The Radiation Safety Interlock System for Top-Up Mode Operation at NSRRC

The radiation safety interlock systems of the National Synchrotron Radiation Research Center (NSRRC) have been operated for more than a decade. Some modification actions have been implemented in the past to perfect the safe operation. The overall performance of this interlock system is reliable and satisfactory. The machine and its interlock system were originally designed to operate at decay mode. During decay mode injection, the safety shutters of beamlines are closed and the radiation loss is contained inside accelerator tunnel. Recently, some modification programs to change operation mode from original decay mode to top-up mode at NSRRC have initiated. For users at experimental area, the radiation dose resulted from top-up refilled injections when safety shutters of beamlines are opened will dominate. To ensure personnel radiation safety for top-up operation, the safety interlock upgrade and other action plans will be implemented. This paper will summarize the original design logic of the Safety Interlock System (SIS), its historical modifications and the new design logic to ensure radiation safety for top-up operation.