Quasi–dc extraction of 70 keV, 5 A ion beam

An ion source that produces a high energy ion beam in quasi‐dc mode has been fabricated and tested. The significant features of the source are effectively cooled accelerator grids with properly shaped apertures and a carefully cooled douPIGatron plasma generator. To opeate the source quasi‐continuously, the heats dissipated in the accelerator grids and in the back plate of the plasma generator were suppressed below permissible values by attaining low pressure in the arc chamber. Under such condition, a 70 keV, 5 A, 10 s ion beam was obtained repeatedly without any deleterious problems. The measurement by photo beam monitor indicates no change of beam divergence during 10 s. The pressure change in the beam drift region during the pulse has also been investigated.