GB523144A - Improvements in or relating to x-ray installations comprising a grid-controlled switching tube - Google Patents

Abstract

523,144. Control systems for space discharge apparatus. PHILIPS LAMPS, Ltd. June 28, 1939, No. 18839. Convention date, July 1, 1938. [Class 38 (iv)] Thermionic and like control.-In X-ray installations in which the X-ray tube 2 is switched on and off by a grid-controlled tube 3 on one pole, the other pole is simultaneously switched on and off by a " separating " tube 27, having a control electrode 30 the potential of which is dependent on the anode current of the tube 3. As shown, the tube 3 also stabilizes the voltage of the X-ray tube through the operation of a potentiometer, including resistances 6, 7, and an amplifier 4 the grid of which is connected between these resistances, the voltage on the X-ray tube is determined by adjustment of resistance 6. The control electrode 30 is connected to a point on resistance 7, so that, on opening a relay switch 16 removing a bias voltage 19 from the grid of amplifier 4, the current established in the potentiometer by the resulting starting of tube 3 causes the elimination of a bias voltage 31 from the electrode 30 and 'the starting of tube 27. This tube, as shown, is a gas discharge tube with incandescent cathode and has potential bushes connected to a high resistance potentiometer 32 and to prevent any gradual rise in potential of the cathode of the X-ray tube due to this potentiometer a comparatively low resistance 35 connects it to earth.