Compton edge

In this case, the electron energy, Te will be maximum and Te = E1 — 0.255 MeV. If we consider all scattering angles 0, then the distribution of scattered electron kinetic energies is as shown in Figure 17.13. The sharp peak at Ey — 0.255 MeV is called the Compton edge. The minimum energy photon, E 225 keV, will be a noticeable... 

In the pulse-height distributions of Compton interactions of y-rays in scintillation detectors there are two prominent features usually present (1) the Compton edge, which corresponds to the maximum energy that can be transferred to an electron by the y-ray, and (2) the backscatter peak, which corresponds to the absorption of a photon which has been scattered through 180° in the material surrounding the detector. 

Fig. 5.12. Energy of Compton edge and backscattered peak for gammas of energy <0.7 MeV.

In a few cases, the peak that is used sits right on the Compton edge of another gamma ray. This overlap causes a severe problem in determining the background under the peak. The way to handle this problem is to treat it as a background interference. 

The Cr 320.0-keV gamma ray has three interferences, all of different types. Nd (319.7 keV) falls under the chromium peak and the correction is monitored by the Nd 531-keV peak. Cr itself is made from the reaction Fe (n,a)Cr k Ta has intense gamma rays of 222.1 and 100.1 keV, which pile up to give a peak at 222.1 keV that is not resolved from the chromium peak. Below this in the box is shown the 311.9-keV peak of Pa by which thorium is measured. This peak has under it a peak of 310.5 keV caused by the double escape from the 1332.5-keV gamma rays of Co (1332.5-1022 keV). The example of a Compton edge correction is that of the 889.6-keV peak of Sc , which lies on the Compton edge of the 1099.2-keV gamma ray of Fe . The photopeak of the 1099.2-keV peak serves as the monitor. 

Figure 12.20 Gamma-ray pulse height spectrum produced by NE 213 for a Na source. The two Compton edges are due to the 1.37-and 0.75-MeV gammas (from Ref. 7).

The Compton edge of a -y-ray peak falls at 0.95 MeV. What is the energy of the photon What is the energy of the backscatter peak ... 

There is a sharp drop at the end of the continuous energy spectrum of the Compton electrons, the Compton edge, distinctly below the full energy of the original photon. The electron energy reaches its maximum when the photon is totally back scattered 9 - 180°). The energy of such backscattered photons - Ey — is therefore at minimum, but for... 

MC Multiple Compton scattering region below the full energy peak and above the Compton edge. 

CE Compton edge about 220-250 keV below the full energy peak. It is a result of a single... 

Compton-event and corresponds to the highest energy left in the detector in a single scattering. The Compton edge is below the FEP with an energy of (1 -I- FJ255.5 keV), as calculated for free electrons. 

Compton edge is 170 keV below the single escape peak. Sometimes a back-scattered peak of one of the escaping 511 keV photons can be identified at 341 keV below the single escape peak (too weak to see inO Fig. 31.3). 

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