ENHANCED RADIATION SHIELDING BY SPACE-CHARGE FIELDS IN INSULATING SLABS

Space charge and the resulting electric fields accumulate in good insu lators during irradiation. In high quality insulators the resulting la rge electric field will alter the trajectories of high energy electron s. The altered trajectories result in decreased flux of high energy el ectrons in some regions of material, thus providing enhanced shielding effectiveness. We experimentally and theoretically investigate the ef fect with high energy electron irradiation (0.7-2 MeV) of planar polym ethylmethacrylate shields. For the slab shield cases which we investig ated, the shielding effectiveness is enhanced by as much as a factor o f 2. By allowing the electric field to extend into vacuum adjacent to the insulator, one obtains improved shielding effectiveness without ad ding mass. (C) 1997 American Institute of Physics.