Patent GB-886129-A (GB)
Title: Improvements in cryogenic electron device and circuit
IPC: G11C11/44
Filed: 1959-10-29
Abstract: 886,129. Semi-conductor devices. GENERAL ELECTRIC CO. Oct. 29, 1959 [Oct. 30, 1958], No. 36744/59. Class 37. [Also in Group XXXIX] A cryogenic device has a first superconductor having a first transition field, a second superconductor having a higher transition field and a third providing a current path around at least a portion of the second. Fig. 1 shows an arrangement in which a central cylindrical conductor of tin is surrounded by a second cylindrical conductor 2 of lead and a winding 4 of niobium, these three materials having successively higher transition fields. Tantalum, vanadium, and lead or niobium are also suggested. Initially all the parts are in the superconducting state. Switch 14 produces an axial field in winding 4 which restores the resistance of both cylinders 2 and 3. When the switching pulse ceases current flow is produced in cylinder 2 which then begins to decay. When the axial field decays below the transition field of cylinder 2 current flow in it continues indefinitely and because of its lower transition field cylinder 1 is held in the resistive state. Cylinder 1 is again made superconducting by closing switch 9. The concentric magnetic field produced reverts cylinders 2 and 1 to the magnetic state and when it decays allows cylinder 2 to become superconductive again. However, the decaying concentric magnetic field cannot produce currents in the cylinder because such currents are axial and there is no closed path. A bundle of superconducting wires each providing a pair of output terminals may be substituted for a cylinder 1. Fig. 2 shows a device having an insulation covered winding 15 wound on cylinder 1 and interconnected by a lead 16 of superconducting material about which is a control winding 17. Initially the device is completely superconducting. The axial magnetic field produced by winding 4 as a result of closing switch 12 produces an axial field in cylinder 1 and winding 15 restoring their resistance. The decaying field in winding 15 allows it to become superconductive while holding cylinder 1 resistive. Switch 8 induces a field in superconductor 16 which makes it resistive so that the current in winding 15 dissipates. The axial magnetic field decays and cylinder 1 becomes superconducting again. Fig. 3 shows a flip-flop circuit made of two devices of the type shown in Fig. 1. Each winding 4 is connected in series with the cylinder 2 of the opposite device and the central cylinders 1 are connected to common terminals 6 and one or other of outer terminals 5. With the cylinder 1 of device 18 initially resistive this resistance appears between the left-hand pair of terminals 5, 6. A pulse supplied to terminals 24, 25 destroys the superconductivity of cylinder 2 of device 18 so that cylinder 1 becomes superconducting. At the same time cylinder 3 of device 19 becomes resistive and this resistance appears at the righthand pair of terminals 5, 6. The original situation is restored by a pulse applied to terminals 22. A similar device using two arrangements as shown in Fig. 2 is described with reference to Fig. 4 (not shown). In all cases winding 4 need not be superconductive but may be resistive so that the superconductivity of cylinder 2 can be destroyed by Joule heat from current flow through winding 4.