Efficiency simulations for the beam collimation system of the Japan Proton Accelerator Research Complex rapid-cycling synchrotron

Abstract

The 3 GeV rapid-cycling synchrotron (RCS) of the Japan Proton Accelerator Research Complex (J-PARC) project generates a 1 MW proton beam. In operation of a high intensity hadron accelerator, the most important issue is to minimize the uncontrolled loss. The RCS beam collimation system is designed for this purpose and the performance is confirmed. In the present design, the physical aperture is 1.5 times wider than the primary collimator aperture, so that the beam loss can be sufficiently localized under this condition. The influence of positioning errors of the collimators is also estimated. Furthermore, the dependence of the collimation efficiency on the impact parameter is investigated taking the growth process of the beam halo into consideration. As a result, the beam loss mechanism changes according to the impact parameter.