Gamma Ray Spectroscopy Using a Na(Tl) Detector with a
Multi-Channel Analyzer
Lab Report Prepared by Sean Garfola
NUC E 450, Radiation Detection and Measurement
Section 003
Team Members:
Jacob Brumbach
Tom Gutowski
Dan Deckman
Date performed: 3/12/2013
Report due: 3/26/2013
Report turned in: 3/26/2013
March 26th, 2013 Gamma Ray Spectroscopy using MCA
Sean Garfola
Abstract
Introduction
In Experiment 5, we utilized a Single Channel Analyzer to develop a gamma ray spectrum for
Cs137 and Co60. Taking each count at different voltage windows is a long and tedious task, and
is impractical for recording the spectrum using many points. In this experiment, we utilize a
Multi-Channel Analyzer (MCA) which allows us to take counts for several hundred channels at
once, creating a more reliable, more accurate spectrum plot. The software we used for this
experiment was Genie 2000, a spectroscopy software that allows for measurement of photo
peaks, and calculates data for specific user-specified regions. The MCA in conjunction with
Genie allows us to accurately identify unknown radio nuclides through measuring reference
samples and matching the photo peaks of the unknown nuclide with known sources.
Theory
The Multi-Channel Analyzer is a computer based spectroscopy tool that can be used to identify
photo peaks for a nuclide, and thus be able to identify what an element is. Whereas the SingleChannel Analyzer can only measure the counts for a single window at a time, the Multi-Channel
Analyzer has the ability to measure several hundred channels at once while retaining a very low
dead time.
Equipment
The system illustrated in Figure 1 was used to conduct this experiment. It consists of a Nal (Tl)
detector connected to both the Amplifier and the High Voltage Power Supply. The MultiChannel Analyzer (MCA) and the Oscilloscope were both connected to the Amplifier, and the
MCA connected straight to the computer. Model and serial numbers for each piece of
equipment are labeled in Table 1.
NaI (Tl)
Detector
with
Preamp
O
I
Amplifier
Preamp Power
Oscilloscope
Personal Computer
O
I
Shelf Box
O
High Voltage Power Supply
I
Multiport II ADC/MCA
Figure 1- System Setup Schematic
2
Sean Garfola
March 26th, 2013 Gamma Ray Spectroscopy using MCA
Component
Serial Number
Model Number
Oscilloscope
CO 31348
TDS 1002
Multiport II ADC/MCA
11065394
MP2-1E
Amplifier
07033169
2022
NaI(Tl) Detector
10062743
802-2x2
Preamplifier
11064348
2007P
NIM Bin and Power Supply
00226056
4001C
Detector High Voltage Supply 07965668
3002D
Table 1- System components and their respective serial and model numbers
Procedure
The procedure used for this experiment followed Experiment 4 in the Spring 2013 NucE 450
Experiment 4 Laboratory Manual.
Data
Cesium Data
Peak Centroid (channel)
FWHM (channel)
FWTM (channel)
Area (counts)
Uncertainty:
X-Ray Photopeak
50
11.034
21.846
16783
±1.04 %
Reference Sample
3
Full-Energy Photopeak
890
56.129
103.242
55194
±0.56 %
March 26th, 2013 Gamma Ray Spectroscopy using MCA
Sean Garfola
2500
2000
1500
1000
500
0
0
200
400
600
800
1000
Unknown Sample
9000
8000
7000
Axis Title
6000
5000
4000
3000
2000
1000
0
0
200
400
600
Axis Title
4
800
1000
Sean Garfola
March 26th, 2013 Gamma Ray Spectroscopy using MCA
Analysis of Data
1. Describe the effects on the cesium-137 spectrum caused by varying the various MCA
controls, gain, and the high voltage settings.
2. Using the cesium-137 spectrum data produced in Section D of the Laboratory Manual
and printed out in Section E of the Laboratory Manual, evaluate the NaI(Tl) detector
used in your experiment. Include in this evaluation the detector resolution, peak
symmetry, and peak-to-Compton ratio. How do your results agree with those obtained
in Experiment 5 and with the theoretical values?
3. Using either the cesium-137 peak data obtained in Section D of the Laboratory
Manual or one of the cobalt-60 peaks obtained in Section F of the Laboratory
Manual, use the procedures given in class to calculate peak centroid location, gross
and net peak areas and their standard errors, FWHM, FWTM, and peak symmetry.
How well do your values compare with those obtained by the Genie 2000 program for
these values? Explain any differences.
4. Using the peak channel centroid data determined in Section F of the Laboratory
Manual and actual peak energies, evaluate the accuracy of the energy calibration
curve obtained in Section F. This requires you to fit a curve or line to your data.
5. Identify, by using a table, all the spectral features in cesium-137 from Section D of
the Laboratory Manual and the calibration spectrum in Section F. Include such items,
if seen, as full energy peaks, escape peaks, backscatter peaks, Compton continuums,
annihilation peaks, sum peaks, etc. Do their shapes and approximate energy or
channel locations agree with the theory given in class?
6. What was the unknown radionuclide? How were the identifications established? How
well did the calibration energies agree with the actual peak energies? Explain any
discrepancies in these values.
Conclusions
Suggestions for Future Work
References
Brenizer, J.S., and Jovanovic, I. et al, Radiation Detection and Measurement Laboratory
Manual, 2013.
5
Sean Garfola
March 26th, 2013 Gamma Ray Spectroscopy using MCA
Knoll, Glenn F., Radiation Detection and Measurement, 4 ed., John Wiley and Sons,
2010.
Shultis, J. Kenneth, and Faw, Richard E., Fundamentals of Nuclear Science and
Engineering, 2 ed., CRC Press, 2008.
Appendices
6