Abstract: Devices and systems as described herein is configured to sense a signal, such as a signal from an individual. In some embodiments, a signal is a magnetic field. In some embodiments, a source of a signal is an individual's organ, such as a heart muscle. A device or system, in some embodiments, comprises one or more sensors, such as an array of sensors configured to sense the signal. A device or system, in some embodiments, comprises a shield or portion thereof to reduce noise and enhance signal collection.

Abstract: An inertial navigation system (INS) device includes three or more atomic interferometer inertial sensors, three or more atomic interferometer gravity gradiometers, and a processor. Three or more atomic interferometer inertial sensors obtain raw inertial measurements for three or more components of linear acceleration and three or more components of rotation. Three or more atomic interferometer gravity gradiometers obtain raw measurements for three or more components of the gravity gradient tensor. The processor is configured to determine position using the raw inertial measurements and the raw gravity gradient measurements.

Abstract: A magnetic field measuring device that can measure a weaker magnetic field is provided. A magnetic field measuring device is provided, the magnetic field measuring device including: a sensor unit that has at least one magnetoresistive element; a reference voltage generating unit that outputs a reference voltage; a magnetic field generating unit that generates a magnetic field to be applied to the sensor unit; a feedback current generating unit that supplies, according to a difference between an output voltage of the sensor unit and the reference voltage, the magnetic field generating unit with a feedback current that generates a feedback magnetic field to diminish an input magnetic field to the sensor unit; a magnetic field measuring unit that outputs a measurement value corresponding to the feedback current; and an adjusting unit that uses the output voltage of the sensor unit to adjust the reference voltage.

Abstract: Quantum annealing may include applying and gradually removing disorder terms to qubits of a quantum processor, for example superconducting flux qubits of a superconducting quantum processor. A problem Hamiltonian may be established by applying control signals to the qubits, an evolution Hamiltonian established by applying disorder terms, and annealing by gradually removing the disorder terms. Change in persistent current in the qubits may be compensated. Multipliers may mediate coupling between various qubits and a global signal line, for example by applying respective scaling factors. Two global signal lines may be arranged in an interdigitated pattern to couple to respective qubits of a communicatively coupled pair of qubits. Pairs of qubits may be communicatively isolated and used to measure a response of one another to defined signals.

Abstract: A superconducting quantum interference devices (SQUID) comprises a superconducting inductive loop with at least two Josephson junction, whereby a magnetic flux coupled into the inductive loop produces a modulated response up through radio frequencies. Series and parallel arrays of SQUIDs can increase the dynamic range, output, and linearity, while maintaining bandwidth. Several approaches to achieving a linear triangle-wave transfer function are presented, including harmonic superposition of SQUID cells, differential serial arrays with magnetic frustration, and a novel bi-SQUID cell comprised of a nonlinear Josephson inductance shunting the linear coupling inductance. Total harmonic distortion of less than ?120 dB can be achieved in optimum cases.

Abstract: SQUIDs may detect local magnetic fields. SQUIDS of varying sizes, and hence sensitivities may detect different magnitudes of magnetic fields. SQUIDs may be oriented to detect magnetic fields in a variety of orientations, for example along an orthogonal reference frame of a chip or wafer. The SQUIDS may be formed or carried on the same chip or wafer as a superconducting processor (e.g., a superconducting quantum processor). Measurement of magnetic fields may permit compensation, for example allowing tuning of a compensation field via a compensation coil and/or a heater to warm select portions of a system. A SQIF may be implemented as a SQUID employing an unconventional grating structure. Successful fabrication of an operable SQIF may be facilitated by incorporating multiple Josephson junctions in series in each arm of the unconventional grating structure.

Abstract: The present invention discloses a novel magnetic sensor device performing direct magnetic field imaging, comprising a probe having a conical tip portion which is configured as a sensor having two superconductors separated by a thin non-superconducting layer (such as a Josephson junction based sensor), where the non-superconducting layer is located at the apex portion of said conical tip, thereby defining electron tunneling region(s) at said apex portion. The technique of the present invention enables the sensor device to be very small and to be brought very close to the sample surface.

Abstract: A superconducting quantum interference devices (SQUID) comprises a superconducting inductive loop with at least two Josephson junction, whereby a magnetic flux coupled into the inductive loop produces a modulated response up through radio frequencies. Series and parallel arrays of SQUIDs can increase the dynamic range, output, and linearity, while maintaining bandwidth. Several approaches to achieving a linear triangle-wave transfer function are presented, including harmonic superposition of SQUID cells, differential serial arrays with magnetic frustration, and a novel bi-SQUID cell comprised of a nonlinear Josephson inductance shunting the linear coupling inductance. Total harmonic distortion of less than ?120 dB can be achieved in optimum cases.

Abstract: A method of searching for a material fated to generate an interband phase difference soliton includes the steps of generating an AC in a soliton candidate material, identifying a loss of AC magnetic susceptibility of the siliton candidate material due to a turn and a twist cut of a vortex line and judging whether or not the soliton candidate material is capable of generating soliton.

Abstract: A magneto-encephalographic equipment superconducting magnetic-shield comprising a vacuum-tight body comprising an outer enclosure wall, a first inner enclosure wall inserted in the outer enclosure wall to define a upper closed space, and a second inner enclosure wall to define a lower open space. The first and second inner enclosure walls are arranged with the bottom of the first inner enclosure wall facing the ceiling of the second inner enclosure wall. A first enclosure of HTSC and a second enclosure of high-permeability material are concentrically arranged in the annular vacuum space defined between the first and second inner enclosure walls and the outer enclosure wall. A head-accommodating area is delimited by the hollow partition between, the bottom of the first inner enclosure wall and the ceiling of the second inner enclosure wall both facing each other, and a plurality of SQUID sensors are arranged in the upper closed space, encircling the head-accommodating area.

Abstract: Multiple SQUID magnetometers that include at least two SQUID loops, each of which is composed of at least two Josephson Junctions connected in parallel with superconducting wires, are provided. The SQUID loops are fabricated such that they share a common Josephson Junction. Devices and application that employ the multiple SQUID magnetometers are also provided.

Abstract: The invention relates to a SQUID arrangement for measuring a change in a magnetic field, the change in the magnetic field being caused by a specimen that is arranged in a magnetization field and the SQUID arrangement including a direct current SQUID. In order to provide a simple design in which the losses in the magnetic flux are also simultaneously minimized, it is provided that the SQUID itself is embodied for generating the magnetization field.

Abstract: Provided is a highly accurate optical pumping magnetometer, in which a static magnetic field and an oscillating field to be applied to a vapor cell are stabilized. To this end, the optical pumping magnetometer includes: Helmholtz coils for applying a constant static magnetic field to a vapor cell serving as a magnetic field detector; fluxgate magnetometers for detecting environmental magnetic noise in two directions of X-axis direction and Y-axis direction other than Z-axis direction which is a direction for detecting a magnetic field coming out of a measurement object while locating the vapor cell in the center thereof; magnetometer drive circuits for driving the fluxgate magneotometers; current converters for converting outputs of the magnetometer drive circuits into amount of currents; and magnetic field generating coils for generating a magnetic field in a phase opposite to the environmental magnetic noise in the two directions.

Abstract: A method of forming a quantum system comprising computational elements, consisting of an insulated ring of superconductive material, and semi-closed rings, which are used as an interface or input/output facility between the quantum bit and the external world, is disclosed. Faraday induction is used to provide electromagnetic coupling between adjacent computational elements and between the computational elements with interface elements of the quantum system. Therefore the corresponding magnetic flux acts as an information carrier. Ferromagnetic cores are used to improve the magnetic coupling between adjacent elements of the quantum system.

Abstract: A method and device for field detection are provided, in which one or more gradiometers (31, 32, 33) are positioned in the field and rotated about their axes. Rotation of a single gradiometer allows an output signal of the gradiometer to be analyzed in the Fourier domain, which allows particular field components to be obtained, and also separates the field signal from noise, in the frequency domain. Use of three such rotating gradiometers with non-parallel axes allows a complete magnetic field gradient tensor to be obtained with data redundancy, and can reduce crosstalk.

Abstract: A superconducting magnetic field detection element (10) comprising at least one superconducting pick-up loop (12) formed on a common flexible substrate (11), wherein the common flexible substrate (11) is in a non-planar position, such that the at least one superconducting pick-up loop (12) is operable to detect magnetic fields of differing orientation.

Abstract: The induced magnetic field detecting apparatus of the present invention is configured so as to irradiate laser light onto an inspection target from the same side as the side on which a pickup coil for magnetic field detection is disposed and be able to perform irradiation of the laser light and detection of a magnetic field induced by the irradiation of the laser light on the same side relative to the inspection target. Furthermore, the induction magnetic field detection apparatus of the present invention adopts a configuration in which laser light is irradiated onto the inspection target through the inside of the loop-shaped pickup coil set up inside the container. This configuration exerts an effect of being able to detect a feeble magnetic field with higher accuracy.

Abstract: There is provided a magnetic shield which can shield external magnetic fields in the direction of an axis of a tubular magnetic shield and in the direction vertical to the axis. A magnetic shield has a cylindrical ferromagnetic substance 2-1 having openings on both ends and two superconducting loops housed in the respective insides of superconducting loop containers 1-1, 1-2. The superconducting loops are constructed of high critical temperature superconducting wire. The two superconducting loops have semicircle shapes and are arranged in x-direction so as to be symmetrical with respect to an axis of the cylindrical ferromagnetic substance 2-1. The superconducting loop containers 1-1, 1-2 are arranged in the insides near both open ends of the cylindrical ferromagnetic substance 2-1 with supports 20. The superconducting loops are arranged to be vertical to the axis of the cylindrical ferromagnetic substance 2-1. The superconducting loops are cooled by liquid nitrogen or a refrigerator.

Abstract: The present invention relates to a method of controlling the characteristics of a double relaxation oscillation SQUID having a reference junction. In the method of controlling characteristics of a reference junction-type double relaxation oscillation SQUID (RJ-DROS) having a signal SQUID and a reference junction, a reference DC current flows through the reference junction in order to control the characteristics of the DROS. A modulation width of an averaged relaxation voltage, which reacts to a magnetic flux, may be controlled at the reference junction. An amount (modulation depth) of an averaged relaxation voltage, which reacts to a magnetic flux, may be controlled at the reference junction. An amount of an operation application current may be controlled at the reference junction. Accordingly, the reference current of the reference junction can be changed by causing the current to flow through the reference junction.

Abstract: An instrument for measuring sub-pico Tesla magnetic fields using a superconducting quantum interference device (SQUID) inductively coupled to an unshielded gradiometer includes a filter for filtering magnetically-and electrically coupled radio frequency interference (RFI) away from the SQUID. This RFI is principally coupled to the SQUID via the unshielded gradiometer. The filter circuit includes a resistor-capacitor (RC) combination interconnected to first and second terminals so that it is parallel to both an input coil of the SQUID and the gradiometer. In addition, a shielding enclosure is used to electromagnetically shield the filter circuit from the SQUID, and a method is employed to increase the impedance between the input coil and the SQUID without diminishing the overall sensitivity of the instrument.

Abstract: An apparatus for controlling and adjusting the magnetic state of a magnetic probe for detecting magnetic signals of a sample, it employs a negative feedback control unit to counter the change of magnetization of the magnetic probe. The local magnetic field of the sample influences the magnetization of the magnetic probe. Through the feedback coil inductively coupled to the magnetic probe, the variation of magnetization of the magnetic probe is compensated by the magnetization induced by the feedback coil. This apparatus is capable of reducing the magnetic interaction between the magnetic probe and sample. Meanwhile, a current bias unit is used for adjusting the magnetization of the magnetic probe to an arbitrary value. This capability allows a scanning probe microscope applying this invention to manipulate magnetic objects.

Abstract: The object of the invention is to provide a biomagnetism measuring device using a high-performance cylindrical shielding apparatus provided with a flange-type plate having an opening formed on a circumferential face, an auxiliary cylinder in which one or plural cylindrical members are connected so that the central axis of the opening of the flange-type plate and each central axis of the cylindrical members are coincident, cylindrical shields having first, second and third angular ranges with the y-axis, a revolving door having a cutout in a portion parallel to the y-axis and acquired by integrating the cylindrical shields, shield bases for supporting the cylindrical shield to which the flange-type plate is connected in a circular-arc part at both ends, revolving parts for revolving the revolving door in a circumferential direction of the y-axis along a circumferential part of the cylindrical shield and opening or closing an opening in the circumferential direction, a cryostat arranged inside the opening of th

Abstract: A scanning SQUID microscope is set forth to provide improved output imaging. The SQUID microscope includes a vertically adjustable housing adapted to securely retain a SQUID loop or sensor. A scanning stage of the SQUID microscope is adapted to support a sample while moving the sample along a predetermined path to selectively position predetermined portions of the sample in close proximity to the SQUID loop or sensor to permit the loop or sensor to detect predetermined magnetic field information provided by the predetermined portions of the sample. A position control processor coupled to the scanning stage is operative to receive and process the predetermined magnetic field information to provide corresponding position noise information. Criteria are also presented for determining the expected level of position noise under given experimental conditions.

Abstract: A scanning microscope for high resolution current imaging by direct magnetic field sensing of a sample maintained in an ambient environment. The scanning microscope uses a magnetic sensor such as a SQUID and a fiber probe magnetically coupled between the SQUID sensor and the sample under study. The fiber probe has a sharply defined tip for high resolution probing and for reaching minute cavities on the surface of the sample. The coupling between the tip of the fiber probe and the sample is controlled by a distance control mechanism, in the range of 1-100 nm. The material of the fiber probe with high permeability and low magnetic noise is chosen to optimize flux transmission to the magnetic sensor. Magnetic coupling to the sensor is maximized by keeping the distance between the end of the fiber probe and the sensor to approximately 0-100 ?m. The fiber probe is integrated into the fiber holder for easy replacement of the fiber probe.

Abstract: A non-destructive method of narrowing down the location of a failure in a sample includes a first step of acquiring first and second images of magnetic-field distributions obtained by scanning a laser beam irradiating first and second samples, respectively, and if there is a difference between the first and second images of the magnetic-field distributions, a second step of acquiring first and second current images from magnetic-field distributions acquired by scanning the first and second samples by a magnetic-field detector in a state in which a prescribed location on the first and second samples is being irradiated by the laser beam. The difference between the first and second current images is found and, based upon the difference image found, it becomes possible to identify a disparity in current paths relating to the prescribed location on the first and second samples.

Abstract: In a SQUID magnetometer, high resolution, a high slew rate, and a high dynamic range are achieved without using expensive circuit components having a large number of processing bits and enabling a high speed processing operation. A digital FLL circuit using a double counter system is provided. This circuit utilizes two or more counters, for example, a change range counter in a digital FLL for carrying out a processing operation at a high speed and a reproducing counter in a control/measuring computer. In addition, in the present invention, hysteresis characteristics having a 1?0 positive margin is used. That is, a change of a state of a magnetic flux is counted by means of a counter. At the time of this change, control is made so as to track a different channel between cases in which a magnetic flux increases and decreases, thereby stabilizing the control.

Abstract: The invention relates to a magnetic flow sensor (1, 21, 51) comprising a) a loop-shaped magnetic field conductor comprising a point (2, 22, 32, 52) which expands to form a bar or a film (3, 23, 52), a loop-shaped part (3a, 23a, 53a) and at least one part (4, 24, 54?, 54?) which guides back the magnetic field lines of the probe, b) SQUID (7, 27, 57), c) and a diaphragm (5, 25, 35, 55) comprising a hole (6, 26, 36, 56), whereby the part (4, 24, 54?, 54?) which guides the magnetic field lines of the probe back to the loop-shaped magnetic field conductor is connected to the diaphragm (5, 25, 35, 55).

Abstract: A scanning SQUID microscope capable of high frequency magnetic field measurements uses a hysteretic SQUID detector and a pulsed sampling technique which permits to extend the bandwidth of the SQUID microscope to above GHz region. The system can be readily incorporated into a 4.2k scanning SQUID microscope for imaging chips at room temperature. By biasing the hysteretic SQUID with pulses of a predetermined amplitude, and adjusting a modulation flux applied to the hysteretic SQUID at a plurality of time delays between the activation of the sample under study and the bias pulse, the hysteretic SQUID can be switched on, and the modulation flux value corresponding to such a switching event as a function of time is considered as representation of the magnetic field emanating from the sample under study.

Abstract: To obtain a superconducting driver circuit which can obtain an output voltage of several millvolts or above, can use a DC power source as a driving power source, can form no capacitance between it and a ground plane, and has a small occupation area, the superconducting driver circuit is constructed by superconducting flux quantum interference devices (SQUIDs) each constructing a closed loop having as components two superconducting junctions and an inductor. The SQUIDs share the inductors and are connected in series in three or more stages.

Abstract: A system (10) for measuring magnetic fields, wherein the system (10) comprises an unmodulated or direct-feedback flux locked loop (12) connected by first and second unbalanced RF coaxial transmission lines (16a, 16b) to a superconducting quantum interference device (14). The FLL (12) operates for the most part in a room-temperature or non-cryogenic environment, while the SQUID (14) operates in a cryogenic environment, with the first and second lines (16a, 16b) extending between these two operating environments.

Abstract: A method and apparatus are disclosed for high resolution imaging. The disclosed apparatus includes a low temperature SQUID sensor mounted in close proximity to a dewar thin window. A radiation shield has an extension surrounding the detection coil.

Abstract: An apparatus for measuring electromagnetic characteristics includes a sample rod with a sample fixed to a lower part thereof, a helium 3 refrigerator, in which the sample rod is inserted, having a main pipe that forms around the sample rod a space that is cooled by helium 3, a device for supplying helium 3 to the helium 3 refrigerator, an inner tube portion, into which the main pipe is inserted, that supports at an upper part thereof the refrigerator, an outer tube that cools an outer periphery of the inner tube with helium, a liquid helium container that supplies liquid helium to the outer tube, and a device for measuring the electromagnetic characteristics of the sample.

Abstract: A device is proposed for high-resolution measurement, in particular for high-resolution absolute measurement of magnetic fields, having a network (1) of transitions (3) between superconductors (5, 6) which exhibit Josephson effects, called junctions below, the network comprising closed meshes (7, 8, 9, 10, 11, 12, 13), denoted by cells below, which in each case have junctions (3), which junctions are connected in a superconducting fashion, and at least three of these cells being connected in a superconducting and/or nonsuperconducting fashion. The object of the invention consists in further developing this device in such a way that it is possible to make absolute measurements of magnetic fields in a highly sensitive fashion.

Abstract: According to this invention, a magnetic sensor (1) for measuring a magnetic field distribution of a measurement target S by using a SQUID (2) is characterized by including a storing portion (10) with an interior held in a vacuum state to store the SQUID (2), and a substantially needle-like flux introducing member (30) made of a high-permeability material to guide a magnetic flux from the measurement target (S) to the SQUID (2), wherein the flux introducing member (30) has one end (30a) located in the storing portion (10) to be away from the SQUID (2) and the other end (30b) located outside the storing portion (10).

Abstract: A signal detector has a SQUID, a bias current supply circuit for supplying a bias current to the SQUID, and a drive circuit for detecting a magnetic flux by receiving a voltage signal of the SQUID and reading out the input signal as an output voltage. The drive circuit has two systems including a flux-locked loop system for converting a voltage signal of the SQUID into a current signal and making a magnetic flux inside the SQUID constant by feeding back a signal whereto, and an output system separate from and operating independently of the flux-locked loop system for converting a voltage signal of the SQUID and reading out the converted voltage signal without feeding back a signal to the SQUID.

Abstract: In order to measure magnetic characteristics of a sample, the latter is positioned above the SQUID so that both the SQUID and the sample are supported in a vessel in a gaseous nitrogen space above a liquid nitrogen coolant so that the measurement can take place at ambient pressure and in a nitrogen atmosphere.

Abstract: In a superconductive quantum interference element comprising Josephson joints, a washer coil and a detecting coil constituting a superconductive loop and a feedback modulation coil, to provide a superconductive quantum interference element capable of promoting spatial resolution by preventing an effective detection area of the detecting coil from enlarging even when a width of a superconductive wiring constituting the detecting coil and a superconductive film at a vicinity of the detecting coil are larger than an inner diameter of the detecting coil, there is constructed a superconductive quantum interference element having a structure provided with a slit at a detecting coil and/or a superconductive film at a periphery of the detecting coil.

Abstract: A self-adjusting assembly and method are disclosed. In the disclosed embodiments, a support assembly for supporting a device comprises a pair of support members for supporting the device. One of the members is adapted to help support the device from a ground, and another of the members is adapted to provide lateral support for the device and to permit free longitudinal movement of the device as it expands or contracts due to temperature variations.

Abstract: A dewar for SQUID is provided. In the dewar for SQUID, an amount of leak gas discharged from absorbent arranged in the upper portion higher than the liquid surface level of liquid helium is small even if the liquid surface level of the liquid helium is lowered.

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 SQUID bias current adjustment device supplies a sinusoidal current at 40 kHz, for example, to a coil to generate magnetic field at a SQUID. The amplitude of the field corresponds to a half period of a field-voltage characteristic. Voltage generated from the SQUID at this time is filtered by using a filter to pick out components of 40 kHz and 80 kHz. The picked out signal components are rectified and converted to direct current, and the bias current is adjusted such that the maximum value is obtained. In this way, a SQUID bias current adjustment device can be provided capable of automatically adjusting bias current properly in a short period of time.

Abstract: Apparatus for measuring gravitational attraction of the Earth comprising a loop formed from a superconductor material. The loop being divided into a first portion and a second portion having a predetermined length and configuration. The loop being positioned under predetermined angle with respect to a horizontal plane. There are also means for initiation of a flow of superconducting carriers in each of first and second portions, and at least one phase shift inducing means formed in the loop. The first portion being positioned with respect to the second portion in such a way that the superconducting carriers conducted through the first portion spend a period of time at a different gravitational potential of the Earth than superconducting carriers conducted through the second portion, thus creating a gravitationally induced phase shift. The apparatus being completely isolated from influence of any external magnetic field.

Abstract: A biomagnetic field measuring apparatus including: a plurality of magnetometers each employing a superconducting quantum interference device for measuring the magnetic field generated from an organism; a unit for calculating a pseudo-current from a normal component of the magnetic field; a unit for calculating the pseudo-current from the magnetic field obtained from the plurality of magnetometers to integrate the pseudo-current in a fixed direction on the circumference at a fixed distance from each of the associated ones of the sensors; a unit for calculating a maximum value or a minimum value of the integral value obtained by the unit for performing the integral; and a unit for calculating a difference value between the absolute value of the maximum value and the absolute value of the minimum value.

Abstract: A magnetic field measuring apparatus for precise cancellation of environmental noise includes a plurality of first SQUID gradiometers to detect noise and biomagnetic fields, a plurality of second SQUID gradiometers to detect noise, a driving circuit to drive these gradiometers, and a computer to execute signal processing after collecting the signals detected by these gradiometers. First and second SQUID gradiometers are provided which include first-order gradient pickup coils with the baselines formed by the coils of second gradiometers being shorter than those of first gradiometers. The apparatus cancels noise, from detected biomagnetic signal waveforms, caused by variant noise cancellation rates of the coils of first gradiometers, different baselines of the coils of second gradiometers, and the frequency property of a magnetically shielded room in which the apparatus is installed.

Abstract: Read-out electronics for DC SQUID sensor systems, the read-out electronics incorporating low Johnson noise radio-frequency flux-locked loop circuitry and digital signal processing algorithms in order to improve upon the prior art by a factor of at least ten, thereby alleviating problems caused by magnetic interference when operating DC SQUID sensor systems in magnetically unshielded environments.

Abstract: A modulation current at a predetermined frequency f is applied from an AC source to a flux locked loop for maintaining magnetic flux supplied to a SQUID at a constant value. An output voltage is picked out from the SQUID in this state to which a predetermined bias current is being applied from a current and field bias application circuit, and the picked out voltage passed through a filter and a rectifier is monitored by a voltage monitor. The filter picks out a frequency component of 80 kHz which is twice as high as the frequency component f, 40 kHz, applied from the AC source, and maximizes it. In this way, a method and a device for easily adjusting magnetic field bias in a modulation drive circuit for a SQUID can be provided.

Abstract: A magnetic field sensor which can be used as an active antenna is disclosed that is capable of small size, ultrawideband operation, and high efficiency. The sensor includes a multiplicity of magnetic field transducers, e.g., superconducting quantum interference devices (SQUIDs) or Mach-Zehnder modulators, that are electrically coupled in a serial array. Dummy SQUIDs may be used about the perimeter of the SQUID array, and electrically coupled to the active SQUIDs for eliminating edge effects that otherwise would occur because of the currents that flow within the SQUIDs. Either a magnetic flux transformer which collects the magnetic flux and distributes the flux to the transducers or a feedback assembly (bias circuit) or both may be used for increasing the sensitivity and linear dynamic range of the antenna.

Abstract: Architecture for frequency multiplexing multiple flux locked loops in a system comprising an array of DC SQUID sensors. The architecture involves dividing the traditional flux locked loop into multiple unshared components and a single shared component which, in operation, form a complete flux locked loop relative to each DC SQUID sensor. Each unshared flux locked loop component operates on a different flux modulation frequency. The architecture of the present invention allows a reduction from 2N to N+1 in the number of connections between the cryogenic DC SQUID sensors and their associated room temperature flux locked loops. Furthermore, the 1×N architecture of the present invention can be paralleled to form an M×N array architecture without increasing the required number of flux modulation frequencies.

Abstract: A magnetic field sensor has a SQUID, which is made of thin film of oxide superconductor deposited on a substrate, and a magnetic flux guide that has a higher permeability than vacuum to increase the effective capture area. The flux guide is positioned and aligned over a hole that is surrounded with superconducting current loop formed in a washer thereof. The SQUID also has a pair of Josephson junction formed on the washer and a pair of opposite terminals for connecting the washer to an outer circuit. In the SQUID, a variation in magnetic flux passing through the hole is detected in a form of variation in output voltage.

Abstract: An apparatus and method for measuring a second-order gradient of a magnetic field using a super conductor quantum interference device (SQUID) which obtains the second-order gradient of the magnetic field with a simple-constructed and low-priced measuring apparatus having three SQUID sensors and one differential circuit only.