Radiation safety issues for top-up operation at SPring-8

Electron beam injection to top-up the stored beam current during the operation of the synchrotron radiation beamlines of an 8 GeV class synchrotron radiation facility, SPring-8, has been conducted for about a year. A description of operations during this period and of the safety systems is described here. In order to carry out the top-up operation safely, the two goals were set. One is that the electron beam shall never be allowed to invade into the beamlines during the operation. The other is that the dose rate outside the shield tunnel due to beam loss shall never be allowed to exceed set limits during the operations including top-up. To achieve these two goals, suitable guidelines for accelerator operation were decided and the interlock systems were reconstructed. Under these conditions the safety analyses were performed, and it was found that top-up operation was executed without any trouble during this period.