A radiotherapy particle emitter positioning device is provided. The positioning device includes first and second arcuate support frames, a mounting carriage and a drive arrangement. The first and second arcuate support frames each include a drive track arrangement defining an arcuate carriage guide path. The mounting carriage is configured for supporting the radiotherapy particle emitter. The mounting carriage is mounted to and supported by the support frames. The mounting carriage is connectable to the drive track arrangements and moveable along the carriage guide path. The mounting carriage also includes the drive arrangement. The drive arrangement engages the drive track arrangements for driving the mounting carriage along the drive track arrangements and the carriage guide path.
