Gamma Spectroscopy Measurement Technique

Gamma spectroscopy is a radiochemistry measurement technique that determines the energy and count rate of gamma rays emitted by radioactive substances. A detailed analysis of gamma ray energy spectrum is used to determine the identity and quantity of gamma emitters present in a material.

The apparatus used in gamma spectroscopy includes a detector, a pulse sorter (multichannel analyzer) and associated amplifiers and data readout devices. The detector is typically a sodium iodide (NaI) scintillation counter. The figure below shows a block diagram of a gamma spectrometer.

The multichannel pulse height analyzer is a device that will separate pulses based on pulse height. Each energy range of pulse height is referred to as a channel. The pulse height is proportional to the energy lost by a gamma ray. The separation of the pulses, based on pulse height, shows the energy spectrum of the gamma rays that are emitted. Multichannel analyzers normally have 100 to 200 channels over an energy range of 0 to 2 MeV. The output is a plot of pulse height and gamma activity as illustrated in the figure below:

By analyzing the spectrum of gamma rays emitted, the user can determine the elements that caused the gamma pulses.

Also read: Radio Frequency (RF) and Microwave Spectral Analysis