Patent GB-935209-A (GB)
Title: Thin film superconductor circuits
IPC: H01L39/20
Filed: 1960-06-27
Abstract: 935,209. Superconductor devices. INTERNATIONAL BUSINESS MACHINES CORPORATION. June 27, 1960 [June 30, 1959], No. 22389/60. Class 37. [Also in Group XXXIX] In a superconductive gating circuit at least a gating section consists of a pair of thin films arranged adjacent each other so that a controlled conductor can drive both of the gating sections conductive. Fig. 1 shows an arrangement in which the gate conductor 16 is of lead and has two " soft " sections 10A, 10B of tin. The control element 12 is of lead and is provided with two narrow portions 12A, 12B which traverse the gate element at the soft sections 10A, 10B. The narrow sections of the control conductor enable a small signal applied by a source 14 to control a larger signal applied by source 16. Because these sections 10A, 10B are driven resistive by signal in control conductor 12, the resistance introduced to the gate is twice that introduced by a single crossing. Additionally each of the two sections of the gate is provided with an image conductor which acts as a superconductor shield for the other, causing the current in each section to be more uniformly distributed and thus to be greater without driving the gate resistive. In the arrangement of Fig. 2 (not shown), the control loop is outside the gate loop while in that of Fig. 3 (also not shown) the control loop is replaced by a single conductor passing between the two arms of the gate conductor. In the arrangement of Fig. 4, current applied to one or the other of control conductors 32, 36 make the corresponding side 26, 28 of the gate loop resistive. If desired, this gate loop can operate external circuits by acting as the control conductors of the gate conductors 42, 41. If the upper and lower arms of the various circuits are not accurately aligned persistent current may be trapped in the circuit. This danger is removed by superconductive shield 50. Fig. 4a shows a section on the line a-a of Fig. 4. The shield 50 consists of hard superconductive material deposited on a substrate 50. Insulating material 54 is then deposited followed by the lower section of control element 36. Next follows a layer of insulating material 56 which does not extend the full width of the section so that when the upper control element is deposited it makes connection with the lower at the lefthand end of the device. Fig. 4a also shows the upper and lower sections of deposited gate conductor 28. Fig. 5 shows a circuit having a bifilar loop in combination with single conductors and upper, lower and intermediate shield conductors. The gate conductor extends from an input terminal 74 along a single strip 72A, upper and lower strips 72B, 72C and a single strip 72D returning through upper and lower shield members 78, 80 to which it is joined at 76 to terminals 84, 92. The bifilar loop is provided with gate sections 72E, 72F between which it passes from terminal 88 between upper and lower shields 78, 80 to a junction with both of the shields at 90. A bridging shield 82 is connected to the lower shield 80 to the right of gate conductor 72B as shown broken away; it is connected to the upper shield 78 to the left of conductor 72C as shown in section in the drawings. All the shields are connected along the left edge of bridging shield 82 and 99. As in the case of Fig. 4 all of the conductors and the shields with spacing insulation are formed of deposited layers. Specifications 862,178 and 935,208 are referred to.