X-ray spectroscopy involves using electromagnetic radiation to study the interaction between matter and radiation. Energy-dispersive X-ray spectroscopy (EDS) relies on the principle that each element has a unique atomic structure that produces a unique electromagnetic emission spectrum. EDS allows elemental composition analysis by measuring the energies of X-rays emitted from a specimen when it is exposed to a high-energy beam. X-rays are generated when high-energy electrons collide with a target in an X-ray tube, with about 1% of the energy emitted as X-rays. Characteristic X-rays are emitted when outer-shell electrons fill an inner-shell vacancy in an atom, releasing X-rays with energies specific to each element. Various

1. [X-RAY
SPECTROSCOPY]
PRESENTED BY
NARESH CHOWDARY NUNE
FACULTY
PRADEEP PATNAIK SIR

2. SPECTROSCOPY :
Spectroscopy is the study of the interaction between matter and electromagnetic radiation. Historically,
spectroscopy originated through the study of visible light dispersed according to its wavelength, by a prism.
Later the concept was expanded greatly to include any interaction with radiative energy as a function of its
wavelength or frequency. Spectroscopic data is often represented by an emission spectrum, a plot of the
response of interest as a function of wavelength or frequency.
Energy-dispersive X-ray spectroscopy:
Energy-dispersive X-ray spectroscopy (EDS, EDX, or XEDS), sometimes called energy dispersive X-ray analysis
(EDXA) or energy dispersive X-ray microanalysis (EDXMA), is an analytical technique used for the elemental
analysis or chemical characterizationof a sample. It relies on an interaction of some source of X-ray
excitation and a sample. Its characterization capabilities are due in large part to the fundamental principle
that each element has a unique atomic structure allowing a unique set of peaks on its electromagnetic
emission spectrum (which is the main principle of spectroscopy).
EDS spectrumofthemineral crust ofthevent shrimpRimicaris exoculata Most ofthesepeaks areX-rays given offas electrons return totheK
electronshell.(K-alpha and K-beta lines) One peak is from the Lshell ofiron.

3. To stimulate the emission of characteristicX-rays from a specimen, a high-energy beam of charged particles
such as electrons or protons (see PIXE), or a beam of X-rays, is focused into the sample being studied. At rest,
an atom within the sample contains ground state (or unexcited) electrons in discrete energy levels or
electron shells bound to the nucleus. The incident beam may excite an electron in an inner shell, ejecting it
from the shell while creating an electron hole where the electron was. An electron from an outer, higher-
energy shell then fills the hole, and the difference in energy between the higher-energy shell and the lower
energy shell may be released in the form of an X-ray. The number and energy of the X-rays emitted from a
specimen can be measured by an energy-dispersive spectrometer. As the energies of the X-rays are
characteristic of the difference in energy between the two shells and of the atomic structure of the emitting
element, EDS allows the elemental composition of the specimen to be measured.
GENERATION OF X-RAYS:
X-rays are typically generated by an X-ray tube. An X-ray tube is a simple vacuum tube that contains a
cathode, which directs a stream of electrons into a vacuum, and an anode, which collects the electrons and is
made of tungsten to evacuate the heat generated by the collision. When the electrons collide with the target,
about 1% of the resulting energy is emitted as X-rays, with the remaining 99% released as heat. Due to the
high energy of the electrons that reach relativistic speeds the target is usually made of tungsten even if other
material can be used particularly in XRF applications.
X-RAY SOURCES: X-ray photons areproduced by an electron beam that is accelerated to a very high speed
and strikes a target. The electrons that make up the beam are emitted from a heated cathode filament. The
electrons are then focused and accelerated by an electrical field towards an angled anodetarget. The pointwhere
the electron beam strikes the target is called the focal spot.Most of the kinetic energy contained in the electron
beam is converted to heat, but around 1% of the energy is converted into X-ray photons, the excess heat is
dissipated via a heat sink. At the focal spot,X-ray photons areemitted in all directions fromthe target surface,the
highest intensity being around 60° to 90° from the beam due to the angleof the anode target to the approaching
electron beam. There is a small round windowin the X-ray tube directly above the angled target. This window
allows theX-rays to exit the tube with littleattenuation while maintaininga vacuumseal required for the X-ray
tube operation. Other than the x-ray tube window or port the remainingportion of the x-ray tube housingis
lined with lead to absorb all remainingx-rays notusablefor image creation.X-ray machines work by applying
controlled voltage and current to the X-ray tube, which results in a beam of X-rays.The beam is projected on
matter. Some of the X-ray beam will pass through the object, whilesome is absorbed.The resultingpattern of the
radiation isthen ultimately detected by a detection medium includingrareearth screens (which surround
photographic film),semiconductor detectors, or X-ray image intensifiers.
GemX-160 - PortableWireless Controlled Battery Powered X-ray Generator for use in Non Destructive Testing and
Security.

4. Characteristic X-ray:
CharacteristicX-rays areemitted when outer-shell electrons fill a vacancy in theinner shell of an atom, releasingX-
rays in a pattern that is "characteristic"to each element. Characteristic X-rayswere discovered by Charles Glover
Barkla in 1909. who later won the Nobel Prize in Physics for his discovery in 1917.
CharacteristicX-rays areproduced when an element is bombarded with high-energy particles,which can be
photons, electrons or ions (such as protons).When the incidentparticlestrikes a bound electron (the target
electron) in an atom, the target electron is ejected from the inner shell of the atom. After the electron has been
ejected, the atom is left with a vacantenergy level,also known as a core hole. Outer-shell electrons then fall into
the inner shell,emittingquantized photons with an energy level equivalent to the energy difference between the
higher and lower states. Each element has a uniqueset of energy levels,and thus the transition fromhigher to
lower energy levels produces X-rays with frequencies that are characteristic to each element. When an electron
falls fromthe L shell to the K shell,the X-ray emitted is called a K-alpha X-ray.Similarly,when an electron falls from
the M shell to the K shell,the X-ray emitted is called a K-beta X-ray.Sometimes, however, instead of releasingthe
energy in the form of an X-ray, the energy can be transferred to another electron, which is then ejected from the
atom.
X-ray detector :
X-ray detectors are devices used to measure the flux,spatial distribution,spectrum,and/or other properties of X-
rays.
Detectors can be divided into two major categories: imagingdetectors (such as photographic plates and X-ray film
(photographic film),now mostly replaced by various digitizingdevices likeimageplates or flatpanel detectors) and
dose measurement devices (such as ionization chambers,Geiger counters, and dosimeters used to measure the
local radiation exposure,dose, and/or dose rate, for example, for verifyingthat radiation protection equipment
and procedures are effective on an ongoing basis).
TYPES OF X RAY DETECTORS :
Gas detectors >> • Ionization chamber • Proportional counter • Geiger-Muller tube
Scintillation counters >> Solid statedetectors • Intrinsicsemiconductor •P-I-N junction • Silicon drift
Charge coupled device detectors>> • Indirect • Direct coupled C. Segre (IIT) P

5. GAS DETECTORS
Ionizationchamber :
The ionization chamber is the simplest of all gas-filled radiation detectors, and is widely used
for the detection and measurement of certain types of ionizing radiation; X-rays, gamma rays
and beta particles. Conventionally, the term "ionization chamber" is used exclusively to
describe those detectors which collect all the charges created by direct ionization within the gas
through the application of an electric field. It only uses the discrete charges created by each
interaction between the incident radiation and the gas, and does not involve the gas
multiplication mechanisms used by other radiation instruments, such as the Geiger-Müller
counter or the proportional counter.
Ion chambers have a good uniform response to radiation over a wide range of energies and are
the preferred means of measuring high levels of gamma radiation. They are widely used in the
nuclear power industry, research labs, radiography, radiobiology, and environmental
monitoring.
Schematic diagramofparallelplateion chamber,showing drift ofions.Electrons typically drift 1000times faster thanpositiveions dueto their
much smallermass.
Principle of operation:
An ionizationchamber measures the charge from the number of ionpairs created withina gascausedbyincident radiation.It
consists ofa gas-filledchamber with twoelectrodes;knownas anode andcathode. The electrodesmaybe in the form of
parallel plates(Parallel Plate IonizationChambers:PPIC), or a cylinder arrangement with a coaxiallylocated intern alanode wire.
A voltage potential is applied betweenthe electrodesto create anelectric field inthe fill gas. Whengas between the electrodes
is ionizedbyincident ionizingradiation, ion-pairs are createdandthe resultant positive ions anddissociatedelectrons move to
the electrodesof the opposite polarityunder the influence of the electric field. This generatesanionizationcurrent which is
measured byanelectrometer circuit. The electrometer must be capable of measuring the verysmall output current whichis in
the regionof femtoamperes to picoamperes, depending onthe chamber design, radiation dose and applied voltage.Eachion
pair createddeposits or removes a small electric charge to or from anelectrode, such that the accumulatedcharge Is

6. proportional to the number of ionpairs created, andhence the radiation dose. This continualgenerationof charge produces an
ionizationcurrent, which is a measure of the total ionizing dose entering the chamber. However, the chamber cannot
discriminate betweenradiationtypes (beta or gamma)andcannot produce a nenergyspectrum of radiation.
The electric fieldalsoenables the device to work continuouslybymopping upelectrons, whichprevents the fillgas from
becoming saturated, where no more ions couldbe collected, andbypreventing the recombinationof ionpairs, whichwould
diminishthe ion current. This mode ofoperationis referredto as "current" mode, meaning that the output signalis a
continuous current, andnot a pulse output as inthe cases ofthe Geiger-Müller tube or the proportional counter.
Referringto the accompanyingionpair collectiongraph, it can be seenthat in the "ion chamber" operatingregionthe
collectionof ionpairs is effectivelyconstant over a range of applied voltage, as due to its relativelylowelectric fieldstrength
the ionchamber doesnot have any"multiplicationeffect". Thisis indistinctionto the Geiger-Müller tube or the proportional
counter wherebysecondaryelectrons, and ultimatelymultiple avalanches, greatlyamplifythe original ion-current charge.
Chamber types and construction
The following chamber types are commonlyused.
Free-air chamber :
This is a chamber freelyopento atmosphere, where the fill gas is ambient air. The domestic smoke detector is a goodexample
of this, where a naturalflow ofair throughthe chamber is necessarysothat smoke particles can be detectedbythe change i n
ion current. Other examplesare applications where the ions are created outside the chamber but are carried in bya forced flow
of air or gas.

7. Chamberpressure
Ventedchamber:
These chambers are normallycylindrical andoperate at atmospheric pressure, but to prevent ingress ofmoisture a filter
containinga desiccant is installed inthe vent line.This is to stop moisture building upinthe interior of the chamber, which
wouldotherwise be introducedbythe "pump"effect of changing atmospheric air pressure. These chambers have a cylindrical
bodymade ofaluminiumor plastic a few millimetres thick. The materiali s selectedto have anatomic number similar to that of
air sothat the wall is saidto be "air equivalent" over a range of ra diationbeamenergies.This has the effect ofensuringthe gas
in the chamber is actingas thoughit were a portion ofaninfinitely large gasvolume, and increases the accuracybyreducing
interactions of gamma withthe wall material. The higher the atomic number of the wall material, the greater the chance of
interaction. The wall thickness is a trade-off between maintainingthe air effect witha thicker wall, andincreasing sensitivityby
using a thinner wall. These chambers oftenhave anend windowmade ofmaterial thinenough, such as mylar, sothat beta
particles canenter the gasvolume. Gamma radiationenters boththrough the endwindow and the side walls. For hand-held
instruments the wallthicknessis made as uniform as possible to reduce photon directionalitythoughanybeta window
response is obviouslyhighlydirectional. Vented chambers are susceptible to small changesine fficiencywithair pressure and
correctionfactors can be appliedfor veryaccurate measurement applications.
Sealedlowpressure chamber:
These are similar inconstruction to the ventedchamber but are sealedandoperate at or aroundatmospheric pressure. They
contain a special fill gas to improve detectionefficiencyas free electrons are easilycaptured in air-filledvented chambers by
neutral oxygenwhich is electronegative, to form negative ions. These chambers alsohave the advantage of not requiring a vent
and desiccant. The beta endwindow limits the differential pressure fromatmospheric pressure that can be tolerated, and
common materialsare stainlesssteel or titanium with a typical thickness of25 µm.
Highpressure chamber:
The efficiencyof the chamber canbe further increasedbythe use of a highpressure gas. Typicallya pressure of 8-10
atmospheres can be used, and various noble gases are employed. The higher pressure results in a greater gas densityand
therebya greater chance of collision withthe fill gasandion pair creationbyincident radiation. Because of the increasedwall
thicknessrequiredto withstand this high pressure, onlygamma radiationcanbe detected.These detectors are usedinsurvey
meters and for environmental monitoring.
Chamber Shape
Thimble chamber:
Most commonlyusedfor radiationtherapymeasurements is a cylindrical or "thimble"chamber. The active volume is housed
within a thimble shaped cavitywithaninner conductive surface (cathode) and a central anode. A biasvoltage applied across
the cavitycollects ions and produces a current which canbe measuredwithanelectrometer.
Parallel-platechambers:
Parallel-plate chambers are shapedlike a smalldisc, withcircular collectingelectrodesseparatedbya smallgap, typically2mm
or less. The upper disc is extremelythin, allowingfor muchmore accurate near-surface dose measurements thanare possible
with a cylindrical chamber.
Monitorchambers :Monitor chambers are typicallyparallel plate ionchambers which are placedinradiation beams to
continuouslymeasure the beam's intensity. For example, withinthe headof linear accelerators used for radiotherapy, multi-
cavityionization chamber canmeasure the intensityof the radiation beaminseveraldifferent regions, providingbeam
symmetryandflatness information.

8. Research and calibration chambers :
Early versions of the Ion chamber were used by Marieand Pierre Curiein their original work in isolating
radioactivematerials.Sincethen the ion chamber has been a widely used tool in the laboratory for research and
calibration purposes.To do this a wide variety of bespoke chamber shapes,some usingliquidsas theionized
medium, have been evolved and used.Ion chambers areused by national laboratories to calibrateprimary
standards,and also to transfer these standards to other calibration facilities.
Ionization chamber made by Pierre Curie, c 1895-1900
Hand-held integral ion chamber survey meter in use
Applications :
Nuclear industry :
Ionization chambers arewidely used in the nuclear industry as they providean output that is proportional to
radiation doseThey find wide use in situations wherea constant high dose rate is beingmeasured as they have a
greater operatinglifetime than standard Geiger-Müller tubes, which suffer from gas break down and are generally
limited to a lifeof about 1011 count events.Additionally,the Geiger-Müller tube cannotoperate above about 104
counts per second, due to dead time effects, whereas there is no similar limitation on the ion chamber.
Smoke detectors :
The ionization chamber has found wide and beneficial usein smoke detectors. In a smoke detector, ambient air is
allowed to freely enter the ionization chamber.The chamber contains a small amountof americium-241,which is

9. an emitter of alpha particles which producea constantion current. If smoke enters the detector, it disrupts this
current because ions strikesmoke particles and areneutralized.This drop in current triggers the alarm.The
detector also has a reference chamber which is sealed but is ionized in the sameway. Comparison of the ion
currents in the two chambers allows compensation for changes due to air pressure,temperature, or the ageing of
the source.
Medical radiation measurement :
In medical physics and radiotherapy,ionization chambers areused to ensure that the dose delivered from a
therapy unit or radiopharmaceutical iswhatis intended. The devices used for radiotherapy arecalled "reference
dosimeters", while those used for radiopharmaceuticals arecalled [[radioisotopedosecalibrators] - an inexact
name for radionuclideradioactivity calibrators,which areused for measurement of radioactivity butnot absorbed
dose]. A chamber will havea calibration factor established by a national standardsl aboratory such as ARPANSA in
Australia or the NPL in the UK, or will havea factor determined by comparison againsta transfer standard chamber
traceableto national standardsatthe user's site.
Geiger –muller (GM) counter :
The Geiger counter is aninstrument used for measuring ionizing radiation used widelyinsuchapplications as radiation
dosimetry, radiologicalprotection, experimental physics andthe nuclear industry.
It detects ionizingradiationsuchas alpha particles, beta particles andgamma rays usingthe ionizationeffect producedin a
Geiger–Müller tube; which gives its name to the instrument. Inwide andprominent use as a hand-heldradiationsurvey
instrument, it is perhaps one of the world's best-known radiation detectioninstruments.
The originaldetectionprinciple was discoveredin1908 at the Cavendishlaboratory, but it was not until the development ofthe
Geiger-Müller tube in1928 that the Geiger-Müller counter became a practical instrument. Since then it hasbeen verypopular
due to its robust sensing element andrelativelylow cost. However, there are limitations in measuring highradiationratesand
the energyof incident radiation.
A "two-piece"bench type Geiger–Müllercounterwithend-window detector

10. Principle of operation :
A Geiger counter consists of a Geiger-Müller tube, the sensingelement whichdetects the radiation, andthe processing
electronics, whichdisplays the result.
The Geiger-Müller tube is filledwith aninert gas suchas helium, neon, or argon at low pressure, to whicha high voltage is
applied. The tube brieflyconducts electrical charge when a particle or photonof incident radiationmakes the gas conductive by
ionization. The ionization is considerablyamplifiedwithinthe tube bythe Townsenddischarge effect to produce aneasily
measured detectionpulse, which is fed to the processinganddisplayelectronics. Thislarge pulse from the tube makes the G-M
counter relativelycheapto manufacture, as the subsequent electronics is greatlysimplified. The electronics also generates the
high voltage, typically400–600 volts, that has to be appliedto the Geiger-Müller tube to enable its operation.
Schematicofa Geiger counterusing an "endwindow"tubefor low penetration radiation.Aloudspeaker is alsoused for indication
Readout:
There are two types ofradiationreadout;counts or radiation dose. The counts displayis the simplest and is the number of
ionizing events displayed either as a count rate, commonly"counts per second", or as a total over a set time period(an
integratedtotal). The counts readout is normallyusedwhenalpha or beta particles are being detected. More complex to
achieve is a displayof radiationdose rate, displayedin a unit suchas the sievert whichis normallyusedfor measuring gamma
or X-raydose rates. A G-Mtube candetect the presence of radiation, but not its energywhich influencesthe radiation's ionising
effect. Consequently, instruments measuringdose rate require the use of an energycompensatedG-Mtube, sothat the dose
displayedrelatesto the counts detected. The electronics will applyknown factors to make this conversion, which is specific to
each instrument andis determinedbydesignandcalibration.
The readout can be analog or digital, andincreasingly, modern instruments are offering serial communications with a host
computer or network.
There is usuallyanoption to produce audible clicks representingthe number of ionizationevents detected. This is the
distinctive sound normallyassociated withhandheldor portable Geiger counters. The purpose of thisis to allow the user to
concentrate onmanipulationof the instrument whilst retaining auditoryfeedback onthe radiationrate.
Limitations:
There are two main limitations of the Geiger counter. Because the output pulse from a Geiger-Müller tube is always the same
magnitude regardless ofthe energyof the incident radiation, the tube cannot differentiate betweenradiationtypes. A further
limitationis the inabilityto measure high radiation rates due to the "deadtime" of the tube. This is aninsensitive period after

11. each ionizationof the gasduring whichanyfurther incident radiationwill not result ina count, and the indicated rate is
therefore lower thanactual. Typicallythe dead time will reduce indicated count rates above about 104 to 105 counts per
second dependingon the characteristic of the tube being used. Whilst some counters have circuitrywhichcancompensate for
this, for accurate measurements ionchamber instruments are preferredfor high radiation rates.
Gamma measurement—personnel protection and process control :
The term "Geiger counter" is commonlyusedto mean a hand-held surveytype meter, however the Geiger principle is in wide
use in installed "area gamma" alarms for personnel protection, andin process measurement and interlock applications. A
Geiger tube is stillthe sensingdevice, but the processing electronics will have a higher degree of sophisticationandreliability
than that usedina handheldsurveymeter.
Proportionalcounter :
The proportionalcounter is a type of gaseous ionizationdetector device usedto measure particlesof ionizingradiation. The key
feature is its abilityto measure the energyof incident radiation, byproducinga detector output that is proportional to the
radiationenergy;hence the detector's name. It is widelyused where energylevels of incident radiationmust be known, such as
in the discriminationbetweenalpha andbeta particles, or accurate measurement of X-rayradiation dose.
A proportional counter uses a combinationof the mechanisms of a Geiger–Müller tube andanionization chamber, and
operatesinan intermediate voltage region between these. The accompanying plot shows the proportional counter operating
voltage regionfor a co-axial cylinder arrangement
Diagramof a proportional counter:(a) region ofelectron drift and(b) region ofgas amplification
OPERATION :
In a proportionalcounterthefillgas ofthechamber is aninertgas whichis ionised by incidentradiation, anda quenchgas to ensureeach pulse
discharge terminates; a common mixture is 90% argon, 10% methane, knownas P-10. An ionising particleentering thegas collides withan
atom of the inertgas and ionises itto produceanelectron and a positively chargedion, commonly known as an "ion pair". As thecharged
particle travels throughthechamber it leaves a trailofion pairs along its trajectory, the numberofwhich is proportional to the energy ofthe
particle if itis fully stoppedwithin thegas.Typically a 1MeV stoppedparticlewill create about 30,000 ion pairs.

12. The chamber geometry and theappliedvoltage is suchthatin mostofthechamber theelectricfield strength is low and the chamberacts as an
ion chamber. However,thefield is strong enough to prevent re-combinationofthe ion pairs and causes positive ions to drift towards the
cathodeand electrons towards the anode. This is the "ion drift"region.In theimmediatevicinity oftheanodewire,thefield strength becomes
large enough toproduceTownsend avalanches. This avalancheregion occurs onlyfractions ofa millimeter fromtheanodewire, whichitselfis
of a very small diameter.The purposeofthis is to use the multiplication effect ofthe avalanche produced by each ion pair. This is the
"avalanche"region.
A key designgoal is thateach original ionising event due toincident radiationproduces only oneavalanche. This is toensureproportionality
betweenthenumber oforiginalevents andthetotal ion current. For this reason the appliedvoltage,thegeometry ofthe chamber andthe
diameter of the anode wireare critical toensure proportional operation.Ifavalanches start toself-multiply dueto UV photons as they do ina
Geiger–Muller tube, thenthecounterenters a regionof"limited proportionality"untilata higher appliedvoltage the Geigerdischarge
mechanism occurs with completeionisationofthe gas enveloping the anodewire andconsequent loss ofparticleenergy information.
Therefore, itcan besaid thattheproportionalcounter has the key design featureoftwo distinct ionisation regions:
1.Ion drift region:in theouter volumeofthechamber –creation ofnumber ion pairs proportional toincident radiation energy.
2. Avalancheregion: in the immediatevicinity oftheanode –Chargeamplification ofion paircurrents, whilemaintaining localisedavalanches.
The process of charge amplification greatly improves the signal-to-noiseratio ofthedetector andreduces thesubsequent electronic
amplification required.
In summary, the proportional counteris aningenious combination oftwoionisation mechanisms inonechamber whichfinds widepractical
use.
APPLICATIONS:
Spectroscopy :
The proportionality between the energy ofthechargedparticle travelling through the chamberandthetotal charge createdmakes
proportional counters usefulfor chargedparticle spectroscopy. By measuring thetotal charge(time integralofthe electric current) between
the electrodes, we candeterminetheparticle's kinetic energy becausethenumber ofion pairs createdby theincidentionizing charged particle
is proportional toits energy. Theenergy resolutionofa proportionalcounter,however,is limitedbecauseboth theinitialionization event and
the subsequent'multiplication'event aresubject to statisticalfluctuations characterisedby a standard deviationequalto the squarerootofthe
averagenumber formed.However,in practicethese arenot as greatas wouldbe predicted due totheeffect oftheempiricalFanofactorwhich
reduces these fluctuations.In thecaseofargon,this is experimentally about 0.2.
Photon detection:
Proportional counters are also usefulfor detectionofhigh energy photons, suchas gamma-rays,providedthesecan penetratetheentrance
window. They arealso used for thedetection ofX-rays to below 1 Kev energy levels, using thin walled tubes operating at or around
atmosphericpressure.
Radioactive contamination detection:
Proportional counters in the formoflargearea planar detectors areused extensivelyto check for radioactivecontamination onpersonnel, flat
surfaces, tools anditems ofclothing. This is normallyin theformofinstalled instrumentation because of thedifficulties ofproviding portable
gas supplies for hand-held devices. Theyareconstructedwith a largearea detection window madefromsuch as metallised mylar whichforms

13. one wall of the detection chamber andis part ofthecathode.The anode wireis routed in a convolutedmanner withinthedetector chamber to
optimise the detection efficiency.They arenormally used to detect alpha and beta particles, and canenablediscriminationbetweenthem by
providing a pulseoutput proportionalto the energy deposited in thechamber by each particle.They havea high efficiency for beta,butlower
for alpha. Theefficiency reductionfor alpha is due totheattenuation effectofthe entry window, thoughdistancefrom the surface being
checked alsohas a significant effect,and ideally a sourceofalpha radiation shouldbe less than10mm fromthedetector due toattenuation in
air.These chambers operateatveryslightpositive pressure aboveambient atmospheric pressure.The gas canbe sealed inthechamber, or can
be changedcontinuously, inwhich casethey areknown as "gas-flow proportionalcounters". Gas flowtypes have the advantagethat they will
tolerate small holes in the mylar screen which can occur in use, but they dorequirea continuous gas supply.
Scintillation counter :
A scintillation counter is aninstrument for detecting and measuring ionizing radiationby using theexcitation effectofincident radiation ona
scintillator material, and detecting theresultant lightpulses.
It consists of a scintillator whichgenerates photons inresponseto incidentradiation, a sensitive photomultiplier tube (PMT) which converts the
light to an electrical signal and electronics to process this signal.
Scintillation counters arewidely used inradiation protection, assay ofradioactivematerials and physics research because they can bemade
inexpensively yet withgood quantum efficiency,and can measureboth the intensity andtheenergyofincidentradiation.
showing incident high energy photonhitting a scintillating crystal, triggering thereleaseoflow-energy photons which arethen converted
into photoelectrons and multipliedin the photomultiplier
OPERATION :
When an ionizing particlepasses into the scintillator material, atoms areionized along a track.For chargedparticles the track is the path ofthe
particle itself. For gamma rays (uncharged), theirenergy is convertedto an energeticelectron via either the photoelectric effect,Compton
scattering or pair production. The chemistry ofatomicde-excitation inthescintillatorproduces a multitudeoflow-energy photons, typically
near the blueend ofthevisiblespectrum. The numberofsuch photons is in proportionto the amountofenergy depositedby theionizing
particle.Someportion ofthese low-energy photons arriveat thephotocathodeofan attached photomultiplier tube.The photocathode emitsat
most one electronfor eacharriving photon by thephotoelectric effect. This group ofprimary electrons is electrostatically acceleratedand
focused by an electrical potential so thatthey strikethefirst dynodeofthetube.The impact ofa singleelectron onthedynodereleases a
number of secondary electrons which arein turnacceleratedto strikethesecond dynode.Eachsubsequentdynodeimpactreleases further
electrons, and so thereis a current amplifying effectateachdynodestage.
Each stageis ata higher potential than the previous to provide the accelerating field. Theresultant output signalattheanodeis intheform ofa
measurablepulsefor eachgroupofphotons thatarrivedat thephotocathode, and is passed to the processing electronics. The pulse carries
information abouttheenergy oftheoriginal incidentradiation on the scintillator.The number ofsuchpulses per unit timegives information
about theintensityofthe radiation. In some applications individualpulses arenot counted,but rather only theaverage currentattheanodeis
used as a measureofradiation intensity.Thescintillator mustbe shielded fromallambientlight so thatexternalphotons do notswamp the
ionization events caused by incident radiation.To achievethis a thin opaquefoil, such as aluminizedmylar,is often used, thoughit must havea
low enough mass to minimize undueattenuation ofthe incidentradiation being measured.

14. Apparatus witha scintillating crystal, photomultiplier,and data acquisitioncomponents.
Detection materials :
The scintillatorconsists ofa transparentcrystal, usuallya phosphor, plastic (usually containing anthracene) or organicliquid (seeliquid
scintillation counting) that fluoresces when struck by ionizing radiation.
Cesium iodide(CsI) in crystalline formis usedas thescintillator for thedetection ofprotons andalpha particles. Sodium iodide(NaI) containing
a smallamount ofthalliumis usedas a scintillator for the detection ofgamma waves and zinc sulfide(ZnS) is widelyuseda s a detectorofalpha
particles. Zinc sulfideis the materialRutherford used toperform his scattering experiment. Lithium iodide(LiI) is used in neutron detectors.
Detector efficiencies :
Gamma
The quantumefficiency ofa gamma-ray detector (perunitvolume) depends upon the densityofelectrons in thedetector, and certain
scintillating materials, suchas sodiumiodide and bismuth germanate, achievehigh electron densities as a result ofthe high atomicnumbers of
some of the elements ofwhich they arecomposed.However, detectors based onsemiconductors,notably hyperpuregermanium,have better
intrinsic energy resolutionthan scintillators, andarepreferred wherefeasiblefor gamma-ray spectrometry.
Neutron
In the case of neutrondetectors, high efficiency is gained through the useofscintillating materials rich inhydrogen that scatter neutrons
efficiently. Liquidscintillation counters arean efficientand practicalmeans ofquantifying beta radiation.
Applications :
Scintillation counters areused to measure radiationin a variety ofapplications including hand held radiation survey meters ,personneland
environmental monitoring for radioactivecontamination, medical imaging, radiometricassay, nuclearsecurity and nuclearplantsafety.

15. Several products have been introduced inthemarket utilising scintillation counters for detection ofpotentiallydangerous gamma-emitting
materials during transport. These include scintillation counters designedfor freight terminals, border security, ports, weigh bridgeapplications,
scrap metal yards and contamination monitoring ofnuclear waste.Thereare variants ofscintillationcounters mountedon pick-up trucks and
helicopters for rapidresponsein caseofa security situationdueto dirtybombs or radioactive waste.[3][4]Hand-heldunits are alsocommonly
used.
Absorption spectroscopy :
Absorptionspectroscopy refers tospectroscopictechniques that measurethe absorptionofradiation, as a function offrequency or
wavelength, dueto its interactionwith a sample. Thesampleabsorbs energy, i.e.,photons,from the radiating field. Theintensityofthe
absorption varies as a function offrequency, and this variation is theabsorption spectrum. Absorptionspectroscopy is performed across the
electromagnetic spectrum.
An overview of electromagnetic radiation absorption. This example discusses the general principle using visible light as a sp ecific example. A white beam source –
emitting light of multiple wavelengths – is focused on a sample (the complementary color pairs are indicated by the yellow dotted lines). Upon striking the sample,
photons that match the energy gap of the molecules present (green light in this example) are absorbed in order to excite the molecule. Other photons transmit
unaffected and, if the radiation is in the visible region (400-700nm), the sample color is the complementary color of the absorbed light. By comparing the
attenuation of the transmitted light with the incident, an absorption spectrum can be obtained.
Absorptionspectroscopy is employed as ananalyticalchemistry tool todeterminethepresenceofa particularsubstancein a sampleand,in
many cases,to quantify theamount ofthesubstancepresent. Infrared and ultraviolet-visiblespectroscopy are particularly common in
analyticalapplications. Absorptionspectroscopy is also employedin studies ofmolecular and atomicphysics, astronomicalspectroscopy and
remote sensing.
An example of applying Absorption spectroscopy is the first direct detection and chemical analysis of the atmosphere of a planet outside our solar system in 2001.
Sodium filters the alien star light of HD 209458 as the hot Jupiter planet passes in front. The process and absorption spectrum are illustrated above. Image Credit: A.
Feild, STScI and NASA website.
Absorption spectrum :
A material's absorption spectrumis thefraction ofincidentradiation absorbedby thematerial over a rangeoffrequencies. Theabsorption
spectrumis primarilydetermined[1][2][3]by theatomic andmolecular compositionofthematerial. Radiation is morelikely to beabsorbed at
frequencies thatmatch the energy difference between two quantum mechanicalstates ofthemolecules. The absorption thatoccurs duetoa
transition between two states is referred toas an absorption lineand a spectrum is typically composedofmany lines.
The frequencies whereabsorption lines occur,as wellas their relativeintensities, primarily depend ontheelectronic and molecularstructureof
the sample. Thefrequencies willalso dependon the interactions between molecules inthesample, the crystalstructure in solids, andon

16. several environmentalfactors (e.g.,temperature, pressure, electromagnetic field). The lines willalsohavea widthand shapethatareprimarily
determined by the spectral density orthedensity ofstates ofthesystem.
Solar spectrumwithFraunhofer linesas it appears visually.
Basic theory :
Absorptionlines aretypicallyclassifiedby thenatureofthe quantum mechanicalchange induced inthemoleculeor atom.Rotational lines, for
instance, occurwhen therotationalstateofa moleculeis changed.Rotational lines are typically found inthemicrowavespectralregion.
Vibrational lines correspond to changes in thevibrational stateofthemoleculeand are typically found intheinfrared region.Electronic lines
correspond toa changein the electronicstateofan atom or moleculeand aretypicallyfound in thevisible andultraviolet region.X-ray
absorptions areassociated with theexcitation ofinner shell electrons in atoms. Thesechanges canalso be combined (e.g.rotation-vibration
transitions), leading to new absorption lines at thecombined energy ofthe two changes.Theenergy associated withthequantummechanical
change primarilydetermines thefrequency ofthe absorptionlinebut the frequency canbe shiftedby severaltypes ofinteractions.Electricand
magneticfields cancause a shift.Interactions withneighboring molecules can causeshifts.For instance,absorption lines ofthegas phase
molecule canshift significantly whenthat moleculeis ina liquidor solid phaseand interacting morestrongly with neighboring moleculesThe
width and shapeofabsorption lines are determined by the instrumentusedfor theobservation, thematerial absorbing theradiation andthe
physical environmentofthat material.It is common for lines to havetheshapeofa Gaussianor Lorentziandistribution. It is alsocommonfor a
line to be describedsolely by its intensity and widthinsteadofthe entireshapebeing characterized.The integratedintensity—obtained by
integrating thearea undertheabsorption line—is proportionalto theamountofthe absorbing substancepresent.The intensity is also related
to the temperatureofthesubstanceand thequantum mechanicalinteractionbetweentheradiation and theabsorber.This interactionis
quantified bythetransition momentand depends ontheparticularlower state the transition starts fromand the upper stateit is connected
to.The widthof absorptionlines maybe determinedby thespectrometerusedto record it. Aspectrometer has aninherent limit on how
narrow a lineit canresolveand so theobserved width may beatthis limit. Ifthewidthis larger than theresolution limit,then itis primarily
determined by the environmentofthe absorber. Aliquid orsolidabsorber, in which neighboring molecules strongly interactwith oneanother,
tends to havebroaderabsorption lines thana gas.Increasing thetemperature or pressure ofthe absorbing material willalso tendto increase
the line width. Itis alsocommon for severalneighboring transitions to beclose enough to oneanotherthat their lines overlapand theresulting
overallline is therefore broader yet.
APPLICATIONS :
Absorptionspectroscopy is useful inchemicalanalysis becauseofits specificity and its quantitativenature.The specificity ofabsorptionspectra
allows compounds tobe distinguished fromoneanother in a mixture, making absorption spectroscopy usefulin wide variety ofapplications.
For instance, Infraredgas analyzers canbe used toidentify thepresenceofpollutants in the air, distinguishing thepollutantfrom nitrogen,
oxygen, waterandotherexpected constituents.
The specificity alsoallows unknownsamples to beidentified by comparing a measured spectrumwith a library ofreferencespectra. Inmany
cases, itis possibleto determine qualitativeinformationabout a sampleeven ifit is notin a library.Infrared spectra, for instance,have
characteristics absorption bands that indicateifcarbon-hydrogenor carbon-oxygen bonds arepresent.
An absorptionspectrum canbe quantitatively related totheamount ofmaterial presentusing the Beer-Lambert law. Determining theabsolute
concentration ofa compound requires knowledgeofthecompound's absorptioncoefficient.The absorptioncoefficient for some compounds is
availablefrom referencesources, andit canalsobe determined by measuring the spectrumofa calibration standard witha known
concentration of thetarget.

17. The infrared absorption spectrum of NASA laboratory sulfur dioxide ice is compared with the infrared absorption spectra of ic es on Jupiter's moon, Io credit NASA,
Bernard Schmitt, and UKIRT.
Remote sensing:
One of the unique advantages ofspectroscopy as ananalyticaltechniqueis thatmeasurements canbe made withoutbringing the instrument
and sampleinto contact.Radiation thattravels between a sample andan instrumentwill containthespectralinformation, so themeasurement
can be made remotely. Remote spectralsensing is valuablein many situations.For example,measurements canbemadein toxic or hazardous
environments without placing anoperator or instrumentatrisk. Also, sample materialdoes not haveto bebrought into contact withthe
instrument—preventing possible cross contamination.
Remote spectralmeasurements presentseveralchallenges compared tolaboratory measurements.The spaceinbetweenthes ample of
interest andtheinstrument may also havespectral absorptions. Theseabsorptions canmask orconfoundtheabsorption spectrum ofthe
sample. Thesebackground interferences may also varyovertime.The sourceofradiationin remotemeasurements is oftenanenvironmental
source, such as sunlight orthethermal radiation froma warmobject,and this makes itnecessary to distinguish spectral absorptionfrom
changes in the sourcespectrum.
To simplify thesechallenges, Differentialopticalabsorption spectroscopyhas gainedsomepopularity, as itfocusses on differential absorption
features and omits broad-band absorptionsuch as aerosol extinction andextinction dueto rayleigh scattering. This methodis applied to
ground-based, air-borne and satellitebased measurements. Someground-based methods providethepossibility to retrievetroposphericand
stratospherictrace gas profiles.
Fluorescence spectroscopy :
Fluorescencespectroscopy (also knownas fluorometry or spectrofluorometry) is a typeofelectromagnetic spectroscopythat analyzes
fluorescencefrom a sample. Itinvolves using a beam oflight,usually ultravioletlight,that excites the electrons in molecules ofcertain
compounds and causes themto emitlight; typically, but not necessarily, visiblelight. Acomplementary techniqueis absorption spectroscopy. In
the special caseofsingle moleculefluorescence spectroscopy, intensity fluctuations from the emittedlight aremeasuredfrom either single
fluorophores, or pairs offluorophores.
THEORY :
Molecules havevarious states referredto as energy levels. Fluorescencespectroscopy is primarily concernedwith electronic andvibrational
states. Generally,thespecies being examinedhas a ground electronicstate (a lowenergy state) ofinterest, and an excited electronicstateof
higher energy. Withineachoftheseelectronicstates there are various vibrationalstates.
In fluorescence, the species is firstexcited, by absorbing a photon, from its ground electronicstate tooneofthevarious vibrationalstates in the
excitedelectronic state. Collisions with other molecules causetheexcited moleculeto lose vibrational energy untilitreaches the lowest
vibrational state oftheexcited electronicstate. This process is oftenvisualized with a Jablonski diagram.

18. The moleculethen drops down tooneofthe various vibrationallevels ofthe groundelectronic stateagain,emitting a photon intheprocess.As
molecules may drop down intoanyofseveral vibrational levels intheground state, the emittedphotons will havedifferent energies, andthus
frequencies. Therefore, by analysing thedifferent frequencies oflight emitted in fluorescent spectroscopy, along with their relativeintensities,
the structure of thedifferentvibrationallevels can bedetermined.
For atomicspecies, theprocess is similar; however, sinceatomicspecies do nothave vibrationalenergy levels,theemitted photons are often at
the samewavelength as theincident radiation.This process ofre-emitting theabsorbedphotonis "resonancefluorescence"and whileitis
characteristicof atomic fluorescence,is seenin molecularfluorescenceas well.
In a typical fluorescence (emission) measurement, the excitation wavelength is fixedand thedetection wavelength varies,whilein a
fluorescenceexcitation measurement the detection wavelength is fixedand theexcitationwavelength is variedacross a region ofinterest. An
emissionmap is measured by recording the emissionspectra resulting from a rangeofexcitation wavelengths and combining them alltogether.
This is a threedimensionalsurfacedata set: emissionintensity as a function ofexcitation andemissionwavelengths, and is typically depictedas
a contour map.
A simplistic designofthe components ofa fluorimeter
Applications :
Fluorescencespectroscopy is used in, among others,biochemical, medical, andchemicalresearchfields for analyzing organic compounds.
There has alsobeena report ofits usein differentiating malignantskin tumors frombenign.
Atomic FluorescenceSpectroscopy (AFS) techniques areusefulin other kinds ofanalysis/measurementofa compoundpresentin airor water,
or other media, such as CVAFS which is usedfor heavy metals detection, such as mercury.
Fluorescencecan alsobe used to redirectphotons, seefluorescent solarcollector.
Additionally, Fluorescencespectroscopy canbe adapted to the microscopic levelusing microfluorimetry
In analytical chemistry, fluorescence detectors areused with HPLC.
construction of Goniometer and Debye-scherrer camera :
A two-axis goniophotometer, in which the light sourceis kept stationary at the centre of the goniometer and thephotometer head is turned around the light source,
is constructedat TUBITAK UME for measuring the detector--based illuminance distribution of a compact light sourceand calculating luminous flux of the lumen. Two
differentlight source holders are designed for keeping light sourcesto be measured at their burning conditions. Figure 2aand b present photographs of designed
goniophotometerthat measure light sources at cap-down and cap-up positions,respectivelyadjustablelegs,which areusedfor keeping the goniometerin
balance andto operate itin vibration-freecondition.Amotorizing rotationstage 1 (RS1) having precisionhoming and accuratepositioning,
manufactured byNewport Corporation (URS150BCC), is usedto movetheL-shaped outer goniometer arminazimuthalangles(ϕ) from 0◦to360◦.
This arm is manufacturedofblack-anodized hollow metalprofile(60.0mm (W) ×40.0 mm(H)) having thickness of1.2mm.Asquare mounting-
plate (90.0 mm×90.0mm) having thicknessof3.0mm is mountedto the bottom centreofthearm forassembling theouter armto thecentre
of the RS1. Thesecondsquaremounting-plate(190.0mm ×190.0mm)having thickness of3.0 mm is screwedto theupper partoftheouter arm
so that to assemble the second rotationstage ofURS150BCC(RS2). This rotation stageacts the interiorarmofthegoniometer withinthe
polarangles (θ) from 0◦to 176◦.The interior arm, whichhasconfiguration ofL-shapeand used for assembling the photometerheadand scanning
of the test lamp within thepolar angles, is manufactured ofstandard black-anodizedhollowmetal profile(30.0mm(W) ×20.0 mm(H))having
thickness of 1.0mm. Asquaremounting-plate(90.0mm ×90.0 mm) having thickness of3.0mm ismounted totherearsideofthe armso that to
fix thecentreof theinteriorarmto the centreoftheRS2.Anappropriatebalancing weight is also addedto a shortersideof the interiorarmfor
obtaining balanced and un--friction movement in wholerotation

19. Debye-ScherrerMethod
a method for studying thestructureoffinely crystallinesubstances using X-ray diffraction(powdered-crystalmethod). Itwas namedafter P.
Debye andtheGerman physicistP. Scherrer, whoproposed this method in1916. Anarrowparallelbeamofmonochromatic X rays, upon falling
onto a polycrystallinesample andbeing reflectedby thecrystallites that makeup the sample, produces a number ofcoaxial, thatis,having one
the primary X ray serves as theaxis ofthecones. Theirvertices liewithin theobject under study, andtheapexangles aredeterminedaccording
to the Bragg-Vul’fcondition n λ =2d sinθ (wheren is a positiveinteger, λ is thewavelength oftheX rays, d is the distancebetweentheparallel
planes of thepoints ofthespacecrystallattice, and θ is theangle between thereflecting plane andtheincident beam). Thecone’s apex angleis
equal to fourtimes the valueofthe angleofreflection ø. Theintensity and position ofthe diffractioncones is recorded on a photographic film
or by one of the ionizationmethods .

21. THANK YOU