High-T c superconducting lenses for relativistic electron beams

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Abstract
New types of focusing lenses for relativistic electron beams (REBs) are proposed, and preliminary experimental results are obtained. The principle of the lenses is as follows: When REBs are injected into the small apertures of cylindrical superconducting lenses, self‐magnetic fields of the REBs are perfectly confined in a region between the REBs and the wall of the lenses. The REBs are focused by those compressed fields. The superiority of superconducting lenses was shown using foilless REB diodes which were operated at 0.15‐Torr Ne and had high‐Tc , cylindrical superconductor anodes made of Y‐Ba‐Cu‐O compounds (axial lengths of 30 and 145 mm and an inner diameter of 20 mm). The focused REBs (0.8 kA, 270 keV, pulse widths of less than 5 ns) had main beam diameters less than 2 mm.