Design Considerations for Medical Proton Accelerators

The design requirements for current heavy-particle accelerators operated within a hospital to deliver radiation therapy must satisfy both clinical and research needs. Advances in dedicated beam delivery systems for clinical utilization and biological studies add requirements that previous accelerators did not have. Eight years experience using the Loma Linda University proton facility has emphasized that the most important requirements are safety, reliability, beam stability, low energy consumption, and efficiency of beam delivery to the treatment rooms. In the future, raster scanning techniques will add further demands on the control of beam energy, intensity, and position stability. Rapid and precise flexibility in changing beam parameters is essential for satisfying clinical needs; electronic rather than mechanical control is clearly preferable for clinical use. Biological research increases the need to expand the margins of some clinical requirements, such as beam size, intensity, and energy ranges. Both clinical and research activities require a totally integrated control system, beginning with the ion source and continuing through the accelerator and switchyard to multiple rooms and each beam delivery system therein. Accordingly, designing the clinical accelerator requires a highly orchestrated design effort, involving the entire facility. Detailed design requirements addressing these issues will be presented.