Development of a compact proton scanning system in Uppsala with a moveablesecond magnet

A scanned proton beam yields dose distributions that in most cases are supe rior to passively scattered proton beams and to other external radiation tr eatment modalities. The present paper gives a description of the scanning s ystem that has been developed at the Svedberg Laboratory (TSL) in Uppsala. The scanning technique and the technical design are described. The solution with a small pole gap of the magnets and a moveable second magnet results in a very compact scanning head, which can therefore be incorporated in a g antry of relatively limited size. A prototype was constructed that has been used to realize Various dose distributions with a scanned beam of 180 MeV protons at TSL.