Direct Comparison of the Penetration of Solids and Liquids by Positrons and Electrons

Abstract

A new experimental technique has been used to investigate the penetration of 1.88-MeV positrons and 1.77-MeV electrons in carbon, aluminum, copper, tin, lead, brass, Teflon, Plaskon, Lumarth, water, benzene, and toluene. These are the first such measurements for liquids. The results, which measure transmissions down to 2%, indicate greater transmission of positrons than electrons in solids and liquids, except in brass and Plaskon. The difference in transmission is 12% for Al, 35% for Pb, and 88% for toluene. The greater transmissions in aluminum and lead are in qualitative agreement with the scattering theory; however, there is at present no theoretical explanation for the measured differences in the rest of the solids and the liquids.