4.1 Pulse Recognition

1. Open the PRA program from the desktop. Go to ‘Settings’ → ‘Load Settings…’ and load the settings ‘Gamma Spectroscopy’, also from the desktop. Now you don’t have to worry about making sure the pulses are the right shapes or how to set the volume from the USB device to work with the sound card.
2. Go to View → Audio input, then go to Action → Start pulse shape acquisition. You should start to see pulses. They should have a relatively small amplitude and be relatively broad. You should see pulses of various heights because the incoming gammas have varied energies. Then you can go right to Action → Stop pulse shape acquisition, then click okay in the pop-up window. This step helps the instrument discriminate against misshapen pulses from multiple instantaneous detections.

4.2 Gamma Background

1. Make sure there are no sources near the detector. Go to Action → start data acquisition. Open the ‘View’ menu and choose ‘Pulse Height Histogram’. You should see a spectrum starting to populate.
2. Collect data for some set amount of time. Something like five minutes is probably sufficient.
3. Look at your background peak and make sure it is similar to the background data shown in Figure 5. Are you able to detect the peak from ?
4. The PRA software has a built-in peak-finder. It tries to fit anything that looks like a Gaussian. That’s the red curve in the peak-height histogram.

Figure 5: An example of the background gamma signal. Note the difficulty in determining the location of the peak.

4.3 Gamma Spectroscopy

1. Measure the spectrum of  for approximately the same amount of time as you did for the background. Look carefully at the spectrum and see if you can notice any of the structure from the ‘small’ or ‘medium’ detector features.
2. Measure the spectra of the rest of the available radioactive isotopes. Keep an eye out for structure in the spectra. Be sure that you are saving a file with each spectrum.
3. Measure the spectrum of the unknown source.
4. Use Python to fit the individual peaks of your known sources and use your data to calibrate the channels of the detector to reflect the energy that each channel measures.
5. Use your calibration data to determine the energy of the emitted radiation. Identify the unknown source based on its gamma spectrum.