Abstract: An apparatus can detect a magnetic field with a high sensitivity using an ordinary-temperature pickup coil even when the pickup coil is arranged outside a cryostat. Specifically, the apparatus for measuring a magnetic field includes a pickup coil for detecting an external magnetic field, a SQUID electrically or magnetically connected to the pickup coil, a cryostat for holding the SQUID at low temperatures, and a driving device for driving the SQUID. The pickup coil is made of a normal-conducting material and is placed at an ordinary temperature outside the cryostat. By arranging outside the cryostat, the pickup coil can be brought close to a subject and can thereby detect a weak magnetic field in the subject with a high sensitivity.

Abstract: A scanning SQUID microscope for acquiring spatially resolved images of physical properties of an object includes a SQUID sensor arranged in perpendicular to the plane of the object under investigation for detecting tangential component of the magnetic field generated by the object. During scanning of the SQUID sensor over the object under investigation, the position signal from a position interpreting unit, as well as relevant output signals from the SQUID sensor are processed by a processing unit which derives from the data, spatially resolved images of the physical properties of the object. The specific orientation of the SQUID sensor with respect to the plane of the object permits an enlarged area of the SQUID chip on which the modulation and feedback line can be fabricated in the same technological process with the SQUID sensor. Additionally, larger contact pads afforded provide for lower contact resistance and ease in forming contact with bias and read-out wires.

Abstract: High balance, in the range of about 4×10−4 to about 10−3, is achieved in a gradiometer using Pyrex as the gradiometer support material. A superior technique is disclosed for winding superconducting wire loops with equal loop areas wherein cyanoacrylate glue is used to reduce slack in the wire in the process of winding. Furthermore, a minimal number of turns for each gradiometer type are used to maintain gradiometer sensitivity and to maintain high degree of mechanical balance. Additionally, low sensitivity SQUID magnetometers with optimally selected loop areas are placed among gradiometer channels in the directions of x, y, and z to measure magnetic fields. These measured fields are then fed into the gradiometer with coefficients roughly equal to (−1) (inversion) to compensate for the imbalances in the x, y, and z direction.

Abstract: A flux locked loop for providing an electrical feedback signal, the flux locked loop employing radio-frequency components and technology to extend the flux modulation frequency and tracking loop bandwidth. The flux locked loop of the present invention has particularly useful application in read-out electronics for DC SQUID magnetic measurement systems, in which case the electrical signal output by the flux locked loop represents an unknown magnetic flux applied to the DC SQUID.

Abstract: A low voltage cutoff circuit, a method of operating the same and a battery backup system incorporating the low voltage cutoff circuit or the method. In one embodiment, the low voltage cutoff circuit includes: (1) a low voltage monitor coupled between an input and an output of the low voltage cutoff circuit, (2) a cutoff switch, coupled between the input and the output and controlled by the low voltage monitor, that closes to couple the input to the output, the cutoff switch subject to failing closed when a voltage of the input is below a threshold and a load couplable to the output contains a short circuit and (3) a short circuit protection circuit, coupled to the low voltage monitor, that senses when the load contains the short circuit and directs the low voltage monitor to prevent the cutoff switch from closing.

Abstract: A semiconductor integrated circuit device including a redundant metal line for replacing a non-operational metal line for connecting to a circuit block. The invention further includes a method for decoupling a defective or otherwise non-operational conductive data line from a circuit block to which it is connected, and replacing the defective conductive data line with a redundant line by coupling it to the same circuit block. A spare conductive block is not needed. The redundant metal lines may be used in multiple levels of hierarchy within an integrated circuit device.

Abstract: An arrangement for coupling an rf-SQUID magnetometer to a superconductive tank circuit on a substrate is constructed in such a way that the two components are fully integrated into each other. Such integration increases the quality of the tank circuit by a factor of 2 to 3 as opposed to an arrangement obtainable by the flip-chip technology. Furthermore, the integrated arrangement permits simple assessment of coupling “k” between the SQUID and the tank circuit.

Abstract: A SQUID magnetometer for low noise, stable measurement of magnetic fields. The magnetometer has a SQUID formed of two Josephson junctions connected in parallel in a superconducting ring. An external damping impedance is connected across the Josephson junctions. The damping impedance has a resistive component and a capacitive component. The damping impedance damps Josephson oscillations occurring at frequencies greater than the frequency response range of said magnetometer. An amplifier stage coupled to said Josephson junctions has a biasing impedance for damping the Josephson junctions in the frequency response range of the magnetometer.

Abstract: A programmable voltage divider has normal and test modes of operation. The divider includes first and second supply nodes, a divider node that provides a data value, and a first divider element that is coupled between the first supply node and the divider node. The divider also includes a controlled node, a second divider element that has a selectable resistivity and that is coupled between the divider node and the controlled node, and a test circuit that is coupled between the controlled node and the second supply node. During the normal mode of operation, the first and second divider elements generate the data value having a first logic level when the second divider element has a first resistivity, and generate the data value having a second logic level when the second divider element has a second resistivity. The test circuit generates a first voltage at the controlled node during the normal mode of operation, and generates a second voltage at the controlled node during the test mode of operation.

Abstract: A magnetometer using a plurality of superconducting quantum interference devices (SQUIDs) includes a detecting part composed of a plurality of SQUIDs each detecting external magnetic flux, converting the detected external flux into a voltage value, and outputting a differential voltage of the converted voltage value, a signal-processing part for modulating, amplifying, and demodulating the differential voltage outputted by the detecting part, and a feedbacking part for converting a signal outputted by the signal-processing part into magnetic flux to feedback the signal to the loop of the SQUIDs.

Abstract: A high frequency signal generator using a superconducting quantum interference device is disclosed including: a magnetic signal generator for supplying a low frequency magnetic signal to a superconducting quantum interference device; a first filter for selectively supplying only the magnetic signal to the superconducting quantum interference device, and preventing a high frequency signal generated from the superconducting quantum interference device from flowing to the magnetic signal generator; the superconducting quantum interference device for frequency-multiplying the magnetic signal generated from the first filter to the high frequency signal of a sinusoidal wave according to the frequency, waveform and amplitude of the magnetic signal; a second filter for preventing the magnetic signal generated from the magnetic signal generator from flowing to a high frequency guide and antenna, and selectively supplying only the high frequency signal generated from the superconducting quantum interference device to t

Abstract: An RF-SQUID magnetometer whose RF-SQUID has an operating frequency, is formed by a superconductive ring having a Josephson element. An electric resonant circuit in the form of a closed superconductive conductor is coupled with the ring and forms a superconductive microwave resonator at that frequency.

Abstract: Disclosed herein are circuits and methods for receiving SFQ data pulses from a superconductor signal source, and first and second clock pulses that are substantially equal in frequency but opposite in phase from clock signal sources, and for encoding and converting the SFQ data pulses into a phase-shift-keying coded dc output voltage. The circuit includes RSFQ T-RS flip-flop means, including quantizing means for storing a current in one of two stable states, which is responsive to the first and second clock pulses and the data pulse, for PSK coding the SFQ data pulses. The circuit also includes a SFQ/DC converter, which is coupled to the quantizing means of the RSFQ T-RS flip-flop means and is responsive to a state of the current stored in the quantizing inductance loop, for converting the PSK coded SFQ data pulses into a PSK coded dc voltage.

Abstract: An effective high frequency oscillator is made of a plurality of Josephson devices. A high frequency converter as a high frequency circuit is made of the high frequency oscillator, nonlinear superconductor devices, and transmission line. Josephson devices are connected in parallel to make a superconductor module. Then superconductive modules are connected in series for high frequency via a phase locking circuit such as a thin film type capacitor to make the high frequency oscillator. Consequently, the high frequency oscillator is used as a local oscillator for a frequency converter. The high frequency system comprises a high frequency package housing a high frequency circuit, a cooling unit including a low temperature stage in thermal contact with the high frequency package, and a shielding case for housing the high frequency circuit and the low temperature stage. The high frequency system of the present invention provides a small-sized and power-saving high frequency circuit having operational stability.

Abstract: Microwave harmonic mixer circuit of SQUID(Superconducting Quantum Interference Device) is disclosed, in which a magnetic flux to voltage conversion characteristics of SQUID is used for generating a higher harmonics from an LO(Local Oscillator) signal, and mixing the higher LO harmonics with a radio frequency(RF) signal, including an SQUID for adding a RF(Radio Frequency) signal to a magnetic flux of an LO(Local Oscillator) signal frequency for having a mixing of the frequencies done; a current applying part and a grounding part disposed on both sides of the SQUID and connected to a current source on one side and grounded on the other side respectively for supplying operation current to the SQUID; RF antenna parts one each disposed between the SQUID and the current applying part and the SQUID and the grounding part for feeding a RF signal into the SQUID; an LO signal source and antenna part for applying a flux of an LO signal frequency to the SQUID; and, an IF signal detecting part for detecting an IF(Intermed

Abstract: Flux of magnetic field generated from an object P of magnetic measurement, which links with the pick-up coils of the fluxmeters, where the flux is converted into electrical signals by each of the SQUID chips driven by the FLL circuits. The electrical signals are sent to the data collection unit via the signal processing circuit. In the data collection unit, the electrical signals are converted into digital data by the A/D converter. The converted digital data are recorded on a hard disk or a magnet-optical disk or the like, of the data recording section. The digital data recorded on the data recording medium are compensated with use of a crosstalk compensation matrix so as to remove the interference due to crosstalk for each channel, by the crosstalk compensation section. The compensated data are displayed directly on the display in the form of a magnetic field distribution or time waveform, and sent to the data analysis section.

Abstract: A high temperature T.sub.c SQUID chip magnetometer has a flux-locked loop circuit including an independent feedback coil having an internal diameter greater than the maximum SQUID chip dimension. The feedback coil is mounted in close co-axial proximity to the SQUID chip to produce a substantially uniform feedback field over the entire area of the SQUID chip to cancel applied fields which penetrate the superconducting material.

Abstract: A signal processing device comprises superconducting wiring for providing an output signal or a transmitted signal correctly corresponding to an input signal without increasing the temperature of the device. The signal processing device has a signal input end, a signal output end, and proper signal processing circuits interposed between the signal input and output ends. The superconducting wiring connects the signal input end with the signal output end. An output end of the wiring is open, and the length of the wiring is set to be approximately 25% of the product of the pulse width and the phase velocity of the signal transmitted through the wiring.

Abstract: A superconducting switch comprising a portion of cable including a resistive central strand that is non-superconducting having a plurality of super-conducting strands or of superconductors twisted thereabout, and separated from the central strand by electrical insulation, the cable as a whole being insulated from the external cooling medium by thermal insulation. The central strand is electrically connected to the superconducting strands or the superconductors at each end of a portion of cable. A portion of the length of the resistive central strand extends outside the cable at a point along the length of the portion of said cable and is coupled to a control device situated outside the cooling medium, wherein the control device injector an electrical current into the circuit formed by the resistive central strand that is connected at its ends to the superconducting strands or to the superconductors.

Abstract: SQUID control apparatus for controlling multiple SQUID probes includes a plurality of head units each corresponding to a respective SQUID probe, each of the head units including a non-cryogenic modulated flux-locked loop feedback circuit operating at a respective modulation frequency. The apparatus also includes a base unit coupled to all of the head units, the base unit providing control signals to control the multiple head units. Means are also provided, such as through the use of a daisy chain topology, for synchronizing the modulation frequency of all of the modulated flux-locked loop feedback circuits.

Abstract: Improved probes for miniaturized scanning magnetometers (scanning microscopes), particularly those utilizing superconducting quantum interference devices (SQUIDs), are provided by the invention. The improved probes can have sub-.mu.m.sup.2 effective pickup loop areas and enhanced shielding through the use of progressively wider double groundplane structures which result in improved probes having high spatial resolution.

Abstract: A SQUID system provides for tracking small input signals to a SQUID. A digital flux tracking loop provides for independently providing orthogonal error signal for signal and modulation feedback errors effective to form a flux tracking loop with the SQUID. A current source biases the SQUID with a current effective to cause the SQUID to output a periodic junction voltage V.sub.j having a period .PHI..sub.o, the V.sub.j having an amplitude as a function of magnetic flux .PHI. within the SQUID. A first processor modulates the magnetic flux within the SQUID to output at least three junction voltages. A second processor combines the at least three junction voltages and outputs first and second signals functionally related to flux tracking errors arising from the signal and modulation lock errors, respectively, the first and second signals forming feedback signals effective to form a flux tracking loop with the SQUID.

Abstract: The feedback current for the flux-locked-loop of a DC-SQUID is conductively supplied directly to the input circuit of the SQUID rather than to a separate feedback or modulation coil that is inductively coupled to the SQUID, thereby eliminating the feedback or modulation coil and simplifying construction of an integrated SQUID module.

Abstract: A hybrid superconducting-semiconducting field effect transistor-like circuit element comprised of a superconducting field effect transistor and a closely associated cryogenic semiconductor inverter for providing signal gain is described. The hybrid circuit functions nearly as an ideal pass gate in cryogenic cross-bar applications.

Abstract: A DC superconductor quantum interference device (i.e. DC SQUID) is used in a flux-locked loop as a sensitive detector of magnetic flux. Prior art devices of this sort had a transfer function which was frequency-limited by the transfer function of impedance matching circuitry which is used to connect the DC SQUID with the first preamplifier, which amplifies the DC SQUID signal before it is applied to a detector circuit. The present invention corrects this frequency limitation by creating a compensating circuit having a transfer function which is the inverse of that of the impedance matching circuitry, and inserting it in the system after the first preamplifier and before the detector circuit.

Abstract: The present invention is a superconducting flux flow mixer which has two control lines. Preferably, the mixer comprises a grounded superconducting signal line wherein portions of the superconducting signal line are etched away to form superconducting weak links within the superconducting signal line, a local oscillator and RF control line disposed on either side of the superconducting weak links, and a substrate upon which the control lines and superconducting signal line are disposed. When cooled to a temperature close to the critical temperature of the superconducting weak links, the resistance of the weak links can be manipulated by a magnetic field created by current flowing through the local oscillator and RF control lines. By using two control lines, better control of frequency is attained while at the same time providing better stability and a decrease in size of prior art mixers.

Abstract: A superconducting switch is composed of anisotropic magnetic material. The switch has a first superconducting section, a variable resistive section and a second superconducting section. An external magnetic field is applied so that the first and second superconducting sections remain superconducting and the resistive section changes resistance when the magnetic field applied exceeds the critical field of the variable resistance section. The different critical field regions are achieved by exploiting the natural critical field anisotropy of the ceramic superconductors (a previously unobserved phenomena in metal superconductors). By making the different sections with different orientations they will exhibit different critical field valves for a given direction of applied fields. The state of the switch is changed by either increasing or decreasing the external magnetic field about the critical field value of the resistive section of the switch.

Abstract: A three-port Josephson memory cell has one input port (a data line) and two output ports (first and second sense lines). The memory cell receives a write enable pulse on a write line to store a bit of data from the data line as circulating supercurrent. The memory cell also receives a first read enable pulse on a first read line to enable assertion of the stored data onto the first sense line, and receives a second read enable pulse on a second read line to enable assertion of the stored data onto the second sense line.