Scintillation Lab - Introduction to Gamma Spectroscopy

Purpose

The purpose of this lab is to learn to operate a scintillator detector and recognize the peaks generated with its use.

Relevant Reading

Tsoulfanidis: Chapter 6, Chapter 9, Chapter 12 pages 389-398.
Knoll: Chapter 8, Chapter 9 pages 265-275 and Chapter 10 pages 307-323.

Equipment

Scintillation Detector (NaI) NaI(Tl) detector Information
MCA Card in Computer (If applicable) or Computer with USB Ports
Genie 2000 Genie 2000 Software Information

You will need to bring a USB Jump Drive to save your Data on. You can not leave it on the lab computers.

Some of the data used to analyze the peaks is presented in a report that is difficult to export in an Excel format. A program has been written to strip out the counts data from the file generated by the Genie 2000 software. This program is called datafltr. The code and a brief instruction sheet will be posted to Blackboard. If you wish, feel free to use this program to help streamline the process of analyzing the data.

Basic Setup

An NaI Detector with PM tube will be provided. The detector will be hooked up to a Multichannel Analyzer (MCA).

Please note that the detector will be using a high-voltage power supply provided by the MCA card. The voltage, which may be set through the MCA software interface, should be set at around 750 volts. The voltage is based on the type of detector and can range from 750 to 1100 volts, ask your lab instructor which voltage is correct for your detector. This will remain constant throughout the lab.

Confirm setup of the detector system and MCA. Make sure the MCA is set to the maximum number of channels allowed by the software (should be either 1024 or 2048 channels).

Experimental Procedure

Place the 133Ba and 60Co sources on top of the 137Cs source. Take a ten minute count. Calibrate the spectrum and save the data.

Take the 137Cs source and place it in front of the detector/PM tube. Take a ten minute count. Save the data generated by the count.

Place a multi-isotope Eu source in front of the detector. Take a ten minute count. Save the data.

Identify the peaks in the spectrum. For each peak, set the Region of Interest bars (ROI) around them and determine the counting area under each peak. Save each ROI file separately.

Remove the Eu source and take a ten minute count to determine background counts. Please note any environmental effects that might influence this count. Save the data.

Using the two sets of data gathered in steps 3 – 5, find the net counting area peak for each peak. Calculate the efficiency for each peak. Make a plot of efficiency vs. energy.

For each peak of the Eu source (focus on 152Eu), find the FWHM and plot FWHM vs. peak energy.

Plot the multi-source spectrum in Excel using data pulled from the data generated by the NaI detector.

Plot the 137Cs spectrum and distinguish all characteristics of the spectrum – photo peak, Compton Continuum, backscatter peak etc. READ YOUR TEXT to make sure you report on the appropriate features.

Your report should contain a description of the theory behind the detector system in this lab, any equations used and a discussion of how the spectrums generated do or do not match up to theoretical models. When writing equations in your lab report, please use an Equation Editor such as Microsoft Equation Editor 3.0 or something similar. Your goal for this lab report is to show the instructor that you have a firm grasp of scintillator detector theory and can relate that theory to real measurements.