GB412427A - Improvements in and relating to x-ray systems - Google Patents

Abstract

412,427. R÷ntgen-ray tubes. BRITISH THOMSON - HOUSTON CO., Ltd., Crown House, Aldwych, London.-(Assignees of Kearsley, W. K. ; 1606, Randolph Road, Schenectady, New York, U.S.A.) July 20, 1933, No. 20533. Convention date, July 21, 1932. [Class 39 (i).] In an X-ray installation of the kind comprising an X-ray tube provided with a control electrode,surrounding the cathode and serving to inhibit flow of current by being charged negatively, and means for altering such charge in the positive direction to permit of flow of current through the tube, the potential of the control electrode 15, Figs. 1 and 2, is controlled by means including an impedance 43 in circuit with the main electrodes of the tube, with connections 44, 45 to a switch 46 for shortcircuiting the impedance, and a connection 32 whereby the fall of potential in the impedance is impressed on the control electrode. The tube is of the thermionic cathode type described in Specification 14892/13, [Class 39 (i)], provided with a tubular focusing electrode 8 surrounding the filament 7 and connected to one end thereof. A conductor 9 connected to the other end of the filament, and a conductor 101 connected to the member 8, are respectively connected by leading-in wires 11, 12 and leads 25, 26 to the low potential secondary of a step-down transformer 27, the primary of which is connected across supply mains 28, 29. A step-up transformer 35 with a switch 42 in its primary connections to the main has its secondary winding connected in series with a rectifier 38 and across a condenser 34, one side of the condenser being connected to the anode 5 and the other side to the junction of the resistance 43 and the control-grid connection 32. In operation, the requisite cathode heating current is obtained by adjusting a resistance 39, and the switch 42 is closed to charge the condenser 34, whereupon the closing of switch 46 causes the negative potential of the control electrode 15 relatively to the filament 7 to be reduced to zero, and the condenser 34 discharges at a high rate. Specification 239,220, [Class 39 (i)], also is referred to.