X-ray shielding estimations for rep-rate high power microwave accelerators

High power microwave research is moving into the high rep-rate regime and it will be common that an electron beam accelerator operates more than a million shots per year. As a result, accumulated bremsstrahlung X-ray produced by the electron beam collector is no longer negligible, and shielding is necessary for personnel safety. By using the BEAMnrc Monte-Carlo code, a typical collector for a ring beam usually used in HPM tube is simulated, which has beam voltage 1 MV, beam current 10 kA, pulse duration 100 ns and rep-rate 100 Hz. The results show the spectrum and spatial distribution of the X-ray generated at the collector. The attenuation factor of the X-ray is estimated from the simulation. The estimation of the skyshine radiation is also considered for the roof of the building.