Video Storage by Secondary Emission from Simple Mosaics

It has been found that the derivation of a video signal in an iconoscope by scanning does not involve bringing each element of the mosaic into an electron-exchange equilibrium while under the beam. Consequently, the mosaic charge is erased, not at the instant of passage of the beam, but continuously by the rain of low-velocity electrons. An output-signal attenuation of less than 1 per cent per scan has been observed. A factor of 10 increase in the number of removal scans per unit time after the creation of the original stored signal has yielded no observable change of attenuation per unit time. Only for storage tubes having a beam-density to capacitance ratio at least 100 times that of the iconoscope can a scanning-exchange equilibrium with charge obliteration be observed. In general, the mosaic escape current constituting the signal can be represented as a linear function of both the beam current and the potential of the mosaic element. The complex stored signals resulting from square-wave grid modulation of an ordinary oscilloscope used as a storage tube are explained in terms of electron loss at the instant of scan, preceded and followed by the gain of secondary electrons from the near-by beam.