Beam chopper for 750 keV LEBT of MMF linac

摘要

A travelling wave beam chopper for the 750 keV H/sup +/, H/sup -/ ions of the INR Linac is described. The chopper consists of a helix and a ground plate. The latter serves as a beam absorber which allows operation with a deflecting voltage below 4.5 kV. The chopper aperture can be varied from 2 to 6 cm, the plate length is 80 cm. The ion beam with unnormalized emittance /spl sim/8/spl pi/.cm.mrad is deflected and absorbed at the water-cooled ground plate. Available chopped beam pulse edges are less than 20 ns. A special shape of ground plate is used in order to depress the secondary electron emission arising from proton beam deflection. The deflecting plate structure and electronic circuits are presented, and theoretical and experimental results are discussed.