Shutter and Collimator with Rotating Radiation-Cooled Elements for the Beam from the Princeton A. V. F. Cyclotron

A beam collimator and shutter assembly has been designed and fabricated to define and interrupt the high maximum areal power density (30 kW/cm2) external beam anticipated for the Princeton A. V. F. Cyclotron. Pairs of graphite cylinders which rotate at 300 r/min about parallel axes a precisely adjustable distance apart, define the beam in each of the horizontal and vertical directions. A similar rotating graphite cylinder which is raised and lowered by an air cylinder operating in a fail-safe mode functions as the beam shutter. The power of the beam incident of these cylinders is dissipated by thermal radiation to surrounding water-cooled structures. Tests with an electron gun have shown that the slit cylinders can successfully dissipate a beam power of 2.2 kW with an areal density power of 10 kW/cm2 with no indication of deterioration or overheating of critical components. Calculations indicate power levels up to 5.0 kW with 50kW/cm2 areal density may be tolerated by these slits.