High-efficiency multi-wire tungsten moderator for slow positron source on SPring-8 hard synchrotron radiation

The paper provides results of numeric simulations of in-target positron pro duction process, processes of moderation, thermalization, diffusion, and re emission of positrons in high-efficiency multi-wire moderator made of tungs ten monocrystalline wire with regular wire spacing. The paper looks into dy namics of slow positrons in the moderator's vacuum gaps taking into account of external fields. The feasibility of using multi-wire moderator with non -regular structure multi-layer "wire felt" moderator is discussed. Accordin g to maximal estimate the multi-wire moderators can reach very high efficie ncy of fast-slow positron transformation similar to 10(-2). Using such mode rator the intensity of slow positron source on hard synchrotron radiation o f SPring-8 can reach the level of similar to 10(11)e(+)/s. (C) 2000 Elsevie r Science B.V. All rights reserved.