A high resolution CRT employing electrostatic deflection

The useful screen diameter of electrostatically deflected cathode ray tubes is limited to relatively small values by deflection distortion. Devlopment of a high speed semi-permanent memory has created the need for a tube of moderate diameter with spot size uniformity appreciably better than that previously attained in the art. This paper describes an experimental tube with the requisite improvement in spot uniformity. It utilizes a tetrode electron gun designed for small spot size and low cathode loading. The tube is nominally operated at 10 kilovolts, a beam current of 10 microamperes, an average cathod loading of 150 ma/cm²and a current efficiency of 60%. Two focus electrodes in the lens provide astigmatism correction. The deflection system consists of curved plates optimized for high sensitivity (160 volts/inch) and low distortion.