Measurement of the occupation lengths of channeled 17-MeV electrons and 54-MeV electrons and positrons in silicon by means of channeling radiation

The occupation length of channeled 17-MeV electrons and 54-MeV electrons and positrons in silicon has been determined by measuring the intensity of the emitted channeling radiation. For 17-MeV electrons the measured 1/e occupation lengths are approximately 16 μm for the (100) plane and 20 μm for the (110) plane. For 54-MeV electrons the occupation lengths are 24 μm for the (100) plane and 36 μm for the (110) plane. For 54-MeV positrons the occupation lengths are 40, 60, and 42 μm for the (100), (110), and (111) planes, respectively. In all cases, the bound-state populations remain equal relative to one another throughout the thickness of the crystal. Multiple scattering appears to modify positron channeling radiation spectra slightly, but multiple scattering has no perceptible influence upon electron channeling radiation spectra.