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 magnetometer includes a support. The support has two support surfaces that intersect each other along an intersection line. The intersection line is perpendicular to a reference axis of the support. The support surfaces are preferably perpendicular to each other and are each inclined at an angle of 45 degrees to the reference axis. A planar sensor/detector array is mounted on each support surface. Each array includes at least two pairs of magnetic field sensors and associated SQUID detectors arranged such that the magnetic field sensors lie on a line that is parallel to the intersection line of the two support surfaces. The magnetometer can be used adjacent to a surface to measure components and spatial variation of the magnetic field near the surface, with the measured components resolved into the magnetic field vectors parallel to and perpendicular to the surface.

Abstract: A biomagnetometer includes a magnetic field sensor unit having a magnetic field pickup coil. A vessel contains the sensor unit. The vessel includes a flexible contact face with the magnetic field sensor unit mounted in the interior of the vessel adjacent to the flexible contact face. Insulation at the flexible contact face of the vessel prevents excessive heat flow through the flexible contact face. Pickup units using this structure can be connected together into flexible or rigid arrays. In operation, the pickup coil is cooled to a temperature of less than its superconducting transition temperature. A detector measures the magnitude of magnetic fields sensed by the sensor unit.

Abstract: A SQUID comprises a substrate, a washer of an oxide superconductor thin film formed on a principal surface of the substrate, a hole shaped a similar figure to the washer at the center of the washer, a slit formed between one side of the washer and the hole, and a Josephson junction which connects portions of the washer at the both sides of the slit across the slit. In the SQUID, the ratio of similarity of the washer to the hole ranges 100 to 2500.

Abstract: A SQUID fluxmeter, which object is to accurately measure magnetic flux even if the input magnetic flux is largely changed in a short time, includes an 1-input superconducting OR gate for outputting pulses to the number of i in response to one input pulse from a SQUID, an AC bias current source for outputting a current I.sub.C of variable frequency 4if to a bias input node of the OR gate, an up/down counter for counting pulses from the SQUID and a control circuit for outputting a control signal CSi to the AC bias current source corresponding to the time differential value of the count value C1 of the counter and present value i. The response speed of the magnetic flux feedback through the feedback coil to the SQUID in response to the magnetic flux input to the SQUID is thereby made i times higher than that in the prior art.

Abstract: A planar SQUID magnetometer for detection and measurement of an applied magnetic flux is disclosed wherein a planar microwave-resonant element overlaps a Josephson device incorporated in a high-T.sub.c superconducting, thin-film SQUID device, thereby providing inductive coupling between the planar microwave-resonant element and the SQUID device. When the microwave-resonant element is excited by incident high-frequency microwave radiation, the intensity of reflected microwave radiation varies in response to a magnetic flux applied to the SQUID device in accordance with non-linear oscillatory behavior of the microwave-resonant element due to inductive loading by the SQUID device. The microwave-resonant element and the SQUID device are preferably fabricated photolithographically on a single substrate.

Abstract: A superconducting gyroscope of the present invention includes a circuit which produces a magnetic field which is synchronous with the rate of rotation experienced by the gyroscope, a sensing circuit for converting the synchronous magnetic field into an electric signal, a first shield made of superconducting material for performing shielding of external stray fields, and a second shield disposed inside the first shield and made of superconducting material for expelling trapped residual magnetic flux. The synchronous magnetic field producing circuit includes a magnetic core shaped in a toroid with an air gap. The magnetic core may alternatively be formed in meandering shape by a plurality of separate magnetic core members with a plurality of air gaps therebetween. The sensing circuit includes at least one SQUID which can be directly coupled to the magnetic core.

Abstract: A magnetic field detecting circuit has a relaxation oscillator SQUID. An oscillator circuit includes a coil and a resistor connected together in series. The oscillator circuit produces an output signal having an oscillating frequency dependent on an applied DC bias current. A magnetic field input circuit is magnetically coupled with the coil of the oscillator circuit for applying a magnetic field. A Josephson device is connected in parallel with the oscillator circuit for converting the magnetic field to an electric signal for varying the oscillating frequency dependent on the magnetic field. The magnetic field is detected by detecting a variation of the oscillating frequency. The sensitivity of the magnetic field detecting circuit is improved by magnetically coupling an RF-SQUID with an input coil to form the magnetic field input circuit.

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: A Josephson break junction device suitable for highly sensitive electronic detecting systems. A superconductor film such as YBa.sub.2 Al.sub.3 O.sub.7 is deposited on a substrate such as a single-crystal MgO. The film is fractured across a narrow strip by at least one indentation in the substrate juxtaposed from the strip to form a break junction. A transducer is affixed to the substrate for applying a bending movement to the substrate to regulate the distance across the gap formed at the fracture to produce a Josephson turned junction effect. Alternatively, or in addition to the transducer, a bridge of a nobel metal is applied across the gap to produce a weak-link junction.

Abstract: A magnetic noise reducing device can effectively produce a practically noiseless space that can reduce environmental magnetic noise harmful for measuring biomagnetism with a high magnetism damping factor in low frequency range. The magnetic noise reducing device comprises a SQUID flux meter 1 and a pair of noise canceling coils 2 as minimum components, the feedback current I produced by the SQUID flux meter 1 being supplied to the noise canceling coils 2, the magnetic flux detecting coil of the SQUID flux meter being arranged within a specific central space 4 defined by the noise canceling coils 2 for effective reduction of magnetic noise within that space.

Abstract: A plurality of SQUID flux sensors are supplied with their respective bias currents at the same time from a bias source. A superconducting multiplexer multiplexes output signals of the SQUID flux sensors during an interval of time when the bias currents are supplied to the SQUID flux sensors. A multiplexer, placed in a room-temperature environment, distributes each of the multiplexed output signals of the SQUID flux sensors to a respective one of the output terminals which correspond to the SQUID flux sensors. Each signal which has been output to an individual output terminal is counted by a counter, so that an external magnetic flux to a corresponding SQUID flux sensor is measured.

Abstract: A superconducting magnetic sensor comprises an adiabatic vessel having an outer wall and an inner wall separated from the outer wall by an evacuated space, for holding a cooling medium, a thermal insulation filling the evacuated space, a cooling member having a first end physically fixed upon the inner wall of the adiabatic vessel and extending toward the outer wall, a superconducting pickup coil of a superconducting material for interlinking with an external magnetic flux, provided in the evacuated space in physical contact with the cooling member so as to be cooled by a cooling medium held in the vessel via the cooling member, a superconducting magnetic detection unit provided in the vessel so as to be immersed in the cooling medium, and a superconducting strip of a superconducting material connecting the superconducting pickup coil and the superconducting magnetic detection unit, the superconducting strip penetrating through the inner wall of the adiabatic vessel.

Abstract: A stochastic excitation, SQUID detection system for determining the frequency response of a sample. A pair of counterwound detection coils are adjacent to an excitation coil. The sample is selectively placed in one of the detection coils for taking measurements. The SQUID sensor is a broadband, high sensitivity device which enables the frequency response of the sample to be determined over a wide bandwidth with a single measurement.

Abstract: Superconducting detection coils for a superconducting quantum interference device are foraged on a flexible printed wiring film having a pair of opposed edges. The flexible printed wiring film is capable of being shaped into a cylinder by bringing the opposed edges toward each other. A superconducting wiring pattern is formed on the flexible printed wiring film and has at least one substantially U-shaped wiring portion. The U-shaped wiring portion forms at least two circular wiring patterns when the printed wiring film is shaped into a cylinder by bringing the opposed edges toward each other. The superconducting wiring pattern also has a first and a second electrode portion for connecting the circular wiring patterns to at least one superconducting quantum interference device. A resistor is electrically connected between the electrode portions of the superconducting wiring pattern.

Abstract: A physical configuration for a parallel multi-junction superconducting quantum interference device that can be used for a variety of applications involving the detection of magnetic flux, including applications where it is desired to measure the absolute magnitude of the flux. The device of this invention features a novel geometry for a multi-junction interference device which significantly enhances the flux-to-voltage transfer function, thereby yielding a significant improvement in the device sensitivity in its use in a magnetometer, gradiometer, or other applications.

Abstract: A thin film dc SQUID and its driving electronic circuitry configured with very high symmetry, having a SQUID loop formed with four holes (24, 24, 26, 27) at the respective ends of crossed slits (22, 23). Each of these holes forms a single turn secondary coil for symmetrically arranged pairs of modulation coils and signal coils. The geometrical placement of the modulation coils with respect to the signal coils results in a device which nominally has no mutual inductance between the two groups of coils when the SQUID is biased for normal operation. The external driving circuit (75-85) is configured to preserve the highly balanced nature of the SQUID and forces an equal magnitude of current to flow in all four of the bias leads.

Abstract: For the determination of all linearly independent components of an Nth order gradient tensor of a magnetic field, at least 3+2N planar gradiometers of the Nth order are arranged on at least 3 non-parallel and non-orthogonal surfaces. As a result, three-dimensional coil structures are not necessary.

Abstract: A sensor element of thin film components and fiber glass, and a support structure of fiber glass; when sensor elements are attached to the support structure, a sensor system for magnetoencephalographic measurements is formed. A substrate containing a planar signal coil and a SQUID is attached on a circuit board of fiber glass using a spring cut on the edge of a body plate. On the sensor element, is a small but mechanically stable connector or several such connectors (5); when the sensor element is plugged in receptacles (6) on the support structure (7), the element settles in a well defined orientation. Support structure (7) is made of a fiber glass shell following the shape of the bottom (10) dewar vessel, adapted to the shape of the head. The receptacles (6) are attached to the glass fiber shell by springs (9) made of thin fiber glass plate such that an array covering the whole skull as evenly as possible is formed when the sensor elements are plugged to the receptacles.

Abstract: A method of manufacturing a DC superconducting quantum interference device comprises forming an insulating film over a portion of a resistance film. A lower electrode superconducting film is formed over the resistance film and the insulating film. A barrier layer is formed on a portion of the lower electrode superconducting film. An upper electrode is formed sandwiching the barrier layer between the lower electrode superconducting film and the upper electrode, so as to form a Josephson junction. To reduce the number of manufacturing steps, the lower electrode superconducting film is photolithographically patterned and/or etched to simultaneously form an input coil, a feedback coil and the Josephson junction. In another embodiment, after forming the upper electrode, an insulating film is formed over at least a portion of the lower electrode superconducting film. A superconducting film is formed over the insulating film in contact with the upper electrode.

Abstract: A magnetometer comprising a superconducting loop including a magnetic flux detecting coil and a SQUID (Superconducting QUantum Interference Device) connected to the superconducting loop via magnetic flux. A negative inductance generating device is provided having two terminals for generating a negative inductance defined by the value of the derivative of generalized magnetic flux between the two terminals with current flowing between the terminals (d.PHI./dI) being negative. The inductance of the superconducting loop is decreased by the negative inductance generating device and input signals intensified by the negative inductance generating device are detected by the SQUID. A plurality of the superconducting loops may be provided to construct a gradiometer and a variable negative inductance generating device is provided to the respective superconducting loop to equalize and intensify the sensitivities of the detection coils.

Abstract: A multichannel weak magnetic field measuring system for neuromagnetic diagnosis is provided having a plurality of dc-SQUID magnetometers. Bias current setting circuits are provided for detecting an even harmonic component of the output across the terminals of the corresponding SQUID and automatically adjusting a DC bias current to the SQUID. Accordingly, the level of the component becomes a predetermined value. Circuitry is also included for equalizing the magnetic flux detection sensitivities of these dc-SQUID magnetometers. Abnormal operation detecting circuits are also provided for producing abnormal operation detected outputs when the level of the corresponding even harmonic component is smaller than a certain threshold value.

Abstract: The invention concerns a pickup coil to measure components of gradients. The coil consists of two pairs of loops connected in series; these pairs are then connected in parallel. The coil so formed has a low inductance, and no shielding currents are induced to superconducting coils in homogeneous magnetic fields. One coil can be employed to measure several field components simultaneously when the coil is coupled to current sensing elements, for example to SQUIDS, so that the current components measured by the sensing elements do not couple magnetically because of the symmetry. This can be accomplished by connecting the said elements between terminals between the loops (5, 6 and 7, 8). The inductance of this coil can be further reduced by subdividing the loops into parts connected in parallel.

Abstract: A digital superconducting quantum interference device type fluxmeter includes a flux sensor unit which detects external magnetic flux to be measured using a SQUID ring, and outputs pulse signals of corresponding directions and numbers, and a counter unit which counts the number of pulse signals output by the flux sensor unit inclusive of the directions thereof, in order to measure the external magnetic flux based on the counted result of the counter unit. The fluxmeter further includes an offset detection unit which detects the offset quantity of the counter unit generated by the magnetic flux trapped by the SQUID ring, and a feedback unit that feeds back to the flux sensor unit a signal that is obtained based on the detected offset quantity and the counted result of the counter unit.

Abstract: Output currents from a superconducting quantum interference device which corresponds to magnetic flux guided thereto are compared with a predetermined value which corresponds to a magnetic flux locking point so as to detect a direction of shift with respect to the magnetic flux locking point. A shift quantity is judged to determine whether or not it is large based upon a history of the shift direction. A variation value component of an estimate feedback quantity is varied by taking this history into consideration. The estimate feedback quantity is used to guide magnetic flux for compensating for variation in the magnetic flux which is guided to the superconducting quantum interference device.

Abstract: A SQUID measurement apparatus for detecting weak magnetic field signals that change over time such as from a biomagnetic field source includes at least one measurement channel, a SQUID, and a superconductive flux transformer disposed in front of the SQUID that includes at least one detection loop for receiving the weak magnetic field signals. The apparatus also includes at least one connection conductor coupled to the detection loop and electromagnetically shielding for at least the at least one connection conductor of the flux transformer. The shielding includes at least one superconductive shielding element that extends in a direction substantially parallel to the at least one connection conductor and substantially equidistant from the at least one detection loop. The shielding element has a discontinuity at a separation point in a region of the detection loop.

Abstract: A superconducting quantum interference device loop, a modulation coil and an input coil are formed in parallel and their axes being parallel to a substrate, on the substrate. At least one tap is formed at a predetermined position on the input coil. In a preferred embodiment, a superconductive shield is formed on the substrate in one body. The superconductive shield surrounds the superconducting quantum interference device loop, the modulation coil and the input coil.

Abstract: An apparatus for detecting a fine magnetic field comprises a DC SQUID which detects and converts a magnetic field to an electrical signal. A flux locked looped circuit drives the DC SQUID. The flux locked loop circuit includes an amplifier for amplifying the electrical signal. A phase detector modulates the amplified electrical signal and an integration circuit outputs a voltage signal corresponding to the detected magnetic field. An oscillator coupled to the phase detector supplies a demodulation frequency signal. A modulator including a first voltage-to-current converter and a second voltage-to-current converter is coupled with the integration circuit and the oscillator for supplying a modulation signal to the DC SQUID. The modulator further includes an external input terminal and a feedback modulation change-over circuit for changing an internal feedback signal to an external test signal inputted to the external input terminal.

Abstract: A high-sensitive magnetometer has two SQUIDs each comprising a superconducting loop with one or more Josephson junctions and also has a coil comprising a continuous loop for providing magnetic flux of input signals to each of the SQUIDs in opposite directions. The magnetic flux of the input signals is detected by sums of output voltages of the SQUIDs. Magnetic flux noises equally applied on the two SQUID are cancelled by the continuous loop and at addition of the output voltages of the SQUIDs, thus large output signals can be obtained because sums of the two SQUID output signals are obtained.

Abstract: A magnetometer having high sensitivity and high resolution is achieved using superconductive circuit elements. The magnetometer includes a pick-up coil, amplifying transformer quantum flux parametron (QFP), latch, feedback gate and feedback inductor fabricated with superconducting elements and coupled to a bidirectional counter. The magnetometer implements an on-chip negative feedback loop. The pick-up coil senses an external magnetic field or gradient resulting in an induced current which is amplified and fed to the QFP which generates a directional indicator signal sent to the latch. When the polarity of the indicator is indicated as corresponding to the polarity of a latch clock signal, a current signal is sent to the feedback gate causing a packet of quantum flux to be generated. The packet is fed back through the feedback inductor, inducing a current in the pick-up coil which opposes the induced current attributable to the external magnetic field.

Abstract: A superconducting device for measuring weak magnetic fields, especially those generated by the human brain and detected simultaneously over the whole skull. The superconducting magnetometer or gradiometer elements of the device are attached with connectors to a cross-connection/support element which, in turn, is attached to a connecting element containing the electric components necessary for connecting the SQUIDs to the room temperature electronics. The connecting element is attached to a neck plug for the dewar flask. The neck plug is made of a stiff thermal insulation to prevent convection and a ribbon cable containing parallel twisted pairs. The latter element is self-supporting and forms an integral part of the magnetometer support structure. The cables in the neck plug have been made out of wires having a relatively high resistance in order to minimize the heat leak between room temperature and the cryogenic environment of the magnetometers.

Abstract: A DC superconducting quantum interference device has a superconductive ring and a feedback modulation coil for detecting a magnetic field. A variable bias current is applied to the superconductive ring and a modulating signal is applied to the feedback modulation coil. A signal change-over circuit is provided for superposing a false signal on the modulating signal, the false signal electrically simulating the effect of an applied magnetic field to enable adjustment of the variable bias current and the modulating signal under measurement conditions. A flux locked loop circuit of the DC superconducting quantum interference device has an external input terminal or a low-frequency oscillator for supplying a low-frequency signal to the signal change-over circuit which is superposed on the modulating signal applied to the feedback modulation coil.

Abstract: In a dc SQUID element having two quasi-planar-type Josephson junction portions, as obtained by laminating a plurality of superconducting thin films on a substrate, a SQUID ring and a counter electrode on either of which quasi-planar-type Josephson junction portions are to be formed, are respectively formed at the lowermost layer and the uppermost layer, or at the uppermost layer and the lowermost layer, so that the value of critical current can be adjusted. The arrangement above-mentioned assures good flatness and film quality of a barrier layer interposed between the lower and upper electrodes of the quasi-planar-type Josephson junction portions.

Abstract: Since a superconducting quantum interference device (SQUID) using a high temperature superconductor operates at the liquid nitrogen temperature 77 K, which is higher than the liquid helium temperature 4.2 K, it is necessary that the value of signal voltages is at a level, which is sufficiently higher than the thermal noise level. The superconducting inductance L should be decreased with increasing current flowing through Josephson junctions in the SQUID. The superconducting inductance can be reduced by various methods such as reduction in the size of the aperture of the superconducting inductance, parallel connection of superconducting inductances, utilization of a superconducting ground plane, etc., in order to realize a SQUID, which can be use in a wide application field at the liquid nitrogen temperature 77 K.

Abstract: Plural vector magnetic flux meters are disposed based on predetermined relationships in their positions, to obtain vector magnetic flux at plural points. The obtained vector magnetic flux includes magnetic flux components in plural directions. Curved surface interpolation is carried out based on the magnetic flux components in the corresponding direction to obtain magnetic flux components for arbitrary points. Magnetic flux components in plural directions for an arbitrary point are obtained by selecting the obtained magnetic flux components for the arbitrary point belonging to a region which overlaps with all interpolation regions for corresponding magnetic flux components of the magnetic flux.

Abstract: A plurality of magnetic flux measurement data corresponding to two dimensional grids are obtained, then the magnetic flux measurement data are convoluted to sampling unit functions in x-direction and y-direction to obtain an interpolation function. Magnetic field is illustrated by isomagnetic contour lines based on magnetic flux measurement data and interpolation values which are obtained based on the interpolation function. One of the sampling unit functions is replaced with a differential function thereof to obtain partial differential values of arbitrary points.

Abstract: A magnetometer is prepared by depositing three thin-film SQUID magnetic field detectors upon a substrate. Two of the detectors incorporate stripline SQUID detectors deposited at right angles to each other, to measure the orthogonal components of a magnetic field that lie in the plane of the substrate. The third detector uses a planar loop SQUID detector that measures the component of the magnetic field that is perpendicular to the substrate. The stripline SQUID detectors have thin-film base and counter electrodes separated by an insulating layer which is at least about 1 micrometer thick, and a pair of Josephson junctions extending between the electrodes through the insulating layer.

Abstract: A constant bias voltage is applied to plural superconducting quantum interference devices which are interconnected in parallel. Output currents from the superconducting quantum interference devices are supplied in added condition. Maximal-sequence codes are modulated by a modulation current corresponding to each device, and the modulated maximal-sequence codes are supplied to the modulation coil of each corresponding superconducting quantum interference device. The added output current is demodulated for each device by a maximal-sequence code which is phase shifted by the same quantity as the maximal-sequence code for modulation for each device.

Abstract: A SQUID package includes a layered SQUID base and a SQUID mounted upon the base. The SQUID base is formed as a first substrate layer of an electrically insulating material, a shielding layer of a material that is superconducting at the SQUID operating temperature overlying the first substrate layer, and a second substrate layer of an electrically insulating material overlying the shielding layer. The shielding layer protects the SQUID from dc and ac interference such as magnetic and electrical fields, which would otherwise interfere with its operation. Related components such as input and output circuitry can be mounted on the base. An input coil used to detect magnetic fields can also be placed on the base, but in that case the shielding layer is made to cover only a portion of the SQUID base, and the input coil is positioned over the portion of the base that has no shielding layer.

Abstract: A pickup coil and a planar type SQUID are formed integrally on a single substrate to form a SQUID magnetometer. The SQUID is disposed on the surface of a projecting portion of the substrate and an insulating layer for spacing is laminated on the SQUID. The top, bottom and side surfaces of the assembly of the SQUID and insulating layer covering the same are all covered with a superconducting layer to form a magnetic shield for enclosing the SQUID. The magnetic shield is remote from the planar type pickup coil disposed on the remaining portion of the substrate by a distance which is equal to or greater than a length of one side of the size of the magnetic shield, thereby preventing magnetic flux distortion due to the presence of the magnetic shield from disturbing coil balance of the pickup coil.

Abstract: A micromechanical sensor comprises a support, a micromechanical element that is movable relative to the support under the application of a stimulus, and a transducer. The transducer comprises a first component carried by the micromechanical element and movable therewith, and a second component stationary relative to the support. One of the first and second transducer components is a member for establishing a magnetic field and the other of the first and second transducer components is a SQUID positioned in the magnetic field for detecting variation in the magnetic field due to relative movement of the micromechanical element and the support.

Abstract: A superconducting pickup coil is provided for interlinking with an unknown magnetic flux and causing an induction current to flow. A superconducting detector is provided magnetically coupled with the superconducting pickup coil for producing output voltage pulses in response to the unknown magnetic flux. A superconducting feedback circuit is provided connected to the superconducting detector for receiving the output voltage pulses therefrom and feeding back a feedback magnetic flux to the superconducting pickup coil in response to each output voltage pulse such that the feedback magnetic flux counteracts the unknown magnetic flux. A resistance fixture is provided in the vicinity of the superconducting pickup coil for causing a transition in a part of the superconducting pickup coil from a superconducting state to a normal conducting state in response to the drive current.

Abstract: A biomagnetometer has a magnetic pickup coil positioned remotely from a detector and inductively coupled to the detector. The detector is preferably made from a low-temperature superconductor, while the pickup coil can be made of a high-temperature superconductor. The detector and pickup coil can therefore be placed into separate containers, with an inductive coupler between the containers. In one approach, the detector is maintained at liquid helium temperature, and the pickup coil and electrical connector are cooled by liquid nitrogen. The resulting biomagnetometer permits the container with the pickup coil to be moved and positioned easily, and to be changed readily between various configurations particularly suited for performing various functions.

Abstract: A plurality of superconducting quantum interference magnetometers are provided corresponding to a plurality of channels. Each of the superconducting quantum interference magnetometers is accommodated in a cooling vessel and has a superconducting detection loop for interlinking with the unknown magnetic flux. A superconducting magnetic sensor is magnetically coupled to the superconducting detection loop for producing an output voltage pulse. A feedback circuit, supplied with the output voltage pulse from the superconducting magnetic sensor, produces a magnetic flux that counteracts the unknown magnetic flux in response to each output voltage pulse. A gate circuit is provided between the superconducting magnetic sensor and the feedback means for controlling the supplying of the output voltage pulse from the superconducting magnetic sensor to the feedback circuit. The gate circuit is supplied with a control signal and selectively passes the output voltage pulse in response to a logic level of the control signal.

Abstract: A magnetometer is prepared by depositing three thin-film SQUID magnetic field detectors upon a substrate. Two of the detectors incorporate stripline SQUID detectors deposited at right angles to each other, to measure the orthogonal components of a magnetic field that lie in the plane of the substrate. The third detector uses a planar loop SQUID detector that measures the component of the magnetic field that is perpendicular to the substrate. The stripline SQUID detectors have thin-film base and counter electrodes separated by an insulating layer which is at least about 1 micrometer thick, and a pair of Josephson junctions extending between the electrodes through the insulating layer.

Abstract: A gradiometer utilizes at least three vector magnetometers (preferably SQUIDs) to measure a magnetic field gradient. The gradiometer includes a reference magnetometer and a plurality of sensor magnetometers, wherein the reference magnetometer (SQUID) used to cancel background magnetic fields from outputs of the sensor magnetometers via a feedback loop provided with a signal from the reference magnetometer. Similarly, higher order gradiometers can be built using a reference magnetometer cube and a plurality of sensor magnetometer cubes.

Abstract: A method of suppressing current distribution noise in a DC SQUID comprising two Josephson junctions (12) in a superconducting current. This current distribution noise is caused by individual fluctuations of the critical currents of the two Josephson junctions used for measuring weak magnetic fields. A DC SQUID is connected to a device which comprises a control device (14) for generating a periodic bias current (I.sub.b), a modulation device (15) for generating a flux modulation via an induced AC current in the loop (11), and a signal detection device (17) for forming a mean output voltage (V.sub.ges). The polarity of the bias current (I.sub.B) is reversed by the control device (14) with the modulation frequency and a time shift of one quarter of the period duration of the modulation frequency, so that the SQUID assumes different bias states.

Abstract: In a multi-channel SQUID fluxmeter for detecting magnetic flux signals by use of an array of SQUID flux sensors each comprising a digital SQUID for providing a pulse output, multiplexers and the like are appropriately used to allow pulse signals output from the SQUID flux sensors to be switched on a time series basis in order to obtain a magnetic flux signal for each channel. Thus, only one processing circuit need to be provided for a large number of SQUID flux sensors, thus reducing the scale of the fluxmeter and making the device small.

Abstract: A sensor for measuring magnetic flux has at least one hole or opening in a strip resonator of superconductive material defining a ring in which a Josephson element is integrated into the strip resonator and coupled thereto so that attenuation in the tank circuit formed by the ring when a standing wave is established in the strip resonator can be picked up capacitively by a further strip conductor.

Abstract: A biomagnetometer has a magnetic pickup coil positioned remotely from the detector. The detector is made from a low-temperature superconductor, while the pickup coil and an electrical connector between the detector and the pickup coil are made of a high-temperature superconductor. Although the detector is maintained in a dewar at a sufficiently low temperature to reduce electronic noise, the pickup coil and the electrical connector need only be maintained at a temperature at which they are superconducting. In one approach, the detector is maintained at liquid helium temperature, and the pickup coil and electrical connector are cooled by liquid nitrogen. The resulting biomagnetometer permits the pickup coil to be moved and positioned easily, and to be changed readily.