high-Tc Superconducting Quantum Interference Device Research Articles

High Tc SQUID Detection System for Metallic Contaminant in Lithium Ion Battery

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 muphi0/Hz1/2 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 mum times 50 mum on the electrode of the lithium ion battery could be clearly detect. This detection level is difficult to achieve using other methods.

Sensitive J-couplingspectroscopy using high-Tc superconducting quantum interference devices in magnetic fields as low as microteslas

In this work we present a sensitiveJ-coupling spectroscopyin one shot using high-Tc superconducting quantum interference devices and a flux transformer in microtesla fields.In the proposed NMR detection scheme the precession of proton spin was inductivelycoupled to the SQUID magnetometer. We enhanced the SNR signal and the spectralresolution significantly by applying a pre-polarization field of 0.045 T. In microtesla fieldswhere chemical shifts are absent, we demonstrate proton–phosphate couplingJ3[H,P] = (10.94 ± 0.08) Hz in trimethyl phosphate. The sensitive NMR spectrometer will be of greatinterest for diagnosis information of molecular structure and biological applications.

High Tc SQUID Detector for Magnetic Metallic Particles in Products

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 a detection system of magnetic foreign matters in industrial products. 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 micron cannot be detected using X-ray imaging, which is commonly used for the inspection. Therefore a 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 a belt conveyer. These detection levels were hard to be achieved using conventional X-ray detection or other methods.

SQUID sensor application for small metallic particle detection

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 μm 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 μm on a belt conveyer and stainless steel balls of 300 μm in water. These detection levels were hard to be achieved by a conventional X-ray detection or other methods.

Modulation SQUID electronics working with high-T c SQUIDs in open space

SQUID electronics optimized for operation in unshielded space with dc high-Tc superconducting quantum interference devices (HTS SQUIDs) are developed, manufactured, and studied. The dynamic characteristics of the SQUID electronics are studied with two magnetic-field sensors based on the HTS SQUIDs: a conventional SQUID sensor with a resolution of 100 fT/Hz1/2 and a supersensitive SQUID sensor with a resolution of 15 fT/Hz1/2 at frequencies exceeding 10 Hz and a resolution of 30 fT/Hz1/2 at a frequency of 1 Hz. Stable operation of the magnetometric channel is demonstrated with both SQUID sensors under urban conditions. On the basis of a complex programmable logic device (CPLD), an ac bias can be realized in the SQUID and the modulation signal can be compensated in the feedback, bias-current, and desired-signal circuits. Such a compensation system is the most appropriate and versatile means of providing stable operation of the magnetometric channel in the presence of the SQUID ac bias, regardless of the type of high-temperature sensor and the configuration of the input contacts in the measurement probe.

Enhancement in low field nuclear magnetic resonance with a high-Tc superconducting quantum interference device and hyperpolarized H3e

In this work, we present a design that improves signals produced by nuclear magnetic resonance (NMR) and magnetic resonance imaging by using optical pumping and a high-Tc superconducting quantum interference device (SQUID) magnetometer. In our design for a NMR detection system, a pickup coil is coupled to the spin procession of a H3e nucleus; the input coil is coupled to a high-Tc SQUID magnetometer; and the capacitor is connected in series to form a tank circuit resonating at the Larmor frequency of the H3e nucleus in the measuring field. A signal-to-noise ratio gain of 2.67 over a conventional Faraday detection coil was obtained with the high-Tc SQUID detection system in a measuring magnetic field equaling 0.1128 mT, at which the central frequency was 3.66 kHz for H3e nucleus. The improvement in the NMR signal for large-size, hyperpolarized H3e coupled to a high-Tc SQUID-based spectrometer in low magnetic fields at room temperature is significant compared to that without flux coupling. This result may be of interest given its potential for use in a low field imager.

High-Tc superconducting quantum interference devices: Status and perspectives

In this paper, an overview of the current status of high-Tc superconducting quantum interference devices (SQUIDs), from device engineering to biomagnetic applications, is given. The authors offer a description of the current status of SQUID sensors, challenges encountered, and the solution of fabricating SQUID sensors with low flux noises. The current challenge that we face is to fabricate high-Tc SQUIDs that are not only more reproducible than the current technology but also capable of providing a high IcRn product and fabricating SQUID with high yield. Improvement of flux noises and fabrication yield in the integrated multichoices directly coupled SQUID magnetometer or gradiometer with series SQUID array are presented. High-Tc SQUID magnetometers exhibiting magnetic field sensitivity of ∼30–50fT∕Hz1∕2 or better at 100Hz was demonstrated by incorporating serial SQUID into the pickup loop of the magnetometers. New technologies currently being developed and applications for high-Tc SQUIDs are addressed.

METALLIC CONTAMINANT DETECTION SYSTEM FOR INDUSTRIAL PRODUCTS BY HIGH TC SQUID MAGNETIC SENSOR

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 μm. This detection level was hard to achieve by conventional X-ray detection methods.

High-Tc SQUID gradiometer system for immunoassays

A high-Tc dc SQUID (superconducting quantum interference device) gradiometer wasdeveloped for magnetic immunoassays where magnetic nanoparticles are usedas markers to detect biological reactions. The gradiometer was fabricated on a5 × 10 mm2 SrTiO3 bicrystal substrate and has a gradiometer resolution of2.1 pT cm−1 Hz−1/2. A magnetic signal was detected from a sample of1 µl ofFe3O4 nanoparticlesin a 40 mg ml−1 solution kept in a microcavity fabricated on Si wafers withSi3N4 membranes using MEMS (micro-electro-mechanical-systems) technology. Itwas found that volumes as small as 0.3 nl in principle would be detectablewith our present device. This corresponds to a total number of particles of2.2 × 107. The estimated average dipole moment per particle is4.8 × 10−22 A m2. We are aiming at reading out immunoassays by detecting the Brownian relaxation ofmagnetic nanoparticles, and we also intend to integrate MEMS technology into our system.

Epitaxial thick film high-Tc SQUIDs

Low-noise operation of superconducting quantum interference devices (SQUIDs) in magnetic fields requires high critical current and strong pinning of vortices in the superconducting electrodes and in the flux transformer. Crack-free epitaxial high-Tc dc-SQUID structures with a total thickness ?5 μm and a surface roughness determined by 30 nm high growth spirals were prepared with YBa2Cu3O7-x (YBCO) films on MgO substrates buffered by a SrTiO3/BaZrO3-bilayer. HRTEM demonstrated a high quality epitaxial growth of the films. The YBCO films and SQUID structures deposited on the buffered MgO substrates had a superconducting transition temperature Tc exceeding 91 K and critical current densities Jc > 3 MA/cm2 at 77 K up to a thickness ~5 μm. The application of thicker superconducting and insulator films helped us to increase the critical current and dynamic range of the multilayer high-Tc flux transformer and improve the insulation between the superconducting layers. An optimization of SQUID inductance allowed us to fabricate 8 mm SQUID magnetometers with SQUID voltage swings of ~60 μV and a field resolution of ~30 fT/√Hz at 77 K.

The balance and noise properties of directly coupled high-Tc superconducting quantum interference device gradiometers with a serial array

We characterize the balance and noise properties of directly coupled high-Tc superconducting quantum interference device (SQUID) gradiometers with a series array. The gradiometer consisted of symmetrical pickup loops, in which a series of SQUID was symmetrically configured and directly coupled to pickup loops. We characterize the balance resolution B from the following formula: B=Aeff,uniformfield∕Aeff,gradientfield, where Aeff,uniformfield and Aeff,gradientfield are the parasitic effective area and the effective area of the gradiometer, respectively. We obtained B=1.25×10−2 which was comparable to the typical balance resolution of ∼10−2 for a gradiometer fabricated onto the 10×10mm2 substrate. This discrepancy was probably due to the many superconducting pads inside the pickup loops which deteriorated the uniformity of applied uniform magnetic fields. The gradient field sensitivity of ∼40fT∕Hz1∕2cm at 1kHz for two-SQUID gradiometers was demonstrated in a magnetically unshielded environment, which was comparable to the best gradient sensitivity of 30fT∕Hz1∕2cm, with gradiometric flip-chip flux transformer with a length of 24mm and a base line of 10mm in shielded environment.

Hyper-high-sensitivity wash-free magnetoreduction assay on biomolecules using high-Tc superconducting quantum interference devices

In this work, we develop a platform for assaying biomolecules involving the measurement of alternating current (ac) magnetoreduction of magnetic reagent mixed with a detected sample. The magnetic reagent contains magnetic nanoparticles coated with a given kind of antibody, which associates with conjugated biomolecules. Then, the biomolecules can be quantitatively detected by measuring the ac magnetoreduction of magnetic reagent. To achieve hyper-high-sensitivity assay, a system utilizing a high-transition-temperature rf superconducting quantum interference device (SQUID) as a sensor to probe the magnetoreduction of reagent due to the association between biomolecules and magnetic nanoparticles. Examples to assay multiactive epitope, single-active epitope, and small molecules are given to demonstrate the validity of the assay platform, as well as the hyper-high sensitivity.

Magnetic dipole imaging by a scanning magnetic microscope

A reconstruction technique to evaluate residual magnetic fields and simulate magnetic images due to dipole distribution in ferromagnetic samples has been proposed in connection with a scanning magnetic microscope based on a high-Tc superconducting quantum interference device (SQUID). We have extended the expression of a point magnetic dipole to represent spatially extended sources and the generated magnetic field has been compared with experiments. In particular, a recently installed scanning SQUID magnetic microscope (model 770 by Tristan Technology) has been used. Magnetic maps obtained at different sample-to-sensor distances and in several configurations have been compared with simulations. With this aim, ferromagnetic rod samples have been modeled as extended magnetic dipoles close to the sensor. Excellent agreement has been obtained, confirming the efficiency of the proposed technique. Such an imaging technique has been demonstrated to be an easy-to-handle tool to identify dipole configurations producing a specific magnetic image.

Liquid Phase Immunoassay Using Magnetic Markers and Superconducting Quantum Interference Device

A liquid phase immunoassay utilizing magnetic markers and a high-Tc superconducting quantum interference device (SQUID) was studied. In this method, the biological target is detected using magnetic markers, i.e., the magnetic signal from the markers that bound to the target is detected with the SQUID. The detection was performed in a solution containing both the bound and unbound (free) markers without using the so-called bound/free (BF) separation process. The bound markers were distinguished from the free markers by utilizing the Brownian rotation of the free markers. First, the properties of the free markers in the solution, such as the M–H curve and magnetic relaxation, were measured to study the background signal from the free markers. Markers that exhibit remanence were used for the experiment. Using the obtained results, we discuss the effects of the residual earth field and aggregation of the markers on the background signal. Next, we detected a fungus, Candida albicans, with the described liquid phase immunoassay. Good relationship was obtained between the detected signal and the number of fungi. The minimum detectable number of fungi was as small as 30.

A high-Tc SQUID micro-detector with a high performance magnetic shield for contaminant detectionin industrial products

A high-Tc superconducting quantum interference device (SQUID) system for the detection ofmagnetic foreign matter in industrial products was developed. There is a possibility thatultra-small metallic foreign matter has been accidentally mixed with industrial productssuch as lithium ion batteries. Metallic particles with outer dimensions less than100 µm cannot be detected by conventional x-ray imaging. Therefore we developed a detection system based ona high-Tc SQUID microscope with a high performance magnetic shield. The use of SQUIDmicroscopes with a 0.5 mm thick vacuum window was proposed. This design enables theSQUID to approach the object to be measured as close as 1 mm and enhancesthe sensitivity. A new magnetic shield with sleeves was carefully designedand built. As a result, we could successfully measure small particles sized100 µm. This detection level was hard to achieve using a conventional x-ray detection method.

Detection of plastic deformation in structural steel using scanning SQUID microscopy

The magneto-mechanical behaviour of structural steel specimens stressed up to a plastic deformation stage using a high-Tc scanning SQUID (superconducting quantum interference device) microscope is investigated. The correlation between the gradient of the normal component of the magnetization and dislocation density, before the crack initiation, is carried out. The capability of scanning SQUID microscopy to detect the residual magnetization, due to the tensile stress, with a non-invasive technique is reported.

High Tc SQUID Based Metallic Contaminant Detection System for Beverage or Ground Meat

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.

Superconducting-quantum-interference-device array magnetometers with directly coupled pickup loop and serial flux dams

In this work, we studied the engineering of high-transition-temperature superconductor Josephson junctions and superconducting quantum interference device (SQUID) by using step-edge or the bicrystal grain-boundary technologies. Serial Josephson junctions and bare SQUID array reveal high quality device characteristics. A high-Tc SQUID magnetometer exhibiting magnetic field sensitivity of 33fT∕Hz1∕2 in the white regime and 80fT∕Hz1∕2 at 1Hz was demonstrated by incorporating the flux dams and serial SQUID into the pickup loop of magnetometer. Furthermore, we demonstrate the opening of the flux dams by applying an external magnetic field to induce a current higher than the critical current of the serial flux dams. We show that the serial flux dams effectively suppress the low frequency 1∕f-like noises.

An Economical Magnetocardiogram System Based on High-TcSQUIDs

An economical magnetocardiogram (MCG) system is built in ourlaboratory. It mainly consists of a MCG data acquisition stage equippedwith two high-Tc superconducting quantum interferencedevice (SQUID) magnetometers, a data processing stage with digitalfiltering and a one-layer μ-metal magnetically shielded room inconjunction with a high-Tc SQUID based active compensation.Experimental results show that a noise level of pico-tesla in MCGprofiles, which is necessary for clinical applications, may be achievedwith the system. Moreover, stable and convenient operations of thesystem are demonstrated with simulating MCG measurements.

Enhancement of nuclear magnetic resonance in microtesla magnetic field with prepolarization field detected with high-Tc superconducting quantum interference device

We applied prepolarization field and high-Tc superconducting quantum interference device (SQUID) detector to enhance nuclear magnetic resonance signal in a microtesla magnetic field. The minimum measuring magnetic field is 8.9μT at which the proton resonance frequency is 380Hz. The specificity instrumentation and the difficulty of using a high-Tc SQUID with prepolarization field were investigated. We applied gradient field to perform one-dimensional proton imaging in a microtesla magnetic field. Additionally, low field high-Tc SQUID-based NMR systems are promising in biomagnetic research due to its use, for example, in imaging with hyperpolarized noble gas.