Gamma spectroscopy

1. indigojoker

247

This is the gamma spectrum for Co-60 from the wikipedia site:http://en.wikipedia.org/wiki/Gamma_spectroscopy

though wikipedia might not be the best of sources, I was just wondering a few things. The two peaks around channel 700 and 800 are referred to as a "photopeak" or "Full Energy Peak." Does this mean that these peaks show the gamma rays that did not interact with atoms or electrons and went right to the detector?

Also, the Compton Edge refers to th peak at channel ~570. I read that the peak shows the highest energy that Compton scattering can occur at. With that said, does this mean that from channel 300 to 570 refers to the Compton scattering at different angles and I'm guess at channel 570, the scattering angle is zero?

and the peak at ~170 refers to the "backscattering peak" what exactly is that?

Also, one last thought. How does the gamma ray's interaction with matter effect this? like if i had a source behind a lead plate vs an aluminum plate, how would that effect the results of the gamma spectrum?

Last edited: Sep 30, 2007
2. Piewie

9

Does this mean that these peaks show the gamma rays that did not interact with atoms or electrons and went right to the detector?

Answer: Yes (they only interact in the detector and their energy is totally absorbed inside the detector)

With that said, does this mean that from channel 300 to 570 refers to the Compton scattering at different angles and I'm guess at channel 570, the scattering angle is zero?

Answer: Indeed, but channel 570 is caused by scattering angle 180° (not 0°) because in that case a maximal amount of energy is transferred to the detector. The resulting photon leaves the detector and the energy of it is therefore not detected.
Find the explanation on http://en.wikipedia.org/wiki/Compton_edge

The "backscattering peak" what exactly is that?

Answer: The backscatter peak is formed when the gamma ray undergoes a large-angle scattering (180°) in the material surrounding the detector and then is absorbed in the detector.

Answer to your last question: This would result in a spectrum with relatively more scatter and lower peaks (I mean the two Co-60 peaks). Thick metal plates might completely absorb most of the rays, but not all. Some of them will always get through wthout having interacted.

Last edited: Oct 2, 2007