GB830252A - Improvements in or relating to gas discharge apparatus - Google Patents

Abstract

830,252. Nuclear fusion reactors; discharge apparatus. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. Oct. 25, 1957 [Oct. 26, 1956], No. 32811/56. Classes 39(1) and 39(4). [Also in Group XL(c)] A gas discharge apparatus for research into thermonuclear reactions comprises a thick-walled toroidal vessel for containing ionised deuterium or a deuterium tritium mixture at low pressure, a primary winding arranged to be transformer coupled with the continuous gas discharge path constituting a secondary winding in the vessel and a toroidal winding on the vessel for establishing a magnetic field along the toroidal axis of the vessel. Referring to Fig. 2 the toroidal vessel T comprises two separable halves terminating in flanges 3 which may be joined together with electrical insulation interposed between the flanges. The torus is fabricated from a plurality of short cylindrical sections of aluminium having a thickness of about 1 inch to achieve the electromagnetic image forces necessary to stabilise the discharge. Transformer cores 4 encircle the torus at the positions of the flanges 3, the ionised gas in the torus forming the secondary of the transformer. On a diameter at right angles to the flanges 3, boxes 7 are provided which contain windows 8 in their top surfaces. and at their bottom surfaces communicate with exhaust manifolds and exhaust pumps. A pipe connection 147 serves to admit deuterium or tritium to the vessel at a pressure of 10<SP>-4</SP> to 10<SP>-3</SP> mm. of mercury, e.g. 0À125 microns. A toroidal stabilising winding 16 (shown on only one quadrant in Fig. 2) is arranged on the torus to provide an axial field, e.g. of 150 gauss, which serves to reduce the inherent instabilities of the gas discharge to a level at which collisions with the walls are no longer significant. The torus is provided with a lining, at least in the region of the seal at the flanges 3 to shield the seal from ion bombardment, and the lining preferably extends round the whole interior of the torus. As shown in Fig. 5 the lines comprises a number of segments 11 each comprising a pipe loop 28 to each side of which a cylindrical sleeve is welded. The outer edge of one sleeve is bifurcated and that of the other is offset, an insulating gasket 153 being provided between segments to provide electrical insulation and to form a partial vacuum seal so that the space between the lines and the torus may be maintained by pumps 155, Fig. 2, at a lower pressure than that within the lines. The segments 11 are supported by upper and lower adjustable electrically insulating and vacuum tight supports provided with means for passing a coolant into and out of the pipe loops 28. As shown in Fig. 5 the flanges 3 of the torus are separated by an insulating gasket 20, the joint being held together during operation by atmospheric pressure. Fig. 12 shows a schematic diagram of the electric circuit and the gas supply circuit of the apparatus. The gas in the torus is initially ionised by a radio-frequency voltage applied between liner segments 125 from a generator 126. The pulse to the transformer winding 6 is generated by changing condenser 12 from a 27 kV D.C. supply 13 and discharging it through the winding 6 by means of a switch 15 operated from a motor driven timer unit 104 to give a pulse every 10 seconds. The reverse current is limited by non-linear resistance 109 and by an ignition 163 which is fired on the reverse half-cycle by a pulse produced from the potentiometer 118. The torus is provided with a hook 124 to detect the ionisation of the gas and with a pick-up coil 110 to detect the main gas current. If the gas is insufficiently ionised the switch 15 is inhibited from closing, and if the gas current fails to rise sufficiently quickly the absence of a pulse from coil 110 causes ignition 113 to fire and discharge condenser 12. A saturable reactor 105 serves to limit the pre-arcing current through the switch 15. Bias windings 66 of the transformer 4 are connected to a D.C. supply 127. The vacuum system comprises four diffusion pumps 10 and eight pumps 155 backed by a common rotary vane pump 140 which can be connected direct to the torus by valve 143 for initial pumping out, and then isolated by a valve 141 to allow operation as a closed system. Gas from the high pressure side of pumps 10 is fed via a trap 150 to a booster pump 149 and thence to the reservoir 145; gas from the reservoir passes through a hot nickel tube gas leak 146 and pipe 147 to the torus. The cooling water supply to the pipe loops 28 of the liners is operated as a closed system by a pump 151 and leak exchanger 152. Specifications 817,681, 830,251, 830,253, 830,254 and 830,256 are referred to.