Tapered Tube Lenses for Intense Electron Beams (Supertrons)

Supertrons, which were previously proposed and demonstrated to function as lenses for intense electron beams (310 keV, 1∿3 kA, a few nanosecond pulse widths), were experimentally evaluated in focusing ability for a tapered tube. The tube was made of Bi-compound and was 20 and 10 mm at the inlet and the exit, respectively, with an axial length of 31 mm. The electron beam focused was 1.7 kA and 2 mm in diam at the exit of the tube. The focusing ability of the tapered tube was better than those of straight tubes which were previously reported.