Multiple scattering measurements of energetic positrons in a thin gold polycrystal

As a step towards developing fast positrons as a probe to measure electron density and spin magnetic density in crystals, an experiment has been perfo rmed to measure the multiple scattering distribution of MeV positrons penet rating through thin polycrystalline films in both random and channeling dir ections. Image plate detectors were used to determine the angular distribut ion of emergent positrons. Image plate sensitivity was measured for high-en ergy positrons and for the background radiation encountered in our experime nt. The image plates showed good sensitivity and good linearity for MeV pos itrons. The multiple scattering results are compared with the theory for ra ndom direction and show disagreement due to crystal effects and quantum mec hanical considerations. (C) 2000 Elsevier Science B.V. All rights reserved.