Energy-Loss Spectra for High-Energy Electrons as a Function of Depth in an Absorber

Collimated beams of electrons with energies of 20 and 35 MeV were available from a betatron used for radiotherapy. A semiconductor detector was used to obtain the spectrum of energy deposits by electrons in its 450-jm thickness. The detector was placed behind Lucite to observe the change in spectra with depth. Features of the spectra were compared with results predicted by calculations. The qualitative influence of secondary electrons was noted.