IMPROVEMENTS IN OR RELATING TO A METHOD AND APPARATUS FOR STORING INFORMATION

摘要

1281991 Cathode-ray storage display tubes UNITED KINGDOM ATOMIC ENERGY AUTHORITY 13 June 1969 [21 June 1968 5 June 1969] 29845/68 and 28605/69 Heading H1D [Also in Divisions C4 and G4] A method of storing information comprises irradiating a phosphor (e.g. single or polycrystalline KI : T1, and 1 mm. thick) with radiation of energy content sufficient to damage the phosphor so as to affect its luminescent properties, irradiating selected regions with radiation of higher energy content so as to anneal at least partially any damage at said regions, the distribution of annealed and damaged regions being representative of the information to be stored. Radiation damage may be by electrons or protons for example, reducing subsequent luminescence by more than 1/ 100 , and annealing may be by electrons from the same source as the damaging electrons by heating to above a few hundred ‹ C., e.g. 400‹ to 500‹ C. In binary digital data storage, a 20 kV., 6À4 W., 2 Ám. diameter electron beam damages in 1/ 5 Ás. Annealing times may be reduced by 1/ 100 by annealing only half the defects. With cathodo- and photoluminescent phosphors, readout may be by an even lower intensity electron beam from the same gun or from U.V. light respectively, e.g. light from source (IT) on to c.r.t. screen (12) (Fig. 2, not shown). The electron beam may be scanned and modulated between the damage and anneal levels. Annealing may be achieved without raising above the m.p. but partial melting produces a faster anneal in which case a thin high melting point metal foil is on the exposed phosphor surface to retain molten phosphor. Annealing by increased defect mobility as well as a purely thermal mechanism is considered. A photocathode, preferably in another tube, e.g. photomultiplier tube (5) with CsSbO photocathode (6) (Fig. 1, not shown) may be combined with the c.r.t. with a 6 mm. square, 1 mm. thick phosphor layer for storing 107 bits of digital information. The three electron beams currents are 1, 200 and 5000 Š and 15 kV. producing a 1 Ám. penetration depth. Access and writing may be sequential or random and analogue storage is referred to the luminescent intensity at a given dose being a linear function of current, and at given current, an exponentially increasing function of dose. The impurity concentration is especially important in the latter case, a polycrystalline compact made by pressed die technique being preferable.