RCMS-a second generation medical synchrotron

The Rapid Cycling Medical Synchrotron (RCMS) is a second generation synchrotron. The transverse beam size is dominated by multiple scattering, if the incoming size is at the 1 mm level. It takes 10 overlapping beam pulses 0.5 cm wide to scan a tumor 5 cm wide with 1 % flatness. Small beam sizes are critical for inexpensive gantries, since small beams permit the use of small, lightweight, magnets which are economical to operate. The RCMS achieves small beam sizes by applying "strong focusing" optics to a small emittance beam. Gantries and nozzles, control systems and the design are discussed.