KJM5911 Lab Exercise 3 - Gamma Spectroscopy
After completing this exercise you should:
- Understand the processes by which gamma radiation is absorbed in the detector.
- Understand how the detector (and it's electronics) transform the absorbed energy from the gamma rays into electrical pulses which is continuously sorted according to pulse height and presented as a histogram (number of events vs. energy) - a "spectrum".
- Know the basic parameters of a spectroscopy system (spectrum, real time, life time, dead time, channels, etc.).
- Know the relationship between channel number and energy, how to derive this relationship ("energy calibration") and be able to evaluate it's uncertainty.
- Recognise the different parts of a gamma-ray spectrum.
- Know how "peaks" in the spectrum are analysed and understand the results (you should understand terms like: ROI, gross count, net count, peak fitting, FWHM, etc.). You should understand how the software calculate and subtract the background under the peaks.
- Know the relationship between number of counts and gamma-rays emitted by the source (and the disintegration rate). I.e. how to perform an efficiency calibration.
- Introduction to Gamma Radiation
- Gamma Spectroscopy and Detectors
- The Theory behind Calibration of a Gamma Detector
- Part 1: Measurements
- Get familar with the detector system and Maestro
- Make energy calibration for Maestr
- Measure various calibration point-sources (sealed)
- Measure various large-volum calibration sources
- Measure some unknown sources
- Part 2: Energy calibration
- Analyse the calibration spectra, for each "good" gamma-peak write down fitted centroid (channel number), net count, FWHM, fitted energy (from Maestro), and library energy (from Berkeley/Lund database).
- Make (in Origin) a plot of library energy as function of gamma-peak centroid (channel number). Then make a linear fit to the data.
- Use the linear fit parameters to calculate the energy /your calibration/ yields for each of your gamma-peaks.
- Part 2: Efficiency calibration