Abstract This paper describes study on remote inspection technology for pipes by using magnetostriction-based ultrasonic guided wave and high temperature superconductor (HTS) superconducting quantum interference device (SQUID) gradiometer. Magnetized nickel plates were adhered on an aluminium pipe sample, in order to use them as magnetostriction-based guided wave transceivers. A pair of 10mm-wide nickel plate with different angle arrangement were used to transceive uniformly distributed guided waves at all angles. A field coil was wound around one set of the nickel plates as a transmitter, while the other was used as a receiver. T (0, 1) mode guided wave was generated on the pipe by supplying a burst sine wave current of one cycle at several tens kHz to the coil. Multipoint measurements of the T (0, 1) mode guided waves around the pipe’s circumference were carried out by setting the HTS-SQUID gradiometer above the receiver with lift-off of about 9 mm and rotating the pipe for 360 degrees. Signal of reflected wave from an artificial slit on the sample was well detected. We simulated the distribution of the guided wave propagating on the pipe with the slit using an ultrasonic simulator and compared the distribution with the experiment result. The guided wave signal distributions including the defect signal obtained by experiment and simulation agreed well.

In this paper, we demonstrated all-round inspections on aluminum pipe samples with different types of defects using HTS-SQUID-based ultrasonic guided waves, and analyzed defect signals using computer simulation. In order to transceive uniformly distributed T (0, 1) mode guided waves on aluminum pipe samples, two pairs of nickel thin plates magnetized in the longitudinal direction using a solenoid coil were glued on each sample with different angle arrangement. They were used as magnetostriction-based guided wave transceivers, and a coil was wound around one pair of the nickel plates as a transmitter, while the other was used as a receiver. Artificial defects, such as a slit perpendicular to axis of the pipe and inclined slit, were made on the respective pipe samples. All-round inspection of the T (0, 1) mode guided waves around circumferences of the pipes were carried out by rotating the pipe for 360° with step of 45°. Signals of reflected wave from the artificial slits were well detected. We simulated distribution of the guided waves propagating on the pipes with the slits using an ultrasonic simulator for two-dimensional models. The guided wave signal distributions including the defect signals obtained by experiments and simulations agreed well.

In this paper, multipoint measurements of ultrasonic guided waves on an aluminum sample pipe were performed using a high-temperature superconductor superconducting quantum interference device (HTS-SQUID) gradiometer. Two magnetized thin nickel plates were glued on the pipe with circumferential defects. One of them was used as a magnetostrictive transmitter by winding a coil around it to generate T (0, 1) mode guided waves. The HTS-SQUID gradiometer was set to measure $dB-{x}/dz$ above the other nickel plate with a lift-off distance of about 3 mm. The multipoint magnetic flux measurements of the guided waves generated on the pipe without and with the defects were conducted while changing position of the HTS-SQUID gradiometer around the pipe. Contour maps of the magnetic signals were made on the plane of time and angle of the SQUID. The magnetic signals due to the defects were successfully measured in the contour maps. Intensity of the magnetic signal due to the defect increased in proportion to width of the defect. The intensities of the magnetic signals slightly varied depending on the angle of the SQUID. We discussed this phenomenon and concluded that magnetization inside the nickel plate of the receiver was no uniform.

In this paper, we investigated ultrasonic guided wave measurements on aluminium pipes with defects using high temperature superconducting (HTS) SQUID gradiometer and magnetostrictive sensors (MsS), which utilized pre-magnetized nickel thin plates. One of the pipes was provided with an axial defect, and the other was provided with a circumferential defect. The MsSs were used by adhering them on circumferences of the pipes to generate ultrasonic guided waves and to receive the waves by converting them into the magnetic signals, which were measured by the HTS-SQUID gradiometer. Guided wave measurements using the MsSs and the gradiometer demonstrated that magnetic signals of about 3.3 mΦ0 due to reflected waves from both the defects were successfully detected. Reflected wave signals of about 1.4 mΦ0 from thin nickel plates of the MsS on the pipes were also detected.

This article describes research on the novel high-temperature superconductor (HTS) superconducting quantum interference device (SQUID) non-destructive evaluation (NDE) technique for metallic pipes based on ultrasonic guided waves. We constructed HTS-SQUID NDE system for pipes based on ultrasonic guided waves, which were generated and received by means of the magnetostrictive effects. Using the system, we measured magnetic signals due to T (0, 1) mode ultrasonic guided waves that transmitted on aluminium pipe, and investigated influences of measurement parameters to the magnetic signals, such as direction of a HTS-SQUID gradiometer, lift-off distance, and intensity and frequency of input current fed to a magnetostrictive transmitter. With the gradiometer oriented parallel to the pipe axis, more than 10 times larger signals were measured compared with that oriented perpendicular to the pipe axis. Magnetic signals measured by the gradiometer were inverse proportional to the power of the list- off distance, and proportional to the intensity of the input current up to 1 App. Relation between the frequency of the input current and the measured signal was shown and discussed.

This paper describes basic research of a novel remote nondestructive evaluation (NDE) technique for pipes combining high-sensitive high-temperature superconductor superconducting quantum interference device (HTS-SQUID) and ultrasonic guided waves. Measurements of magnetic signals due to acoustic emission (AE) and ultrasonic-guided waves on a steel pipe were demonstrated using an HTS-SQUID gradiometer. To convert the guided waves into magnetic signals, the inverse magnetostrictive effect of a magnetized nickel thin plate glued around the pipe's circumference was utilized. An AE sensor and alternative magnetized nickel thin plate with wound coil were used as AE and ultrasonic-guided wave transmitters. Magnetic signals due to AE and ultrasonic guided waves were successfully measured by the HTS-SQUID gradiometer, which was set above the nickel film with a lift-off of about 2 mm.

In this paper, we demonstrated detection of deeplying defects in aluminum alloy samples utilizing an eddy current technique while moving a robust HTS-SQUID magnetometer integrated on a robot-based NDE system in an unshielded environment. A bicrystal-Josephson-junction-based HTS-SQUID magnetometer, which was covered by an alternative HTS film as a superconducting shield, both having amesh structure with a 5-mu m line width, was used in the system. An active magnetic shield scheme was also utilized in order to cancel magnetic flux coupling to the magnetometer during motion. For comparison, detection of the same defects using a ramp-edge-Josephson-junction-based HTS-SQUID gradiometer, which has the roughly equivalent area with the magnetometer, was also carried out. Experimental results showed that the magnetometer had better capability to detect deeper defects in conductive materials than the gradiometer.

In this study, we developed a practical magnetic metallic contaminant detector using three high-Tc RF superconducting quantum interference devices (SQUIDs) for food inspection. Finding small metallic contaminants is important for food safety. When contamination occurs, the manufacturer of the product suffers a great loss to recall the tainted products. Therefore we developed a practical food contaminant detection system based on high-Tc RF SQUIDs. The system was covered with waterproof stainless steel plates, and the outer dimensions of the system were 2450 mm (W) x 714 mm (D) x 1555 mm (H). An acceptable inspected object size was 150 mm (W) x 100 mm (H), which is sufficiently large for practical food inspection. A digital filtering technique has been newly introduced to reduce noise. As a result, the signal-to-noise ratio (SNR) was dramatically improved, and we were able to robustly detect a steel ball as small as 0.3 mm in diameter.

We developed a robust HTS-SQUID magnetometer utilizing bicrystal SrTiO3 substrates, single-layer YBa2Cu3O7-x films and flip-chip technique, aiming for movable robot-based NDE system in unshielded environment. Robustness in the unshielded environment was achieved by coverage of the SQUID magnetometer with another cross-shaped HTS film in flip-chip configuration, and introduction of mesh structure in both the magnetometer and the HTS film. SQUID parameters, such as critical current 2I(c), resistance R-n/2, modulation voltage depth V-PP, and flux noise S-Phi(1/2) F, were measured in DC and AC fields. The SQUID magnetometer was rotated in unshielded environment, and moved by a robot arm, resulting in stable operation during the motion at 20 mm/s with active magnetic shielding technique.

We report the fabrication of magnetic metallic contaminant detectors using multiple high-Tc SQUIDs (superconducting quantum interference devices) for a lithium-ion battery cathode sheet. Finding ultrasmall metallic foreign matter is an important issue for a manufacturer because metallic contaminants carry the risk of an internal short. When contamination occurs, the manufacturer of the product suffers a great loss from recalling the tainted product. Hence, a detection method of small contaminants is required. Preventing such accidents is also an important issue for manufacturers of industrial products. Given the lower detection limit for practical X-ray usage is in the order of 1 mm, a detection system using a SQUID is a more powerful tool for sensitive inspections. We design and set up an eight-channel roll-to-roll high-Tc dc-SQUID inspection system for a lithium ion battery cathode sheet. We report the evaluation results that the detection of a small phi 18 -mu m steel particle on a lithium-ion battery cathode sheet was successfully done.

We have developed a method to improve the detection sensitivity for the magnetization M of magnetic nanoparticles (MNPs) using a high Tc superconducting quantum interference device magnetometer. The M response of MNP to an applied magnetic field H(M-H characteristics) can be divided into a linear region and a saturation region, which are separated at a transition point H-k. When applying an excitation ac magnetic field (Hac) and an additional dc bias field H-dc = H-k, the second harmonic of M reaches a maximum due to the nonlinearity of its M-H characteristics. This harmonic is stronger than any other harmonics, including a third harmonic. The advantage of using the second harmonic response is that the response can be measured even in a small field Hac. The M response of MNP was systematically analyzed and experimentally demonstrated. For conventional detection using a third harmonic, the amplitude of the Hac must be larger than the threshold level, which is almost the same as H-k. Detection methods using a second harmonic can be applied to magnetic particle imaging. We finally demonstrate the construction of a 1-D image of two separated bottle-shaped MNP samples using the method with a lock-in amplifier.

We report the fabrication of magnetic metallic contaminant detectors using multiple high-Tc superconducting quantum interference devices (SQUIDs) for food. Finding small metallic contaminants is important for food safety. People may ingest contaminants that are accidentally mixed in with the food. Hence, a detection method of small contaminants in food is required. Given the lower detection limit for practical X-ray usage is in the order of 1 mm, a detection system using a SQUID is a more powerful tool for sensitive inspections. We design and set up a three-channel high-Tc rf-SQUID inspection system for food. We report the successful detection of a small phi 0.3-mm steel particle for the food detection system.

Metallic particles with outer dimensions smaller than 100 microns in Li-ion battery cannot be detected using a conventional X-ray imaging system. We propose two systems using high Tc SQUIDs: One is a direct detection type and the other is an indirect type. In the direct detection system, an object with a contaminant is magnetized by a permanent magnet and then the remanent field of the contaminant is detected by SQUID. In the indirect detection system, the principle is based on Faraday's law of electromagnetic induction. The diameter of the detection coil is 2 to 3 times larger than the SQUID as a result, less number of SQUIDs, two or three is enough to inspect a specimen with a width of 65 mm. This method is applicable for an inspection of metallic contaminants in non-magnetic film such as a separator for Li-ion battery. We discuss the results of the evaluation of the new system as compared with a direct detection system. © (2014) Trans Tech Publications, Switzerland.

Metallic particles with outer dimensions smaller than 100 microns in Li-ion battery cannot be detected using a conventional X-ray imaging system. We propose two systems using high Tc SQUIDs: One is a direct detection type and the other is an indirect type. In the direct detection system, an object with a contaminant is magnetized by a permanent magnet and then the remanent field of the contaminant is detected by SQUID. In the indirect detection system, the principle is based on Faraday's law of electromagnetic induction. The diameter of the detection coil is 2 to 3 times larger than the SQUID; as a result, less number of SQUIDs, two or three is enough to inspect a specimen with a width of 65 mm. This method is applicable for an inspection of metallic contaminants in non-magnetic film such as a separator for Li-ion battery. We discuss the results of the evaluation of the new system as compared with a direct detection system.

We constructed a ultra-low field (ULF) nuclear magnetic resonance (NMR) / magnetic resonance imaging (MRI) system employing a high-temperature superconductor (High Tc) SQUID with a separated Cu-wound flux transformer. The pickup coil consisted of two single solenoid coils and each coil was differentially connected each other. The flux transformer consisted of a pickup coil at room temperature and an input coil, which was put in liquid nitrogen and was magnetically coupled with a high-Tc SQUID. The ratio of the transformer was considered and optimized. A water phantom of 10 mL was located in the one side of pickup coil. In the system, we applied polarizing field B-p perpendicular to the measurement field B-m before measurements. B-p was 0.8 T and permanent magnet was used. By using this system, free induction decay (FID) signals of H-1 were measured at B-m of 30 mu T to evaluate the system. The longitudinal relaxation times T-1 of water were also estimated by changing the polarizing time of B-p.

We have developed an ultra-low field (ULF) NMR/MRI system using an HTS-rf-SQUID and evaluated performance of the system as a contaminant detection system for foods and drinks. In this work, we measured 1D MRIs from water samples with or without various contaminants, such as aluminum and glass balls using the system. In the 1D MRIs, changes of the MRI spectra were detected, corresponding to positions of the contaminants. We measured 2D MRIs from food samples with and without a hole. In the 2D MRIs, the hole position in the sample was well visualized. These results show that the feasibility of the system to detect and localize contaminants in foods and drinks.

We have developed an ultra-low frequency (ULF) nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) system utilizing an HTS-SQUID for an application of contaminant detection in food and drink. In the system, a permanent magnet of 1.1 T was used to pre-polarize protons in a water sample. We measured NMR signals from water samples with or without various contaminants, such as stainless steel (SUS304), aluminum, and glass balls using the system. In the case that the contaminant was the SUS304 ball, the NMR signal intensity was reduced compared to that from the sample without the contaminant due to the remnant field of the contaminant. One-dimensional (1D) MRIs of the samples were also acquired to detect non-magnetic contaminants. In the 1D MRIs, changes of the MRI spectra were detected, corresponding to positions of the contaminants. These results show that the feasibility of the system to detect various contaminants in foods. (C) 2013 Elsevier B. V. All rights reserved.

We introduce a method to improve the detection sensitivity for the magnetization M of superparamagnetic nanoparticles (MNP). The M response of MNP to an applied magnetic field H (M-H characteristics) could be divided into a linear region and a saturation region, which are separated at a transition point H-k. When applying an excitation magnetic field (H-ac) with a frequency omega(0) and an additional dc bias field H-dc = H-k, the second harmonic of M reaches the maximum due to the nonlinearity of the M-H characteristics. It is stronger than any other harmonics and responsible for small H-ac without a threshold. The second harmonic selected as the readout criterion for M response of MNP is systematically analyzed and experimentally proven. (C) 2013 AIP Publishing LLC.

In this paper, a roll-to-roll eight-channel (8-ch) high-T-c superconducting quantum interference device (SQUID) detection system for magnetic contaminants in a lithium-ion (Li-ion) battery anode sheet was developed. Finding ultra-small metallic foreign matter is an important issue for a manufacturer because metallic contaminants carry the risk of an internal short. When contamination occurs, the manufacturer of the product suffers a great loss from recalling the tainted product. Metallic particles with outer dimensions smaller than 100 mu m cannot be detected using a conventional X-ray imaging system. Therefore, a highly sensitive detection system for small foreign matter is required. We have already developed a detection system based on a single-channel SQUID gradiometer and horizontal magnetization. For practical use, the detection width of the system should be increased to at least 65 mm by employing multiple sensors. In this paper, we present an 8-ch high-T-c SQUID roll-to-roll system for inspecting a Li-ion battery anode with a width of 65 mm. A special microscopic type of a cryostat was developed upon which eight SQUID gradiometers were mounted. As a result, small iron particles of phi 35 mu m on a real Li-ion battery anode with a width of 70 mm were successfully detected. This system is practical for the detection of contaminants in a Li-ion battery anode sheet.

We constructed an ultra-low field nuclear magnetic resonance (NMR)/magnetic resonance imaging (MRI) system utilizing a high-temperature superconductor (HTS) SQUID and permanent magnet for application of contaminant detection in food and drink. In order to compensate shortage of signal-to-noise ratio of the HTS-SQUID-based system, a pair permanent magnet of 1.1 T was employed for prepolarization field. It was combined with a sample transfer apparatus, which transferred a water sample with contaminant in a 10-ml glass bottle from the magnet to under the SQUID magnetometer within 0.5 s. Feasibility of contaminant detection in drink was demonstrated using the system by measuring NMR and 1-D MRI of water samples including contaminants of stainless steel, aluminum, and polymer. 2-D MRI measurement of a sample with partitioned water by silicone bulk was demonstrated employing the filtered back projection reconstruction method.

We have developed magnetic metallic contaminant detectors using multiple high-Tc SQUIDs (superconducting quantum interference devices) for food and industrial products. For manufacturers producing items such as processed food and industrial products, problems with metallic contaminants are critical issues. When contamination occurs, the manufacturer of the product suffers a great loss from recalling the tainted product. The lower detection limit for practical X-ray usage is on the order of 1 mm. A detection system using a SQUID is a powerful tool for sensitive inspections. For practical use, the detection width of the system should be increased by employing multiple sensors. We designed and set up a multi-channel high-Tc SQUID inspection system with a width of at least 130 mm for food and 70 mm for industrial products. As a result, a small 0.3-mm stainless steel particle for food and a 27-μm iron particle for industrial products were successfully detected. © 2012 Springer Science+Business Media New York.

In this paper, visualization of flowing current in various braided carbon fiber reinforced plastics (CFRPs) was demonstrated using high-temperature superconductor (HTS) superconducting quantum interference device (SQUID) gradiometer, in order to study electrical properties and integrity of the braided CFRP samples. Step-by-step tensile loading was also applied to the samples, in order to study their mechanical properties and destructive mechanism. Experimental results indicated that the addition of carbon nano fibers and middle-end carbon fiber bundles attributed to modify not only the mechanical properties, but also the electrical properties of the samples. Combining the results by the both methods, a scenario of the destructive mechanism of one sample was estimated.

We have constructed an ultra-low field (ULF) nuclear magnetic resonance (NMR)/magnetic resonance imaging (MRI) system using an HTS-rf-SQUID and room-temperature electromagnets in a magnetically shielded room (MSR). In this study, in order to improve the signal to noise ratio (S/N) of the system, we introduced a permanent magnet instead of the electromagnet for pre-polarizing the sample to enhance the pre-polarizing field (B-p). The cylindrical permanent magnet of 270 mT was used to magnetize a water sample for several seconds outside the MSR and about 1.5 m away from the SQUID. We constructed an instrument to transfer the magnetized sample from the permanent magnet to under the SQUID in 0.5 s. Since the non-adiabatic condition cannot be kept in such sample transfer scheme, an AC pulse coil to apply an AC pulse field B-AC to rotate the magnetization moments for pi/2 was introduced to measure a free induction decay (FID) signal from the sample. By this system, we obtained an NMR signal from the water sample of 10 ml while applying a static field of 45 mu T and pi/2 pulse after the transfer. The S/N of the NMR spectrum was about 100 by a single shot, which was 10 times larger than that obtained with the electromagnet of 32 mT. In addition, we demonstrated the measurements of the longitudinal relaxation time (T-1) and the spin echo signal of the water sample by the system. (C) 2012 Elsevier B.V. All rights reserved.

Three braided carbon fiber reinforced polymer (CFRP) samples with different middle-end fibers were fabricated. Damage mechanisms of the samples under step-by-step tensile loading were investigated using a nondestructive evaluation (NDE) method utilizing a high-temperature superconducting SQUID gradiometer. Commercial carbon fibers UTS50 were used for base braided fabrics, while UTS50, XN05 with higher electric resistivity, and XN60 with lower resistivity were used for the middle-end fibers. In the step-by-step tensile tests, observation of surfaces and measurements of stress-strain curves of the samples were carried out. At certain damage stages, the SQUID NDE method, which visualizes flowing currents in the samples, were applied to detect damage and assess the integrity of the carbon fiber yarns in the samples after removal of the loading. As a result, different damage mechanisms and stress-strain curves were observed and measured. From the results using the SQUID NDE method, it was shown that the current distributions in the samples were determined by the middle-end fibers at respective virgin stages, and the middle-end fibers XN60 were broken in some parts of the sample at its final fracture. © 2013 IEEE.

Step-by-step tensile tests were applied to flat-braided carbon-fiber-reinforced polymers with and without added dispersions of carbon nanofibers (CNFs) and with and without sample sides cut off to study their mechanical properties and destructive mechanisms by means of in situ observation and stress-strain measurements. An ex situ nondestructive evaluation technique, using a high-temperature superconductor superconducting quantum interference device gradiometer, was also applied to the samples to study their electrical properties; the relationships between the mechanical and electrical properties by visualizing current maps in the samples during ac current injection was also studied. Clear differences were observed in the mechanical and electrical properties and the destructive mechanisms between the samples with and without CNFs and with and without cut off sides. These differences were mainly attributed to the addition of CNFs, which enhanced the mechanical and electrical connections between the carbon fiber bundles. (C) 2012 Elsevier B.V. All rights reserved.

We have developed the magnetic metallic contaminant detectors using multiple high Tc SQUID gradiometers for industrial products. Finding ultra-small metallic contaminants is a big issue for manufacturers producing commercial products. The quality of industrial products such as lithium ion batteries can deteriorate by the inclusion of tiny metallic contaminants. When the contamination does occur, the manufacturer of the product suffers a great loss to recall the tainted products. Metallic particles with outer dimension less than 50 mu m cannot be detected by a conventional X-ray imaging. Therefore a high sensitive detection system for small foreign matters is required. However, in most of the cases, the matrix of an active material coated sheet electrode is magnetized and the magnetic signal from the matrix is large enough to mask the signal from contaminants. Thus we have developed a detection system based on a SQUID gradiometer and a horizontal magnetization to date. For practical use, we should increase the detection width of the system by employing multiple sensors. We successfully realized an eight-channel high-Tc SQUID gradiometer system for inspection of sheet electrodes of a lithium ion battery with width of at least 60 to 70 mm. Eight planar SQUID gradiometers were mounted with a separation of 9.0 mm. As a result, small iron particles of less than 50 mu m were successfully measured. This result suggests that the system is a promising tool for the detection of contaminants in a lithium ion battery. (C) 2012 Published by Elsevier B.V.

This paper reviews the recent development of mobile nondestructive evaluation (NDE) systems using high-T_c superconducting quantum interference devices (SQUIDs) for conductive materials and structures. The contents of this paper include a noise cancellation scheme using active shielding, a novel high-T_c SQUID gradiometer with robustness in magnetic fields, mobile SQUID NDE systems and NDE of complex composite-metal structures. Using the novel high-T_c SQUID gradiometer, the superior capability of the mobile SQUID NDE system compared to conventional NDE techniques is demonstrated and discussed.

A high temperature superconducting quantum interface device (HTS SQUID) is an extremely sensitive magnetic sensor. The HTS SQUID is required to have a high robustness with respect to magnetic noise for stable operation outside a magnetic shielding room. In order to achieve the high robustness of HTS SQUID, use of a magnetic shield with a superconducting film has been proposed, and its effectiveness has been confirmed in the experiments. In this paper, an electromagnetic field simulation was performed using the 3-D edge finite element method to confirm the effectiveness of the superconducting film magnetic-shield. Since both the SQUID magnetometer and the superconducting film magnetic-shield are made of HTS, it is required to consider the HTS characteristics in the electromagnetic field simulation. Additionally, the SQUID magnetometer has Josephson junction. In this paper, the property of the Josephson junction is also considered. The simulation accuracy depending on the type of the finite element mesh is also investigated.

Step-by-step tensile tests were applied to flat-braided carbon-fiber-reinforced plastics with dispersion of carbon nanofibers (CNFs) or insertion of different middle-end carbon-fiber bundles to study their mechanical properties and destructive mechanism. A nondestructive evaluation technique, using a high-temperature superconductor superconducting quantum interference device gradiometer, was also applied to the samples to study their electrical properties and the integrity of the carbon-fiber bundles in the samples. Experimental results indicated that the addition of the CNFs and the insertion of the middle-end bundles attributed to modify not only the mechanical properties, but also the electrical properties of the samples.

For high sensitive detection of magnetic contaminant in electrode of lithium-ion battery, high-temperature superconductor (HTS) radio-frequency (rf) superconducting quantum interference devices (SQUIDs) based on a bicrystal SrTiO3 (STO) substrate was designed, and fabricated employing YBa2Cu3O7-x thin films of about 200 nm in thickness. To improve characteristics such as effective area and 1/f noise profile of the SQUID, HTS thin films on normal STO substrates were overlapped on a wide superconducting weak link and/or a slit of the SQUID in flip-chip configuration. The noise profiles of the SQUID covered with the films on the respective positions were well improved compared to that of the bare SQUID. A magnetic contaminant detection system was developed employing the HTS-rf-SQUID covered with the films on both the positions. Using this system, a tungsten ball of 30 mu m in diameter was successfully detected with a signal to noise ratio of about 14.

We developed a magnetic contaminant detection system for industrial products such as electrode foils of lithium ion battery employing eight high-T-c SQUID gradiometers. The system was based on pre-magnetization of a contaminant in an object under test by means of permanent magnets of 0.5 T, which magnetization direction was horizontal, in order to suppress the edge effect from the object composed of magnetic material. The object was conveyed to pass under the eight-channel gradiometer array, in which a pair of four gradiometers was aligned in two rows to cover target foils of several tens mm in width. The magnetization from the contaminant in the object was detected by the gradiometers of averaged flux white noise level of 25 mu phi(0)/Hz(1/2). In case that an iron ball passed just under one gradiometer, an iron ball of about phi 30 mu m in diameter was successfully detected with a signal to noise ratio (S/N) of 5. From measurement results using an iron ball of about 100 mu m in diameter, it was demonstrated that the system had a detectable range of 70 mm in width. There results suggest that the system is a promising tool for the quality control of lithium ion batteries.

We constructed an ultra-low field (ULF) nuclear magnetic resonance (NMR) / magnetic resonance imaging (MRI) system with a high temperature superconductor (HTS) radio-frequency (rf) superconducting quantum interference device (SQUID) coupled with a LC circuit inside a cryostat filled with liquid nitrogen. Several LC resonant circuits with 139 to 1500 turns coils made from copper wires of 0.2, 0.4, and 0.6 mm in diameter were tested to obtain the optimum configuration for the circuit. For each coil, a capacitance was selected to fix the resonance frequency at around 10 kHz. The LC resonant circuit using a 500 turns coil made from 0.2 mm diameter wire offered the largest signal-to-noise ratio (S/N) of 11.9 with a quality factor of 53.3 at 10.2 kHz and 77 K. With this circuit, the S/N of free induction decay (FID) signals was tested using the ULF SQUID-NMR/MRI system. (C) 2011 Published by Elsevier B.V. Selection and/or peer-review under responsibility of ISS Program Committee.

Braided carbon fiber reinforced plastics (CFRPs) are one of multifunctional materials with superior properties such as mechanical strength to normal CFRPs since the braided CFRPs have continuous fiber bundles. In this paper, we applied the current-injection-based nondestructive evaluation (NDE) method using a HTS-SQUID gradiometer to the braided CFRP for the detection of the breakage of the bundles. We prepared planar braided CFRP samples with and without artificial cracks of 1 and 2 mm lengths, and measured the current density distribution above the samples using the NDE method. In the measurement results, not only a few completely-cut bundles but also the additional partially-cut bundles were detected from decrease in the measured current density along the cut bundle around the cracks. From these results, we showed that it is possible to inspect a few partially-cut bundles in the braided CFRPs by the NDE method. (C) 2011 Elsevier B.V. All rights reserved.

In this paper, we investigated detailed behavior of novel HIS-dc-SQUID gradiometers with ramp-edge Josephson junctions (JJs) in both an ac magnetic field and a dc magnetic field. In the both fields, the novel gradiometers shows the superior performance to the conventional YBa(2)Cu(3)O(7-x) (YBCO) HIS-dc-SQUID gradiometer and a bare HIS-dc-SQUID ring with bicrystal JJs concerning durability against entry and hopping of flux vortices, probably due to their differential pickup coils without a grain boundary and multilayer structure of the ramp-edge JJs. A robot-based compact HIS-SQUID NDE system utilizing the novel gradiometer was reviewed, and detectability of the system to detect non-through cracks in a carbon fiber reinforced plastic (CFRP)/Al double-layer structure was demonstrated. A new excitation coil in which the supplied currents flowed in the orthogonal directions was applied to detect cracks that oriented vertical and parallel to the baseline of the gradiometer. (C) 2011 Elsevier B.V. All rights reserved.

A two-channel high-T(c) SQUID gradiometer system for the detection of magnetic foreign matter in a lithium-ion battery was developed. Finding ultra-small metallic foreign particles can be a big issue for a manufacturer that produces commercial products such as lithium-ion batteries. If the presence of such particles is detected in its products, the manufacturer has to recall the products and thereby suffers a significant loss. Previously, we developed a detection system based on a single-channel SQUID gradiometer and horizontal magnetization. For practical use, we need to increase the detection width of the system by employing multiple sensors. In this paper, we present a two-channel high-T(c) SQUID gradiometer system for the inspection of a lithium-ion battery. In order to increase the inspection width, two SQUID gradiometers were employed along with a specially designed cryostat. As a result, small iron particles with a diameter of less than 100 mu m were detected by the system with a width of 22 mm. This is the first multi-channel high-T(c) SQUID gradiometer system for detection of the contaminants in a lithium-ion battery.

We have developed metallic contaminant detection systems using HTS-SQUIDs. In this study, we designed and fabricated a single-chip HTS rf-SQUID using SQUID microscope techniques to reduce both the lift-off and cooling temperature as compared with the substrate resonator HTS rf-SQUID. The HTS rf-SQUID was a washer-type rf-SQUID without a flux focuser. By lengthening and narrowing the SQUID hole, we showed that the inductance of the SQUID ring was reduced, and the effective area and the field noise were improved consequently. By introducing a single-chip HTS rf-SQUID with hole size of 800 mu m x 50 mu m into the detection system, we obtained a field sensitivity of 150 fT/Hz(1/2) and a lift-off of 1.5 mm. Since this SQUID has advantages in the reduction of lift-off and cooling temperature, its detectability and magnetic field resolution are superior to that of the substrate resonator SQUID. Finally, we showed the single-chip SQUID can detect 20 mu m in diameter iron balls.

In our study, we constructed a ultra-low field (ULF) nuclear magnetic resonance (NMR)/magnetic resonance imaging (MRI) system employing a high-temperature superconductor (HTS)-rf-SQUID and room-temperature coils. In the system, we employed a pulsed polarizing field B(p) perpendicular to a measurement field; a high-speed switching circuit with an optical FET was used to switch off B(p) of approximately 30 mT. When a field gradient dB(z)/dz of approximately 10 nT/cm was applied to a sample, which was designed to contain water in two compartments, a (1)H-NMR spectrum with two peaks was observed. The frequency difference between the two peaks roughly corresponded to the distance between each center of the water in the two parts. We measured the (1)H-NMR signals for water and mineral oil and found a clear difference in their signal amplitudes owing to their different molecular compositions. The longitudinal relaxation times T(1) of water and the oil were also estimated by changing the polarizing time of B(p). From these results, it was confirmed that (1)H- and T(1)-weighted contrast imaging could be realized by using this system.

We developed integrated high-temperature superconductor (HTS) rf superconducting quantum interference devices (SQUIDs) with various hole shapes on bicrystal SrTiO3 substrates. Single-layer YBa2Cu3O7-x thin-film technology and bicrystal Josephson junctions were employed to take advantage of a simple fabrication process. The HTS rf SQUID with a hole of 800 x 50 mu m(2) had the lowest inductance and showed the best noise characteristics among the tested SQUIDs. The 1/f noise profile of the HTS rf SQUID, which was covered with HTS thin films on the grain boundary and/or the slit of the SQUID in a flip-chip configuration, was dramatically improved in a frequency range of less than 100 Hz. (C) 2011 The Japan Society of Applied Physics

Effect of an addition of a cooled step-up transformer to a flux locked loop (FLL) circuit was studied to reduce indirect rf interference to HTS-dc-SQUID. First, we demonstrated that a noise level of an HTS-dc-SQUID system using the FLL circuit with single room-temperature transformer could be easily degraded by radiation of rf electromagnetic wave to cables in the FLL circuit. It is thought that the rf radiation induced if current in the circuit, and was transmitted to the SQUID to modulate the bias current, resulting in the increase of the noise level. To avoid the degradation due to such indirect if interference, the cooled set-up transformer was added to the FLL circuit since it was expected that the additional transformer would work as a "step-down" transformer against the induced rf current. It was shown that the noise level of a HTS-SQUID system (SQUITEM system) operated in an electromagnetically unshielded environment could be improved to the same level as that measured in a magnetically shielded room by the additional cooled transformer and appropriate impedance matching.

We applied the current-injection-based NDE method using the HTS-SQUID gradiometer for the braided CFRP before, during and after the tensile test. In the measurement results, the line oriented toward the angle of +45° with the lower field gradient was detected above the virgin specimen. By the observation of the cross-section of the specimen, it is verified that the intensity of the field gradient corresponds to the density of the carbon-fiber bundles. From these results, we showed that the density of the carbon-fiber bundles can be estimated, and there is a possibility to predict the initiation site of the destruction in braided CFRPs by the SQUIDNDE method.

The goal of this research is to provide a sufficient understanding for the damage mechanism of ±45° flat braided CFRP composites under tensile loading based on in-situ macroscopic observations of surface cracking and off-line measurements for the state-of-fibers by Superconducting Quantum Interference Device (SQUID) technique to analyze the effect of the continuously oriented of all braided fiber bundles on the tensile and in-plane shear properties. SQUID technique displays an effective capability in inspection the state-of-fiber failure, whereas the in-situ surface macroscopic observation technique is very useful in observing the surface matrix cracking at different stages of damage. The damage mechanism of uncut-edges and cut-edges of ±45° flat braided CFRP composites are identified adequately by the above-mentioned experimental procedure. The cut-edges ±45° flat braided CFRP composites exhibit a pure shear damage mechanism associated with large shear deformation and no significant fiber failure, while the uncut-edges ±45° flat braided CFRP composites exhibit a slight fiber scissoring mechanism followed by a partially fiber failure. The enhancement of the tensile and in-plane strengths of the uncut-edges ±45° flat braided CFRP composites by about 60% higher than those of the cut-edges ±45° flat braided CFRP composites achieves not only by the effect of the continuously oriented carbon fibers at the edges but also by the effect of re-orientation of braiding fiber bundles with smaller angle than the original ±45° braiding angle of the fabricated composites, or so called fiber scissoring mechanism in composites. Copyright © 2011 by ASME.

We constructed and studied an ultra low-field nuclear magnetic resonance imaging system using a HTS rf SQUID and room-temperature coils. We recorded the free induction decay signals of (1)H by employing a measuring field, B (m), of 44.8 mu T and a polarizing field, B (p), of 36.8 mT; in the presence of a, B (Z) /a, z and a, B (Z) /a, y gradients of the order of 0.8 mu T/m, we were able to obtain a quasi two-dimensional 4-pixels image of a simple water phantom.

In this study, we investigated conductive properties of joint interfaces of friction stir welding (FSW) between dissimilar metals, stainless steel SUS304 and aluminum A6063, using a SQUID nondestructive evaluation (NDE) system. With current injection method, the current maps above the FSW specimens jointed under various conditions were measured by a HTS-SQUID gradiometer. The conductivities of the joint interfaces, which were estimated from the current maps, differed between the joint conditions. By destructive tests using optical microscope, large voids were observed on the joint interfaces with low welding speed that generated excess heating. In case of one specimen, which was welded with welding speed of 500 and 200 mm/min, the conductivity of the former was higher than that of the latter, although the inside voids in the respective regions were not much different. From these results, it is suggested that the current maps were influenced not only by the conductivity of the joint interface but also by inside voids. By hardness test on the SUS boards near the interfaces, only the SUS jointed with 200 mm/min was about half softer than its matrix. (C) 2010 Elsevier B.V. All rights reserved.

We have developed a magnetic metallic contaminant detector using a high-temperature superconducting quantum interference device (HTS-SQUID) gradiometer for industrial products such as lithium ion batteries. Finding ultrasmall metallic contaminants is a critical issue for manufacturers producing commercial products such as lithium ion batteries. When contamination occurs, the manufacturer incurs a great loss in recalling the tainted products. We employed a permanent ring magnet for magnetizing the products in order to generate remnant fields only at the ends of the products, thereby reducing their impact in masking the field from a contaminant. For practical applications, the detection width of a sensor must be sufficiently large to identify an inclusion from above the product during inspection. Here, we made a large SQUID gradiometer 8 mm in width and compared its detection width with that of a conventional small sensor 3 mm wide. We found that the effective detection width of the 8 mm sensor was 11.6 mm. It was 1.8 times larger than that of the small sensor. Finally, a test of the system's performance revealed that iron particles as small as 50 mu m x 50 mu m on the electrode of a lithium ion battery could be detected clearly. (C) 2010 Elsevier B.V. All rights reserved.

We develop magnetic metallic contaminant detectors using high-temperature superconducting quantum interference devices (HTS-SQUIDs) for industrial products. Finding ultra-small metallic contaminants is an important issue for manufacturers producing commercial products such as lithium ion batteries. If such contaminants cause damages, the manufacturer of the product suffers a big financial loss due to having to recall the faulty products. Previously, we described a system for finding such ultra-small particles in food. In this study, we describe further developments of the system, for the reduction of the effect of the remnant field of the products, and we test the parallel magnetization of the products to generate the remnant field only at both ends of the products. In addition, we use an SQUID gradiometer in place of the magnetometer to reduce the edge effect by measuring the magnetic field gradient. We test the performances of the system and find that tiny iron particles as small as 50 x 50 mu m(2) on the electrode of a lithium ion battery could be clearly detected. This detection level is difficult to achieve when using other methods.

Braided carbon fiber reinforced plastics (CFRP) is one of the multifunctional materials for applications to industrial products. We applied the superconducting quantum interference devise (SQUID) nondestructive evaluation (NDE) technique with high magnetic sensitivity and spatial resolution to inspect the state of the fabric in the braided CFRP. We prepared flat braided CFRP samples with nonuniform, uniform and cut-out bundles, which were fabricated with fold biaxial (±45°) tubular fabric and epoxy resin. While injecting ac current into each sample, the diagonal magnetic field gradients dBZ/dx and dBZ/dy above each sample were measured by the NDE system employing a SQUID gradiometer and xy-scanning stage, and then, the current flow in each sample was visualized by the field-gradient-to-current conversion method. In the measurements, it was shown that the current flowed along the continuous bundles in the cases of nonuniform and uniform samples, and it transmitted between bundles in the case of the sample with cut-out bundles. From these results, we showed the possibility that the NDE method can be applied to the nondestructive inspection of the integrity of the textile of braided CFRP. © (2010) Trans Tech Publications.

We constructed a low-field (LF) nuclear magnetic resonance (NMR) system using a HTS rf SQUID and room-temperature (RT) coils. In the system, a measurement field coil, a polarizing coil and ac pulse coil were employed. In addition, gradient coils were introduced to compensate the remnant field gradient around the sample and to improve the homogeneity of B-m. With gradient coils, the spin-spin relaxation time T-2* of a free induction decay (FID) signals of H-1 was 2.2 s, 1.7 times longer than that without gradient coil in an experiment employing B-m of 44.8 mu T and B-p of 36.8 mT. The conditions of B-ac (amplitude, duration) to rotate the magnetized vector of H-1 by a certain angle were experimentally studied for application of a 90 degrees - 180 degrees spin echo sequence. It was also found that the minimum delay time for applying the 180 degrees pulse to obtain the spin echo signal of H-1 was approximately 2.5 s.

A simple flip-chip configuration of YBa(2)Cu(3)O(7-x) (YBCO) square and cross-shaped films overlapping on a directly coupled multi-pickup-loop HTS dc-SQUID magnetometer was tested to enhance the robustness of the HTS SQUID magnetometer in an ac magnetic field. The YBCO films were expected to work as a superconducting shield to prevent flux vortices from entering and moving in the device. With the shields, most of the SQUID's characteristics such as critical current I(c), modulation voltage V(pp), magnetic flux noise S(phi)(1/2), effective area A(eff), and magnetic field noise S(B)(1/2) were enhanced. The robustness of the magnetometer in an applied ac magnetic field was successfully enhanced by the coverage with the shields, particularly the cross-shaped shield. It is inferred that the cross-shaped shield reduced flux trapping and jumping in the SQUID ring and at the edges of the pickup loops.

A highly sensitive detection system for magnetic contaminants using a High-Tc superconducting quantum interference device ( SQUID) was developed. Finding ultra-small metallic contaminants is a big issue for manufacturers producing commercial products such as lithium ion batteries. When the contamination does occur, the manufacturer of the product suffers a great loss to recall the tainted products. The outer dimension of metallic particles less than 100 microns can not be detected by X-ray imaging, which is commonly used as the inspection method. In most cases, the matrix of industrial products is magnetized and the magnetic signal from the matrix is large enough to mask the signal from contaminants. We developed a detection system based on a high-Tc SQUID gradiometer. A specially designed low noise planar gradiometer for the system was developed. The flux white noise level of the SQUID gradiometer was 8-16 Hz mu phi(0)/Hz(1/2) at 1 kHz. Use of the gradiometer and horizontal magnetization could solve problem above. We tested the performances of the system and found that small iron particles as small as 50 mu m x 50 mu m on the electrode of the lithium ion battery could be clearly detect. This detection level is difficult to achieve using other methods.

We have proposed the application of nondestructive evaluation (NDE) using HTS-SQUID gradiometer to detect wire breakage in compressive conductor joints in overhead transmission line. In this study, we prepare an aluminum conductor steel reinforced (ACSR) transmission line with a broken wire. The ends of the ACSR cable were compressed with Al sleeves. An AC current was injected toward into the cable axis by applying AC voltage across the both ends of the sleeves. Then the two-dimensional distribution of magnetic field gradient above the cable was measured by a HTS-SQUID gradiometer. In the case of the compressed ACSR with a wire breakage, the field gradient changed periodically along the spiral of the broken wire. In contrast, such changes did not appear above the ACSR cable without defects. These results suggested the possibility to detect the wire breakage in the compressive conductor joints by this method. We also conducted electromagnetic field simulation to verify the experimental results. (C) 2009 Elsevier B.V. All rights reserved.

An eddy-current-based SQUID-NDE system has been developed to detect shallow surface defects of less than 50 mu m in depth on heat-exchanger copper tubes using a HTS-SQUID and excitation coil. In this system, small surface displacement of a tube, variation of the tube thickness and inner ripples cause background magnetic noise besides the surface defects. In this study, main factors of the background magnetic noise were investigated by a HTS-SQUID gradiometer, laser displacement sensor and laser microscope. The magnetic response, surface displacement, outer diameter variation and radial thickness of straight tubes of 9.6 mm in outer diameter and 0.4mmin thickness were measured. The experimental results suggested that the main factor of the background magnetic noise was not due to local shape displacement near the SQUID, but nonuniformity in tube shape mainly originated inside of the tube. In the case of a tube with inner ripples and a outer-surface defect, large periodical magnetic noise from ripples was measured. Noise reduction method to reduce the periodical magnetic background noise due to the inner ripple was also investigated. The periodical noise due to the ripples was significantly decreased at higher frequency than 300 kHz, where the skin depth into copper was about 0.1 mm, while the magnetic response from the defect of 30 mu m depth on the tube surface was successfully detected.

A novel HTS-SQUID gradiometer with ramp-edge Josephson junctions (JJs) composed of SmBa(2)Cu(3)O(y) base-electrode and La(01)Er(0.95)Ba(1.95)Cu(3)O(y) counter-electrode was developed. The robustness of the gradiometer in AC field perpendicular to the device plane was investigated. In an AC field of less than 2.8 mT(pp) at 100 Hz, flux-trapping, jumping and increase in noise did not happen in the gradiometer, while a traditional HTS-SQUID gradiometer with YBa(2)Cu(3)O(7-x) thin film and bicrystal JJs with the same dimension as the novel gradiometer could not be operated properly in an AC field of about several tens nT(pp). A robot-based NDE system utilizing the novel HTS-SQUID gradiometer was developed. The system could move the gradiometer three-dimensionally (3D) in an unshielded environment without magnetic shielding or compensation technique. Eddy-current-based detection of a through hole in magnetized stainless steel board was demonstrated by the robot-based HTS-SQUID NDE system.

A three channel High-Tc SQUID system for detection of magnetic contaminants in industrial products was developed. Finding ultra-small metallic contaminants is a big issue for manufacturers producing commercial products such as lithium ion batteries. When the contamination does occur, the manufacturer of the product suffers a great loss to recall the tainted products. The outer dimension of metallic particles less than 100 micron can not be detected by X-ray imaging, which is commonly used as the inspection method. Therefore, a highly sensitive detection system for small contaminants is required. We developed a detection system based on a three channel high-Tc SQUID microscope with a high performance magnetic shield. Three SQUIDs were installed in one microscope-type cryostat with a 3 sapphire vacuum window which separates the SQUID and atmosphere. This design enables the SQUID to approach an object to be measured as close as 1 mm. The minimal detectable size of the particle is also highly dependent on the magnetic field noise of the SQUID. Therefore, we employed double transformer coupling, which lowers the noise. One transformer was placed at 77 K and the other was at room temperature (RT). As a result, the magnetic field noise of the SQUID was reduced by 36%. Finally we could successfully measure small iron particles as small as 30 micron. This detection level was difficult to achieve when using a conventional X-ray detection method.

Taking advantage of the unsurpassed high-magnetic sensitivity of high-temperature superconductor (HTS) superconducting quantum interference device (SQUID). HTS-SQUID-non-destructive evaluation (NDE) technique was applied to detection of single wire breakage in hard-drawn aluminum transmission line (HAL), which was twisted from 19 aluminum wires. While applying AC current of 2.6 mA at 200 Hz to the HAL, distribution of magnetic field gradient above the HAL was two-dimensionally scanned by a HTS-SQUID gradiometer. A periodic pattern was detected along the locus of the broken wire in the distribution from the HAL with wire breakage, while such pattern was not observed in that from normal HAL without wire breakage. These results indicate the possibility of detection of single wire breakage by the magnetic inspection technique. (c) 2008 Elsevier Ltd. All rights reserved.

High-Tc superconducting quantum interference device ( SQUID) is an ultra-sensitive magnetic sensor. Since the performance of the SQUID is improved and stabilized, now it is ready for application. One strong candidate for application is a detection system of magnetic foreign matters in industrial products or beverages. There is a possibility that ultra-small metallic foreign matter has been accidentally mixed with industrial products such as lithium ion batteries. If this happens, the manufacturer of the product suffers a great loss recalling products. The outer dimension of metallic particles less than 100 mm cannot be detected by an X-ray imaging, which is commonly used for the inspection. Ionization of the material is also a big issue for beverages in the case of the X-ray imaging. Therefore a highly sensitive and safety detection system for small foreign matters is required. We developed detection systems based on high-Tc SQUID with a high-performance magnetic shield. We could successfully measure small iron particles of 100 mm on a belt conveyer and stainless steel balls of 300 mm in water. These detection levels were hard to be achieved by a conventional X-ray detection or other methods. (C) 2008 Published by Elsevier B. V.

High-T-c superconducting quantum interference device (SQUID) is an ultra-sensitive magnetic sensor. After the discovery of the high-T-c superconducting, materials, the performance of the high-T-c SQUID has been improved and stabilized. One strong candidate for application is it detection system of magnetic foreign matters in industrial products. There is it possibility that ultra-small metallic foreign matter has been accidentally mixed with industrial products such its lithium ion batteries. If this happens. the manufacturer of the product suffers a great loss recalling products. The Outer dimension of metallic particles less than 100 micron cannot be detected using X-ray imaging, which is commonly used for the inspection. Therefore it highly sensitive system for small foreign matters is required. We developed detection systems based on high-T-c SQUID for industrial products. We Could successfully detect small iron particles of less than 50 micron on it belt conveyer. These detection levels were hard to he achieved using conventional X-ray detection or other methods.

A nondestructive inspection method to detect wire breakage in power transmission lines using an HTS SQUID gradiometer was examined. Hard-aluminum transmission lines composed of 19 twisted Al wires, with or without wire breakage, were prepared as specimens. While applying AC voltage to the specimens to induce the equivalent current in each wire, distributions of magnetic field gradient above the transmission lines were scanned by the gradiometer. A periodic pattern in the gradient distribution due to wire breakage was observed in the results of the line with wire breakage, while such pattern was not observed in that of the line without wire breakage. The effect of wire breakage in the transmission line appearing in field gradient generated by the line with current was also investigated by computer simulation, and the result was in approximate agreement with the experimental results.

Three-channel directly-coupled-type high-T(c) SQUID magnetometer array, with pick-up coil size of 1.5 mm(2) comparable to the lift-off distance of the developed multi-channel SQUID system, was designed. In this design, two slits were introduced in the SQUID ring to improve the inductive coupling between the pick-up coil and the SQUID ring to obtain the field sensitivity of about 700 fT/Hz(1/2). With the SQUID array that was mounted on the multi-channel SQUID system, the measurements of magnetocardiogram of rat were demonstrated to evaluate the system performance.

This paper describes an optimal length and combination of short shield ducts to prevent the leakage of magnetic flux through the openings of a double-layered magnetically shielded room (MSR) used for electron-beam lithography systems and biomagnetic measurements. A number of openings as large as 500 x 500 mm must be provided in the walls, ceiling, and floor of such MSRs for air conditioning and cables. First, the magnetic field leakage from the openings, using a small model of an MSR, was measured with short shield ducts of various lengths in order to confirm the validity of the analysis and practical realization. Next, the distributions of the magnetic fields inside the small model were evaluated using 3-D magnetic field analysis and the finite element method. The method of analysis was verified by comparing computed results with those measured. We show the optimal length of shield duct attached around the openings as follows: The optimal combination of short shield ducts is an outer layer duct which is the same length as the width of the opening with an inner layer duct which is half the length of the opening. These lengths of duct accord with the optimal lengths when the outer and inner layer ducts are employed as a single duct. The leakage flux of the optimal single duct through the opening can be decreased to a half by the optimal combination of shield ducts. This also corresponds to the fact that the length of the inner layer duct should not protrude from the outer layer in order to avoid collecting surplus fluxes outside the magnetically shielded room.

A robot-arm-based mobile HTS-SQUID NDE system was developed for inspection of advanced structures such as hydrogen fuel cell tanks. In order to realize stable operation of HTS-SQUID exposed in Earth's field and robot arm's noise without flux trapping, flux jumping and unlocking during motion, a new active magnetic shielding (AMS) technique using fluxgate was introduced. The high sensitive fluxgate, which could measure magnetic field of up to several 10 mu T, was mounted near an HTS-SQUID gradiometer on the robot arm to measure the ambient noise and feed back its output to a compensation coil, which surrounded both SQUID and fluxgate to cancel the ambient noise around them. The AMS technique successfully enabled the FITS-SQUID gradiometer to be moved at 10 mm/s by the robot arm in unshielded environment without flux trapping, jumping and unlocking. Detection of hidden slots in multi-layer composite-metal structures imitating the fuel cell tank was demonstrated. (c) 2008 Elsevier B.V. All rights reserved.

High-Tc superconducting quantum interference device (SQUID) system for detection of magnetic foreign matter in industrial products was developed. There is a possibility that ultra-small metallic foreign matter has been accidentally mixed with industrial products, such as lithium ion batteries. The outer dimension of metallic particles less than 100 microns cannot be detected by conventional X-ray imaging. Therefore, we developed a detection system based on high-Tc SQUID microscopes with a high-performance magnetic shield. Using SQUID microscopes with a 0.5 mm-thick vacuum window was proposed. This design enables the SQUID to approach an object to be measured as close as 1 mm and enhances the sensitivity. A new magnetic shield with sleeves was carefully designed and built. As a result, we could successfully measure a small iron particle with 100 mu m. This detection level was hard to achieve by conventional X-ray detection methods.

SQUID-NDE technique was applied to detection of wire breakage in aluminium transmission line, and aluminium clamp composed of compressed conductor joint. Hard aluminium transmission lines twisted from 19 aluminium wires with or without a wire breakage were prepared. While applying ac current of 2.6 mA at 200 Hz to the line, distributions of magnetic field gradient above the transmission lines were measured by a SQUID-NDE system using a HTS SQUID gradiometer. A periodic pattern was detected along the locus of broken wire in the distribution of the field gradient generated from the line with wire breakage, while such pattern was not observed in the normal line without wire breakage. Numerical simulation of distribution of field gradient from the aluminium transmission line was also carried out to compare it with the experimental results.

A robot-arm-based mobile HTS SQUID system was developed for NDE of fixed targets. To realize the system, active magnetic shielding technique using fluxgate as reference sensor for ambient field was applied to a cryocooler-based HTS SQUID gradiometer that was mounted on commercial robot-arm. In this technique, ambient field noise and pulse noise of 550 nT from robot were measured by the fluxgate near the SQUID, and then the fluxgate output was negatively fed back to generate compensation field around the SQUID and fluxgate. The noise from robot was reduced by a factor of about 20 and the shielding technique enabled the HTS SQUID to move in unshielded environment by the robot-arm without flux-trapping or unlocking at 10 mm/s. System noise measurement and inspection of hidden cracks in multi-layer composite-metal structure were demonstrated using the mobile SQUID-NDE system.

A high-T-c superconducting quantum interference device (SQUID) system for the detection of magnetic foreign matter in industrial products was developed. There is a possibility that ultra-small metallic foreign matter has been accidentally mixed with industrial products such as lithium ion batteries. Metallic particles with outer dimensions less than 100 mu m cannot be detected by conventional x-ray imaging. Therefore we developed a detection system based on a high-T-c SQUID microscope with a high performance magnetic shield. The use of SQUID microscopes with a 0.5 mm thick vacuum window was proposed. This design enables the SQUID to approach the object to be measured as close as 1 mm and enhances the sensitivity. A new magnetic shield with sleeves was carefully designed and built. As a result, we could successfully measure small particles sized 100 mu m. This detection level was hard to achieve using a conventional x-ray detection method.

An eddy-current-based SQUID non-destructive inspection (NDI) system to detect deep-lying cracks in multi-layer composite-Al vessels was developed taking advantage of the uncontested sensitivity of HTS-SQUID in low-frequency range. An HTS-SQUID gradiometer was mounted in a pulse tube cryocooler. A pair of differential coils with C-shaped ferrite cores was employed to induce an enhanced eddy current in an Al vessel wrapped in a carbon fiber reinforced plastic (CFRP) cover. Ellipsoidal dome-shaped Al liners containing through cracks, which were made by pressure cycle tests, in the CFRP covers with total thickness of 6 mm (CFPR 3 mm, and Al 3 mm) were inspected by the system. While inducing eddy currents in the vessels with excitation fields at 100 Hz or 7 kHz, the vessels were rotated under the HTS-SQUID. Above the cracks, anomalous signals due to the cracks were clearly detected at both frequencies. These results suggested the SQUID-NDI technique would be a possible candidate for inspection of high-pressure multi-layer composite-Al vessels. (C) 2007 Elsevier B.V. All rights reserved.

We have developed an SQUID-NDI technique for evaluation of friction stir welding (FSW) between aluminum alloy A6063 and stainless steel SUS304 from the electric conductivities in board specimens bonded by FSW. A SQUID-NDI system employing an HTS-SQUID gradiometer was constructed to measure current distribution in the FSW specimens by applying voltage to the specimen. By measuring field gradients dB(z)/dy and dB(z)/dx above the FSW specimens made with various FSW conditions and then converting them to current vector J(x) and J(y), conductivities of FSW areas were estimated. Due to the difference in the FSW conditions, the conductivity distributions varied dramatically. From these results, it was suggested that the conductivities in FSW areas should be varied due to the temperature heated by the friction between the milling tool and the materials. (C) 2007 Elsevier B.V. All rights reserved.

An eddy-current-based SQUID-NDE system has been developed to detect shallow surface flaws of less than. 50 mu m in depth on heat-exchanger copper tubes using an HTS-SQUID gradiometer and an Helmholtz-coil-type inducer. In this study, detectable flaw sizes on the tubes were investigated by experiments and simulation. Copper tube specimens with flaws of various sizes were inspected by the system with an excitation field of 5.6 mu T at 3 kHz. A magnetic anomaly due to the shallowest flaw of 10 mu m depth, 100 mu m width and 15 mm length was successfully detected. The experimental results showed that the magnetic signal amplitude due to a flaw was proportional to the effective flaw size given by the product of flaw depth, width and length. A numerical simulation was carried out to calculate the magnetic signal from a flaw on a copper tube to determine the dependence on the flaw size. It is concluded that a flaw with a volume of 10(6) mu m(3) should be detectable by improving the system parameters.

A computer controlled contaminant detection system based on high-Tc Superconducting Quantum Interference Device (SQUID) for a beverage or ground meat has been designed and constructed. There is a strong demand for detection of metallic contaminants in ground meat or juice with pulp because a strainer cannot be applied to such a pulpy liquid. Two identical SQUIDs Were employed so that they can keep the sensitivity over the full width of the tube. As a result, we could successfully measure small iron particles in the order of hundreds of microns. This detection level is hard to achieve by a conventional X-ray detection or eddy current methods. We believe that this system is the first practical SQUID based metallic contaminant detector for a beverage.

A personal computer PC controlled high sensitive food contaminant detector was designed and constructed. The system we have developed is the High-T-c SQUID based system, which is covered with waterproof stainless steel plates and acceptable to HACCP (Hazard Analysis Critical Control Point) program. This system employed double layered permeable metals with thickness of 1mm as a magnetically shielded box. The distribution of the magnetic field in the box was simulated by finite element model (Maxwell, Ansoft Corporation). There is also a strong demand for detection of metallic contaminants in minced flesh or juice with pulp because a strainer cannot be applied to such a pulpy liquid. We have developed the detection system based on high-T-c SQUID for a beverage.

We investigate the high- temperature YBa2Cu3O7-x superconductors by method using a free electron laser ( FEL). The method is a type of photoelectron spectroscopy and called a FEL internal photoemission. It is found that when the YBa2Cu3O7-x. film is irradiated by FEL, the photocurrent is induced in an unbias condition. (c) 2006 Elsevier B. V. All rights reserved.

A typical magnetically shielded room (MSR) for an electron beam lithography system and biomagnetic measurements is composed by multi-layered ferromagnetic materials such as μ-metal. However, a number of openings must be provided in the wall and floor for air conditioning and cables. In this paper, the optimal structure of a duct to prevent leakage flux from entering through the openings was investigated by 3-D magnetic field analysis. We found that the duct should be connected to the inner layer in order to reduce the introduction of the leakage fluxes from the middle and outer layers. When magnetic noise is applied vertically to the opening, the duct protruding from the outer layer should be short, in order to avoid gathering surplus fluxes from outside the MSR. Inner partition plates dividing the hole of the duct are also effective for this purpose.

Detectable sizes of shallow flaws on thin copper tubes were experimentally investigated. using an eddy-current-based nondestructive inspection system with a high-T-c superconducting quantum interference device (SQUID) gradiometer. At an excitation field of 5.6 mu T at 3 kHz, a magnetic anomaly due to the shallowest flaw of 10 mu m depth, 100 mu m width, and 15 mm length on the surface of a tube specimen of 6.35 mm outer diameter and 0.8 mm thickness was successfully measured. Signal amplitude due to a flaw was proportional to effective flaw volume that made an induced eddy current detour. The experimental results indicate that the detectable volume of a surface flaw on a copper tube should be 1 x 10(6) mu m(3) with some increase in signal-to-noise ratio.

We have designed and constructed a computer controlled food contaminant detection system for practical use, based on high-T-c SQUID detectors. The system, which features waterproof stainless steel construction, is acceptable under the HACCP (Hazard Analysis and Critical Control Point) programme guidelines. The outer dimensions of the system are 1500 mm length x 477 mm width x 1445 mm height, and it can accept objects up to 200 mm wide x 80 mm high. An automatic liquid nitrogen filling system was installed in the standard model. This system employed a double-layered permeable metallic shield with a thickness of 1 mm as a magnetically shielded box. The distribution of the magnetic field in the box was simulated by FEM; the gap between each shield layer was optimized before fabrication. A shielding factor of 732 in the Z-component was achieved. This value is high enough to safely operate the system in a non-laboratory environment, i.e., a factory. During testing, we successfully detected a steel contaminant as small as 0.3 mm in diameter at a distance of 75 mm.

An eddy-current-based SQUID NDE system was constructed for in situ inspection of copper heat exchanger tubes using an HTS SQUID gradiometer and a Helmoltz-type-coil inducer. Thin copper tubes of 6.35 mm in diameter and 0.8 mm in thickness were selected from products as specimens. Artificial flaws of 100 mu m in width, 15-25 mm in length and 10-50 mu m in depth were made on the surfaces of the tubes. The tubes were moved at a velocity of 1.6-32 m min(-1) by a motor through the Helmholtz-type coil, which generated an excitation field of 10 mu T at 3 kHz. The SQUID NDE system Could detect an anomalous magnetic response due to a flaw of 10 mu m in depth on the tube moving at 32 m min(-1).

A pulse tube cryocooler superconducting quantum interference device (SQUID) cooling system, in which temperature was controlled by an infrared source, was proposed. A high-Tc SQUID magnetometer was mounted and cooled by a coaxial pulse tube cryocooler. A light from a halogen lamp was guided by a quartz flexible bundle fiber and was introduced to the cold head. The output power of the lamp was controlled by a temperature controller in accordance with the cold-stage temperature. As a result, the flux noise of the SQUID output was not changed in the range of 1 to 1000 Hz regardless of the lamp power. The temperature could be controlled at 77 K with an accuracy of 0.03 K +/- for a long time duration of more than 2 h. This demonstrated that the system can be applied to any application such as non destructive evaluation (NDE) systems.

This study is aimed at developing an eddy-current-based SQUID-NDE system for in-situ inspection of micro flaws on thin copper heat exchanger tubes. The system employs a high temperature superconductor (HTS-) SQUID gradiometer and a Helmholtz-coil-type inducer. As specimens, copper tubes 6.35 mm in outer diameter and 0.8 mm in thickness with artificial surface flaws of several tens mu m in depth were inspected using the system. Magnetic response due to a flaw of 10 mu m in depth on the tube moving at 32 m/min was successfully detected while applying an excitation field of 10 mu T at 3 kHz to the tube. Numerical simulations were also conducted to evaluate how many sensors would be required for inspection around the circumference of an entire tube.

A PC controlled food contaminant detection system for practical use was designed and constructed. The system we have developed is the High-Tc SQUID based system, which is covered with waterproof stainless steel plates and acceptable to HACCP (Hazard Analysis and Critical Control Point) program. The outer dimension of the system is 1500L mm x 477W mm x 1445H mm and the acceptable object size is 200W mm x 80H mm. This system employed a double-layered permeable metallic shield with thickness of 1 mm as a magnetically shielded box. The distribution of the magnetic field in the box was simulated by FEM; the gap between each shield layer was optimized before fabrication. Then the shielding factor of 732 in Z-component was achieved. This value is good enough to operate the system in a factory. As a result, we successfully detected a steel ball as small as 0.3 mm in diameter with a distance of 75 mm.

We constructed a SQUID-NDI system for inspection of micro-flaws on heat exchanger copper tubes employing HTS-SQUID gradiometer and Helmholtz-coil-type inducer. The HTS-SQUID gradiometer was cooled using a coaxial pulse tube cryocooler. The detection of artificial flaws several tens of mu m in depth on copper tubes, 6.35 mm in outer diameter and 0.825 mm in thickness, was demonstrated using the SQUID-NDT system. With excitation field of 1.6 mu T at 5 kHz, the system could detect a 30-mu m-depth flaw with SN ratio of about 20, where conventional NDI methods should fail to detect. The amplitude of the magnetic signal due to the flaw was in proportion to the square of flaw depth. Taking into account of the system's noise level, the results suggest that the SQUID-NDI system has a potential to detect sub-10-mu m-depth flaws on copper tubes. (c) 2005 Elsevier B.V. All rights reserved.

We propose a pulse tube cryocooler SQUID cooling system, which temperature was controlled by an infrared Source. A high-T-c SQUID magnetometer was mounted and cooled by a coaxial pulse tube cryocooler. A light from a halogen lamp was guided by a quartz flexible bundle fiber and was introduced to the cold head. The output power of the lamp was controlled by a temperature controller in accordance with the cold stage temperature. As a result, the flux noise of the SQUID output was not changed in the range of 1-1000 Hz regardless of the lamp power. The temperature could be controlled at 77 K with accuracy of +/- 0.03 K for long time duration more than 2 h. This demonstrated that the system can be applied to any applications such as NDE systems. (c) 2005 Elsevier B.V. All rights reserved.

A mobile cryocooler-based SQUID NDE system was developed for realization of NDE of fixed targets that can't be moved or rotated. In order to move the SQUID in an ambient field, an active magnetic shielding technique employing a compensation coil and feedback circuit including a band elimination filter was introduced in a SQUID NDE system. The HTS SQUID gradiometer was cooled by a coaxial pulse tube cryocooler to 74 K +/- 0.04 K. The flux noise caused by moving the SQUID at 32 mm/s was well suppressed. Unlocking of the flux-locked loop (FLL) circuit or a significant increase in noise did not occur during the motion. Detection of hidden slots in fixed single and double-layered carbon/carbon composites in ambient field was demonstrated by moving the HTS SQUID gradiometer.

A high Tc SQUID system for biological molecules (DNA) detection is developed. This system is based on a hybridization process. Two strands in a DNA molecule are held together by hydrogen bonds between base pairs like a ladder. The two strands are referred to as being complementary each other. HPVB 33 (Human Papillomavirus Probes 33) was prepared as a DNA. One strand (Sample DNA) was labeled with Fe3O4 ultra-small magnetic particles and the other (probe DNA) was anchored on a glass slide. Then they were hybridized each other on the slide. After washing the excess sample DNA, the hybridized DNA was evaluated in the presence of excitation ac field by high Tc SQUID. The signal was initially proportional to the concentration of the sample DNA and then saturated. It means that the hybridization occurred successfully between the sample DNA and the probe DNA.

There is a possibility that individuals ingest contaminants that have been accidentally mixed with food because processed foods have become very common. Therefore a detection method of small contaminants in food and pharmaceuticals is required. High-T-c SQUID detection systems for metallic contaminants in foods and drugs have been developed for safety purposes. We developed two systems; one large system is for meat blocks and the other small system is for powdered drugs or packaged foods. Both systems consist of SQUID magnetometers, a permanent magnet for magnetization and a belt conveyor. All samples were magnetized before measurements and detected by high T-c SQUIDs. As a result, we successfully detected small syringe needles with a length of 2 mm in a meat block and a stainless steel ball as small as 0.3 mm in diameter.

Experiments of nondestructive inspection (NDI) on copper heat exchanger tubes using an HTS-SQUID have been conducted. An eddy-current-based NDI system using HTS-SQUID gradiometer cooled using a cryocooler was developed for the detection of micro flaws on thin copper tubes 6.35 mm in diameter and 0.825 mm in thickness. With an excitation field of 1.6μT at 5 kHz, a 30-um-depth flaw was successfully detected by the system, where the conventional NDI techniques would fail to detect. Numerical simulations were also investigated to know how many sensors would be required for inspection around a whole circumference of a copper tube.

An eddy-current-based nondestructive inspection (NDI) system using superconducting quantum interference device (SQUID) cooled using a coaxial pulse tube cryocooler was constructed for the inspection of microflaws on copper tubes employing a high-T-c SQUID gradiometer and a Helmholtz-like coil inducer. The detection of artificial flaws several tens of mum in depth on copper tubes 6.35 mm in outer diameter and 0.825 mm in thickness was demonstrated using the SQUID-NDI system. With an excitation field of 1.6 pT at 5 kHz, a 30-mum-depth flaw was successfully detected by the system at an SN ratio of at least 20. The magnetic signal amplitude due to the flaw was proportional to both excitation frequency and the square of flaw depth. With consideration of the system's sensitivity, the results indicate that sub-10-mum-depth flaws are detectable by the SQUID-NDI system.

in this paper, we present our latest progress in the studies on SQUID-NDE for carbon fiber composites (CFCs), including carbon fiber reinforced plastics (CFRPs) and carbon fiber reinforced carbon matrix composites (C/Cs). We have developed a new SQUID-NDE system for the CFCs utilizing a pulse tube cryocooler for more practical and easy-handling use. Electromagnets using U-shaped ferrite cores have been introduced to the system in order to induce enough eddy current density in the relatively low-electric-conductivity CFCs. By using this system, we demonstrated the detection of deep-lying defects in thick and/or multi-layer CFCs specimens, partly including metal layer upon/below CFCs layer. CFRP plates and multi-layer C/C plates with total thickness of 20 mm having deep-lying slots at various depths were prepared. The slots at 15 mm below the surface in the CFRP plate and multi-layer C/C plate were successfully detected. Defect detections on more "real" multi-layer structures, including aluminum plates upon/below C/C plates, were also examined. (C) 2004 Elsevier B.V. All rights reserved.

There is a strong demand for detection of small contaminants in food and pharmaceutical medicines. High-T-c SQUID detection systems for a metallic contaminant in foodstuffs and drugs are developed for safety. We developed two systems; one large system is for meat blocks and the other small system is for powdered drugs or packaged foodstuffs. Both systems consist of SQUID magnetometers, a permanent magnet for magnetization and a belt conveyer. All the samples were magnetized before measurements and measured by high T-c SQUIDs. As a result, we successfully measured small syringe needles with length of 2 mm in a meat block and a stainless steel ball as small as 0.3 mm. in diameter.

We have proposed and demonstrated a high-T-c SQUID system for detecting metallic contaminants in foodstuffs. There is a demand for the development of systems for detecting not only magnetic materials but also non-magnetic materials such as Cu and aluminium in foodstuffs to ensure food safety. The system consists of a SQUID magnetometer, an excitation coil and a permanent magnet. For a non-magnetic sample, an AC magnetic field is applied during detection to induce an eddy current in the sample. For a magnetizable sample, a strong magnetic field is applied to the sample prior to the detection attempt. We were able to detect a stainless steel ball with a diameter of 0.1 mm and a Cu ball less than 1 mm in diameter, for example.

A small, low-magnetic-noise nondestructive inspection (NDI) system that uses a high-T_c superconducting quantum interference device (SQUID) cooled by a coaxial pulse tube cryocooler (PTC) has been developed. The key components for realizing the compact, low-noise system developed in this study, include the following: a high-T_c SQUID gradiometer, the coaxial PTC, and a SQUID-mount stage separated from the cold head of the cryocooler. The high-T_c SQUID gradiometer contributes not only to stable system operation when subjected to the environmental noise without magnetic shielding, but also a decrease in magnetic noise caused by the mechanical vibration of the SQUID, which is transmitted from the cryocooler. By using the coaxial PTC, which was constructed of non-magnetic materials, both magnetic noise and the mechanical vibration are well suppressed compared to conventional two-axial PTCs. In addition, the coaxial PTC is designed to be compact (50 mm diameter, 400 mm height, and 4 kg weight) for practical use. The SQUID-mount stage separation contributes to stable operation by reducing the transmitted vibration to the SQUID, and thermal stability at the SQUID-mount stage. The magnetic flux noise spectrum of the cryo-cooled system was measured and compared with that of a liquid-nitrogen-cooled system using the same SQUID. From the comparison, no increase in magnetic noise due to the cryocooler was observed, although the magnetic flux noise level of the cryo-cooled system was dominated by SQUID operation noise, which was rather high, (i.e., around 100 μΦ₀/Hz^1/2 at 100 Hz). The relation between the mechanical vibration at the SQUID and magnetic noise is discussed.

The use of carbon-fiber-reinforced plastic (CFRP) in aircraft and space structures is recently increasing. We investigated the possibility of nondestructively detecting a delamination in CFRP using a low-Tc first-order gradiometric superconducting quantum interference device (SQUID) loop. A CFRP plate including a thin insulator sheet between the central layers was prepared. The injected current method was adopted. The magnetic field due to the sheet was measured by a SQUID nondestructive evaluation system using the lock-in detection technique. The position and size of the sheet were successfully detected by mapping the measured field. The result agreed with that by ultrasonic testing. Future application of this method for detecting deep-lying flaws was discussed.

The widespread use of the SQUID-NDE requires the visualization of defects, We have developed a method to obtain depth information by monitoring the SQUID output while changing the frequency of the current flowing in a sample, The effectiveness of this method was verified by experiment and simulation.

In this research, we developed and investigated novel ultrasonic guided wave testing technique for early detection of defects in pipes and board structures, which person can not easily access, based on magnetic striction and electromagnetic fields. While applying electromagnetic field on target such as metallic and/or ferromagnetic pipe in order to generate ultrasonic guided waves which propagate on the pipe in long distance, we utilized extremely high-sensitive SQUID magnetic sensor to receive magnetic signal induced by the guided wave. By using the SQUID sensor, we realized higher sensitive and longer distance testing compared to the conventional method using induction coils and piezo sensors. Also it enables us to conduct all-round inspection of a pipe, resulting in capability to localize not only axial position of a defect on the pipe, but also circumferential position of the defect.

We aimed to develop an ultra-low-field (ULF) NMR/MRI system, which will be basis of functional MRI microscopy in the future. In this study, an ultra-sensitive SQUID magnetic sensor, which has extremely high sensitivity in low frequency range, which correspond to Larmor frequency in ULF, was used in the ULF NMR/MRI system. Using the system, we showed that the signal amplitude and line width of NMR signal in ULF increased and decreased with the static field intensity, respectively. Achievement of MRI in ULF was also demonstrated. We also studied possibility of realization of ULF NMR/MRI in normal environment, by combining robust SQUID and noise cancelling techniques.

In this research, we developed a magnetic flux transformers, which was composed of high-temperature superconductor (HTS) wire, to measure weak magnetic signal. It was shown that the noise level of the transformer was about 30 μΦ0/Hz 1/2. We utilized the transformer to construct a ultra-low field (ULF) NMR/MRI system. Based on the system, we measured proton-NMR signal and 1-demensional MRI of water phantom in Earth’ s magnetic field. We also clarified property of magnetic shielding of H TS cylindrical bulks.

Nuclear magnetic resonance(NMR) is a phenomenon that atoms absorb and radiate electromagnetic energy at a frequency corresponding to a static field applied to the object. One of the applications of EMF(Earth Magnetic Field)-NMR is NMR logging tool. This technology is a method to prospect oil reservoir by detecting the NMR signal of 1^H protons in porous oil reservoir in EMF. We have successfully obtained the 1^H NMR spectrum, which has a signal to noise ratio(SNR) of more than 7. Therefore we conclude that we have developed a prototype of SQUID-EMF-NMR system as a basis for NMR logging tool.

In this study, we developed a sensing system using ultra-sensitive SQUID magnetic sensors to detect magnetic nano-particles as a component technology for magnetic drug delivery system (MDDS). An array of 3 channel SQUID was installed on the system, to study the magnetic characteristics of magnetic nano-particles, whose diameters were less than 100 nm. An appropriate method to magnetize and detect the magnetic nano-particles was also investigated. As a result, we found that the particles with diameter of 50 nm generated the largest magnetic signal among the tested particles, and that a dc magnetization method was best suited because this method enabled to suppress energy due to the Brownian motion and convection in ferrofluid of 3 micron litter by means of the static magnetic field, and to detect moving particles in a tube.

本研究では、従来の検査技術の適用が困難な、燃料電池用水素燃料タンクの欠陥検出実現のため、現在最も高感度なSQUID磁気センサを用いたタンク欠陥早期検出装置の開発を行った。本装置は、磁気シールドのない環境でも動作する、高磁場耐性・高感度特性をもつSQUID磁気センサを開発・使用しており、本センサをロボットアームに搭載して、タンクを低周波数励磁しながらスキャンすることにより、タンク内亀裂検出が可能なことを示した。

自発的な収縮が有り比較的に計測が行いやすい心筋細胞(ラット)を用いて磁気信号の計測技術確立を中心に研究を進めた。これまでのパイロット実験では、数十ミクロンサイズの心筋培養細胞から、活動電位変化に起因する200pT(10^<-12>テスラ)程度の信号が得られていたが、大抵の場合は信号強度がその1/10〜1/100であり、信号が小さすぎて検出できないこともあった。これを高感度で検出するためには細胞の電流の向きと磁気センサの相対位置の検討をおこなった。電磁解析シミュレーションによって最も感度が高くなるような細胞形状とセンサの位置関係を検討した結果、細胞を培養ディッシュ内で縦方向に置いて培養することが必要となった。縦方向の培養を試みたが、細胞が定着せず、この方法はうまくいかなかった。昨年、センサの形状の検討を行い、マルチチャンネルタイプのSQUID(3ch)を新規に開発、設計試作し、これを用いて10dayラットの心臓片からの磁気計測を行うことができた。H18年度は3chで位置分解能が優れた1mm×1mmのSQUIDを試作し、特性評価を行った。その結果、0.01mm2の有効捕獲面積を得られ、従来の0.1×0.1mm2の約2倍の大きさを得ることができた。また、試作したSQUIDのホワイトノイズレベルは約5pT/Hz1/2であった。これはこれまで作製してきたSQUIDの約半分であり、感度が約2倍向上したことを示している。しかし、残念ながら、細胞からの信号を計測するには至らなかった。さらに磁場分解能と、位置分解能の最適化が必要と思われる。

本研究では、地磁気(約50μT)などの環境磁気雑音が存在する環境で、現在最も高感度なSQUID磁気センサを移動させて構造物の非破壊検査が可能なモバイル型検査装置の開発を目的とした。そこで、まずH17年度では、SQUID磁気センサ移動時に鎖交する環境磁気雑音をリアルタイムに相殺することによりセンサ移動を可能にするアクティブシールド技術の開発を行った。アクティブシールド技術として、SQUID磁気センサに鎖交する環境磁気の出力電圧を利用して、センサ近傍に設置した補償コイルから相殺磁気を発生させて、環境磁気を打ち消す帰還回路を開発した。本帰還回路には、狭帯域遮断フィルタを導入して非破壊検査に用いる特定周波数の磁気信号は相殺せずに、検査信号以外の全周波数帯域の磁気雑音を相殺するという特徴を持たせた。本アクティブシールド技術により、磁気ノイズの増加なしに32mm/sの速度でSQUID磁気センサの環境磁気中移動が可能となった。また、雑音の相殺を行った状態でSQUID磁気センサを二次元移動させて、ロケットなどの構造物に使用されている先進複合材料であるC/C(炭素繊維炭素強化複合材料)の非破壊検査を行い、深さ15mmに位置する欠陥を非破壊、非接触で検出することができた。 H18年度では、本科研費にて購入したロボットアームにこのSQUID非破壊検査を実装した。この際、ロボットアーム本体が移動できるような機構を導入した。また、実用性を考慮してSQUIDの冷却に取り扱いの容易なパルス管冷凍機を導入した。本研究では、ロボットが動作する際に発生する数μTの磁気ノイズがSQUIDに侵入して安定動作を妨げることが分かった。そこで、SQUIDよりも感度の点では数桁劣るが、数μTの磁場中でも安定動作するフラックスゲート磁気センサをSQUIDの代用に用いたアクティブシールドを開発し、ロボット式SQUID非破壊検査装置に適用した。この結果、ロボット動作時のノイズを相殺して、かつSQUID安定動作と二次元移動が可能な検査装置の開発に成功した。

Immunoassay using ultra sensitive SQUID magnetic sensors and chemically-stable magnetic nano-particle markers has been proposed. In this method, so far, a single marker has been connected with one antibody. If it is possible to connect much more magnetic particles with one antibody, the sensitivity of this method must be notably improved. Use of thermo responsive magnetic nano-particles (Therma-Max : TM) was proposed by our research group. TM can aggregate and disperse by themselves associated with temperature of solution around them. However, there was a problem that reproducibility and quantization of the results were hard to achieve. Therefore, in this work, the detail of the characteristics of aggregation and dispersion of the TMs was researched, and the number of aggregated TMs was quantified. Besides, confirmation of all reaction from antigen to antibody to TM was studied by using enzymes. Finally, the detection of the antigen-antibody reaction through magnetism from the labeled and aggregated TMs by a SQUID was examined respectively. At first, by means of optical method, the size of aggregated TMs in solution was researched. TMs have Fe_3O_4 core surrounded by thermo-responsive polymer. It was found that the averaged diameter of aggregated TMs increased with temperature above 29 degrees, and became 400 nm at 30.5 degrees. Above 31 degrees, aggregated particles became so large that most particles went down. Next, magnetic detection of antigen-antibody reaction labeled by TMs was examined using a SQUID. Myosin was used as antigen, while connecting anti-Myosin (first antibody), biotin-antibody (second antibody) and TMs in turn with Myosin. Furthermore, TMs were labeled by third anti-avidin antibody and fourth antibody with enzyme. By detecting the enzyme, all reactions from Myosin to TMs were confirmed. By means of SQUID measurements using AC magnetization method, magnetic signals of about 2.4 mφ_0 from aggregated TMs in the reaction plates were detected. However, the signal amplitude was not approximately proportional to the amount of antigen. It was found that this disproportion was caused by remaining surplus aggregated TMs on the bottom and wall of the reaction plates. A possible solution to remove the remaining surplus TMs was discussed. We believe that immunoassay using TMs and SQUID will realize higher sensitivity than ever by establish this technique.