Residual gas pressure dependence of beam loss

Miura, Akihiko ; Sako, Hiroyuki   ; Wei, G.; Ikegami, Masanori*

Residual gas in beam line essentially affects the beam loss and residual radiation on the accelerator. It is important to understand a cause of beam loss and relation between beam loss and residual gas pressure. We measured beam loss at the normal and worse vacuum condition in both SDTL and A0BT sections. The result indicates that the beam loss depends on the residual gas pressure and position where the beam loss occurs is about 20 to 30 meter downstream. This suggests the optimum position for installation of vacuum system to minimize the beam loss. In this paper, we describe the experimental result and its discussions. In addition, the cause of the beam loss is considered to be a stripping from negative hydrogen ions to neutral hydrogen atoms (H).