Spectral Distribution of Electron Flux in a Beta-radioactive Medium

Beta rays from a sample of P32 uniformly dispersed in a bakelite medium of size larger than the beta range produce secondary electrons as they slow down. The total flux including both primary and secondary electrons may be calculated from the Spencer-Fano-Attix theory and may be compared with the flux emerging from a channel into a vacuum cavity in the medium. Measurements made with a magnetic spectrometer show good agreement with the theory in the energy region above 0.35 MeV. Slight disagreement in the region 0.05 to 0.35 MeV is not considered serious because of approximations made to the exact theory and because of loss of spectrometer transmission at these lower energies.