Effect of injection energy on residual dose around the charge exchange foil

Abstract

The rapid cycling synchrotron (RCS) of Japan Proton Accelerator Research Complex (J-PARC) and the accumulator ring (AR) of Spallation Neutron Source (SNS) can be used as high-power pulsed neutron sources. In both cases, the injection region becomes one of the highest activation areas in the ring. However, residual dose distributions have revealed that the highest activation points in the J-PARC RCS and the SNS AR are different in detail. The dose of the charge exchange chamber in the SNS is more than 100 times larger than that of the RCS though the ratio of beam power is less than 10. We investigated the reason of this difference by Geant4 and MARS, and the calculation results indicated that the difference was due to the dependence of the neutron and pion production rate on the injection energy.