Scintillator Detectorand

Gamma Radiation Detection

Kailash Dhaker (09024)

MS Batch 2009

Department of Physical Science

IISER Bhopal

IntroductionGamma Radiation

Interaction of Gamma Radiation with Matter

Scintillator Detector

• NaI(Tl) Scintillator Detector

Experimental Procedure and Observations

Conclusion

References

Gamma RadiationWhen a nucleon is in a high-energy orbit while a low-

energy orbit is unfilled, it can jump to the lower-energy orbit with the energy thereby released coming of as a quantum of electromagnetic radiation, which we call a gamma ray.

These g-rays can be detected, and their energies can be measured, using several types of detectors

Interaction of Gamma RadiationA gamma ray can interact with matter in three ways-

1. Photoelectric Interaction

2. Compton Interaction

3. Pair Production

Scintillator Detector

Detector absorb incident radiation and emit there energy (photon) in the form of light

These photons are then used to release avalanche of electrons by a photomultiplier tube which can be detected to give the output pulse

Scintillator DetectorSequence of events:

1. Scintillator:

In a solid crystal, the incident radiation ionizes some of the atoms at the lattice sites knocking out electrons which on recombination releases low energy radiation (300-500 nm)

Scintillator Detector2. Photomultiplier Tube: These photons are then

directed towards the photomultiplier tube (PMT) which releases photoelectrons from the photocathode. They are then accelerated by the electric field and strikes to the dynode surface (from which more electrons can be easily knocked out). The process of striking the several dynode surfaces continues until they are collected by the anode giving it a charge which flows to the capacitor to give the output voltage.

Scintillator Detector

NaI(Tl) Scintillator Detector[Ref: http

://www.thefullwiki.org/Basic_Physics_of_Nuclear_Medicine/Scintillation_Detectors]

Scintillator Detector Two types of scintillator material is used

1. Organic: Contain molecules like Benzene, Naphthalene or Anthracene

2. Inorganic: Crystals like NaI and CsI is used as scintillator material with some impurity (as activator)

NaI(Tl) Scintillator Detector

NaI(Tl) is a second type (inorganic) scintillator detector

Sodium Iodide (NaI) crystal with small amount of Thallium (Tl) as an impurity

Tl is present as Tl+ (activator) in place of Na+ in the lattice

NaI(Tl) Scintillator Detector

NaI(Tl) is a second type (inorganic) scintillator detector

Sodium Iodide (NaI) crystal with small amount of Thallium (Tl) as an impurity

Tl is present as Tl+ (activator) in place of Na+ in the lattice

Experimental ProcedureExperimental Setup

1. NaI(Tl) Scintillator Detector

2. Radioactive Samples

3. Computer setup with pre-installed software to obtain

Gamma Spectrum

Energy calibration using Na-22 sample

Gamma Spectrum were obtained for Cs-137 and Mn-54

ObservationsGamma Ray Spectrums of Cs-137 and Mn-54 were

obtainedFrom Gamma Ray Spectrum, Gamma ray energy were

calculated and compared with literature value

Gamma Ray Energy of Na-22 (Calibration)

Gamma Ray Energy for Peak-1 Gamma Ray Energy for Peak-2

510 keV 1272 keV

ObservationsGamma Ray Spectrum of Na-22

(Calibration)

ObservationsGamma Ray Spectrum of Cs-137

ObservationsGamma Ray Spectrum of Mn-54

ObservationsGamma Ray Spectrum of Ba-133

Observations

Sample Experimental Value Literature Value

Cs-137 660 keV 661.64 keV

Mn-54 811 keV 834.83 keV

Ba-133 Peak-1 87 keV 80 keV

Peak-2 374 keV 356 keV

Gamma Ray Energy for Cs-137 , Mn-54 and Ba-133 (Calculated from Spectrum)

Conclusion

Gamma Ray Energy obtained from gamma spectrum is quit close to literature value of

gamma energy for Cs-137, Mn-54 and Ba-137

ReferencesGamma Radiation-

Bernard L Cohen – Concepts of Nuclear Physics

Scintillator Detector-

Glenn F. Knoll, Radiation Detection and Measurement

Literature value of gamma energy –

www.csupomona.edu/~pbsiegel/bio431/genergies.html

Thank You…