KJM5911 Lab Exercise 3 - Gamma Spectroscopy

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Revision as of 20:19, 14 October 2012 by Jonpo@uio.no (talk | contribs) (Experimental Procedure)

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UnderConstruction pict22.gifUnderConstruction pict17.gifWarning - under construction - you are welcome to read it, but it will change...

Learning Goals

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.


Experimental Procedure

  • 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

Safety Aspects