BRE.M%~HLUNG RADIATION EFFECTS IN RARE EARTH I’E~NENT h’lAGNET,$

.Advances in rare earth permanent magnet (REPM) technology have made possible new applications. Two such applications are the use of permanent magnetic lenses for accelerator and beam transport systems, and the expanding use in undulators and wigglers ef synchrotron radiation and free electron laser systems. Both applications involve potential exposure of REPMs to high radiation fields. WC have investigated the radiation hardness of several different varieties of REPMs up to 2 Grad of absorbed dose from a mixed Sm2Cot7. Nd,Fe,,B and an experimental REPM. Pr,,Fe,,$, from several di= f the samples irradiated, Sm,Co,, proved to be the most resistant to bremsstrahlung radiation, However, details of manufacturing techniques produced significantly different results. We observed that REPMs of nommally identical stoichiometric composition from different manufacturers did not show the same rate of remanence loss. We present details of our experiment, absorbed dose modeling and a summary of radiation effects measurements of which we are aware. Our study of these radiation damage experiments leads us to the empirical observation that the order of radiation hardness is Sm:Co,,, SmCo, and Nd,Fe,,B, regardless of the source of radiation, i.e., gammas, electrons, protons or neutrons. 1