Improvements in cryogenic electronic devices

摘要

921,783. Superconductive circuits. GENERAL ELECTRIC CO. Aug. 31, 1959 [Sept. 2, 1958], No. 29626/59. Class 40 (9). [Also in Group XXXVI] A cryogenic device is so constructed that the control circuit produces only a narrow area of normal material across the width of superconductive gate material. Fig. 1 shows a construction of cryogenic device consisting of a base 1 of sapphire, quartz, glass or aluminium with an insulating layer of Al 2 O 3 carrying a superconductive film 2 of tin having a narrow portion 3. The control circuit consists of a further film of superconductive material 4 at right angles to film 2 and insulated from it by a silicon monoxide film 5. Material 4 has a higher critical temperature and field than film 2; lead is suitable. In operation, a current source applied across terminals 10 produces a field greater than the critical field of material 2. A small area of the latter across the neck 3 reverts to normal resistance. The normal material is then propagated through strip 3 by the Joule heat produced by the gate current which raises the temperature of the strip above the critical temperature. The critical temperature of film 2 should be close to that of the temperature of liquid between at atmospheric pressure so that the vacuum arrangements necessary are very simple. Dimensions of the device are: width of portion 3, 1-4 mms., tin thickness, .1 to 1 micron, length of portion 3, 1-10 mms. The thickness of film 4 may be of the order of thickness of film 2 and the width 1/ 10 to 1/ 1000 of the length of the narrow portion of film 2. Film 4 need not be superconductive. It may be an ordinary conductor or even have a high resistance so that the heat produced in it assists the action of the magnetic field. Alternatively, the reversion of the narrow band to normal may be effected by heat alone. Film 4 may not be insulated from film 2 and may merely be a continuation of it. Circuit (Fig. 6).-Superconductive film 2 short-circuits the supply from pulse source 32 feeding load 34. When a switching pulse is also applied from source 35 the film 2 becomes resistive and current passes through the load. The film then begins to cool. Provided the pulses from source 32 are not longer than the time taken for the material to become superconductive again the reversion of the material to the superconductive state does not affect the load current.