Fujitsu Corporation

Norio Fujimaki

Yoshiyasu Nakashima

Yutaka Igarashi

Kohtaroh Gotoh

Takehiko Hayashi

Hajime Hayashi

Takao Goto

Shinya Hasuo

Kohtaro Gotoh

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.

Multichannel SQUID flux meter having multiplexed SQUID flux sensors

An apparatus for eliminating a magnetic flux from a superconducting circuit comprises a substrate on which a superconducting circuit is formed, a heating fixture including resistance heating elements and provided in the vicinity of the superconducting circuit, a driving unit connected to the heating fixture for energizing the same by supplying a drive current to each resistance heating elements in the heating fixture. The heating fixture is so configured that, upon energization of the resistance heating elements in the heating fixture, there is formed a region of normal conduction state characterized by a temperature that exceeds the critical temperature of the normal conduction-superconduction transition, in at least a part of the superconducting circuit, and such that the heating fixture produces a minimized magnetic field upon the energization of the resistance heating elements. The driving unit controls energization of the heating fixture such that the region of normal conduction state moves consecutively and continuously to a periphery of the superconducting circuit.

Device for eliminating trap of magnetic flux in a superconduction circuit

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. A controller is provided connected to the resistance fixture and the superconducting detector for receiving the output pulses therefrom and producing a drive current for energizing the resistance fixture. Simultaneously with the energization of the resistance fixture, the controller resets the feedback circuit such that the counteracting feedback magnetic flux is deenergized.

Superconducting quantum interference magnotometer having a feedback

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. Further, a selection circuit provided in the cooling vessel to selectively provide the control signal to the gate circuit in response to a selection signal.

Superconducting quantum interference magnetometer having a plurality of

A SQUID system, such as a SQUID magnetometer, including a SQUID and a bias circuit supply a pulsed bias current to cause an output of a pulsed output from an injection point in the SQUID. The SQUID has a predetermined threshold characteristic which is asymmetrical with respect to a coordinate defined by a current to be measured and flowing through a first junction line and the bias current. The bias current supplied from the bias circuit comprises pulses which are alternately positive polarity pulses and negative polarity pulses, and has a first frequency. The threshold characteristic and the bias current are defined to output an output signal comprising pulses, the number thereof being proportional to the current to be measured and a polarity thereof corresponding to a polarity of the current to be measured.

Digital squid system adaptive for integrated circuit construction and

A Josephson-junction logic circuit comprises at least one Josephson-junction logic gate which has a variable threshold-type superconductive quantum interference element. The Josephson-junction logic gate comprises a superconductive inductance loop, and at least two Josephson junctions included in the superconductive loop. At least two current-injection lines connected to the superconductive loop and at least one magnetically coupled line are provided. The magnetically coupled line is placed so as to be magnetically coupled to the inductance. Because of this construction, the number of inputs can be increased. Also, various logical functions can be obtained. Further, various logic circuits can be formed by simply changing the photomask for the wiring between the gates.

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Atsugi, Japan

Norio Fujimaki