GB624332A - Improvements in or relating to x-ray tubes and energising systems therefor - Google Patents

Abstract

624,332. Supply systems for X-ray tubes; condenser arrangements. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. July 3, 1947, No. 17544. Convention date, May 25, 1940. [Class 38 (iv)] [Also in Groups XL (a) and XL (c)] Fig. 5 shows a supply system for an X-ray tube. The condensers 36, 39 are charged by rectifiers 35, 38 but cannot discharge through the X-ray tube 5 owing to the spark gaps 37, 46. Condenser 62 is charged by rectifier 69 and is connected across valve 54 which is non- conducting owing to the large bias from battery 56 applied to its grid. When switch 59 is opened, valve 54 conducts, discharging condenser 62 and generating a pulse in the primary of transformer 43. The pulse from the secondary of this transformer breaks down spark gap 46 which in turn enables the gap 37 to be broken. The H.T. thus supplied to the tube initially falls between the cathode 13 and auxiliary electrode 14 and the high potential gradient causes field emission of electrons from the cathode. This causes current to flow in resistance 47 so that the auxiliary electrode drops almost to cathode potential and the discharge transfers to the main anode 8. A resistance 48 is provided in parallel with the tube and serves to control the breakdown voltage of gap 37 so that it is always uniform. The entire discharge may take about 2 microseconds and currents of several hundred amps may be used.