VARIATION OF BETA-RAY BACKSCATTERING WITH TARGET THICKNESS

Backscattering of beta rays from 204Tl and 90Sr- 90Y beta emitters has been studied as a function of target thickness for elemental targets of aluminum, copper, tin, and lead. Values of target thickness corresponding to saturation backscattering intensity are found to be independent of the nature of target material and geometry but depend strongly on beta end-point energy. From thin-target approximation, values of self-absorption coefficients and Z dependence have been obtained and are found to agree with semiempirical results.