Selective erasure and non-storage writing in direct-view storage tubes

A new concept in direct-view half-tone storage tube operation has been developed, based on the use of a special storage target which exhibits dual charging phenomena. One phenomenon, secondary emission, charges the storage surface positively, while the other, bombardment induced conductivity, charges it toward the backplate potential, which in this case is negative. Selection of the charging effect, and therefore the charging direction, is determined by the incident beam energy. At lower beam energies the secondary emission effect predominates, while at higher energies bombardment induced conductivity prevails. This is in contrast to the operation of conventional direct-view half-tone storage tubes which depend only on secondary emission for both positive and negative charging. With such a mode of operation, it is not practical to achieve either selective erasure or non-storage writing. Selective erasure is the ability to rapidly erase one or more of the smallest written elements as distinct from erasure of the entire storage target. By non-storage writing is meant the presentation of cathode-ray information on the viewing screen without disturbing the written or erased areas of the storage target.