Abstract: In a nondestructive method of quantitatively evaluating a degree of plasticity of ferromagnetic materials, a magnetic field of a surface of a ferromagnetic test body is measured using a magnetic sensor, and the surface of the ferromagnetic test body is partitioned into regions corresponding to domains of the ferromagnetic test body. A difference between a maximum value and a minimum value of a magnetic signal corresponding to the magnetic field for each of the domains is calculated as a spatial difference amount. A distribution width of the spatial difference amounts and an amount of residual strain corresponding to an amount of plastic deformation of the ferromagnetic test body is measured. A correlation between the distribution width of the spatial difference amounts and the amount of residual strain is calculated. A degree of plasticity of the ferromagnetic test body in calculated in accordance with the correlation.

Abstract: A detecting coil of a SQUID is made of a superconductive film material having a critical temperature higher than a critical temperature of a superconductive film material composing a Josephson junction part. It is possible to measure the sample even when its temperature is higher than the critical temperature of the Josephson junction section by increasing the critical temperature of the detecting coil than that of the Josephson junction section.

Abstract: To provide an effective method of nondestructively and easily judging plasticization of steel used in a real construction. A magnetic sensor 10 is made to scan along the surface of steel to detect a magnetic field caused by a magnetic anisotropy induced by plastic deformation of the steel, and the existence and position of the plasticization is judged from the state of distribution of the magnetic field. As a magnetic sensor, a differential type one comprised of detection coils 10a and 10b, the winding directions of which are opposite to each other, is used to compensate a magnetic field intrinsic to the steel.

Abstract: A nondestructive inspection apparatus having a SQUID is made with compact configuration and is capable of detecting a metallic or non-metallic metal for defects, corrosion, and the like, by forming the SQUID and a magnetic field applying coil on the same substrate. The SQUID comprises two Josephson junctions, a washer coil connected to the Josephson junctions to form a superconducting loop, shunt resistors, a damping resistor, and a feedback modulation coil, all of which are formed from a superconducting thin film on a supporting substrate. A magnetic field applying coil is formed on the same supporting substrate with a superconducting thin film or a normal conducting metal thin film. The magnetic field applying coil, which generally has plural turns around the SQUID, applies a dc or ac magnetic field to a sample. The change in magnetic field caused by a defect in the sample is detected by the washer coil, and the position and size of the defect may thus be determined.

Abstract: To provide a nondestructive inspection apparatus with a reduced distance between a superconducting magnetic sensor and an object under inspection, a cryostat for cooling the sensor to a superconducting state is provided with inner and outer vessels. The inner vessel has a baseplate on which the magnetic sensor is disposed, and has an inner wall defining a central chamber for containing a refrigerant for cooling the magnetic sensor. The outer vessel has an inner wall defining a central chamber for containing the inner vessel, the magnetic sensor and the stage. A gap between the inner and outer vessels is evacuated to insulate the inner chamber from the ambient atmosphere. To facilitate ease of transferring an object to and from the stage for inspection, a load lock area is provided adjoining the outer vessel.

Abstract: In order to enhance the sensitivity of a nondestructive testing system, a pair of superconducting coils are disposed in the same plane such that a current flowing through the respective coils when exposed to a uniform magnetic field cancels out. As a result of this configuration, the detection coils are immune to noise, offset fields or other uniform ambient phenomena. In one embodiment, the nondestructive testing unit includes a plurality of detection coils, a SQUID having a pair of connectors for connection to the detection coils, a probe for supporting the detection coils and the SQUID in a coolant, a cryostat for supporting the probe and for keeping the coolant constant, a controller for processing a signal transmitted from the SQUID, and a display device for displaying the result of the processing. At least two detection coils are disposed in the same plane, are directly connected to the SQUID and are integrated on a semiconductor substrate.

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: 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 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.