Performance of the True Coincidence Correction Method in GammaVision

Some nuclides emit multiple gamma rays or X-rays when they decay to the ground state. If these gamma rays and X-rays are emitted essentially at the same time, it is possible that multiple photons will be detected at the same time in the detector and appear as one full-energy peak in the spectrum. This is known as “Cascade” or “True Coincidence” summing. The most common example of this is Co, where the 1173 and 1332 keV gamma ray peaks are emitted in cascade and can sum to become the 2505 keV gamma ray peak. This True Coincidence Summing has two effects, one is the reduction of the net peak count in the individual component peaks in the cascade. The second is the creation (or increase) of the extra peaks in the spectrum of the summation of the individual peaks. Both of these can cause the spectrum analysis to give erroneous results.