GB1391102A - Charged particle beam scanner - Google Patents

Abstract

1391102 Discharge apparatus TEXAS INSTRUMENTS Inc 24 July 1972 [9 Sept 1977] 34528/72 Heading H1D A charged particle beam apparatus of the type wherein the flow of particles from an extended area source 11 to a target 15 is controlled by electrodes (not shown) arranged in finger patterns on the sides of apertured plate electrodes 12, is characterized by the provision of a collector plate 14 and a charge storage target arranged in that order between electrodes 12 and 15; preferably a further electrode 16 is provided between electrodes 13 and electrode 15 which may be a fluorescent screen. Electrodes 14 and 16 may be apertured plates with their apertures aligned with those of electrodes 12. Electrode 13 may comprise a metal mesh 13a with a dielectric coating 13b 1-5 microns thick. Alternatively it may comprise a metal plate with apertures aligned with those of electrodes 12 and coated with dielectric over its surface facing the cathode 11 and round the inside of the apertures (Fig. 6, not shown). A further construction comprises an apertured dielectric plate coated on the side away from the cathode and round the inside and the edges of the apertures with secondary emissive metal. In operation, signals are erased from the storage electrode 13 by reducing its potential below the secondary emission crossover potential and flooding it with electrons. During this mode electrode 16 is maintained negative thereby preventing excitation of screen 15 and so reducing its average brightness and increasing the contrast. In the write mode electrode 13 is raised above the cross-over potential and electrode 14 is somewhat higher so that negative charges are stored during the scanning. In the read mode, electrode 13 is brought near cathode potential (20v) and electrode 15 to 50 volts whilst the storage target is flooded with electrons so that electrons pass through it in accordance with the charges stored. As described the tube operates with electrons, but the use of positive or negative ions is also mentioned.