GB801038A - Improvements in or relating to electron beam tubes for stabilizing high voltages - Google Patents

Abstract

801,038. Permanent magnets. PHILIPS ELECTRICAL INDUSTRIES, Ltd. Jan. 21, 1955 [Jan. 22, 1954], No. 1896/55. Classes 35 and 38 (4). [Also in Group XL (a)] ] A voltage stabilizer tube comprises a gun for generating an electron beam and for projecting it tangentially into a deflecting magnetic field between two polepieces adjacent the arcuate edges of the polepieces, there being a region of high uniform magnetic field between the polepieces and an adjacent region of lower magnetic field, the beam thus being differentially deflected according to its velocity and so generating a varying output across a collector electrode system. The regions of high and low magnetic field are between and outside the polepieces respectively, Figs. 1, 2, and additional regions can be produced by saw cuts, slots or grooves 20, 21, Fig. 4, in the polepieces, the polepieces being energized by a permanent magnet. Thus by applying the source of unstabilized voltage between the cathode 6 and anode 7 the output voltage will vary in amplitude with voltage fluctuations and is compared with a reference voltage to derive an error voltage which is used to stabilize the unstabilized source of voltage. The beam passes along the edge of the semi-circular polepieces in Fig. 2 if the unstabilized voltage has the correct value, but otherwise is deflected into the region of high or low magnetic field (corresponding to increase of the unstabilized voltage) it is shared between collectors 13, 14 but if it passes through the region of high magnetic field (corresponding to decrease of the unstabilized voltage) it falls wholly on electrode 13. The reference voltage can be obtained from a potentiometer supplied by a source stabilized by a neon discharge tube. In Fig. 4, the two grooves plus curved edge gives three regions of large and three of small magnetic field and the voltage may be stabilized at any one of three values. The reference voltage can be the same or different for each .value, of stabilized voltage. Non-magnetic (copper) strips in the slots of the polepieces, and narrower than those slots, separate the three sets of electron paths, and the collector is a multiply slotted plate. In a modification there may be more than two slots or grooves in the polepieces and a plurality of collectors with separate output resistors. In a further form the collector 13 may be so constructed and arranged that as the voltage to be stabilized increases, the collector current (to 13) increases. Variations in the voltage to be stabilized due to temperature variations can be compensated by known means or avoided by the provision of temperature control devices. The invention is applicable to electron diffraction apparatus and to electron microscopes.