Exposure from residual radiation after synchrotron shutdown

Personnel exposure from residual radiation present after an accelerator is shutdown for preventative or corrective maintenance is an important aspect that governs the manner in which a light ion facility can be used. This radiation is not only a safety issue for maintenance personnel but also can affect the patient throughput of the facility. Measurements were made with survey instruments around the synchrotron accelerator at the Loma Linda University Proton Treatment Facility and personnel dosimetry records of maintenance staff were reviewed. Results showed that the residual radiation in this facility design is very low, does not significantly impact maintenance staff safety, and has placed no restrictions on patient throughput.