TESTING OF A NUCLEAR-REACTOR-BASED POSITRON BEAM

This paper describes the testing of a positron beam which is primarily based on copper activation near the core of a nuclear reactor and ext raction of the positrons through a beam guide tube. An out-of-core tes t with a Na-22 source and an in-core test with the reactor at reduced power have been performed. Both tests indicated a high reflectivity of moderated positrons at the tungsten surfaces of the moderation discs which enhanced the expected yield. Secondary electrons generated in th e source materials during the in-core test caused electrical field dis tortions in the electrode system of the system by charging of the insu lators. At 100 kW reactor power during one hour, positrons were observ ed with an intensity of 4.4 x 10(4) e(+) s(-1) of which 90% was due to positrons created by pair formation and 10% by copper activation.