Patent GB-854246-A (GB)
Title: Improvements in or relating to gas discharge apparatus
Inventor: CARRUTHERS ROBERT
IPC: H05H1/04
Filed: 1957-10-11
Abstract: 854,246. Nuclear fusion reactors. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. Oct. 9, 1958 [Oct. 11, 1957 ; Dec. 6, 1957], Nos. 31855/57 and 38098/57. Class 39(4). [Also in Group XL(c)] A gas discharge apparatus wherein a high current ring discharge is induced in gas in a vessel by the application of a short highvoltage pulse from a first energising circuit to a primary winding of a pulse transformer whereof the discharge forms the secondary winding, is characterised in that there is provided a second energising circuit adapted to produce a relatively low voltage output of relatively long duration and means for coupling the second energising circuit to the secondary winding in order to maintain the discharge current at a high value for a prolonged period when the high-voltage pulse has fallen to a low value. In the arrangement shown in Fig. 1 the pulse transformer T 1  energising the discharge has five primary windings fed in parallel from five identical energising circuits, of which only that energising the primary winding L 8  is shown in detail. Each of these circuits comprises a capacitor C 5  which is charged from a source 3 through a resistance R 6  and a high vacuum switch S 8  and is shorted by a safety switch S 10  and a resistance. Capacitor C 6  can discharge through winding L 8  through ignitron H 1  ; a second ignitron H 2  is connected between the cathode of H 1  and earth, and a capacitor C 7  and a mechanical switch S 7  are connected between the anode of H 1  and earth. A protective resistance R 7  damps any oscillations produced by the accidental breakdown of H 2 . Return connections from the five primary windings of T 1  are taken through the five secondary windings of transformer T 2 . The primary winding of T 2  is connected through a mechanical switch S 6  to a delay line comprising five capacitors, each provided with a safety shorting switch and resistances, and form inductances, ignitrons H 3  and H 4  being connected across the beginning and end of the line. The line can be charged from a source 16 through a switch S 9  and resistance R 9 . In operation, after the line and capacitor C 6  have been charged switch S 6  is closed and about 2 milliseconds later H 1  is fired to allow C 6  to discharge. When the current has reached its peak value and the voltage on C 6  has dropped almost to zero, H 2  is fired, shorting out C 6  to prevent the voltage across it reversing. About 2 milliseconds later switch S 7  is closed so that the current passes through it instead of through H 1  and H 2 . The peak current is now mantained for the time taken by the delay line to complete its discharge, after which H 4  is fired. Switches S 6  and S 7  are controlled by a timing unit 6 controlled by a master timer 7 which operates the charging switches S 8  and S 9 . H 2  is fired by a control circuit 8 tripped from potentiometer R 11 , and H 4  is fired by a similar control circuit. H 3  is provided to prevent the voltage on the delay line reversing and is fired by a similar control circuit. Capacitor C 7  is provided so that the firing of one of the five ignitrons H 1  will not prevent the others from firing. The repetition period of the discharges is variable between 50 and 150 seconds, and to keep the reactor conditioned between discharges a series of smaller discharges of a period of about 10 seconds may be induced by a lower energy energising circuit 15 feeding on additional primary winding on T 1 . The transformer Tz can be omitted by stowing the maintaining charge at low voltage in larger capacitors or by using a homopolar generator or other device giving a high current at low voltage. The build-up circuit and maintaining circuit could be arranged in parallel with respect to the primary winding of T 1  instead of in series. Specification 830,252 is referred to.