GAMMA SPECTROSCOPY - OVERVIEW

[Pages:71]GAMMA SPECTROSCOPY OVERVIEW

The Identification of Gamma Emitting Radionuclides

6/1/2011

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Contents

General

Direct gamma Spec Analysis of Radionuclides Non-Gamma Emitting Radionuclides Non-Gamma Emitting Radionuclides ? Secular Equilibrium Non-Gamma Emitting Radionuclides ? Scaling Factor Spectroscopy vs. Spectrometry Advantages of Gamma Spec Disadvantages of Gamma Spec

Components of a Gamma Spectroscopy System

The Most Basic Components

Detector Types

Two "Functions" of the Detector Multichannel Analyzer Two "Functions" of the MCA

Major Components of the MCA

Amplifier

Analog to Digital Convertor

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Contents

Pulse Height Analysis General

The Spectrum

General The Big Picture Real Spectra Resolution

Energy Calibration General Peak Centroid Energy Calibration Curve

Identifying Unknown Gamma Emitting Nuclides

General

Gamma Library

Use of Computer

Common Problems

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Contents

Appendix Dead Time Gain Shifts Upper and Lower level Discriminators Single Channel Analyzer

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General

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General

Direct Gamma Spec Analysis of Radionuclides

? Radionuclides must emit gamma rays to be analyzed directly by gamma spectroscopy

? Gamma rays are like fingerprints: they have specific energies that can be used to identify the radioactive material.

? The next two slides show a somewhat random selection of common gamma emitting radionuclides.

? Many of these nuclides emit gamma rays at many different energies. Only the most important gamma rays are shown.

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General

Direct Gamma Spec Analysis of Radionuclides

Radionuclide

Na-22 K-40 Cr-51 Co-57 Fe-59

Co-60 Zn-65 Ga-67 Mo-99

Gamma Ray Energy (keV)

1274.5 511.0 (annihilation)

1460.8 320.1 122.1 1099.2 1291.6 1173.2 1332.5 1115.5 93.3 300.2 739.6

Gamma Intensity

1.0

1.8

0.11

0.098

0.855

0.565

0.432

1.0

1.0

0.507

0.357

0.16

0.128

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General

Direct Gamma Spec Analysis of Radionuclides

Radionuclide

Tc-99m Cd-109 (Ag-109m)

I-131 Ba-133

Cs-134

Cs-137 (Ba-137m) Ir-192 Tl-201 Ra-226

U-235

Am-241

Gamma Ray Energy (keV)

140.5 88.0 364.5 356.0 604.7 795.8 661.6 316.5 167.4 186.2 143.8 185.7 59.5

Gamma Intensity

0.89

0.037

0.81

0.60

0.976

0.854

0.85

0.829

0.10

0.036

0.1

0.54

0.36

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