GB1215297A - Vacuum tube arrangements - Google Patents

Abstract

1,215,297. Cathode-ray tubes; transit-time tubes. NATIONAL RESEARCH DEVELOPMENT CORP. 5 Feb., 1968 [10 Feb., 1967], No. 6546/67. Heading H1D. In a discharge tube in which a portion of the electron stream from a photocathode 5 is trapped and transits back and forth through a drift tube 13 between a pair of mesh grid electrodes 8 and 9, gating pulses are applied to mesh grid 9 periodically permitting a sample of the stream to pass between deflection plates 16 to an output display screen 6 to provide a sequence of mutually displaced images of successive phases of a high speed event seen by the photocathode 5, the axial extent of the decelerating field provided by the electrode 9 being kept small, to minimize time dispersion effects. This result may be achieved by interposing between the drift tube 13 and the second mesh grid 9 a further, short, tubular electrode (21, Fig. 3, not shown) having, adjacent the mesh grid 9, a closed end provided with a slot, and held at a high positive potential with respect to the drift tube 13. Other, but less advantageous, arrangements referred to include the provision of a mesh grid across the end of drift tube 13, together with a reduction of the spacing of that tube from the mesh grid 9; and the provision of a further mesh grid, held at a small negative potential, disposed a fraction of a millimetre in the front of the mesh grid 9. The electron stream is accelerated by annular electrodes 14 and 17, and focused by solenoid 7. The tubular electrodes may be formed by conductive coatings on the tube envelope. The theory is discussed, and dimensions and operating data given.