GB794603A - Improvements in or relating to electron precision oscillographs - Google Patents

Abstract

794,603. Cathode-ray tubes. ARDENNE M. VON. Oct. 13, 1955 [May 20, 1955], No. 29149/55. Class 39(1). An electron precision, micro-or high-speedoscillograph for internal photography includes electron optical means for reducing the initial cross-section of the electron beam to provide a recording spot of 1 to 10 Á with a scanned area of more than 5À10<SP>6</SP> times that of the recording spot, in order to keep the errors of deflection for large angles within the order of magnitude of a few microns. The beam aperture αL at the spot may be about 5À10<SP>-5</SP> to 2À10<SP>-4</SP> radian for a recording surface of about 10 x 10 cm.<SP>2</SP>. A diaphragm with an aperture smaller than 5À10<SP>-4</SP> radians on the recording spot side is preferably disposed at, or adjacent to, the focus of the final lens. The diaphragm is preferably rendered free of electrostatic charges. It may be e.g. made of platinum, and adapted to be heated to a high temperature e.g. over 500‹C. There may be one or more electron lenses of short focal length for reducing the cross-over of the beam to a diameter of 1 to 10Á and an associated main lens for projecting the image on to the recording surface. The main lens is strongly screened. Electrostatic or magnetic lenses may be used. The dimensions and optical distances of suitable lenses are given. The length of the deflection field may be more than 15 per cent of the distance of the deflection system from the screen. High speed oscillograms are recorded on fine-grained photographic material for subsequent evaluation by means of a measuring microscope. A non-granular fluorescent screen may be provided for centering and focussing the instrument. Tables are given showing deflection sensitivities and deflection errors in practical cases.