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Scancross: a new electron-optical device for investigation of low-intensive short-light phenomena

A new model of a Scancross-type streak tube is proposed. It can be useful in studies of short light flashes aimed at elucidation of not so much spatial as temporal light flux energy distribution. The Scancross tubes differ from their predecessors in that photoelectrons escaping a 40 mm photocathode surface are gathered in an aberration-free crossover due to an electrostatic field formed by a special `quasispherical' electron-optical system. At the crossover output, the electron beam aperture is compressed, whereupon the beam is accelerated and focused onto the phosphor screen plane. The focusing system field also performs an anisotropic transformation of a point crossover, i.e., compression of the latter's image on the screen in the scanning direction with simultaneous crosswise extension. A rectangular crossover image in the form of a 0.035 mm X 3 mm dash was obtained with the screen size of about 40 mm in the scanning direction. Sensitivity of the high-frequency deflection system was 25 V/mm. A strong compression of the electron beam emanated from the photocathode enabled a 4 orders of magnitude brightness magnification. Employment of such a streak tube allows a much more simple oscilloscope optical system for collection of radiation to be used, since there is no longer need for a small-dimension focusing spot on the photocathode as when using conventional streak tubes. This also simplifies detection of electromagnetic radiation in a very wide spectral range. Calculations suggest the possibility of extending the detection dynamic range by at least two orders using special signal procession accounting for light distribution both in the scanning direction and crosswise.