Top-Off Injection and Higher Currents at the Stanford Synchrotron Radiation Lightsource

The Stanford Synchrotron Radiation Lightsource (SSRL) at the SLAC National Accelerator Laboratory (SLAC) is currently working on increasing its stored current from originally 100 to 500 mA. SSRL worked with the SLAC Radiation Protection Department on mitigating the possible radiological hazards from these upgrades. This paper describes the related analyses, new safety systems, and beam tests. The top-off injection mode (injection with beamline stoppers open) is essential for operation at high currents. The radiological consequences of various situations were analyzed, a new Beam Containment System (BCS) was implemented, and radiation surveys were performed during tests. Since March 2010, all beamlines have been operating in top-off mode. Operation with higher beam currents was also analyzed for radiological hazards, and a new Beamline BCS was installed. The storage ring is now operating with 200 mA during user runs, and tests are ongoing with higher beam currents. Soon the power of the injection current will also be raised from 1.5 W at present to 5 W maximal.