The document provides an overview of a course on radiation detection and protection. It discusses topics like the interaction of radiation with matter, basic principles of radiation detection using devices like ionization chambers and scintillation detectors. It also covers radiation quantities and units, shielding design, dose estimation from internal and external radiation exposures, transportation and disposal of radioactive materials, and safety standards.
2. Course Briefing PAM-504 RADIATION DETECTION AND
PROTECTION, 3 Credit hours, Pre Requisite: Nil
1. Interaction of radiation with matter 8. Probability distributions (discrete & continuous);
Counting statistics.
2. Basic principles of radiation detection; ionization
chambers, Proportional and Geiger-Muller counters:
9. Safety standards for medical exposure, Estimation &
control of external & internal exposure hazards,
Absorbed dose estimation from external exposure,
3. Various types of scintillators; Scintillation
detectors; Radiation spectroscopy using Scintillation
detectors:
10. Shielding design of neutron and gamma sources
4. Semiconductor detectors; CdZnTe detectors, 11. Dose estimation from internally deposited
radionuclides
5. Neutron detection techniques.
6. Basic electronic circuits and electronic equipment
used in nuclear radiation detection systems;
13. IAEA Safety regulations for transport of radioactive
materials, Radiation accident management & early
medical treatment of radiation injury,
7. Radiation quantities & units, 13. Radioactive waste disposal methods, Calibration of
survey meters
3.
4. • Radioactivity is defined as the spontaneous split of a nuclei
into another nuclei or particle. In this process radiations are
emitted.
• Number of decaying atoms is proportional to the initial number of atoms present at
time.
• Disintegration of one nuclei per second is known as 1.0 Bq.
• 3.7 x 1010 Bq is known as 1 Ci. Currie is a large unit and generally milli Currie (mCi) is
7
Natural
Artificial.
8. Type of Decay Particle Emitted Change in A Change in Z
Alpha decay Helium Nuclei Decrease by 4 Decrease by 2
Beta decay Beta particle No change Increase by 1
Gamma Emission Energy No change No change
Positron Emission Positron No change Decrease by 1
Electron capture X-Ray photon No change Decrease by 1
11. • Emitted radiations are of several
types, including Alpha, Beta, Gamma
and Neutrons.
• By passing them through electrostatic
field we can distinguish most of them.
12. • Alpha and Beta are
charged particles.
• Gamma and Neutrons
are neutral radiations.
• Alpha and Beta are called
directly ionizing while
gamma and neutron are
called indirectly ionizing
radiations.
13.
14. • Alpha radiations can penetrate
into few um in paper/human
skin.
• Beta radiation are electrons and
can penetrate up to 3 mm of
Aluminum sheet.
• Gamma are electromagnetic
radiations and can penetrate in
to few cm of Pb depending on
their energy.
• Neutrons are neutral particles
and penetrate into few feet of
concrete.
15.
16. • An electron in an atom can be moved to a higher energy
orbit when the atom absorbs an amount of energy that
exactly equals the energy difference between the orbits.
• An electron in an atom can be moved to a lower energy
orbit when the atom emits an amount of energy that exactly
equals the energy difference between the orbits.
• Fluorescence and Phosphorescence are two examples.
17. • Ionization energy, also called ionization
potential, is the amount of energy required to
remove an electron from an
isolated atom or molecule.
• There is an ionization energy for each
successive electron removed; the ionization
energy associated with removal of the first (most
loosely held) electron, however, is most
commonly used.
• One mole of hydrogen atoms has an atomic
weight of 1.00 gram, and the ionization energy
18.
19. • The average energy deposited per unit length of track by ionizing
radiation as it passes through and interacts with a medium along its
path.
• Is described in units of keV/um
• Is a very important factor in assessing potential tissue and organ
damage from exposure to ionizing radiation.
20. • LET (linear energy transfer) is the amount of energy
released by a radioactive particle or wave over the
length of its decay track. Specific Ionization is the
number of ion pairs produced per unit track length.
High LET radiation (like alpha & beta particles)
ionizes water into H and OH radicals over a very short
track. In the example, two events occur in a single cell
so as to form a pair of adjacent OH radicals that
recombine to form peroxide, H2O2, which can produce
oxidative damage in the cell.
Low LET radiation (like X- or gamma rays) also ionizes
water molecules, but over a much longer track. In the
example, two events occur in separate cells, such that
adjacent radicals are of the opposite type:
the H and OH radicals reunite and reform H2O.
21.
22. • Ionization mainly depends on charge, mass, and K.E.
of the incoming radiation.
• Range is inversely proportional to the ionization
power of the radiation.
• High ionization means short range
• Low ionization means long range
• Similarly,
• High energy or momentum means long range
• Low energy means short range
• However,
• High Energy low ionization
• Low energy high ionization
24. • Energies below approximately 10 keV.
• Sometimes called classical scattering or
Thompson scattering, Rayleigh Scattering.
• No ionization.
• Most probable in heavy atoms.
• Hence, less important in biological tissues.
• Question: which material is more suitable for
coherent scattering, Carbon, Oxygen, Lead.
25. • In the Compton effect, the incident x-ray interacts
with an outer shell electron and ejects it from the
atom,
• thereby ionizing the atom.
• The ejected electron is called a Compton
electron or a secondary electron.
• The probability of the Compton effect is
inversely proportional to x-ray energy (1/E) and
independent of atomic number.
26. • Interacts with inner shell electrons
• X-rays are absorbed
• The electron removed from an atom is called
photoelectron.
• The probability of the photoelectric effect is
inversely proportional to the third power of the x-
ray energy (1/E)3.
• The probability of photoelectric effect is directly
proportional to the third power of the atomic
number of the absorbing material (Z3).
27. • Incident electron interacts with the nuclear field.
• The interaction between the x-ray and the nuclear field
causes the x-ray to disappear,
and in its place,
two electrons appear, one positively charged
(positron) and one negatively charged (electron).
• This satisfies the E=mc2 relation. One 1.02 MeV
photon converts into two 511 keV electrons.
28.
29. • An incident photon causes a nucleus to split up
or disintegrate.
• Occurs with x-ray energies > 10 MeV
• The nucleus is raised to an excited state and
instantly emits a nucleon or other nuclear
fragments.
• These nuclear fragments can be of any form.
30. • Illustration of an alpha particle interacting with
matter.
• The alpha particle has a linear trajectory
through matter
• And
• loses energy through Coulomb collisions with
electrons in the
31. • Illustration of a beta particle interacting with
matter.
• The beta particle primarily loses energy
through Coulombic collisions with electrons
in the cloud.
• These electrons are energetic and can
undergo secondary, tertiary and high order
interactions.
32. • Illustration of fast neutron interactions with a proton rich
form of matter.
• The neutron undergoes an elastic collision with a proton
in the target material.
• The proton recoils and then interacts with the electron
cloud, much like the reaction between an alpha particle and
matter.
• The scattered neutron proceeds onward and may have
enough energy remaining to undergo another elastic
scattering collision with a proton in the material and so
forth.
• On average, a fast neutron will undergo 19 collisions in
33.
34. • In the energy range of radiation therapy, 4 types of interaction of
photons with matter are of interest:
• Coherent scattering, photoelectric effect, Compton scattering, and
pair production.
coh c
Incoming particle: 1 photon
Outgoing particle(s):
coherent photoelectric compton
Pair
production
1 photon 1 electron
1 electron +
1 photon
1 electron +
1 positron
