陽電子加速器リングでの二次電子マルチパクタリングによる非線形圧力上昇のシミュレーション

Abstract

A non-linear dependence of vacuum pressure on the beam current has been observed in the KEKB positron ring. The behaviour changes by the bunch fill pattern, the bunch current and the external magnetic field. A simple simulation on the non-linear pressure rise is proposed assuming that the behaviour occurs by the electron multipactoring. The simulation well reproduces the observed non-linear pressure behaviours. Since the beam size blow up, which is also observed in the positron ring, is similar to the non-linear pressure rise, the results would support an explanation that the beam size blow up is related to the electrons in the beam chamber.