Gamma double escape peak

Figure 12.7 presents the spectrum of Na. The single- and double-escape peaks due to the 2.754-MeV gamma are clearly shown. The single- and double-... 

Figure 12.7 A gamma spectrum showing single- and double-escape peaks (from Chap. 4.4.2 of Bertolini and Coche).

The double-escape peak efficiency is important if the energy of the gamma E is greater than about 1.5 MeV, in which case pair production becomes important. The energy of the double-escape peak, equal to P — 1.022 MeV, is used... 

Single and double escape peaks from the gamma-rays of greater than 1022keV can be expected. Not all were observed, however. 

DOUBLE ESCAPE PEAK An extra peak in a spectrum due to the loss of two photons of 511 key energy each during the absorption of a high energy gamma-ray. See escape peaks. 

ESCAPE PEAKS Extra peaks often Seen in a gamma spectrum that contains full-energy peaks greater than 1022 key. They are caused by the escape from the detector of one or two annihilation photons of 511 keV each. The single escape peak is at (full-energy -511) keV the double escape peak is at (full-energy -1022) keV. 

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. 

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