our radiation exposure from occupational sources of radiation
Why Detection& Measurement: How most of us Can feel about radiation until we understand the principles of safe use, For that purpose their Detection & Measurement is must:
Probes and “probees” E = h /  Energy of probe correlated with sizes of probee and production devices/Need of high energy Accelerators Atoms – lasers – table top Nuclei – tandems, cyclotrons, etc. – room size
What Is Atomic Radiation/ Excitation/De excitation
Nuclear system A finite quantum many-body system of protons and neutrons electrons nucleus atom neutron proton nuclear force: Attractions Confined by the external field 1. Independent-particle feature in self-consistent mean-field 2. Strong nucleon-nucleon correlations Self-bound Electron motion Nucleon motion orbit, shell Analogy & Differences cluster
Introduction to Radioactivity(The Active Which Radiate) 23/05/2023 Some substances are classed as “radioactive” – this means that they are unstable and continuously give out radiation: Radiation The nucleus is more stable after emitting some gamma radiation – this is called “radioactive decay”. Increased exposure to gamma radiation can cause cancer or cell death.
• Wilhelm Roentgen (1845–1923) • 1895-invisible rays were emitted when electrons bombarded the surface of certain materials. The Discovery of Radioactivity • caused photographic plates to darken. • named the invisible high-energy emissions X rays.
• Henri Becquerel (1852–1908) was studying phosphorescence • minerals that emit light after being exposed to sunlight The Discovery of Radioactivity •phosphorescent uranium salts produced spontaneous emissions that darkened photographic plates.
• Marie Curie (1867–1934) and her husband Pierre (1859–1906) took Becquerel’s mineral sample (called pitchblende) and isolated the components emitting the rays. The Discovery of Radioactivity • darkening of the photographic plates was due to rays emitted specifically from the uranium atoms present in the mineral sample.
The Curies refined several tons of pitchblende (shown above) progressively concentrating the radioactive components. Eventually they isolated the chloride salts of the two new chemical elements, and then the elements themselves. The first they named polonium (Po) after Marie's native country Poland; and, the other they named radium (Ra) from its intense radioactivity.
The Discovery of Radioactivity • Marie Curie named the process by which materials give off such rays radioactivity • the rays and particles emitted by a radioactive source are called radiation.
– “Radioactive” substances = radiation- emitting (Curie) – Radioactivity = a inherent property of certain ATOMS, as opposed to a chemical property of compounds (Curie)
Radioactivity is the process by which an unstable nucleus gives off nuclear radiation. Uranium Plutonium
The Atom/The Nucleous  In their normal state, atoms are electrically neutral (no net charge) # protons = # electrons/Neutrons  An atom that has gained or lost electrons/Neutrons/Protons is called an ion /Active Positive and negative charges cancel/Non Active
One of Becquerel’s students, Marie Curie, discovered 2 new radioactive elements, radium and polonium.
Who’s the Famous “Madame” of Radiological Fame? Marie Curie • With her husband Pierre, discovered radium and coined the term “radioactive” • First woman to win two Nobel Prizes
Nuclear Radiation(Decay)  This is what you can visualize in your head for how the electron can be emitted from a neutron.  See what happens to the neutron after the electron leaving that is (beta emission)  N,down,P,up, two States of Nucleous
Quarks 23/05/2023 Basically, scientists think everything in the universe is made Up from 12 fundamental particles. Two of these particles are called “up quark” and “down quark”. Protons and neutrons are made of different combinations of three up and down quarks: Proton u u d Neutron u d d Some questions: 1) Quarks have charges that are multiples of 1/3. Given the composition and charge of the proton and the neutron what are the charges on the up and down quark? 2) What happens in terms of quarks during beta + and beta – decay? Up = +2/3, down = -1/3 An up quark turns into a down quark and vice versa
Beta Decay  A neutron transforms into a proton, an electron, and an anti-neutrino H-3 He-3
Gamma Decay (Cs-137) Cs-137 T1/2 30 yr Ba-137m T1/2 2.55 min Ba-137 STABLE 661 keV Gamma Beta
Tl-204 Decay Tl-204 (T1/2 3.779 yr) Pb-204 Hg-204 97.4% 2.6%
What makes nuclei unstable?  The ratio of neutrons to protons determines whether a nucleus is stable or unstable.  Small isotopes 1 neutron:1 proton  Large isotope 3 neutrons: 2 protons  Generally, nuclei with too many or too few neutrons compared to the numbers are unstable or radioactive.
Why Are Elements Radioactive?(1500 nuclides.1/5th Stable,4/5th Unstable) Unstable nucleus: • Has excess energy/BE. • Wants to go to “ground state.” • Becomes stable by emitting ionizing radiation. What does “ionizing” mean?
Forces at work in the nucleus  Electrostatic repulsion: pushes protons apart  Strong nuclear force: pulls protons together  Nuclear force is much shorter range: protons must be close together    
Neutrons only experience the strong nuclear force  Proton pair experiences both forces  Neutrons experience only the strong nuclear force  But: neutrons alone are unstable  
Neutrons act like nuclear glue  Helium nucleus contains 2 protons and 2 neutrons – increase attractive forces  Overall nucleus is stable      
As nuclear size increases, electrostatic repulsion builds up/Peutron Excess  There are electrostatic repulsions between protons that don’t have attractive forces  More neutrons required(N/Z Rule)/Neutron Excess      Long range repulsive force with no compensation from attraction 
Stability Isotopes shown here in black are stable. Radioisotopes are unstable. As the proton number increases, an increasing fraction of neutrons is needed to form a stable nucleus. http://prezi.com/hllfbv98zptq/p2-nuclear-decay/
Nuclear Stability (1)  The Segre chart below shows neutron number and proton number for stable nuclides. For low mass numbers, NZ. The ratio N/Z increases with A. Points to the right of the stability region represents nuclides that have too many protons relative to neutrons/Proton Excess To the left of the stability region are nuclides with too many neutrons relative to protons Neutron Excess.
Nuclear Stability (2)
Nuclear Stability (3)
Radioactive Equilibrium  Often a nucleus or particle can decay into different states and/or through different interactions  The branching fraction or ratio tells you what fraction of time a nucleus or particle decays into that channel  A decaying particle has a decay width Γ  Γ = ∑Γi where Γi are called the partial widths  The branching fraction or ratio for channel or state i is simply Γi/Γ 79
Radioactive Equilibrium  Sometimes we have the situation where  The daughter is both being created and removed Po Rn Ra 218 222 226 3 2 1 2 1       80
Radioactive Equilibrium  We have (assuming N1(0)=N0 and N2(0)=0)             1 2 1 2 max 1 2 2 0 2 2 2 1 2 1 0 2 2 2 1 1 2 1 1 1 / ln at activity maximum and then 2 1 2 1                                    t e e A t N t A e e N t N dt N dt N dN dt N dN t t t t 81
Radioactive Equilibrium  Case 1 (parent half-life > daughter half-life)  This is called transient equilibrium           1 2 2 1 2 1 2 2 1 1 2 2 1 2 1 0 2 0 1 2 1 1 2 2 1 1 1 becomes                                  A A e N N e e N t N e N t N t t t t 82
Radioactive Equilibrium  Transient equilibrium  A2/A1=2/(2-1)  Example is 99Mo decay (67h) to 99mTc decay (6h)  Daughter nuclei effectively decay with the decay constant of the parent 83
Radioactive Equilibrium  Case 2 (parent half-life >> daughter half-life)  This is called secular equilibrium  Example is 226Ra decay           1 2 1 0 2 2 2 1 0 2 1 2 1 0 2 2 1 2 2 1 1 becomes A A N t N e N t N e e N t N t t t                        84
Radioactive Equilibrium  Secular equilibrium  A1=A2  Daughter nuclei are decaying at the same rate they are formed 85
Radioactive Equilibrium  Case 3 (parent half-life < daughter half-life)  What happens?/Not Possible Simply 86
A series of elements produced from the successive emission of alpha & beta particles
Decay Series Tro: Chemistry: A Molecular Approach • In nature, often one radioactive nuclide changes into another radioactive nuclide  i.e. the daughter nuclide is also radioactive • All of the radioactive nuclides that are produced one after the other until a stable nuclide is made is called a decay series • To determine the stable nuclide at the end of the series without writing it all out 1. count the number of a and b decays 2. from the mass no. subtract 4 for each a decay 3. from the atomic no. subtract 2 for each a decay and add 1 for each b
The Four Known Decay Series Parent Radioisotope # of Decay Steps Final Product of Series Uranium-238 14 Lead-206 Thorium-232 10 Lead-208 Uranium-235 11 Lead-207 Plutonium-241 13 Bismuth-209
Positron Decay Occurs in nuclei with a low neutron to proton ratio. A proton decays into a neutron and an electron inducing a shift up and to the left in the nuclear stability plot. Electron Capture Decay Electron capture is common in heavier elements that have a low neutron to proton ratio. Gamma-ray Decay Gamma-ray decay generally accompanies another radioactive decay process because it carries off any excess energy within the nucleus resulting from the radioactive decay. Nuclear Stability (4)
•Magic numbers(Solution Of SWE,For Nuclear Potential Of The Nucleus)  Certain numbers of protons and/or neutrons convey unusual stability/abnormal behavior like Zero Electric, Magnetic & Quadruple Moment of the nucleus& Positive Parity on these numbers 2, 8, 20, 28, 50, 82, 126  There are ten isotopes of Sn (Z=50); but only two of In (Z=49) and Sb (Z=51)  Magic numbers are associated with the nuclear structure, which is analogous to the electronic structure of atoms(2n Square)/which means paired nucleons & Completely filled energy levels
Magic Numbers  Besides the N/Z ratio, the actual numbers of protons and neutrons affects stability  Most stable nuclei have even numbers of protons and neutrons  Only a few have odd numbers of protons and neutrons  If the total number of nucleons adds to a magic number, the nucleus is more stable  same principle as stability of the noble gas electron configuration  most stable when N or Z = 2, 8, 20, 28, 50, 82; or N = 126 Tro: Chemistry: A Molecular Approach
Marie Curie, Nobel Prize Winner
What is Radioactivity?  When nuclei of unstable isotopes gain stability by undergoing changes/Balancing their Neutron & Proton Excess  These reactions:  are called nuclear reactions(Transition via bombardment from outside) OR Spontaneous Transition Called Radio Active Decay)  are always accompanied by the emission of large amounts of energy  are spontaneous  are not affected by changes in temp, pressure, or presence of catalysts  cannot be slowed down, speeded up, or turned off
 The process by which atoms emit rays is called radioactive decay OR nuclear decay  Unstable nucleus = can be due to the overall size of the nucleus, having too many or too few neutrons  Eventually, unstable radioisotopes of one element are transformed into stable, nonradioactive isotopes of a different element
Discovery/Protection of Radioactivity Henri Becquerel discovered that uranium compounds spontaneously give off radiation.
Discovery of Radioactivity (cont.) Marie and Pierre Curie concluded that a nuclear reaction was taking place within the uranium atoms. Radioactivity is the spontaneous emission of radiation by an unstable atomic nucleus. **Objects do not become radioactive when subjected to radiation unless they actually absorb radioactive elements.
Random decay Radioactivity is a chance process. • The chance of decay for each nucleus is constant with time, independent of temperature, pressure, other physical conditions. • The properties of random decay are best displayed if large numbers of events are involved. • The rate of decay is proportional to the number of undecayed nuclei present. • The half-life of a radioisotope is the average time for half the nuclei present to decay (for the activity to fall to ½ its previous value).
We know that the popcorn will go ‘pop’, but we don’t know exactly which kernel will pop at any given time. Popping of Popcorn/Physical Example!
Operating Engineers National Hazmat Program 101 The Search for Stability  An atom is stable based on it’s proton to neutron ratio (N/Z Rule, BE, Curve ,Stability Curve, Shell Model)  If there are too many or too few neutrons or protons, the atom will give off excess energy as  Rays &  Particles This process is called radioactive decay
What is Radiation? Radiation – general term for energy The Energy which can also moves like matter, Some times particles, Sometimes in Waves Operating Engineers National Hazmat Program 102
Energy In terms of the energy associated with each type of radiation: Increasing energy a b g Good news…………………………Bad news
Penetrating Ability Depending upon its energy, different types of radiation are stopped by different materials Called Absorbers Or Shielding Materials. a b g Good News………………………Bad news
Ionisation Radiation is dangerous because it “ionises” atoms – in other words, it turns them into ions by giving them enough energy to “knock off” electrons: Ionisation causes cells in living tissue to mutate, usually causing cancer.
Electromagnetic Spectrum 10 -14 10 -12 10 -10 10 -8 10 -6 10 -4 10 -2 1 10 2 10 4 10 6 10 8 Wavelength in Meters 10 10 10 8 10 6 10 4 10 2 1 10 -2 10 -4 10 -6 10 -8 10 -10 10 -12 10 -14 Broadcast Short wave TV FM Radar Infrared Near Far Visible Ultraviolet X Rays Gamma Rays Cosmic Rays Power Transmission Ionizing Radiation Nonionizing Radiation Energy - Electron Volts High Low
Paper Aluminum Acrylic resin Lead H2O (Hydrogen rich) β e- γ α P+ n n P+ Neutron radiation n Penetrating Ability of Radiations
The Electromagnetic Spectrum(The Soul of Human Existence, Body needs all types of radiations for proper functioning & the same is the case for telecommunication) NONIONIZING IONIZING Radio Microwaves Infrared Visible light Ultraviolet X-rays Gamma rays 110
 Radiation is the emission and transmission of energy through space or material medium.  Radiation can be in the form of sub-atomic particles (protons, neutrons and electrons) or electromagnetic waves
Introduction to Radiation “Radiation” refers to any form of energy originating from a source, and usually falls into two types: Radiation A wave, such as light coming from the sun A particle, such as this alpha particle coming from the nucleus
What is Radiation?  Radiation is energy transmitted by particles or electromagnetic waves  Radiation can be ionizing or non-ionizing
William Hutton –a founder of modern geology After many years of studying the history of the earth he said that he saw “no vestige of a beginning and no prospect of an end“/The Universe, Same is True for the RADIO –ACTIVITY”
Radioactivity is everywhere because every element on the periodic table has some atomic nuclei that are radioactive.
What is Radiation?  Form of energy  Emitted by nucleus of atom or orbital electron  Released in form of electromagnetic waves or particles(Both are necessary for conserving Energy ,Matter Content of the Universe) 117
 Ionizing Radiation (IR) causes ions to be produced when radiation is absorbed in matter  Non-Ionizing radiation (NIR) refers to radiation energy that, instead of producing charged ions, when passing through matter, has sufficient energy only for excitation.
Ionizing radiation High energy radiation • Gamma-rays, x-rays - photons • Particles: alpha, beta, neutron Ejects electrons from atoms • Produces an altered atom - an ion Non-ionizing radiation Low energy • Lasers, RF, microwaves, IR, visible Excites electrons Produces heat Or any other physio chemical effect,
Natural Background Radiation
Man-Made Radiation
Natural background radiation  The natural radiation energy between few KeV to MeV from primordial radionuclides are called background radiation.  Background radiation is of terrestrial and extra- terrestrial origin. PLANTS ATMOSPHERE SOURCE (BEDROCK) MAN, ANIMALS SOILS
1. Terrestrial radiation components  The terrestrial component originates from primordial radionuclides in the earth’s crust, present in varying amount.  Components of three chains of natural radioactive elements viz. the uranium series, the thorium and actinium series.  238U, 226Ra, 232Th, 228Ra, 210Pb, 210Po, and 40K, contribute significantly to natural background radiation.
2. Extra terrestrial radiation  Among the singly occurring radionuclides tritium and carbon-14 (produced by cosmic ray interactions) and 40K (terrestrial origin) are prominent.  Radionuclides from these sources are transferred to man through food chains or inhalation. 1. Terrestrial radiation components contd… • The extra terrestrial radiation originates in outer space as primary cosmic rays. • The primary cosmic rays mainly comprise charged particles, ionised nuclei of heavy metals and intense electromagnetic radiation.
3. Artificial Radionuclides  Over the last few decades man has artificially produced hundreds of radionuclides.  Artificial radioisotopes to the atmosphere during the course of operation of the nuclear fuel cycle, nuclear tests (mainly atmospheric) and nuclear accidents  Most of the artificial radioisotopes decay -short half-lives. Therefore only a few of them are significant from the point of human exposure.
Radon  Radon is a radioactive gas decay product of radium, created during the natural breakdown of uranium in rocks and soils  It is one of the heaviest substances that remains a gas under normal conditions and is considered to be a health hazard causing cancer  It has three isotopes, namely, 222Rn (238U), 220Rn (232Th) and 219Rn (235U). 222Rn has longer half life (3.84 days) than the other two isotopes
Radon-222  Originates from U-238 which occurs naturally in most types of granite  Radon-222 has a half-life of 3.825 days  It decays via alpha emissions  This isotope is a particular problem because it is a gas which can leave the surrounding rock and enter buildings with the atmospheric air
Radon/Thoron in Buildings There are two main sources for the radon in home's indoor air, soil and water supply.
Where does your radiation exposure come from?
Sources of background radiation
Dr Manjunatha S, CCIS
Sources of Annual Radiation Dose Radon 55% Cosmic 8% Terrestrial 8% Internal 11% Medical X-Rays 11% Nuclear Medicine 4% Consumer Products (3%) Other (<1%) Occupational 0.3% Fallout <0.3% Nuclear Fuel Cycle 0.1% Miscellaneous 0.1%
Applications of Nuclear Radiation  Medical diagnosis, treatment, and sterilization  Nuclear power (both fission and fusion)  Semiconductor fabrication (lithography, doping)  Food preservation through irradiation  Density measurements (soil, oil, concrete)  Gauging (thickness) measurements in manufacturing (steel, paper) and monitoring (corrosion in bridges and engines)  Flow measurements (oil, gas)  Insect control (fruit fly)  Development of new crop varieties through genetic modification  Curing (radiation curing of radial tires)  Heat shrink tubing (electrical insulation, cable bundling
Effect of Ionising Radiation on Living Organisms Effect of Ionising Radiation at a Molecular Level • When molecules in cells become ionised there a number of effects such as disrupted bonds, alteration of the tertiary and quaternary structure and by crosslinking which in turn damages cells. • Most damage is caused by the generation of hydroxyl free radicals
Effect of Ionising Radiation Free radicals are generated by radiolysis of water. 2H20 H2O+ + H20- H2O+ OH. + H+ Hydroxyl radicals react with other molecules (such as DNA) damaging them. Note that the indirect effect is responsible for a significant proportion of cell damage Effect of Ionising Radiation at a Molecular Level cont’d
Cellular Radiosensitivity (Law of Bergonne and Tribondeau) 1. Rapidly dividing tissue is more radiosensitive 2. Rapidly growing cells are more radiosensitive 3. Younger and more immature cells are more radiosensitive 4. Mature cells are less radiosensitive NB: Dividing cells are more radiosensitive. This is why radiotherapy is effective on rapidly dividing tumor cells. Unfortunately rapidly dividing cells such as bone marrow, gut epithelium and hair follicles are also radiosensitive Organ toxicity The lens of the eye is particularly sensitive Effect of Ionising Radiation on Tissues and Cells
Biological Effects of Radiation 14-2-1426 The Secrets of Atomic Radiation Hadeed 143 How Radiation can Lead to Damage in Tissue Radiation Damage to DNA Cell Death Cell Transformation Early Effect Cancer Physical & Chemical Changes Electrical Effect (Ionization) Hereditary Defects
RADIATION DIRECT IONIZATION OF DNA IONIZATION OF OTHER MOLECULES, e.g.,H2O radiation + H2O  H2O+ + e H2O+  H+ + OH0 e + H2O  H0 + OH OXIDATION OF DNA BY OH RADICALS NO EFFECT ENZYMATIC REPAIR CHEMICAL RESTORATION DNA RESTORED PERMANENT DAMAGE IN DNA BIOLOGICAL EFFECTS 1. GENETIC EFFECTS 2. SOMATIC EFFECTS CANCER STERILITY
Why are we concerned about Radiation? Ionizing Radiation Human Cells Atoms in Cells Form Ions Change in Cell Cell Dies No/Neutral Change in Cell Not Replaced Replaced Reproduces Malignant Growth Benign Growth
Biological Effects(Somatic ,Someone,Genetic ,Generations) Mechanisms of Injury Ionizing Radiation Cell Death Cell Damage Repair Transformation
Three Cellular Effects Cell death Cell repair Cell change Is this change good or bad?
Ionizing Radiation at the Cellular Level  Causes breaks in one or both DNA strands or;  Causes Free Radical formation
DNA and Radiation
Our Bodies Are Resilient  DNA damage is most important and can lead to cell malfunction or death.  Our body has ~ 60 trillion cells  Each cell takes “a hit” about every 10 seconds, resulting in tens of millions of DNA breaks per cell each year.  BACKGROUND RADIATION causes only a very small fraction of these breaks (~ 5 DNA breaks per cell each year).  Our bodies have a highly efficient DNA repair mechanisms(Catabolic & Metabolic Processes)
Effect of Ionising Radiation on Humans The effects of ionizing radiation are classified on human in two broad categories: • Deterministic • Stochastic
Goals of Radiation Safety  Eliminate deterministic effects  Reduce incidence of stochastic effects
Deterministic Effects These effects have thresholds above which damage occurs and effects are then dose dependent e.g. lens opacification, burns, hair loss. Determinisitic effects like the burns below suffered by those who put their hands in the path of a x-ray beam are relatively easy to avoid Effect of Radiation on Humans
Stochastic Effects • Mutational, non-threshold effects in which the chance of occurring rather than the severity are dose dependent. • These affects are not predictable e.g. cancer • Note that stochastic effects are not predictable and give rise to the notion that there is no absolutely safe dose and the concept of ALARA. Effect of Radiation on Humans
Dose versus Effect/ S, Shape:  Nobody knows for sure what radiation dose does to us below the shaded region. There may be a threshold where there is no effect from radiation below a certain dose.  In Radiation Protection, as a protective measure, it is assumed that all dose carries some risk, this is represented by the straight red line on the diagram.  FYI: There are other theories regarding the effects of radiation dose (as represented by the other lines – blue and gray), to include radiation hormesis. Radiation hormesis is a theory that chronic low doses of radiation is good for the body.
Applications for Radioactivity
Applications Popular products included radioactive toothpaste for cleaner teeth and better digestion, face cream to lighten the skin; radioactive hair tonic, suppositories, and radium-laced chocolate bars marketed in Germany as a "rejuvenator." In the U.S, hundreds of thousands of people began drinking bottled water laced with radium, as a general elixir known popularly as "liquid sunshine." As recently as 1952 LIFE magazine wrote about the beneficial effects of inhaling radioactive radon gas in deep mines. As late as 1953, a company in Denver was promoting a radium-based contraceptive jelly.
Radium Girls "Not to worry," their bosses told them. "If you swallow any radium, it'll make your cheeks rosy.“ The women at Radium Dial sometimes painted their teeth and faces and then turned off the lights for a laugh. From: 'Radium Girls' By Martha Irvine, Associated Press, Buffalo News, 1998
Lessons from the Past The Radium Dial Painters Photo by Carmelina Rattrovo from the Playwrights Theatre production of Radium Girls, by D.W. Gregory
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First Known Human Misuse of Uranium/ Coloration & Discoloration/Magic Water.ToothPaste,Sexual Power:  79 A D  Roman artisans produce yellow colored glass in mosaic mural near Naples, Italy Radium - A radioactive element discovered in 1898 by Curie - Found to glow in the dark! - Many (at the time) thought it had health benefits
The radium dial painters • Watch-dial painters - United States Radium factory in Orange, New Jersey, around 1917 . • The Radium Girls (4000) were female factory workers who contracted radiation poisoning from painting watch dials with self-luminous paint. • They were used to tip (i.e., bring to the lips) their radium-laden brushes to achieve a fine point. • Unfortunately this practice led to ingested radium, and many of the women died of sicknesses related to radiation poisoning. • The paint dust also collected on the workers, causing them to “glow in the dark.” • Some also painted their fingernails and teeth with the glowing substance.
More Radiation Misconceptions  Radiation does not give you super human powers  Radiation will not make you glow in the dark
Radium Effects Confirmed  1925  Suspicions develop around watch dial painters’ jaw lesions  Dentists diagnose lesions as jaw necrosis due to radium deposits in jaw bone  Doctor notes bone changes and anemia in dial painters
The mouth of a man who has suffered a 10 to 20 Gy dose 21 days after the exposure, note the damage to normal skin, the lips and the tongue.
Importance of Radiation in Daily Life  Medicine: Radiology, Radiation Therapy  Power Production and Space Exploration  In Agriculture to improve variety & yield production  Weapons of mass destruction  Industrial applications: Gauges, Radiography, Mineral exploration
Beauty of Medical Research: As a “Tracer” Technique. • Radioactivity is an excellent tool! • Detectable in minute quantities Result is the same for mega quantities (like finding one grain of sand on a small beach containing 6,000,000,000 granules)
Why We Measure(Hidden Enemy, Silent Killer, We Should Know How Much Dangerous/Defensive Strategy.  Personal Dosimetry vs Regulatory requirements  Classification of safe and dangerous zones  Safety vs Protective measures  Quality control and Quality assurance  Data consistancy and standardization
Why is Radiation Detection Difficult/Five Senses(Not Capable), Need of Sixth Sense ?  Can’t see it  Can’t smell it  Can’t hear it  Can’t feel it  Can’t taste it  Can’t touch it  We take advantage of the fact that radiation produces ionized pairs, or some other physio chemical change to try to create an electrical signal or current pulse, capacitor charge /discharge to produce deflection = to radiation effect(Cause & Effect)
YOUR ATTITUDE/Best Friend OR Bitter Enemy --- AND ACTIONS --- COUNT!(Change your Attitude change your life) You must want to do your job safely and you must understand and use safe practices and methods. That’s what being part of an effective safety Individual is all about!
How Do I Protect Myself? Reducing the dose from any source radiation exposure involves the use of three protective measures: – TIME – DISTANCE – SHIELDING
Campfire Analogy
Benifit Risk Benifit and risk/Balanced Rather Benefit > Risk:
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Basic Concepts  Radioactive Decay: A = Aoe-λt ○ A = λN ○ λ = 0.693 / T1/2  Inverse Square Law  Shielding I = IoBe-t /D= c(1-S) Where S= Shielding Material 2 2 2 1 1 2 d d I I 
Time(T) − The amount of exposure an individual accumulates is directly proportional to the time of exposure − Keep handling time to a minimum(less time Sun Bath, More time Sun Burn)
Distance(D) − The relationship between distance and exposure follows the inverse square law. The intensity of the radiation exposure decreases in proportion to the inverse of the distance squared(Near fire place more heat, Away less heat) − Dose2 = Dose1 x (d1/d2)2
Shielding(S) − To shield against beta emissions, use Plexiglas to decrease the production of bremsstrahlung radiation. − If necessary, supplement with lead after the Plexiglas − To shield against gamma and x-rays, use lead, leaded glass or leaded plastic(Rain vs. Umbrella no wetting otherwise yes)
Self Protection Measures  1st Avoid exposure and contamination  Detect radiation exposure  Back away when too high  2nd Use Personal Protective Equipment (PPE)  3rd Decontaminate yourself
Simplified Radiation PPE  Protect your respiratory tract  Respirator, surgical mask, etc.  Protect your skin  Gloves!  Outer clothing  Chemical suit is not always needed
Self Decontamination  Wash it off  Hand washing  Taped water, mild soap  No scrubbing  If showering, use shampoo  Remove and launder clothing  Monitor after decontamination
ASARA Goal of exposure management: keep radiation exposures to a level As Safe As Reasonably Achievable (ASARA)
ALARA(Optimization &Cost Effectiveness) As Low As Reasonably Achievable—means making every reasonable effort to maintain exposures to radiation as far below the dose limits as is practicable consistent with the purpose for which the licensed activity is undertaken, taking into account the state of technology, the economics of improvements in relation to the state of technology, the economics of improvements in relation to benefits to the public health and safety, and other societal and socioeconomic considerations, and in relation to utilization of nuclear energy and licensed materials in the public interest.
Adequate Protection
Adequate Protection
Adequate Protection
Adequate Protection Adequate and Appropriate?
Radiation Units Units of radiation include • Curie - measures activity as the number of atoms that decay in 1 second. • rad (radiation absorbed dose) - measures the radiation absorbed by the tissues of the body. • rem (radiation equivalent) - measures the biological damage caused by different types of radiation. 196
Radiation Units Exposure  A measure of ionization produced in air by X or gamma radiation.  Highly specific in that the unit specifies the matter being exposed and radiation producing the ionizations.  Unit: roentgen (R)  1 R = 1000 mR Absorbed Dose • A measure of energy deposition per unit mass irradiated. • Considers all radiations imparting energy to all types of matter. • Unit: rad • 1 rad = 1000 mrad • SI Units: gray (Gy) • 1 Gy = 100 rad Dose Equivalent • It is numerically equal to the absorbed dose by a quality factor • Dose equivalent is needed because the biological effect from a given absorbed dose is dependent upon the type of radiation producing the absorbed dose. • Unit: rem • 1 rem = 1000 mrem • SI Units: sievert (Sv) • 1 Sv = 100 rem Now that you have a little understanding of the physics behind ionizing radiation, how do we measure or quantify radiation? Here are a few units of measure that are used (often interchangeably) in radiation protection:
Units of Radiation Measurement 198
An Analogy... Here's a way to think about measures of radiation: Imagine that you're out in a rainstorm. • The amount of rain falling is measured in Becquerel (Activity). • The amount of rain hitting you is measured in grays (Absorbed Dose). • How wet you get is measured in sieverts. (Biological Damage)
What is a Personnel Monitoring Program? 201 A systematic process for monitoring, recording, evaluating, and reporting the radiation doses received by occupationally exposed individuals
Purpose of Personnel Monitoring  To ensure compliance with established dose limits  To keep radiation doses as low as reasonably achievable (ALARA) 202
Dose Limits 203 Occupational Adult(whole body) Public Eye Embryo/Fetus Minor(whole body) Extremities Individual Organs Body Part Limit Quantity TEDE TEDE Hd+HT,50 Heye Hs 5.0 rem 0.5 rem 0.5 rem 15 rem 50 rem 50 rem General Public 0.1 rem Hd+HT,50 TEDE LARPD Chapter 4 Subchapter B
Wipe Samples  With a cotton wafer, wipe an area of approximately 100cm2 (about the size of a U.S. dollar bill). You should wipe about 1% of the accessible surface area in “hot area”.  In “clean” areas, take wipes of frequently used items or areas – calculators, phones, door knobs, high traffic floors, etc.  Count the wafer with at least 3 ml of “safe” scintillation cocktail, along with a background sample consisting of a new/unused, damp, cotton wafer, in a liquid scintillation counter (set to “open” or “wide” window). The results should be reviewed and data taped on the appropriate lab schematic, sign and date the form.
Wipe Tests How do I determine if an area is “contaminated”? Note: Take gloves off before entering room.  If the open-window count exceeds 200 cpm above background, you should recount the wipe vial before making it public to the other users in the room.  If result is still above 200 cpm, you must decontaminate the area and perform another wipe test.  A meter reading two times background in any part of your lab area that has no nearby radioactive material storage or radioactive waste storage needs to be decontaminated. If area cannot be cleaned after two attempts, contact Radiation Safety officer for assistance.
Detection of Radioactivity and the Concept of Half- life • Achilles( "Sardi ki haalat mein“) and the tortoise • “In a race, the quickest runner can never overtake the slowest, since the pursuer must first reach the point whence the pursued started, so that the slower must always hold a lead.”— Aristotle, Physics VI:9, 239b15 • Give a tortoise a head start…… • The answer is obvious if you consider infinite converging theories…
Introduction  Importance and relevance  Radiation is often the only observable available in processes that occur on very short, very small, or very large scales  Radiation detection is used in many diverse areas in science and engineering  Often a detailed understanding of radiation detectors is needed to fully interpret and understand experimental results 207
Detecting particles  Every effect of particles or radiation can be used as a working principle for a particle detector. Claus Grupen 208
RADIATION DETECTORS • Instruments used in the practice of health & Medical physics serve a wide variety of purposes, Mainly of two classes, Survey INSTRUMENTS, Based on Processes Personal Dosimeters, Based on Physio-chemical changes. • one finds instruments designed specifically for the measurement of a certain type of radiation, such as Alpha Particles, Beta Particles low-energy X-rays, high-energy gamma rays. fast neutrons, and so on
Electroscope When charged, the metal foils spread apart due to like charge repulsion When exposed to ionizing radiation, the radiation knocks electrons off the air molecules, which jump onto the foils and discharge them, allowing them to drop down 210 Tro: Chemistry: A Molecular Approach
• The basic requirement of any such instrument is that its detector interact with the radiation in such a manner that the magnitude of the instrument's response like development of current or voltage pulse, Charging and Discharging of Capacitors is proportional to the radiation effect or radiation property being measured Called Current Mode of operation. If Signal is produced by Individual Particle,Amlified and Counted, Called Pulse Mode or Counter.
Overview of Detection Mechanism 212 Ionizing Radiation Ionizing radiation interacts with matter in various ways: ionization (photoelectric effect), excitation, braking radiation, Compton effect, pair production, annihilation etc. Mechanisms of interaction are utilized for the detection of ionizing radiation. Function and principles of electroscope, ionization chambers, proportional Counters, Geiger-Muller counters, solid-state detectors, and scintillation counters, depends on those ways of interaction. and cloud chambers, Bubble chamber &Emulsion have been described.
Radiation Measurement Principles (One Can not really claim to know much about a thing until one can measure it.(KELVIN,1824-1907) Detector Signal Physical Chemical Biological Reader Calibration Assessment Amplificatio n
How a Radiation Detector Works(KERMA ,Kinetic Energy Released in the Medium) The radiation we are interested in detecting all interact with materials of the detector and cause different Physio chemical,Biological,Chemical etc changes used for detection purposes. We can measure or detect these Changes through many different ways/Processes to get a multitude of information
Interactions of Particles with Matter - Radiation Damage  Particles can have lasting effects on the detector materials.  Nuclear Collision  Particle undergoes interaction directly with atomic nucleus.  May transmute the element (radiation damage).  May lead to secondary particles which themselves are detectable.  Lattice Dislocation  Crystalline structure of a material may be disrupted.  Chemical Change  Photographic Film or Emulsion While these effects can be exploited as a type of particle detection, they may also cause permanent damage to detector components resulting in a detector which stops working. This is sometimes referred to as “aging”.
Interactions of Particles with Matter - Effect on the Particle  For a particle to be detected it must interact with Material of the Detector.  ACTION = REACTION  The properties of the particle may be different after we have detected it.  Lower Energy  Different Momentum (direction)  Completely Stopped In fact, one method of determining a particle’s energy is simply to measure how far it goes before stopping.
Interactions of Particles with Matter - Summary  When particles pass through matter they usually produce either free electric charges (ionization) or light (photoemission).  How can we use this?  Most “particle” detectors actually detect the light or the charge that a particle leaves behind.  In all cases we finally need an electronic signal to record.
Particle Detectors… aside: Avalanche Multiplication We need devices that are sensitive to only a few electron charges: ( An Ampere is 6.2x1018 electrons/second! ) we need to amplify this charge. By giving the charges a push, we can make them move fast enough so that they ionize other atoms when they collide. After this has happened several times we have a sizeable free charge that can be sensed by an electronic circuit.
Particle Detection Mechanism An Overview:  Detect Particles by Letting them Interact with Matter within the Detectors.  Choose appropriate detector components, with awareness of the effects the detectors have on the particles.  Design a System of Detectors to provide the measurements we need.
Basic Structure of Experimentation/Need of Accelerator & Detector Physics Ion Source Accelerator Beam Target Detectors
Detection and Measurement includes the following components:  Detector  Preamplifier(conversion of I,to,V,pulse ,Impedance Matching)  Amplifier  Single channel analyzer  Multi-channel analyzer  Scalar-Timer
 a detector produces a signal for every particle entering in it.  Every detector works by using some interaction of particles with matter.  Use characteristic effects from interaction of radiation with matter to detect, identify and/or measure properties of radiation.  Respond to radiation by producing various physical effects
Processes Used For Detection  Ionization: Gas/Liquid chambers and Semiconductor Detectors  Scintillation: Scintillation counters and TLDs  Sparking: Sparking chamber  Blackening of photographic film: Nuclear Emulsion detector and Film dosimetry  Bubbling/Clouding of supersaturated liquids/vapors: Cloud Chambers and Bubble Chambers
 Physical Changes: NMR Dosimetry and SSNTDs  Themodynamical Changes: Calorimetric Dosimetry  Activation: Neutron Activation Detectors  Biological Changes: ESR Detectors and Biosensors
Today: most signals are electronic  photographic emulsions and bubble chambers have largely disappeared  the few remaining such systems (e.g. OPERA) are usually also processed electronically  most modern detectors yield electronic signals  wire (drift) chambers  silicon (semiconductor) devices  photo detectors (photomultipliers)  WHY ?  GOOD ?  BAD ?
Advantages of electronic signals  digitize and write directly to “logbook” (data storage)  no human errors  much faster  possible to use a trigger  automatic selection of events to be stored
Detector types  today, we directly “see” in detectors only particles we know already  “Messenger” particles  “new” particles are too short-lived to reach detectors  which are these “messenger” particles?
Detector types  today, we directly “see” in detectors only particles we know already  “messenger” particles  “new” particles are too short-lived to reach detectors  which are these “messenger” particles?  electrons / positrons / photons  protons / charged pions / other charged hadrons  neutrons / other neutral hadrons  muons  missing (transverse) momentum
Detector types  today, we directly “see” in detectors only particles we know already  “messenger” particles  “new” particles are too short-lived to reach detectors
“De-randomization” n fluctuations in arrival time absorbed by queue n FIFO – first in, first out – “de-randomized” output rate n additional latency
Following is the list of most common types of detectors:  Gas-filled counters ionization chamber Proportional Counter Geiger-Muller counter  Scintillation detectors  Semiconductor detectors  Nuclear Emulsions  Bubble/Cloud Chambers  SSNTD  Personal Dosimeters etc
Gas Detectors  Most common form of radiation detector  Relatively simple construction ○ Suspended wire or electrode plates in a container ○ Can be made in very large volumes (m3)  Mainly used to detect b-particles and neutrons  Ease of use  Mainly used for counting purposes only ○ High value for W (20-40 eV / ion pair) ○ Can give you some energy information  Inert fill gases (Ar, Xe, He)  Low efficiency of detection  Can increase pressure to increase efficiency  g-rays are virtually invisible
Ionization Chambers  Two electric plates surrounded by a metal case  Electric Field (E=V/D) is applied across electrodes  Electric Field is low  only original ion pairs created by radiation are collected  Signal is very small  Can get some energy information  Resolution is poor due to statistics, electronic noise, and micro phonics Good for detecting heavy charged particles, betas
Proportional Counters  Wire suspended in a tube  Can obtain much higher electric field  E a 1/r  Near wire, E is high  Electrons are energized to the point that they can ionize other atoms  Detector signal is much larger than ion chamber  Can still measure energy  Same resolution limits as ion chamber  Used to detect alphas, betas, and neutrons
Six-Region Gas Amplification Curve a, b, g each produce the same detector response. a _____ b- _____ g _____ Voltage Pulse Height 100 1013 Recombination Region Ionization Region Proportional Region Limited Proportional Region Geiger-Mueller Region Continuous Discharge Region 1 2 3 4 5 6
5/23/2023 DST SERC EHEP SCHOOL (Nov 7-27, 2017)
1. Recombination Region  Applied voltage too low  Recombination occurs  Low electric field strength 2. Ionization Chamber Region (aka Saturation Region)  Voltage high enough to prevent recombination ○ All primary ion pairs collected on electrodes  Voltage low enough to prevent secondary ionizations  Voltage in this range called saturation voltage  As voltage increases while incident radiation level remains constant, output current remains constant (saturation current) Six-Region Gas Amplification Curve
3. Proportional Region  Gas amplification (or multiplication) occurs ○ Increased voltage increases primary ion energy levels ○ Secondary ionizations occur ○ Add to total collected charge on electrodes  Increased output current is related to # of primary ionizations via the proportionality constant (aka gas multiplication factor) ○ Function of detector geometry, fill-gas properties, and radiation properties Six-Region Gas Amplification Curve
4. Limited Proportional Region  Collected charge becomes independent of # of primary ionizations  Secondary ionization progresses to photoionization (photoelectric effect)  Proportionality constant no longer accurate  Not very useful range for radiation detection Six-Region Gas Amplification Curve
5. Geiger-Mueller (GM) Region  Any radiation event strong enough to produce primary ions results in complete ionization of gas  After an initial ionizing event, detector is left insensitive for a period of time (dead time) ○ Freed primary negative ions (mostly electrons) reach anode faster than heavy positive ions can reach cathode ○ Photoionization causes the anode to be completely surrounded by cloud of secondary positive ions ○ Cloud “shields” anode so that no secondary negative ions can be collected ○ Detector is effectively "shut off" ○ Detector recovers after positive ions migrate to cathode  Dead time limits the number of radiation events that can be detected ○ Usually 100 to 500 s Six-Region Gas Amplification Curve
6. Continuous Discharge Region  Electric field strength so intense that no initial radiation event is required to completely ionize the gas  Electric field itself propagates secondary ionization  Complete avalanching occurs  No practical detection of radiation is possible. Six-Region Gas Amplification Curve
Scintillation Detectors  Phosphors (NaI(Tl), CsF, BGO, LSO)  Photomultiplier Tube (PMT) dynodes, counting chain, spectra  Liquid Scintillation Counting (“wipes”)
Photon Interaction with NaI(Tl) Crystal ”.
NaI(Tl) – PMT Assembly ”.
NaI(Tl) – PMT Assembly .
Scintillator Characteristics  Phosphors (NaI(Tl), CsF, BGO, LSO)  Photoelectric interaction ~ Z4  NaI(Tl): reference, decay const. ~ 1μs  CsF : faster than NaI(Tl), TOF PET  BGO : slower but more efficient, PET  LSO : very fast (~1ns), high res. PET .
Phosphor- PMT Assembly easurements”.
Photomultiplier Tube (PMT) ents”.
Electron Multiplication in PMT .
Counting Chain (1) ”.
Counting Chain (2) ”.
Counting Chain (3) ”.
Fluorescence Screens, Some Historical Facts. 254 Ionizing Radiation Fluorescence materials absorb invisible energy and emit visible light. J.J. Thomson used fluorescence screens to see electron tracks in cathode ray tubes. Electrons strike fluorescence screens on computer monitors and TV sets give dots of visible light. Rontgen saw the shadow of his skeleton on fluorescence screens. Rutherford observed alpha particle on scintillation material zinc sulphide. Fluorescence screens are used to photograph X-ray images using films sensitive visible light.
Semiconductor Detector  A semiconductor detector acts as a solid- state ionization chamber  The operation of a semiconductor radiation detector depends on its having either an excess of electrons or an excess of holes.  A semiconductor with an excess of electrons is called an n-type semiconductor, while one with an excess of holes is called a p-type semiconductor
Semiconductor Detectors
 one of the oldest devices used to detect and measure ionizing (nuclear) radiation  Named for Hans Geiger who invented the device in 1908, and Walther Muller who collaborated with Geiger in developing it further in 1928  one of the most sensitive, especially for the low radiation levels typically found in most situations.
 Following is the assembly of the components of GM counter: to get as max precision as possible  Power-supply  GM tube  Discriminator  Scalar/timer
GM Counter Assembly  Variable voltage source  Gas-filled counting chamber  Two coaxial electrodes well insulated from each other  Electron-pairs  produced by radiation in fill gas  move under influence of electric field  produce measurable current on electrodes, or  transformed into pulse
GM Tube In Action wall fill gas R Output A or Anode (+) Cathode (-) End window Or wall
Indirect Ionization Process wall Incident gamma photon
Direct Ionization Process wall Incident charged particle e - e - e - e - e - e - e - e - beta (β-)
Competing Processes - recombination R Output e - e - + +
5/23/2023 DST SERC EHEP SCHOOL (Nov 7-27, 2017)
5/23/2023 DST SERC EHEP SCHOOL (Nov 7-27, 2017) Avalanche process via ionization important for gain factor & gas detectors
5/23/2023 DST SERC EHEP SCHOOL (Nov 7-27, 2017)
5/23/2023 DST SERC EHEP SCHOOL (Nov 7-27, 2017)
Voltage versus Ions Collected Voltage Number of Ion Pairs collected Ionization region Saturation Voltage 100 % of initial ions are collected Recombination region
 The characteristics curve depends on three factors  Plateau: the part of the curve where the number of counts per second is (almost) independent of the voltage.  Threshold voltage: always lies in the plateau region and is a function of the gas pressure and the anode diameter  Figure of merit: is always less than 1%
 A process causing the discharge to terminate  Two methods used for quenching are: ○ External quenching ○ Internal quenching
 Used to restore the counter to its quiescent state after the passage of ionizing radiation  An RC circuit is used for reducing the high voltage applied to the tube, for a fixed time after each pulse, to a value that is too low to support further gas multiplication  The voltage must be reduced for a few hundred secs which is greater than the transit time of the positive ions  A counter with 98% pure argon is used
 The advantage of external quenching is that it gives long life time to GM tube  The disadvantage is that it has long recovery time
 The quenching agent gas in the Geiger counter stops the flow of electrical current after a few microseconds.  the quenching gas is of low ionization potential (halogens or organic vapors)  Halogens are preferably used because it increases the life of GM tube  Organic quenched tubes usually have a flatter plateau than halogen quenched tubes
 The purpose of the quenching additive to the gas is to effectively absorb UV-photons emitted from the electrodes when the ions produced in the multiplication process impact on the electrodes.  Such photons otherwise liberate secondary electrons (via the photo-electric effect) which may initiate the avalanche process all over again, thereby leading to catastrophic breakdown of the tube (i.e. a spark).
 Device serving as pulse height selector  able to make selection from output analogical pulses, rejecting the impulses with voltage amplitude inferior to a certain threshold voltage  Threshold voltage should neither too low nor too high to avoid noise and data-loss respectively  Its function is double: ○ To eliminate the noise ○ To provide a standard shaped pulse to scaler
 Scalar: counts the number of pulses  Timer: measures the length of counting time in a given measurement  Collectively used to:  Make measurement of pulses for a preset length of time (set on timer) recording the number of counts by the scaler  Determine the count-rate by measuring duration with timer for a preset number of counts(like car,s window shield wiper via adjustment of time constant of RC network)
Geiger-Muller Counter
Resolving Time  The negative ions, being electrons, move very rapidly and are soon collected, while the massive positive ions are relatively slow-moving and therefore travel for a relatively long period of time before being collected  These slow-moving positive ions form a sheath around the positively charged anode, thereby greatly decreasing the electric field intensity around the anode and making it impossible to initiate an avalanche by another ionizing particle. As the positive ion sheath moves toward the cathode, the electric field intensity increases, until a point is reached when another avalanche could be started
Resolving Time  dead time  The time required to attain this electric field intensity  recovery time  the time interval between the dead time and the time of full recovery  resolving time  The sum of the dead time and the recovery time
Resolving Time  dead time, recovery time, resolving time
Resolving Time  Measurement of Resolving Time  the "true“ counting rate ○ the observed counting rate of a sample is R0
 Objective: to extract the amplitude or timing information the electrical signal is coupled to an amplifier, sent through gain and filtering stages, and finally digitized to allow data storage and analysis.  amplitude or timing information include the different characteristics of the radiation, such as the type, the intensity and energy of the radiation  The signal can be either processed entirely through analog circuit or can be converted into digital form
 The signal can be a continuously varying signal  a sequence of pulses, occurring periodically at known times randomly  All of these affect the choice of signal processing techniques.
 First steps in signal processing: ○ Formation of the signal in the detector (sensor) ○ Coupling the sensor to the amplifier  Detectors use either ○ direct detection or ○ indirect detection
 The detector pulse has a very low amplitude & time duration i.e. narrow band width  To extract any kind of information requires amplification of detector signal  Preamplifier is a simple and efficient amplifier directly connected to detector
 A preamplifier, in effect, acts as a capacitance terminator thus preventing deterioration of detector.  Matches the high electric impedance of detector with low impedance of the coaxial cable connected to subsequent signal processing circuit  Basically plays a role as an impedance matcher between the detector and the rest of the circuit
 The function is to amplify the pulses from detector via a preamplifier  Also used to shape a pulse for further detection
 High-voltage power supply typically provides 800 to 1,200 volts to the PMT  Raising voltage increases magnitude of voltage pulses from PMT  Preamp connected to PMT using very short cable  Amplifies voltage pulses to minimize distortion and attenuation of signal during transmission to remainder of system
SCA Contd.  Amplifier further amplifies the pulses and modifies their shapes – gain typically adjustable  SCA allows user to set two voltage levels, a lower level and an upper level  If input pulse has voltage within this range, output from SCA is a single logic pulse (fixed amplitude and duration)  Counter counts the logic pulses from the SCA for a time interval set by the timer
SCA energy modes  LL/UL mode – one knob directly sets the lower level and the other sets the upper level  Window mode – one knob (often labeled E) sets the midpoint of the range of acceptable pulse heights and the other knob (often labeled E or window) sets a range of voltages around this value.  Lower-level voltage is E - E/2 and upper-level voltage is E + E/2
 An MCA system permits an energy spectrum to be automatically acquired much more quickly and easily than does a SCA system  The detector, HV power supply, preamp, and amplifier are the same as for SCA systems  The MCA consists of an analog-to-digital converter, a memory containing many storage locations called channels, control circuitry, a timer, and a display
 Advantages  Variety of sizes and shapes  Inexpensive  The slightest radiation event strong enough to cause primary ionization results in ionization of the entire gas volume  Thus detector is highly sensitive, even in lowest intensity radiation fields  Only simple electronic amplification of the detector signal is required ○ Hardware lasts longer ○ Requires less power  Strong output signal means G-M needs less electrical noise insulation than other detectors NET 130 303
 Disadvantages  Incapable of discriminating between type and energy of the radiation event  Only counts events and yields output in events per unit time or dose rate  A beta particle or gamma ray, high or low energy, represents one event counted  Only capable of detecting fields to some upper limit of intensity ○ Limited to lower intensity fields due to detector dead time NET 130 304
Personnel Monitor Devices The most common monitor devices to determine the personal exposure history are: Radiation Film Badges Pocket Dosimeter
Radiation film badges are composed of two pieces of film, covered by light tight paper in a compact plastic container. Various filters in the badge holder allow areas to be restricted to X-ray, g-ray, b-rays only. Radiation causes a blackening (silver) of the film material (mostly a silver bromide emulsion) The sensitivity of the film material is limited For g-radiation the sensitivity is in the range of 10 - 1800 mrem. For b-radiation the sensitivity is in the range of 50 - 1000 mrem. Special film material is used for neutron monitoring. The badge is usually not sensitive for a radiation because the a-particles are absorbed in the light-tight paper.
Pocket dosimeter The pocket dosimeter or pen dosimeter is a common small sized ion chamber which measures the originated charge by direct collection on a quartz fiber electroscope. The U-shaped fiber is close to a U-shaped wire. If the fiber is charged it will be deflected away from the wire. The position of deflection is a measure of the accumulated radiation dose.
The dosimeter records total exposure from the initial charging to the time of reading. It is an active device as the radiation exposure can be read immediately as opposed to the passive film badge which is only read after approximately six months.
Dosimeters which are also available in high or low ranges, can be in the form of a badge, pen/tube type, or even a digital readout and all measure exposure or the total accumulated amount of radiation to which you were exposed. (The Civil Defense pen/tube tube would show a reading like below when looking through it.) It's also similar to the odometer of a car; where both measure an accumulation of units. The dosimeter will indicate a certain total number of R or mR exposure received, just as the car odometer will register a certain number of miles traveled.
MSc-REP Regan Dosimetry 310 Photographic Emulsion Dosimetry The photographic emulsion is a suspension of silver halide crystals in a gelatine matrix. The film badge has an emulsion coating on both sides but of differing sensitivities, one for a high dose range, and the other for low dose ranges. When the film is exposed to X-rays, secondary ionisation makes one or more of the silver halide ions latent. When developed this produces metallic silver which varies spatially according to the amount of dose absorbed within the matrix, this forms the photographic negative. 20m 200m protective coating base material silver halide grains in a gelatin matrix
MSc-REP Regan Dosimetry 311 Photographic Emulsion Dosimetry A typical film density versus exposure curve is shown below,
314 Personal Dosemeters Film Badges and TLDs
315 Personal Dosemeter Badges Thermoluminescent dosemeter (a.k.a. “TLD”) This is a reusable dosimeter which uses lithium fluoride to measure radiation dose. It stores dose information until heated to over 250°C when it gives out light the amount of which is proportional to the dose received. It is environmentally robust and excellent for use in all working environments. Photographic film dosemeter (a.k.a. “film badge”) Film is worn in a holder containing several different filters. When developed the film darkens in proportion to the amount of radiation energy received. Due to the differing amounts of filtration we can gain information on the energy of radiation causing the dose. Radioactive contamination of the film can be readily identified. Extremity dosemeter (a.k.a. “finger TLD”) This is a miniature TLD which can be supplied in different forms to suit your needs (stalls, straps or rings). The finger stall is most commonly used and is worn like the finger of a glove.
Thermoluminescence  (TL) is the ability to convert energy from radiation to a radiation of a different wavelength, normally in the visible light range.  Two categories  Fluorescence - emission of light during or immediately after irradiation  Not a particularly useful reaction for TLD use  Phosphorescence - emission of light after the irradiation period. Delay can be seconds to months.  TLDs use phosphorescence to detect radiation.
Thermoluminescence  Radiation moves electrons into “Traps”  Heating moves them out  Energy released is proportional to radiation  Response is ~ linear  High energy trap data is stored in TLD for a long time
TL Process Valence Band (outermost electron shell) Conduction Band (unfilled shell) Phosphor atom Incident radiation Electron trap (meta stable state) -
TL Process, continued Valence Band (outermost electron shell) Conduction Band Phosphor atom Thermo luminescent photon Heat Applied -
Output – Glow Curves  A glow curve is obtained from heating  Light output from TL is not easily interpreted  Multiple peaks result from electrons in "shallow" traps  Peak results as traps are emptied.  Light output drops off as these traps are depleted.  Heating continues  Electrons in deeper traps are released.  Highest peak is typically used to calculate dose  Area under represents the radiation energy deposited in the TLD
Trap Depths - Equate to Long Term Stability of Information Time or temperature
TLD Reader Construction Power Supply PMT DC Amp Filter Heated Cup TL material To High Voltage To ground Recorder or meter
 Crystal retains this energy until heat is applied.  The “trapped” energy is then released in the form of light, as the atoms of the crystal return to their “ground state”  The light emitted is then correlated to dose received  Once the TLD has been “read”, memory is cleared  TLD is then available for re-use Thermoluminescent Dosimeter
MSc-REP Regan Dosimetry 324 Thermo luminescent/OSL Dosimeters Currently the most common used personal dosimeter. The dosimeter consists of two thermo luminescent detectors containing the radiation- sensitive material lithium fluoride (LiF). The detectors are located in a plate which is identified uniquely by means of an array of holes. The lithium fluoride stores the energy it receives from ionising radiations until it is heated/Stimulated with light during processing (in this case to about 250°C) when the energy is released as light. The amount of light released is proportional to the radiation dose. The plate is supplied to the wearer in a plastic wrapper which protects the detectors from light and contaminants. LiF inserts Current NRPB TLD and new Harshaw TLD
Optically-stimulated luminescence (OSL) is based on a principle similar to that of the TLD. Instead of heat, light (from a laser) is used to release the trapped energy in the form of luminescence. OSL is a novel technique offering a potential for in vivo dosimetry in radiotherapy. The integrated dose measured during irradiation can be evaluated using OSL directly afterwards. • The optical fibre OSL dosimeter consist of a small (~1 mm3 ) chip of carbondoped aluminium oxide (Al2O3:C) coupled with a long optical fibre, a laser, a beam- splitter and a collimator, a PM tube, electronics and software. To produce OSL, the chip is excited with a laser light through an optical fibre and the resulting luminescence (blue light) is carried back in the same fibre, reflected through a 90o by the beam-splitter and measured in a PMT.
The optical fiber dosimeter exhibits high sensitivity over the wide range of dose rates and doses used in radiotherapy. The OSL response is generally linear and independent of energy as well as the dose rate, although the angular response requires correction.
Water Calorimetry: Basic Principles very simple principle: absorbed-dose-to-water [Gy = 1 J/kg] at position x absorbed W E T c   Radiation : Specific heat capacity of water (very well known, since 1930‘s) Dose-to-water : Main advantage: direct determination of dose-to-water k c T D W W W     W c 1  k
 Water calorimeters offer a more direct determination of the absorbed dose to water at the reference point in a water phantom. The absorbed dose to water is derived from the measured temperature rise at a point in water relying on an accurate knowledge of the specific heat capacity. No scaling laws are required as is the case in graphite calorimetry. However, there are technical complications related to a heat defect due to water radiolysis and heat transport, which need to be corrected for. • Water calorimeters are calibrated through the calibration of their themistors in terms of the absolute temperature difference rather than through the energy depositing as it is the case of graphite calorimeters. 3.9. SUMMARY OF SOME COMMONLY USED DOSIM
329 Bubble Chamber In the early 1950ies Donald Glaser tried to build on the cloud chamber analogy: Instead of supersaturating a gas with a vapor one would superheat a liquid. A particle depositing energy along it’s path would then make the liquid boil and form bubbles along the track. In 1952 Glaser photographed first Bubble chamber tracks. Luis Alvarez was one of the main proponents of the bubble chamber. The size of the chambers grew quickly 1954: 2.5’’(6.4cm) 1954: 4’’ (10cm) 1956: 10’’ (25cm) 1959: 72’’ (183cm) 1963: 80’’ (203cm) 1973: 370cm
333 W. Riegler/CER N Bubble Chambers The excellent position (5m) resolution and the fact that target and detecting volume are the same (H chambers) makes the Bubble chamber almost unbeatable for reconstruction of complex decay modes. The drawback of the bubble chamber is the low rate capability (a few tens/ second). E.g. LHC 109 collisions/s. The fact that it cannot be triggered selectively means that every interaction must be photographed. Analyzing the millions of images by ‘operators’ was a quite laborious task. That’s why electronics detectors took over in the 70ties.
Who Discovered X Rays? Wilhelm Conrad Roentgen Roentgen worked with a Crookes tube to study cathode rays.
X Rays (continued)
Nuclear Medicine Diagnostic Procedures • Radioactive injection • Short half-life radionuclide • Pictures taken with special gamma camera • Many different studies: Thyroid Lung Cardiac White Blood Cell Photo by Karen Sheehan
Radiation Therapy/Phantoms/ Artificial Humans/The Ghost/Fictitious/Illusion/Image Used for treating cancer. Why does it work? External Beam Brachytherapy (implants) Image courtesy of Photo by Karen Sheehan
Measurements An Overview:  Measurements when written down are interpreted as absolute values  Interpretation is whatever people do believe  sources of uncertainty  Usually unknown or neglected  Randomness means all measurements are only “best estimates”  Measurements may lead to fears, which then drive the interpretation Radiation Safety Counseling Institute 348
 Common assumptions  If its measurable - it must be bad  Written data are always good  Must take immediate action  Common to make decisions (cry wolf)  Without verifying the measurement  Stay calm  As minimum – repeat at least once  For confirmation, ideally with other instruments and people, if possible Radiation Safety Counseling Institute 349
 What do the numbers mean ?  Measurements only have meaning in terms of interpretation By the Experts  Data interpretation may be driven by fears  Of radiation  Of consequences, health risks, liabilities  Of making a mistake  Is your interpretation defensible ?  What are you willing to commit ?  Is your Instrument telling you what you think it is ? Y/N(Please think over it) Radiation Safety Counseling Institute 350
990 Recommendations of the International Commission on Radiological Protection, ICRP Publication 60, Permagon Press, Oxford Brennen S.E. and Putney R.G., eds (1983) Dose reduction in diagnostic radiology, The Hospital Physicist’s Associtaion Plaut S., (1993) Radiation protection in the x-ray department, Butterworth-Heinemann, Oxford Bushong S.C., (2004) Radiological science for technologists: Physics, Biology and Protection, 8th Ed. Mosby, St Louis Faulkner K. and Wall B.F., eds (1988) Are x-rays safe enough? Patient dose and risks in diagnostic radiology, The Institute of Physical Science in Medicine, Report No. 55 Norris, Teresa G., Radiation Safety in Fluoroscopy. Radiologic Technology. Vol 73 No 6, August 2002, 511 Seeram E., (1997) Radiation protection, Lippincott, Philadelphia Sherer, Mary Alice., Visconti, Paul J., Ritenour, Russell.,(2002) Radiation Protection in Medical Radiography, 8th Ed. Mosby, St Louis. Web D.V., Solomon S.B. and Thomson J.E.M., (1999) Background radiation levels and medical exposure in Australia, Radiation Protection in Australia, Vol 16 No 2 pp.25-32 REFERENCES

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RD&M 2020(New).pptx

  • 1.
  • 2.
  • 3. We Are Learning To What do we know? How do we know? What should be the next?
  • 4. ACKNOWLEDGEMENTs: To All those who donate me their live, lighten my way by candles, learned me and guided me along with My Mother, Father, Teachers, Brothers, Sisters and Friends . I thank Almighty GOD too much that I could become capable after a lot of effort and constraints that faced by me during my Academic cum Administrative Journey. I Also have full thanks for my M Phil /PhD supervisor (Late) Dr K.Hussain for his Scholastic Guidance suggested ideas and orientations through out my R&D Caliber May God Bless his soul in an Eternal Peace Ameen!. 4
  • 5. Abstract  Atomic radiation as a phenomenon is as old as the universe itself. It is a normal part of nature and life. At this very moment, thousands of rays are penetrating your body every second. The majority of radiation originates in nature and is totally independent of what man does. Today, our environment also contains a small amount of extra “unnatural” radiation which is caused by the activities of mankind.  The use of radiation has become an integral part of modern life. From the x-ray picture of broken limb to the treatment of cancer, the medical applications of radiation are now accepted as commonplace, and x-ray facilities are available in almost every community hospital.  Radiation contributes in the production of electricity, agriculture, and in other industry.  In my presentation I will try to describe in simple terms, what ionizing radiation to which man is exposed and second to review its sources and then I will shed a light on the applications of radiation in different walks of life, their detection& measurements along with some protective measures.
  • 6. An Overview :The Presentation covers the following key points. 1. The Atom 2. Atomic Radiation 3. Our Radiation Heritage(Natural Sources of Radiation) 4. Man Made Radiation(Artificial Sources Of Radiation) 5. Application of Atomic/Nuclear Radiation In:  Medicine  Power Production  Weapons  Agriculture  Industry 6. Biological Effects of Radiation 7. Radiation Protection 8. Radiation Detection & Measurements/Dosimetry 9. Summary
  • 7. Discovery & study of radioactivity 1898 Marie &.Pierre Curie Introduction of quantum concept 1900 Max Planck h Theory of special relativity 1905 Albert Einstein E=m·c2 Quantization of light (photoelectric effect) 1905 Albert Einstein E=h· Discovery of atomic nucleus 1911 Ernest Rutherford Interpretation of atom structure 1913 Nils Bohr Particle waves 1924 Louis de Broglie Wave mechanics 1925 Erwin Schrödinger Uncertainty principle 1927 Werner Heisenberg Discovery of Neutron 1932 James Chadwick Artificial Radioactivity (Reactions) 1934 Frederic Joliot & Irene Curie Discovery of fission 1938 Otto Hahn, Fritz Strassmann Interpretation of fission 1938 Liese Meitner, Otto Frisch Prediction of thermonuclear fusion 1939 C.F. v. Weizsäcker, H. Bethe The Development of Scientific Thought in the 20th Century x·p=ђ
  • 8.
  • 9.
  • 10. The Basics of Radiation Radioactive materials have an unstable nucleus that release one or more particles or energy Nuclear radiation refers to the released energy and matter. A large part of the radiation you are exposed to comes from background radiation (from the sun – solar and the earth – terrestrial. Radiation is going through you all the time.
  • 11.
  • 12. Contents/Concepts:  Aiming only at a general introduction  obviously more examples from my own practical experience  important to understand the concepts, not to memorize the details  interrupt and ask if something is not clear!  You do not have the slides  but sometimes it is the Best Practice that you will try to arrive at answers to questions yourselves – don’t cheat by looking at the following slides !
  • 14. The Good, The Bad, and the Ugly…
  • 15. Training/Refresher Course Requirements  In order to work with radioactive material you must be properly trained on the safe use and the minimization of risk associated with each isotopes.  To keep your radiation worker status, you must have radiation safety refresher training once a year
  • 17. 17 Describing the hazard We need to know how much of a hazardous substance a worker can breathe without harm This is given by the Occupational Exposure Limit OEL
  • 18. 18 Occupational Exposure Limits The OEL is the concentration in the air to which nearly all workers may be repeatedly exposed day after day without adverse health effects to themselves or their children. Termed Threshold Limit Value TLV by ACGIH (ACGIH is an American organisation for industrial hygiene)
  • 19. Setting an OEL – how it is calculated LAD (mg/kg/day) * BW OEL = --------------------------------------------------- V*T*SF*a LAD lowest active dose BW body weight (50 kg) V volume inhaled air (10 m3) T time, in days, to reach steady state in plasma SF safety factor a % absorption (assumed = 100%)
  • 20. 20 Acceptable Surface Limits  The ASL is the acceptable mass on a specified surface area (typically 10 x 10 cm, the area of palms of hand)  Often set at 10 times the OEL for an area of 100cm2  Not as frequently used as OEL  Not set by ACGIH for any substance Acceptable Surface Limit OEL
  • 21. Exposure to different substances or mixtures = rule of cumulative effect = S Cn / GWn < 1 C1/GW1 + C2/GW2 + C3/GW3 + …. < 1 C1 … n = measured concentration of the substance in the air GW1 … n = OEL of the measured substance Cumulative effect
  • 22. Miracles of the Qur’an Qur’an in Focus Qur’an is not a book of SCIENCE but it is a book of SIGNS. It clearly states a number of scientific truths that were uncovered only with the help of modern technology in the 20th century. Therefore, we will use science as a yardstick to measure the accuracy of the statements in Qur’an. “Science without Religion is lame and Religion without Science is blind”. Albert Einstein – A Physicist & a Noble Price Winner
  • 23. Oklo, Gabon – A natural fission reactor (Pitchblende)  235U natural abundance is well known: 0.00720 ± 0.00001  Uranium deposit where self- sustained nuclear chain reactions have occurred.  235U abundance 0.00717, about 3 standard deviations below the accepted value.  The only process which can lead to reduction of U is fission by low- energy neutrons.  2 x 109 y, 235U (~3%) reactor moderated by groundwater.  Fission product isotope signatures Nd, Ru Geological Situation in Gabon leading to natural nuclear fission reactors: 1. Nuclear reactor zones 2. Sandstone 3. Ore layer 4. Granite
  • 24. Fossil Reactor 15, located in Oklo, Gabon. Uranium oxide remains are visible as the yellowish rock. Source: NASA
  • 25. Oklo Estimations  5 tonnes of 235U were fissioned.  Total energy released 2 x 1030 MeV or 108 MW∙h. A contemporary power reactor can operate at 103 MW.  Average power 0.01 MW, operating for 106 y. Important feature: the fission products are still in place in the reactor zone and have migrated very little. Despite climate changes, no substantial movement of the fission products has taken place over the past 2 x 109 y.
  • 26.
  • 29.
  • 30. Orphans Radioactive sources or materials or waste that does not have an ‘owner’ Creates a lot of work for RPO RPO has to pay for its legal disposal PLEASE NO ORPHANS X
  • 32. Introduction  Scientists have studied radiation for over 150 years and we know a great deal about it.  Radiation is part of nature. All living creatures, from the beginning of time, have been, and are still being, exposed to radiation.
  • 33. Radiation is really everywhere?  Yep, it sure is! We live in a radioactive world, and radiation has always been all around us as a part of our natural environment.  The annual average dose per person from all sources is about 360 mrem, but it is not uncommon for any of us to receive more than that average does in a given year (largely as a result of medical procedures).
  • 34. Natural Radioactivity  There are small amounts of radioactive minerals in the air, ground, and water  Even in the food you eat!  The radiation you are exposed to from natural sources is called background radiation(Radioactive Equilibrium, Natural Radioactive Series) Tro: Chemistry: A Molecular Approach
  • 35.  There is a small amount of radiation around us all the time because of radioactive materials in the environment. This is called background radiation.
  • 36.
  • 37.
  • 38. - Each exposure to radiation carries its own very small risk. So, the third or fourth scan you have carries the exact same risk as the very first. - The benefit of having a correct diagnosis and discovering what is going on in your body outweighs the risk of the exam itself. Risk or Benefit?
  • 39. Risk Assessment Must be made prior to commencing any new work involving ionising radiation. Identify hazards Who could be harmed Evaluate risks Record findings Review / revise Significant hazard but is it a risk?
  • 40. Fear of radiation • usually undetectable by human senses • serious consequences – cancers (time-delayed) – contamination long-lasting • unaware of background radiation • media scares - especially after Chernobyl Reactor Accident • secrecy - industrial, military & political interests
  • 41. We Live (And Have Always Lived) in a “Sea of Radiation”/Human Beings and Auora
  • 42. 42 Nonmedical Uses of Radioactive Isotopes Tro: Chemistry: A Molecular Approach • Smoke detectors  Am–241  smoke blocks ionized air, breaks circuit • Insect control  sterilize males • Food preservation • Radioactive tracers  follow progress of a “tagged” atom in a reaction • Chemical analysis  neutron activation analysis
  • 43. 43 Nonmedical Uses of Radioactive Isotopes Tro: Chemistry: A Molecular Approach • Authenticating art object  many older pigments and ceramics were made from minerals with small amounts of radioisotopes • Crime scene investigation • Measure thickness or condition of industrial materials  corrosion  track flow through process  gauges in high temp processes  weld defects in pipelines  road thickness
  • 44. Nonmedical Uses of Radioactive Isotopes Tro: Chemistry: A Molecular Approach • Agribusiness  develop disease-resistant crops  trace fertilizer use • Treat computer disks to enhance data integrity • Nonstick pan coatings  initiates polymerization • Photocopiers to help keep paper from jamming • Sterilize cosmetics, hair products and contact lens solutions and other personal hygiene products
  • 45.
  • 46. Radiation Exposure  We are all exposed to radiation:  Cosmic radiation ○ sun, space  Terrestrial radiation ○ soil, rocks  Internally ○ Food (potassium-40), air  Medical treatment Cosmic Rays Internal Sources Terrestrial Radiation
  • 47. Radiation Exposure/Over or Under Exposure  We cannot avoid radiation exposure from sources of background radiation (cosmic and terrestrial radiation) or as a result of medical treatment  However, by following safe work habits, we can minimize our radiation exposure from occupational sources of radiation
  • 48. Why Detection& Measurement: How most of us Can feel about radiation until we understand the principles of safe use, For that purpose their Detection & Measurement is must:
  • 49. Probes and “probees” E = h /  Energy of probe correlated with sizes of probee and production devices/Need of high energy Accelerators Atoms – lasers – table top Nuclei – tandems, cyclotrons, etc. – room size
  • 50. What Is Atomic Radiation/ Excitation/De excitation
  • 51.
  • 52. Nuclear system A finite quantum many-body system of protons and neutrons electrons nucleus atom neutron proton nuclear force: Attractions Confined by the external field 1. Independent-particle feature in self-consistent mean-field 2. Strong nucleon-nucleon correlations Self-bound Electron motion Nucleon motion orbit, shell Analogy & Differences cluster
  • 53. Introduction to Radioactivity(The Active Which Radiate) 23/05/2023 Some substances are classed as “radioactive” – this means that they are unstable and continuously give out radiation: Radiation The nucleus is more stable after emitting some gamma radiation – this is called “radioactive decay”. Increased exposure to gamma radiation can cause cancer or cell death.
  • 54. • Wilhelm Roentgen (1845–1923) • 1895-invisible rays were emitted when electrons bombarded the surface of certain materials. The Discovery of Radioactivity • caused photographic plates to darken. • named the invisible high-energy emissions X rays.
  • 55. • Henri Becquerel (1852–1908) was studying phosphorescence • minerals that emit light after being exposed to sunlight The Discovery of Radioactivity •phosphorescent uranium salts produced spontaneous emissions that darkened photographic plates.
  • 56. • Marie Curie (1867–1934) and her husband Pierre (1859–1906) took Becquerel’s mineral sample (called pitchblende) and isolated the components emitting the rays. The Discovery of Radioactivity • darkening of the photographic plates was due to rays emitted specifically from the uranium atoms present in the mineral sample.
  • 57. The Curies refined several tons of pitchblende (shown above) progressively concentrating the radioactive components. Eventually they isolated the chloride salts of the two new chemical elements, and then the elements themselves. The first they named polonium (Po) after Marie's native country Poland; and, the other they named radium (Ra) from its intense radioactivity.
  • 58. The Discovery of Radioactivity • Marie Curie named the process by which materials give off such rays radioactivity • the rays and particles emitted by a radioactive source are called radiation.
  • 59. – “Radioactive” substances = radiation- emitting (Curie) – Radioactivity = a inherent property of certain ATOMS, as opposed to a chemical property of compounds (Curie)
  • 60. Radioactivity is the process by which an unstable nucleus gives off nuclear radiation. Uranium Plutonium
  • 61. The Atom/The Nucleous  In their normal state, atoms are electrically neutral (no net charge) # protons = # electrons/Neutrons  An atom that has gained or lost electrons/Neutrons/Protons is called an ion /Active Positive and negative charges cancel/Non Active
  • 62. One of Becquerel’s students, Marie Curie, discovered 2 new radioactive elements, radium and polonium.
  • 63. Who’s the Famous “Madame” of Radiological Fame? Marie Curie • With her husband Pierre, discovered radium and coined the term “radioactive” • First woman to win two Nobel Prizes
  • 64. Nuclear Radiation(Decay)  This is what you can visualize in your head for how the electron can be emitted from a neutron.  See what happens to the neutron after the electron leaving that is (beta emission)  N,down,P,up, two States of Nucleous
  • 65. Quarks 23/05/2023 Basically, scientists think everything in the universe is made Up from 12 fundamental particles. Two of these particles are called “up quark” and “down quark”. Protons and neutrons are made of different combinations of three up and down quarks: Proton u u d Neutron u d d Some questions: 1) Quarks have charges that are multiples of 1/3. Given the composition and charge of the proton and the neutron what are the charges on the up and down quark? 2) What happens in terms of quarks during beta + and beta – decay? Up = +2/3, down = -1/3 An up quark turns into a down quark and vice versa
  • 66. Beta Decay  A neutron transforms into a proton, an electron, and an anti-neutrino H-3 He-3
  • 67. Gamma Decay (Cs-137) Cs-137 T1/2 30 yr Ba-137m T1/2 2.55 min Ba-137 STABLE 661 keV Gamma Beta
  • 68. Tl-204 Decay Tl-204 (T1/2 3.779 yr) Pb-204 Hg-204 97.4% 2.6%
  • 69. What makes nuclei unstable?  The ratio of neutrons to protons determines whether a nucleus is stable or unstable.  Small isotopes 1 neutron:1 proton  Large isotope 3 neutrons: 2 protons  Generally, nuclei with too many or too few neutrons compared to the numbers are unstable or radioactive.
  • 70. Why Are Elements Radioactive?(1500 nuclides.1/5th Stable,4/5th Unstable) Unstable nucleus: • Has excess energy/BE. • Wants to go to “ground state.” • Becomes stable by emitting ionizing radiation. What does “ionizing” mean?
  • 71. Forces at work in the nucleus  Electrostatic repulsion: pushes protons apart  Strong nuclear force: pulls protons together  Nuclear force is much shorter range: protons must be close together    
  • 72. Neutrons only experience the strong nuclear force  Proton pair experiences both forces  Neutrons experience only the strong nuclear force  But: neutrons alone are unstable  
  • 73. Neutrons act like nuclear glue  Helium nucleus contains 2 protons and 2 neutrons – increase attractive forces  Overall nucleus is stable      
  • 74. As nuclear size increases, electrostatic repulsion builds up/Peutron Excess  There are electrostatic repulsions between protons that don’t have attractive forces  More neutrons required(N/Z Rule)/Neutron Excess      Long range repulsive force with no compensation from attraction 
  • 75. Stability Isotopes shown here in black are stable. Radioisotopes are unstable. As the proton number increases, an increasing fraction of neutrons is needed to form a stable nucleus. http://prezi.com/hllfbv98zptq/p2-nuclear-decay/
  • 76. Nuclear Stability (1)  The Segre chart below shows neutron number and proton number for stable nuclides. For low mass numbers, NZ. The ratio N/Z increases with A. Points to the right of the stability region represents nuclides that have too many protons relative to neutrons/Proton Excess To the left of the stability region are nuclides with too many neutrons relative to protons Neutron Excess.
  • 79. Radioactive Equilibrium  Often a nucleus or particle can decay into different states and/or through different interactions  The branching fraction or ratio tells you what fraction of time a nucleus or particle decays into that channel  A decaying particle has a decay width Γ  Γ = ∑Γi where Γi are called the partial widths  The branching fraction or ratio for channel or state i is simply Γi/Γ 79
  • 80. Radioactive Equilibrium  Sometimes we have the situation where  The daughter is both being created and removed Po Rn Ra 218 222 226 3 2 1 2 1       80
  • 81. Radioactive Equilibrium  We have (assuming N1(0)=N0 and N2(0)=0)             1 2 1 2 max 1 2 2 0 2 2 2 1 2 1 0 2 2 2 1 1 2 1 1 1 / ln at activity maximum and then 2 1 2 1                                    t e e A t N t A e e N t N dt N dt N dN dt N dN t t t t 81
  • 82. Radioactive Equilibrium  Case 1 (parent half-life > daughter half-life)  This is called transient equilibrium           1 2 2 1 2 1 2 2 1 1 2 2 1 2 1 0 2 0 1 2 1 1 2 2 1 1 1 becomes                                  A A e N N e e N t N e N t N t t t t 82
  • 83. Radioactive Equilibrium  Transient equilibrium  A2/A1=2/(2-1)  Example is 99Mo decay (67h) to 99mTc decay (6h)  Daughter nuclei effectively decay with the decay constant of the parent 83
  • 84. Radioactive Equilibrium  Case 2 (parent half-life >> daughter half-life)  This is called secular equilibrium  Example is 226Ra decay           1 2 1 0 2 2 2 1 0 2 1 2 1 0 2 2 1 2 2 1 1 becomes A A N t N e N t N e e N t N t t t                        84
  • 85. Radioactive Equilibrium  Secular equilibrium  A1=A2  Daughter nuclei are decaying at the same rate they are formed 85
  • 86. Radioactive Equilibrium  Case 3 (parent half-life < daughter half-life)  What happens?/Not Possible Simply 86
  • 87. A series of elements produced from the successive emission of alpha & beta particles
  • 88. Decay Series Tro: Chemistry: A Molecular Approach • In nature, often one radioactive nuclide changes into another radioactive nuclide  i.e. the daughter nuclide is also radioactive • All of the radioactive nuclides that are produced one after the other until a stable nuclide is made is called a decay series • To determine the stable nuclide at the end of the series without writing it all out 1. count the number of a and b decays 2. from the mass no. subtract 4 for each a decay 3. from the atomic no. subtract 2 for each a decay and add 1 for each b
  • 89. The Four Known Decay Series Parent Radioisotope # of Decay Steps Final Product of Series Uranium-238 14 Lead-206 Thorium-232 10 Lead-208 Uranium-235 11 Lead-207 Plutonium-241 13 Bismuth-209
  • 90. Positron Decay Occurs in nuclei with a low neutron to proton ratio. A proton decays into a neutron and an electron inducing a shift up and to the left in the nuclear stability plot. Electron Capture Decay Electron capture is common in heavier elements that have a low neutron to proton ratio. Gamma-ray Decay Gamma-ray decay generally accompanies another radioactive decay process because it carries off any excess energy within the nucleus resulting from the radioactive decay. Nuclear Stability (4)
  • 91. •Magic numbers(Solution Of SWE,For Nuclear Potential Of The Nucleus)  Certain numbers of protons and/or neutrons convey unusual stability/abnormal behavior like Zero Electric, Magnetic & Quadruple Moment of the nucleus& Positive Parity on these numbers 2, 8, 20, 28, 50, 82, 126  There are ten isotopes of Sn (Z=50); but only two of In (Z=49) and Sb (Z=51)  Magic numbers are associated with the nuclear structure, which is analogous to the electronic structure of atoms(2n Square)/which means paired nucleons & Completely filled energy levels
  • 92. Magic Numbers  Besides the N/Z ratio, the actual numbers of protons and neutrons affects stability  Most stable nuclei have even numbers of protons and neutrons  Only a few have odd numbers of protons and neutrons  If the total number of nucleons adds to a magic number, the nucleus is more stable  same principle as stability of the noble gas electron configuration  most stable when N or Z = 2, 8, 20, 28, 50, 82; or N = 126 Tro: Chemistry: A Molecular Approach
  • 93. Marie Curie, Nobel Prize Winner
  • 94. What is Radioactivity?  When nuclei of unstable isotopes gain stability by undergoing changes/Balancing their Neutron & Proton Excess  These reactions:  are called nuclear reactions(Transition via bombardment from outside) OR Spontaneous Transition Called Radio Active Decay)  are always accompanied by the emission of large amounts of energy  are spontaneous  are not affected by changes in temp, pressure, or presence of catalysts  cannot be slowed down, speeded up, or turned off
  • 95.  The process by which atoms emit rays is called radioactive decay OR nuclear decay  Unstable nucleus = can be due to the overall size of the nucleus, having too many or too few neutrons  Eventually, unstable radioisotopes of one element are transformed into stable, nonradioactive isotopes of a different element
  • 96. Discovery/Protection of Radioactivity Henri Becquerel discovered that uranium compounds spontaneously give off radiation.
  • 97. Discovery of Radioactivity (cont.) Marie and Pierre Curie concluded that a nuclear reaction was taking place within the uranium atoms. Radioactivity is the spontaneous emission of radiation by an unstable atomic nucleus. **Objects do not become radioactive when subjected to radiation unless they actually absorb radioactive elements.
  • 98. Random decay Radioactivity is a chance process. • The chance of decay for each nucleus is constant with time, independent of temperature, pressure, other physical conditions. • The properties of random decay are best displayed if large numbers of events are involved. • The rate of decay is proportional to the number of undecayed nuclei present. • The half-life of a radioisotope is the average time for half the nuclei present to decay (for the activity to fall to ½ its previous value).
  • 99.
  • 100. We know that the popcorn will go ‘pop’, but we don’t know exactly which kernel will pop at any given time. Popping of Popcorn/Physical Example!
  • 101. Operating Engineers National Hazmat Program 101 The Search for Stability  An atom is stable based on it’s proton to neutron ratio (N/Z Rule, BE, Curve ,Stability Curve, Shell Model)  If there are too many or too few neutrons or protons, the atom will give off excess energy as  Rays &  Particles This process is called radioactive decay
  • 102. What is Radiation? Radiation – general term for energy The Energy which can also moves like matter, Some times particles, Sometimes in Waves Operating Engineers National Hazmat Program 102
  • 103. Energy In terms of the energy associated with each type of radiation: Increasing energy a b g Good news…………………………Bad news
  • 104. Penetrating Ability Depending upon its energy, different types of radiation are stopped by different materials Called Absorbers Or Shielding Materials. a b g Good News………………………Bad news
  • 105. Ionisation Radiation is dangerous because it “ionises” atoms – in other words, it turns them into ions by giving them enough energy to “knock off” electrons: Ionisation causes cells in living tissue to mutate, usually causing cancer.
  • 106.
  • 107. Electromagnetic Spectrum 10 -14 10 -12 10 -10 10 -8 10 -6 10 -4 10 -2 1 10 2 10 4 10 6 10 8 Wavelength in Meters 10 10 10 8 10 6 10 4 10 2 1 10 -2 10 -4 10 -6 10 -8 10 -10 10 -12 10 -14 Broadcast Short wave TV FM Radar Infrared Near Far Visible Ultraviolet X Rays Gamma Rays Cosmic Rays Power Transmission Ionizing Radiation Nonionizing Radiation Energy - Electron Volts High Low
  • 108.
  • 109. Paper Aluminum Acrylic resin Lead H2O (Hydrogen rich) β e- γ α P+ n n P+ Neutron radiation n Penetrating Ability of Radiations
  • 110. The Electromagnetic Spectrum(The Soul of Human Existence, Body needs all types of radiations for proper functioning & the same is the case for telecommunication) NONIONIZING IONIZING Radio Microwaves Infrared Visible light Ultraviolet X-rays Gamma rays 110
  • 111.
  • 112.  Radiation is the emission and transmission of energy through space or material medium.  Radiation can be in the form of sub-atomic particles (protons, neutrons and electrons) or electromagnetic waves
  • 113. Introduction to Radiation “Radiation” refers to any form of energy originating from a source, and usually falls into two types: Radiation A wave, such as light coming from the sun A particle, such as this alpha particle coming from the nucleus
  • 114. What is Radiation?  Radiation is energy transmitted by particles or electromagnetic waves  Radiation can be ionizing or non-ionizing
  • 115. William Hutton –a founder of modern geology After many years of studying the history of the earth he said that he saw “no vestige of a beginning and no prospect of an end“/The Universe, Same is True for the RADIO –ACTIVITY”
  • 116. Radioactivity is everywhere because every element on the periodic table has some atomic nuclei that are radioactive.
  • 117. What is Radiation?  Form of energy  Emitted by nucleus of atom or orbital electron  Released in form of electromagnetic waves or particles(Both are necessary for conserving Energy ,Matter Content of the Universe) 117
  • 118.  Ionizing Radiation (IR) causes ions to be produced when radiation is absorbed in matter  Non-Ionizing radiation (NIR) refers to radiation energy that, instead of producing charged ions, when passing through matter, has sufficient energy only for excitation.
  • 119. Ionizing radiation High energy radiation • Gamma-rays, x-rays - photons • Particles: alpha, beta, neutron Ejects electrons from atoms • Produces an altered atom - an ion Non-ionizing radiation Low energy • Lasers, RF, microwaves, IR, visible Excites electrons Produces heat Or any other physio chemical effect,
  • 122. Natural background radiation  The natural radiation energy between few KeV to MeV from primordial radionuclides are called background radiation.  Background radiation is of terrestrial and extra- terrestrial origin. PLANTS ATMOSPHERE SOURCE (BEDROCK) MAN, ANIMALS SOILS
  • 123. 1. Terrestrial radiation components  The terrestrial component originates from primordial radionuclides in the earth’s crust, present in varying amount.  Components of three chains of natural radioactive elements viz. the uranium series, the thorium and actinium series.  238U, 226Ra, 232Th, 228Ra, 210Pb, 210Po, and 40K, contribute significantly to natural background radiation.
  • 124. 2. Extra terrestrial radiation  Among the singly occurring radionuclides tritium and carbon-14 (produced by cosmic ray interactions) and 40K (terrestrial origin) are prominent.  Radionuclides from these sources are transferred to man through food chains or inhalation. 1. Terrestrial radiation components contd… • The extra terrestrial radiation originates in outer space as primary cosmic rays. • The primary cosmic rays mainly comprise charged particles, ionised nuclei of heavy metals and intense electromagnetic radiation.
  • 125. 3. Artificial Radionuclides  Over the last few decades man has artificially produced hundreds of radionuclides.  Artificial radioisotopes to the atmosphere during the course of operation of the nuclear fuel cycle, nuclear tests (mainly atmospheric) and nuclear accidents  Most of the artificial radioisotopes decay -short half-lives. Therefore only a few of them are significant from the point of human exposure.
  • 126. Radon  Radon is a radioactive gas decay product of radium, created during the natural breakdown of uranium in rocks and soils  It is one of the heaviest substances that remains a gas under normal conditions and is considered to be a health hazard causing cancer  It has three isotopes, namely, 222Rn (238U), 220Rn (232Th) and 219Rn (235U). 222Rn has longer half life (3.84 days) than the other two isotopes
  • 127. Radon-222  Originates from U-238 which occurs naturally in most types of granite  Radon-222 has a half-life of 3.825 days  It decays via alpha emissions  This isotope is a particular problem because it is a gas which can leave the surrounding rock and enter buildings with the atmospheric air
  • 128.
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  • 134. Radon/Thoron in Buildings There are two main sources for the radon in home's indoor air, soil and water supply.
  • 135. Where does your radiation exposure come from?
  • 136. Sources of background radiation
  • 138. Sources of Annual Radiation Dose Radon 55% Cosmic 8% Terrestrial 8% Internal 11% Medical X-Rays 11% Nuclear Medicine 4% Consumer Products (3%) Other (<1%) Occupational 0.3% Fallout <0.3% Nuclear Fuel Cycle 0.1% Miscellaneous 0.1%
  • 139. Applications of Nuclear Radiation  Medical diagnosis, treatment, and sterilization  Nuclear power (both fission and fusion)  Semiconductor fabrication (lithography, doping)  Food preservation through irradiation  Density measurements (soil, oil, concrete)  Gauging (thickness) measurements in manufacturing (steel, paper) and monitoring (corrosion in bridges and engines)  Flow measurements (oil, gas)  Insect control (fruit fly)  Development of new crop varieties through genetic modification  Curing (radiation curing of radial tires)  Heat shrink tubing (electrical insulation, cable bundling
  • 140. Effect of Ionising Radiation on Living Organisms Effect of Ionising Radiation at a Molecular Level • When molecules in cells become ionised there a number of effects such as disrupted bonds, alteration of the tertiary and quaternary structure and by crosslinking which in turn damages cells. • Most damage is caused by the generation of hydroxyl free radicals
  • 141. Effect of Ionising Radiation Free radicals are generated by radiolysis of water. 2H20 H2O+ + H20- H2O+ OH. + H+ Hydroxyl radicals react with other molecules (such as DNA) damaging them. Note that the indirect effect is responsible for a significant proportion of cell damage Effect of Ionising Radiation at a Molecular Level cont’d
  • 142. Cellular Radiosensitivity (Law of Bergonne and Tribondeau) 1. Rapidly dividing tissue is more radiosensitive 2. Rapidly growing cells are more radiosensitive 3. Younger and more immature cells are more radiosensitive 4. Mature cells are less radiosensitive NB: Dividing cells are more radiosensitive. This is why radiotherapy is effective on rapidly dividing tumor cells. Unfortunately rapidly dividing cells such as bone marrow, gut epithelium and hair follicles are also radiosensitive Organ toxicity The lens of the eye is particularly sensitive Effect of Ionising Radiation on Tissues and Cells
  • 143. Biological Effects of Radiation 14-2-1426 The Secrets of Atomic Radiation Hadeed 143 How Radiation can Lead to Damage in Tissue Radiation Damage to DNA Cell Death Cell Transformation Early Effect Cancer Physical & Chemical Changes Electrical Effect (Ionization) Hereditary Defects
  • 144. RADIATION DIRECT IONIZATION OF DNA IONIZATION OF OTHER MOLECULES, e.g.,H2O radiation + H2O  H2O+ + e H2O+  H+ + OH0 e + H2O  H0 + OH OXIDATION OF DNA BY OH RADICALS NO EFFECT ENZYMATIC REPAIR CHEMICAL RESTORATION DNA RESTORED PERMANENT DAMAGE IN DNA BIOLOGICAL EFFECTS 1. GENETIC EFFECTS 2. SOMATIC EFFECTS CANCER STERILITY
  • 145. Why are we concerned about Radiation? Ionizing Radiation Human Cells Atoms in Cells Form Ions Change in Cell Cell Dies No/Neutral Change in Cell Not Replaced Replaced Reproduces Malignant Growth Benign Growth
  • 146. Biological Effects(Somatic ,Someone,Genetic ,Generations) Mechanisms of Injury Ionizing Radiation Cell Death Cell Damage Repair Transformation
  • 147. Three Cellular Effects Cell death Cell repair Cell change Is this change good or bad?
  • 148. Ionizing Radiation at the Cellular Level  Causes breaks in one or both DNA strands or;  Causes Free Radical formation
  • 150. Our Bodies Are Resilient  DNA damage is most important and can lead to cell malfunction or death.  Our body has ~ 60 trillion cells  Each cell takes “a hit” about every 10 seconds, resulting in tens of millions of DNA breaks per cell each year.  BACKGROUND RADIATION causes only a very small fraction of these breaks (~ 5 DNA breaks per cell each year).  Our bodies have a highly efficient DNA repair mechanisms(Catabolic & Metabolic Processes)
  • 151. Effect of Ionising Radiation on Humans The effects of ionizing radiation are classified on human in two broad categories: • Deterministic • Stochastic
  • 152. Goals of Radiation Safety  Eliminate deterministic effects  Reduce incidence of stochastic effects
  • 153. Deterministic Effects These effects have thresholds above which damage occurs and effects are then dose dependent e.g. lens opacification, burns, hair loss. Determinisitic effects like the burns below suffered by those who put their hands in the path of a x-ray beam are relatively easy to avoid Effect of Radiation on Humans
  • 154. Stochastic Effects • Mutational, non-threshold effects in which the chance of occurring rather than the severity are dose dependent. • These affects are not predictable e.g. cancer • Note that stochastic effects are not predictable and give rise to the notion that there is no absolutely safe dose and the concept of ALARA. Effect of Radiation on Humans
  • 155. Dose versus Effect/ S, Shape:  Nobody knows for sure what radiation dose does to us below the shaded region. There may be a threshold where there is no effect from radiation below a certain dose.  In Radiation Protection, as a protective measure, it is assumed that all dose carries some risk, this is represented by the straight red line on the diagram.  FYI: There are other theories regarding the effects of radiation dose (as represented by the other lines – blue and gray), to include radiation hormesis. Radiation hormesis is a theory that chronic low doses of radiation is good for the body.
  • 157. Applications Popular products included radioactive toothpaste for cleaner teeth and better digestion, face cream to lighten the skin; radioactive hair tonic, suppositories, and radium-laced chocolate bars marketed in Germany as a "rejuvenator." In the U.S, hundreds of thousands of people began drinking bottled water laced with radium, as a general elixir known popularly as "liquid sunshine." As recently as 1952 LIFE magazine wrote about the beneficial effects of inhaling radioactive radon gas in deep mines. As late as 1953, a company in Denver was promoting a radium-based contraceptive jelly.
  • 158. Radium Girls "Not to worry," their bosses told them. "If you swallow any radium, it'll make your cheeks rosy.“ The women at Radium Dial sometimes painted their teeth and faces and then turned off the lights for a laugh. From: 'Radium Girls' By Martha Irvine, Associated Press, Buffalo News, 1998
  • 159. Lessons from the Past The Radium Dial Painters Photo by Carmelina Rattrovo from the Playwrights Theatre production of Radium Girls, by D.W. Gregory
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  • 161. p721
  • 162. First Known Human Misuse of Uranium/ Coloration & Discoloration/Magic Water.ToothPaste,Sexual Power:  79 A D  Roman artisans produce yellow colored glass in mosaic mural near Naples, Italy Radium - A radioactive element discovered in 1898 by Curie - Found to glow in the dark! - Many (at the time) thought it had health benefits
  • 163. The radium dial painters • Watch-dial painters - United States Radium factory in Orange, New Jersey, around 1917 . • The Radium Girls (4000) were female factory workers who contracted radiation poisoning from painting watch dials with self-luminous paint. • They were used to tip (i.e., bring to the lips) their radium-laden brushes to achieve a fine point. • Unfortunately this practice led to ingested radium, and many of the women died of sicknesses related to radiation poisoning. • The paint dust also collected on the workers, causing them to “glow in the dark.” • Some also painted their fingernails and teeth with the glowing substance.
  • 164. More Radiation Misconceptions  Radiation does not give you super human powers  Radiation will not make you glow in the dark
  • 165.
  • 166. Radium Effects Confirmed  1925  Suspicions develop around watch dial painters’ jaw lesions  Dentists diagnose lesions as jaw necrosis due to radium deposits in jaw bone  Doctor notes bone changes and anemia in dial painters
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  • 170. The mouth of a man who has suffered a 10 to 20 Gy dose 21 days after the exposure, note the damage to normal skin, the lips and the tongue.
  • 171. Importance of Radiation in Daily Life  Medicine: Radiology, Radiation Therapy  Power Production and Space Exploration  In Agriculture to improve variety & yield production  Weapons of mass destruction  Industrial applications: Gauges, Radiography, Mineral exploration
  • 172. Beauty of Medical Research: As a “Tracer” Technique. • Radioactivity is an excellent tool! • Detectable in minute quantities Result is the same for mega quantities (like finding one grain of sand on a small beach containing 6,000,000,000 granules)
  • 173. Why We Measure(Hidden Enemy, Silent Killer, We Should Know How Much Dangerous/Defensive Strategy.  Personal Dosimetry vs Regulatory requirements  Classification of safe and dangerous zones  Safety vs Protective measures  Quality control and Quality assurance  Data consistancy and standardization
  • 174. Why is Radiation Detection Difficult/Five Senses(Not Capable), Need of Sixth Sense ?  Can’t see it  Can’t smell it  Can’t hear it  Can’t feel it  Can’t taste it  Can’t touch it  We take advantage of the fact that radiation produces ionized pairs, or some other physio chemical change to try to create an electrical signal or current pulse, capacitor charge /discharge to produce deflection = to radiation effect(Cause & Effect)
  • 175. YOUR ATTITUDE/Best Friend OR Bitter Enemy --- AND ACTIONS --- COUNT!(Change your Attitude change your life) You must want to do your job safely and you must understand and use safe practices and methods. That’s what being part of an effective safety Individual is all about!
  • 176. How Do I Protect Myself? Reducing the dose from any source radiation exposure involves the use of three protective measures: – TIME – DISTANCE – SHIELDING
  • 178. Benifit Risk Benifit and risk/Balanced Rather Benefit > Risk:
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  • 181. 181
  • 182. Basic Concepts  Radioactive Decay: A = Aoe-λt ○ A = λN ○ λ = 0.693 / T1/2  Inverse Square Law  Shielding I = IoBe-t /D= c(1-S) Where S= Shielding Material 2 2 2 1 1 2 d d I I 
  • 183. Time(T) − The amount of exposure an individual accumulates is directly proportional to the time of exposure − Keep handling time to a minimum(less time Sun Bath, More time Sun Burn)
  • 184. Distance(D) − The relationship between distance and exposure follows the inverse square law. The intensity of the radiation exposure decreases in proportion to the inverse of the distance squared(Near fire place more heat, Away less heat) − Dose2 = Dose1 x (d1/d2)2
  • 185. Shielding(S) − To shield against beta emissions, use Plexiglas to decrease the production of bremsstrahlung radiation. − If necessary, supplement with lead after the Plexiglas − To shield against gamma and x-rays, use lead, leaded glass or leaded plastic(Rain vs. Umbrella no wetting otherwise yes)
  • 186. Self Protection Measures  1st Avoid exposure and contamination  Detect radiation exposure  Back away when too high  2nd Use Personal Protective Equipment (PPE)  3rd Decontaminate yourself
  • 187. Simplified Radiation PPE  Protect your respiratory tract  Respirator, surgical mask, etc.  Protect your skin  Gloves!  Outer clothing  Chemical suit is not always needed
  • 188. Self Decontamination  Wash it off  Hand washing  Taped water, mild soap  No scrubbing  If showering, use shampoo  Remove and launder clothing  Monitor after decontamination
  • 189. ASARA Goal of exposure management: keep radiation exposures to a level As Safe As Reasonably Achievable (ASARA)
  • 190. ALARA(Optimization &Cost Effectiveness) As Low As Reasonably Achievable—means making every reasonable effort to maintain exposures to radiation as far below the dose limits as is practicable consistent with the purpose for which the licensed activity is undertaken, taking into account the state of technology, the economics of improvements in relation to the state of technology, the economics of improvements in relation to benefits to the public health and safety, and other societal and socioeconomic considerations, and in relation to utilization of nuclear energy and licensed materials in the public interest.
  • 191.
  • 196. Radiation Units Units of radiation include • Curie - measures activity as the number of atoms that decay in 1 second. • rad (radiation absorbed dose) - measures the radiation absorbed by the tissues of the body. • rem (radiation equivalent) - measures the biological damage caused by different types of radiation. 196
  • 197. Radiation Units Exposure  A measure of ionization produced in air by X or gamma radiation.  Highly specific in that the unit specifies the matter being exposed and radiation producing the ionizations.  Unit: roentgen (R)  1 R = 1000 mR Absorbed Dose • A measure of energy deposition per unit mass irradiated. • Considers all radiations imparting energy to all types of matter. • Unit: rad • 1 rad = 1000 mrad • SI Units: gray (Gy) • 1 Gy = 100 rad Dose Equivalent • It is numerically equal to the absorbed dose by a quality factor • Dose equivalent is needed because the biological effect from a given absorbed dose is dependent upon the type of radiation producing the absorbed dose. • Unit: rem • 1 rem = 1000 mrem • SI Units: sievert (Sv) • 1 Sv = 100 rem Now that you have a little understanding of the physics behind ionizing radiation, how do we measure or quantify radiation? Here are a few units of measure that are used (often interchangeably) in radiation protection:
  • 198. Units of Radiation Measurement 198
  • 199. An Analogy... Here's a way to think about measures of radiation: Imagine that you're out in a rainstorm. • The amount of rain falling is measured in Becquerel (Activity). • The amount of rain hitting you is measured in grays (Absorbed Dose). • How wet you get is measured in sieverts. (Biological Damage)
  • 200.
  • 201. What is a Personnel Monitoring Program? 201 A systematic process for monitoring, recording, evaluating, and reporting the radiation doses received by occupationally exposed individuals
  • 202. Purpose of Personnel Monitoring  To ensure compliance with established dose limits  To keep radiation doses as low as reasonably achievable (ALARA) 202
  • 203. Dose Limits 203 Occupational Adult(whole body) Public Eye Embryo/Fetus Minor(whole body) Extremities Individual Organs Body Part Limit Quantity TEDE TEDE Hd+HT,50 Heye Hs 5.0 rem 0.5 rem 0.5 rem 15 rem 50 rem 50 rem General Public 0.1 rem Hd+HT,50 TEDE LARPD Chapter 4 Subchapter B
  • 204. Wipe Samples  With a cotton wafer, wipe an area of approximately 100cm2 (about the size of a U.S. dollar bill). You should wipe about 1% of the accessible surface area in “hot area”.  In “clean” areas, take wipes of frequently used items or areas – calculators, phones, door knobs, high traffic floors, etc.  Count the wafer with at least 3 ml of “safe” scintillation cocktail, along with a background sample consisting of a new/unused, damp, cotton wafer, in a liquid scintillation counter (set to “open” or “wide” window). The results should be reviewed and data taped on the appropriate lab schematic, sign and date the form.
  • 205. Wipe Tests How do I determine if an area is “contaminated”? Note: Take gloves off before entering room.  If the open-window count exceeds 200 cpm above background, you should recount the wipe vial before making it public to the other users in the room.  If result is still above 200 cpm, you must decontaminate the area and perform another wipe test.  A meter reading two times background in any part of your lab area that has no nearby radioactive material storage or radioactive waste storage needs to be decontaminated. If area cannot be cleaned after two attempts, contact Radiation Safety officer for assistance.
  • 206. Detection of Radioactivity and the Concept of Half- life • Achilles( "Sardi ki haalat mein“) and the tortoise • “In a race, the quickest runner can never overtake the slowest, since the pursuer must first reach the point whence the pursued started, so that the slower must always hold a lead.”— Aristotle, Physics VI:9, 239b15 • Give a tortoise a head start…… • The answer is obvious if you consider infinite converging theories…
  • 207. Introduction  Importance and relevance  Radiation is often the only observable available in processes that occur on very short, very small, or very large scales  Radiation detection is used in many diverse areas in science and engineering  Often a detailed understanding of radiation detectors is needed to fully interpret and understand experimental results 207
  • 208. Detecting particles  Every effect of particles or radiation can be used as a working principle for a particle detector. Claus Grupen 208
  • 209. RADIATION DETECTORS • Instruments used in the practice of health & Medical physics serve a wide variety of purposes, Mainly of two classes, Survey INSTRUMENTS, Based on Processes Personal Dosimeters, Based on Physio-chemical changes. • one finds instruments designed specifically for the measurement of a certain type of radiation, such as Alpha Particles, Beta Particles low-energy X-rays, high-energy gamma rays. fast neutrons, and so on
  • 210. Electroscope When charged, the metal foils spread apart due to like charge repulsion When exposed to ionizing radiation, the radiation knocks electrons off the air molecules, which jump onto the foils and discharge them, allowing them to drop down 210 Tro: Chemistry: A Molecular Approach
  • 211. • The basic requirement of any such instrument is that its detector interact with the radiation in such a manner that the magnitude of the instrument's response like development of current or voltage pulse, Charging and Discharging of Capacitors is proportional to the radiation effect or radiation property being measured Called Current Mode of operation. If Signal is produced by Individual Particle,Amlified and Counted, Called Pulse Mode or Counter.
  • 212. Overview of Detection Mechanism 212 Ionizing Radiation Ionizing radiation interacts with matter in various ways: ionization (photoelectric effect), excitation, braking radiation, Compton effect, pair production, annihilation etc. Mechanisms of interaction are utilized for the detection of ionizing radiation. Function and principles of electroscope, ionization chambers, proportional Counters, Geiger-Muller counters, solid-state detectors, and scintillation counters, depends on those ways of interaction. and cloud chambers, Bubble chamber &Emulsion have been described.
  • 213. Radiation Measurement Principles (One Can not really claim to know much about a thing until one can measure it.(KELVIN,1824-1907) Detector Signal Physical Chemical Biological Reader Calibration Assessment Amplificatio n
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  • 215. How a Radiation Detector Works(KERMA ,Kinetic Energy Released in the Medium) The radiation we are interested in detecting all interact with materials of the detector and cause different Physio chemical,Biological,Chemical etc changes used for detection purposes. We can measure or detect these Changes through many different ways/Processes to get a multitude of information
  • 216. Interactions of Particles with Matter - Radiation Damage  Particles can have lasting effects on the detector materials.  Nuclear Collision  Particle undergoes interaction directly with atomic nucleus.  May transmute the element (radiation damage).  May lead to secondary particles which themselves are detectable.  Lattice Dislocation  Crystalline structure of a material may be disrupted.  Chemical Change  Photographic Film or Emulsion While these effects can be exploited as a type of particle detection, they may also cause permanent damage to detector components resulting in a detector which stops working. This is sometimes referred to as “aging”.
  • 217. Interactions of Particles with Matter - Effect on the Particle  For a particle to be detected it must interact with Material of the Detector.  ACTION = REACTION  The properties of the particle may be different after we have detected it.  Lower Energy  Different Momentum (direction)  Completely Stopped In fact, one method of determining a particle’s energy is simply to measure how far it goes before stopping.
  • 218. Interactions of Particles with Matter - Summary  When particles pass through matter they usually produce either free electric charges (ionization) or light (photoemission).  How can we use this?  Most “particle” detectors actually detect the light or the charge that a particle leaves behind.  In all cases we finally need an electronic signal to record.
  • 219. Particle Detectors… aside: Avalanche Multiplication We need devices that are sensitive to only a few electron charges: ( An Ampere is 6.2x1018 electrons/second! ) we need to amplify this charge. By giving the charges a push, we can make them move fast enough so that they ionize other atoms when they collide. After this has happened several times we have a sizeable free charge that can be sensed by an electronic circuit.
  • 220. Particle Detection Mechanism An Overview:  Detect Particles by Letting them Interact with Matter within the Detectors.  Choose appropriate detector components, with awareness of the effects the detectors have on the particles.  Design a System of Detectors to provide the measurements we need.
  • 221. Basic Structure of Experimentation/Need of Accelerator & Detector Physics Ion Source Accelerator Beam Target Detectors
  • 222. Detection and Measurement includes the following components:  Detector  Preamplifier(conversion of I,to,V,pulse ,Impedance Matching)  Amplifier  Single channel analyzer  Multi-channel analyzer  Scalar-Timer
  • 223.  a detector produces a signal for every particle entering in it.  Every detector works by using some interaction of particles with matter.  Use characteristic effects from interaction of radiation with matter to detect, identify and/or measure properties of radiation.  Respond to radiation by producing various physical effects
  • 224. Processes Used For Detection  Ionization: Gas/Liquid chambers and Semiconductor Detectors  Scintillation: Scintillation counters and TLDs  Sparking: Sparking chamber  Blackening of photographic film: Nuclear Emulsion detector and Film dosimetry  Bubbling/Clouding of supersaturated liquids/vapors: Cloud Chambers and Bubble Chambers
  • 225.  Physical Changes: NMR Dosimetry and SSNTDs  Themodynamical Changes: Calorimetric Dosimetry  Activation: Neutron Activation Detectors  Biological Changes: ESR Detectors and Biosensors
  • 226. Today: most signals are electronic  photographic emulsions and bubble chambers have largely disappeared  the few remaining such systems (e.g. OPERA) are usually also processed electronically  most modern detectors yield electronic signals  wire (drift) chambers  silicon (semiconductor) devices  photo detectors (photomultipliers)  WHY ?  GOOD ?  BAD ?
  • 227. Advantages of electronic signals  digitize and write directly to “logbook” (data storage)  no human errors  much faster  possible to use a trigger  automatic selection of events to be stored
  • 228. Detector types  today, we directly “see” in detectors only particles we know already  “Messenger” particles  “new” particles are too short-lived to reach detectors  which are these “messenger” particles?
  • 229. Detector types  today, we directly “see” in detectors only particles we know already  “messenger” particles  “new” particles are too short-lived to reach detectors  which are these “messenger” particles?  electrons / positrons / photons  protons / charged pions / other charged hadrons  neutrons / other neutral hadrons  muons  missing (transverse) momentum
  • 230. Detector types  today, we directly “see” in detectors only particles we know already  “messenger” particles  “new” particles are too short-lived to reach detectors
  • 231. “De-randomization” n fluctuations in arrival time absorbed by queue n FIFO – first in, first out – “de-randomized” output rate n additional latency
  • 232. Following is the list of most common types of detectors:  Gas-filled counters ionization chamber Proportional Counter Geiger-Muller counter  Scintillation detectors  Semiconductor detectors  Nuclear Emulsions  Bubble/Cloud Chambers  SSNTD  Personal Dosimeters etc
  • 233. Gas Detectors  Most common form of radiation detector  Relatively simple construction ○ Suspended wire or electrode plates in a container ○ Can be made in very large volumes (m3)  Mainly used to detect b-particles and neutrons  Ease of use  Mainly used for counting purposes only ○ High value for W (20-40 eV / ion pair) ○ Can give you some energy information  Inert fill gases (Ar, Xe, He)  Low efficiency of detection  Can increase pressure to increase efficiency  g-rays are virtually invisible
  • 234. Ionization Chambers  Two electric plates surrounded by a metal case  Electric Field (E=V/D) is applied across electrodes  Electric Field is low  only original ion pairs created by radiation are collected  Signal is very small  Can get some energy information  Resolution is poor due to statistics, electronic noise, and micro phonics Good for detecting heavy charged particles, betas
  • 235. Proportional Counters  Wire suspended in a tube  Can obtain much higher electric field  E a 1/r  Near wire, E is high  Electrons are energized to the point that they can ionize other atoms  Detector signal is much larger than ion chamber  Can still measure energy  Same resolution limits as ion chamber  Used to detect alphas, betas, and neutrons
  • 236. Six-Region Gas Amplification Curve a, b, g each produce the same detector response. a _____ b- _____ g _____ Voltage Pulse Height 100 1013 Recombination Region Ionization Region Proportional Region Limited Proportional Region Geiger-Mueller Region Continuous Discharge Region 1 2 3 4 5 6
  • 237. 5/23/2023 DST SERC EHEP SCHOOL (Nov 7-27, 2017)
  • 238. 1. Recombination Region  Applied voltage too low  Recombination occurs  Low electric field strength 2. Ionization Chamber Region (aka Saturation Region)  Voltage high enough to prevent recombination ○ All primary ion pairs collected on electrodes  Voltage low enough to prevent secondary ionizations  Voltage in this range called saturation voltage  As voltage increases while incident radiation level remains constant, output current remains constant (saturation current) Six-Region Gas Amplification Curve
  • 239. 3. Proportional Region  Gas amplification (or multiplication) occurs ○ Increased voltage increases primary ion energy levels ○ Secondary ionizations occur ○ Add to total collected charge on electrodes  Increased output current is related to # of primary ionizations via the proportionality constant (aka gas multiplication factor) ○ Function of detector geometry, fill-gas properties, and radiation properties Six-Region Gas Amplification Curve
  • 240. 4. Limited Proportional Region  Collected charge becomes independent of # of primary ionizations  Secondary ionization progresses to photoionization (photoelectric effect)  Proportionality constant no longer accurate  Not very useful range for radiation detection Six-Region Gas Amplification Curve
  • 241. 5. Geiger-Mueller (GM) Region  Any radiation event strong enough to produce primary ions results in complete ionization of gas  After an initial ionizing event, detector is left insensitive for a period of time (dead time) ○ Freed primary negative ions (mostly electrons) reach anode faster than heavy positive ions can reach cathode ○ Photoionization causes the anode to be completely surrounded by cloud of secondary positive ions ○ Cloud “shields” anode so that no secondary negative ions can be collected ○ Detector is effectively "shut off" ○ Detector recovers after positive ions migrate to cathode  Dead time limits the number of radiation events that can be detected ○ Usually 100 to 500 s Six-Region Gas Amplification Curve
  • 242. 6. Continuous Discharge Region  Electric field strength so intense that no initial radiation event is required to completely ionize the gas  Electric field itself propagates secondary ionization  Complete avalanching occurs  No practical detection of radiation is possible. Six-Region Gas Amplification Curve
  • 243. Scintillation Detectors  Phosphors (NaI(Tl), CsF, BGO, LSO)  Photomultiplier Tube (PMT) dynodes, counting chain, spectra  Liquid Scintillation Counting (“wipes”)
  • 244. Photon Interaction with NaI(Tl) Crystal ”.
  • 245. NaI(Tl) – PMT Assembly ”.
  • 246. NaI(Tl) – PMT Assembly .
  • 247. Scintillator Characteristics  Phosphors (NaI(Tl), CsF, BGO, LSO)  Photoelectric interaction ~ Z4  NaI(Tl): reference, decay const. ~ 1μs  CsF : faster than NaI(Tl), TOF PET  BGO : slower but more efficient, PET  LSO : very fast (~1ns), high res. PET .
  • 254. Fluorescence Screens, Some Historical Facts. 254 Ionizing Radiation Fluorescence materials absorb invisible energy and emit visible light. J.J. Thomson used fluorescence screens to see electron tracks in cathode ray tubes. Electrons strike fluorescence screens on computer monitors and TV sets give dots of visible light. Rontgen saw the shadow of his skeleton on fluorescence screens. Rutherford observed alpha particle on scintillation material zinc sulphide. Fluorescence screens are used to photograph X-ray images using films sensitive visible light.
  • 255. Semiconductor Detector  A semiconductor detector acts as a solid- state ionization chamber  The operation of a semiconductor radiation detector depends on its having either an excess of electrons or an excess of holes.  A semiconductor with an excess of electrons is called an n-type semiconductor, while one with an excess of holes is called a p-type semiconductor
  • 257.  one of the oldest devices used to detect and measure ionizing (nuclear) radiation  Named for Hans Geiger who invented the device in 1908, and Walther Muller who collaborated with Geiger in developing it further in 1928  one of the most sensitive, especially for the low radiation levels typically found in most situations.
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  • 259.
  • 260.
  • 261.  Following is the assembly of the components of GM counter: to get as max precision as possible  Power-supply  GM tube  Discriminator  Scalar/timer
  • 262. GM Counter Assembly  Variable voltage source  Gas-filled counting chamber  Two coaxial electrodes well insulated from each other  Electron-pairs  produced by radiation in fill gas  move under influence of electric field  produce measurable current on electrodes, or  transformed into pulse
  • 263. GM Tube In Action wall fill gas R Output A or Anode (+) Cathode (-) End window Or wall
  • 265. Direct Ionization Process wall Incident charged particle e - e - e - e - e - e - e - e - beta (β-)
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  • 268. 5/23/2023 DST SERC EHEP SCHOOL (Nov 7-27, 2017)
  • 269. 5/23/2023 DST SERC EHEP SCHOOL (Nov 7-27, 2017) Avalanche process via ionization important for gain factor & gas detectors
  • 270. 5/23/2023 DST SERC EHEP SCHOOL (Nov 7-27, 2017)
  • 271. 5/23/2023 DST SERC EHEP SCHOOL (Nov 7-27, 2017)
  • 272. Voltage versus Ions Collected Voltage Number of Ion Pairs collected Ionization region Saturation Voltage 100 % of initial ions are collected Recombination region
  • 273.  The characteristics curve depends on three factors  Plateau: the part of the curve where the number of counts per second is (almost) independent of the voltage.  Threshold voltage: always lies in the plateau region and is a function of the gas pressure and the anode diameter  Figure of merit: is always less than 1%
  • 274.  A process causing the discharge to terminate  Two methods used for quenching are: ○ External quenching ○ Internal quenching
  • 275.  Used to restore the counter to its quiescent state after the passage of ionizing radiation  An RC circuit is used for reducing the high voltage applied to the tube, for a fixed time after each pulse, to a value that is too low to support further gas multiplication  The voltage must be reduced for a few hundred secs which is greater than the transit time of the positive ions  A counter with 98% pure argon is used
  • 276.  The advantage of external quenching is that it gives long life time to GM tube  The disadvantage is that it has long recovery time
  • 277.  The quenching agent gas in the Geiger counter stops the flow of electrical current after a few microseconds.  the quenching gas is of low ionization potential (halogens or organic vapors)  Halogens are preferably used because it increases the life of GM tube  Organic quenched tubes usually have a flatter plateau than halogen quenched tubes
  • 278.  The purpose of the quenching additive to the gas is to effectively absorb UV-photons emitted from the electrodes when the ions produced in the multiplication process impact on the electrodes.  Such photons otherwise liberate secondary electrons (via the photo-electric effect) which may initiate the avalanche process all over again, thereby leading to catastrophic breakdown of the tube (i.e. a spark).
  • 279.  Device serving as pulse height selector  able to make selection from output analogical pulses, rejecting the impulses with voltage amplitude inferior to a certain threshold voltage  Threshold voltage should neither too low nor too high to avoid noise and data-loss respectively  Its function is double: ○ To eliminate the noise ○ To provide a standard shaped pulse to scaler
  • 280.
  • 281.  Scalar: counts the number of pulses  Timer: measures the length of counting time in a given measurement  Collectively used to:  Make measurement of pulses for a preset length of time (set on timer) recording the number of counts by the scaler  Determine the count-rate by measuring duration with timer for a preset number of counts(like car,s window shield wiper via adjustment of time constant of RC network)
  • 283. Resolving Time  The negative ions, being electrons, move very rapidly and are soon collected, while the massive positive ions are relatively slow-moving and therefore travel for a relatively long period of time before being collected  These slow-moving positive ions form a sheath around the positively charged anode, thereby greatly decreasing the electric field intensity around the anode and making it impossible to initiate an avalanche by another ionizing particle. As the positive ion sheath moves toward the cathode, the electric field intensity increases, until a point is reached when another avalanche could be started
  • 284. Resolving Time  dead time  The time required to attain this electric field intensity  recovery time  the time interval between the dead time and the time of full recovery  resolving time  The sum of the dead time and the recovery time
  • 285. Resolving Time  dead time, recovery time, resolving time
  • 286. Resolving Time  Measurement of Resolving Time  the "true“ counting rate ○ the observed counting rate of a sample is R0
  • 287.  Objective: to extract the amplitude or timing information the electrical signal is coupled to an amplifier, sent through gain and filtering stages, and finally digitized to allow data storage and analysis.  amplitude or timing information include the different characteristics of the radiation, such as the type, the intensity and energy of the radiation  The signal can be either processed entirely through analog circuit or can be converted into digital form
  • 288.  The signal can be a continuously varying signal  a sequence of pulses, occurring periodically at known times randomly  All of these affect the choice of signal processing techniques.
  • 289.  First steps in signal processing: ○ Formation of the signal in the detector (sensor) ○ Coupling the sensor to the amplifier  Detectors use either ○ direct detection or ○ indirect detection
  • 290.  The detector pulse has a very low amplitude & time duration i.e. narrow band width  To extract any kind of information requires amplification of detector signal  Preamplifier is a simple and efficient amplifier directly connected to detector
  • 291.  A preamplifier, in effect, acts as a capacitance terminator thus preventing deterioration of detector.  Matches the high electric impedance of detector with low impedance of the coaxial cable connected to subsequent signal processing circuit  Basically plays a role as an impedance matcher between the detector and the rest of the circuit
  • 292.  The function is to amplify the pulses from detector via a preamplifier  Also used to shape a pulse for further detection
  • 293.  High-voltage power supply typically provides 800 to 1,200 volts to the PMT  Raising voltage increases magnitude of voltage pulses from PMT  Preamp connected to PMT using very short cable  Amplifies voltage pulses to minimize distortion and attenuation of signal during transmission to remainder of system
  • 294.
  • 295. SCA Contd.  Amplifier further amplifies the pulses and modifies their shapes – gain typically adjustable  SCA allows user to set two voltage levels, a lower level and an upper level  If input pulse has voltage within this range, output from SCA is a single logic pulse (fixed amplitude and duration)  Counter counts the logic pulses from the SCA for a time interval set by the timer
  • 296.
  • 297. SCA energy modes  LL/UL mode – one knob directly sets the lower level and the other sets the upper level  Window mode – one knob (often labeled E) sets the midpoint of the range of acceptable pulse heights and the other knob (often labeled E or window) sets a range of voltages around this value.  Lower-level voltage is E - E/2 and upper-level voltage is E + E/2
  • 298.
  • 299.  An MCA system permits an energy spectrum to be automatically acquired much more quickly and easily than does a SCA system  The detector, HV power supply, preamp, and amplifier are the same as for SCA systems  The MCA consists of an analog-to-digital converter, a memory containing many storage locations called channels, control circuitry, a timer, and a display
  • 300.
  • 301.
  • 302.
  • 303.  Advantages  Variety of sizes and shapes  Inexpensive  The slightest radiation event strong enough to cause primary ionization results in ionization of the entire gas volume  Thus detector is highly sensitive, even in lowest intensity radiation fields  Only simple electronic amplification of the detector signal is required ○ Hardware lasts longer ○ Requires less power  Strong output signal means G-M needs less electrical noise insulation than other detectors NET 130 303
  • 304.  Disadvantages  Incapable of discriminating between type and energy of the radiation event  Only counts events and yields output in events per unit time or dose rate  A beta particle or gamma ray, high or low energy, represents one event counted  Only capable of detecting fields to some upper limit of intensity ○ Limited to lower intensity fields due to detector dead time NET 130 304
  • 305. Personnel Monitor Devices The most common monitor devices to determine the personal exposure history are: Radiation Film Badges Pocket Dosimeter
  • 306. Radiation film badges are composed of two pieces of film, covered by light tight paper in a compact plastic container. Various filters in the badge holder allow areas to be restricted to X-ray, g-ray, b-rays only. Radiation causes a blackening (silver) of the film material (mostly a silver bromide emulsion) The sensitivity of the film material is limited For g-radiation the sensitivity is in the range of 10 - 1800 mrem. For b-radiation the sensitivity is in the range of 50 - 1000 mrem. Special film material is used for neutron monitoring. The badge is usually not sensitive for a radiation because the a-particles are absorbed in the light-tight paper.
  • 307. Pocket dosimeter The pocket dosimeter or pen dosimeter is a common small sized ion chamber which measures the originated charge by direct collection on a quartz fiber electroscope. The U-shaped fiber is close to a U-shaped wire. If the fiber is charged it will be deflected away from the wire. The position of deflection is a measure of the accumulated radiation dose.
  • 308. The dosimeter records total exposure from the initial charging to the time of reading. It is an active device as the radiation exposure can be read immediately as opposed to the passive film badge which is only read after approximately six months.
  • 309. Dosimeters which are also available in high or low ranges, can be in the form of a badge, pen/tube type, or even a digital readout and all measure exposure or the total accumulated amount of radiation to which you were exposed. (The Civil Defense pen/tube tube would show a reading like below when looking through it.) It's also similar to the odometer of a car; where both measure an accumulation of units. The dosimeter will indicate a certain total number of R or mR exposure received, just as the car odometer will register a certain number of miles traveled.
  • 310. MSc-REP Regan Dosimetry 310 Photographic Emulsion Dosimetry The photographic emulsion is a suspension of silver halide crystals in a gelatine matrix. The film badge has an emulsion coating on both sides but of differing sensitivities, one for a high dose range, and the other for low dose ranges. When the film is exposed to X-rays, secondary ionisation makes one or more of the silver halide ions latent. When developed this produces metallic silver which varies spatially according to the amount of dose absorbed within the matrix, this forms the photographic negative. 20m 200m protective coating base material silver halide grains in a gelatin matrix
  • 311. MSc-REP Regan Dosimetry 311 Photographic Emulsion Dosimetry A typical film density versus exposure curve is shown below,
  • 312.
  • 313.
  • 315. 315 Personal Dosemeter Badges Thermoluminescent dosemeter (a.k.a. “TLD”) This is a reusable dosimeter which uses lithium fluoride to measure radiation dose. It stores dose information until heated to over 250°C when it gives out light the amount of which is proportional to the dose received. It is environmentally robust and excellent for use in all working environments. Photographic film dosemeter (a.k.a. “film badge”) Film is worn in a holder containing several different filters. When developed the film darkens in proportion to the amount of radiation energy received. Due to the differing amounts of filtration we can gain information on the energy of radiation causing the dose. Radioactive contamination of the film can be readily identified. Extremity dosemeter (a.k.a. “finger TLD”) This is a miniature TLD which can be supplied in different forms to suit your needs (stalls, straps or rings). The finger stall is most commonly used and is worn like the finger of a glove.
  • 316. Thermoluminescence  (TL) is the ability to convert energy from radiation to a radiation of a different wavelength, normally in the visible light range.  Two categories  Fluorescence - emission of light during or immediately after irradiation  Not a particularly useful reaction for TLD use  Phosphorescence - emission of light after the irradiation period. Delay can be seconds to months.  TLDs use phosphorescence to detect radiation.
  • 317. Thermoluminescence  Radiation moves electrons into “Traps”  Heating moves them out  Energy released is proportional to radiation  Response is ~ linear  High energy trap data is stored in TLD for a long time
  • 318. TL Process Valence Band (outermost electron shell) Conduction Band (unfilled shell) Phosphor atom Incident radiation Electron trap (meta stable state) -
  • 319. TL Process, continued Valence Band (outermost electron shell) Conduction Band Phosphor atom Thermo luminescent photon Heat Applied -
  • 320. Output – Glow Curves  A glow curve is obtained from heating  Light output from TL is not easily interpreted  Multiple peaks result from electrons in "shallow" traps  Peak results as traps are emptied.  Light output drops off as these traps are depleted.  Heating continues  Electrons in deeper traps are released.  Highest peak is typically used to calculate dose  Area under represents the radiation energy deposited in the TLD
  • 321. Trap Depths - Equate to Long Term Stability of Information Time or temperature
  • 322. TLD Reader Construction Power Supply PMT DC Amp Filter Heated Cup TL material To High Voltage To ground Recorder or meter
  • 323.  Crystal retains this energy until heat is applied.  The “trapped” energy is then released in the form of light, as the atoms of the crystal return to their “ground state”  The light emitted is then correlated to dose received  Once the TLD has been “read”, memory is cleared  TLD is then available for re-use Thermoluminescent Dosimeter
  • 324. MSc-REP Regan Dosimetry 324 Thermo luminescent/OSL Dosimeters Currently the most common used personal dosimeter. The dosimeter consists of two thermo luminescent detectors containing the radiation- sensitive material lithium fluoride (LiF). The detectors are located in a plate which is identified uniquely by means of an array of holes. The lithium fluoride stores the energy it receives from ionising radiations until it is heated/Stimulated with light during processing (in this case to about 250°C) when the energy is released as light. The amount of light released is proportional to the radiation dose. The plate is supplied to the wearer in a plastic wrapper which protects the detectors from light and contaminants. LiF inserts Current NRPB TLD and new Harshaw TLD
  • 325. Optically-stimulated luminescence (OSL) is based on a principle similar to that of the TLD. Instead of heat, light (from a laser) is used to release the trapped energy in the form of luminescence. OSL is a novel technique offering a potential for in vivo dosimetry in radiotherapy. The integrated dose measured during irradiation can be evaluated using OSL directly afterwards. • The optical fibre OSL dosimeter consist of a small (~1 mm3 ) chip of carbondoped aluminium oxide (Al2O3:C) coupled with a long optical fibre, a laser, a beam- splitter and a collimator, a PM tube, electronics and software. To produce OSL, the chip is excited with a laser light through an optical fibre and the resulting luminescence (blue light) is carried back in the same fibre, reflected through a 90o by the beam-splitter and measured in a PMT.
  • 326. The optical fiber dosimeter exhibits high sensitivity over the wide range of dose rates and doses used in radiotherapy. The OSL response is generally linear and independent of energy as well as the dose rate, although the angular response requires correction.
  • 327. Water Calorimetry: Basic Principles very simple principle: absorbed-dose-to-water [Gy = 1 J/kg] at position x absorbed W E T c   Radiation : Specific heat capacity of water (very well known, since 1930‘s) Dose-to-water : Main advantage: direct determination of dose-to-water k c T D W W W     W c 1  k
  • 328.  Water calorimeters offer a more direct determination of the absorbed dose to water at the reference point in a water phantom. The absorbed dose to water is derived from the measured temperature rise at a point in water relying on an accurate knowledge of the specific heat capacity. No scaling laws are required as is the case in graphite calorimetry. However, there are technical complications related to a heat defect due to water radiolysis and heat transport, which need to be corrected for. • Water calorimeters are calibrated through the calibration of their themistors in terms of the absolute temperature difference rather than through the energy depositing as it is the case of graphite calorimeters. 3.9. SUMMARY OF SOME COMMONLY USED DOSIM
  • 329. 329 Bubble Chamber In the early 1950ies Donald Glaser tried to build on the cloud chamber analogy: Instead of supersaturating a gas with a vapor one would superheat a liquid. A particle depositing energy along it’s path would then make the liquid boil and form bubbles along the track. In 1952 Glaser photographed first Bubble chamber tracks. Luis Alvarez was one of the main proponents of the bubble chamber. The size of the chambers grew quickly 1954: 2.5’’(6.4cm) 1954: 4’’ (10cm) 1956: 10’’ (25cm) 1959: 72’’ (183cm) 1963: 80’’ (203cm) 1973: 370cm
  • 330.
  • 331.
  • 332.
  • 333. 333 W. Riegler/CER N Bubble Chambers The excellent position (5m) resolution and the fact that target and detecting volume are the same (H chambers) makes the Bubble chamber almost unbeatable for reconstruction of complex decay modes. The drawback of the bubble chamber is the low rate capability (a few tens/ second). E.g. LHC 109 collisions/s. The fact that it cannot be triggered selectively means that every interaction must be photographed. Analyzing the millions of images by ‘operators’ was a quite laborious task. That’s why electronics detectors took over in the 70ties.
  • 334. Who Discovered X Rays? Wilhelm Conrad Roentgen Roentgen worked with a Crookes tube to study cathode rays.
  • 336. Nuclear Medicine Diagnostic Procedures • Radioactive injection • Short half-life radionuclide • Pictures taken with special gamma camera • Many different studies: Thyroid Lung Cardiac White Blood Cell Photo by Karen Sheehan
  • 337. Radiation Therapy/Phantoms/ Artificial Humans/The Ghost/Fictitious/Illusion/Image Used for treating cancer. Why does it work? External Beam Brachytherapy (implants) Image courtesy of Photo by Karen Sheehan
  • 338.
  • 339.
  • 340.
  • 341.
  • 342.
  • 343.
  • 344.
  • 345.
  • 346.
  • 347.
  • 348. Measurements An Overview:  Measurements when written down are interpreted as absolute values  Interpretation is whatever people do believe  sources of uncertainty  Usually unknown or neglected  Randomness means all measurements are only “best estimates”  Measurements may lead to fears, which then drive the interpretation Radiation Safety Counseling Institute 348
  • 349.  Common assumptions  If its measurable - it must be bad  Written data are always good  Must take immediate action  Common to make decisions (cry wolf)  Without verifying the measurement  Stay calm  As minimum – repeat at least once  For confirmation, ideally with other instruments and people, if possible Radiation Safety Counseling Institute 349
  • 350.  What do the numbers mean ?  Measurements only have meaning in terms of interpretation By the Experts  Data interpretation may be driven by fears  Of radiation  Of consequences, health risks, liabilities  Of making a mistake  Is your interpretation defensible ?  What are you willing to commit ?  Is your Instrument telling you what you think it is ? Y/N(Please think over it) Radiation Safety Counseling Institute 350
  • 351.
  • 352.
  • 353. 990 Recommendations of the International Commission on Radiological Protection, ICRP Publication 60, Permagon Press, Oxford Brennen S.E. and Putney R.G., eds (1983) Dose reduction in diagnostic radiology, The Hospital Physicist’s Associtaion Plaut S., (1993) Radiation protection in the x-ray department, Butterworth-Heinemann, Oxford Bushong S.C., (2004) Radiological science for technologists: Physics, Biology and Protection, 8th Ed. Mosby, St Louis Faulkner K. and Wall B.F., eds (1988) Are x-rays safe enough? Patient dose and risks in diagnostic radiology, The Institute of Physical Science in Medicine, Report No. 55 Norris, Teresa G., Radiation Safety in Fluoroscopy. Radiologic Technology. Vol 73 No 6, August 2002, 511 Seeram E., (1997) Radiation protection, Lippincott, Philadelphia Sherer, Mary Alice., Visconti, Paul J., Ritenour, Russell.,(2002) Radiation Protection in Medical Radiography, 8th Ed. Mosby, St Louis. Web D.V., Solomon S.B. and Thomson J.E.M., (1999) Background radiation levels and medical exposure in Australia, Radiation Protection in Australia, Vol 16 No 2 pp.25-32 REFERENCES