High-temperature Superconducting Quantum Interference Research Articles

Analyzer-to-Analyzer Variations in Assaying Ultralow Concentrated Biomarkers Associated with Neurodegenerative Diseases Using Immunomagnetic Reduction.

By utilizing a high-temperature superconducting quantum interference device (high-Tc SQUID) magnetometer, an alternating current (AC) magnetosusceptometer, referred to as an analyzer, was developed for ultrasensitive immunoassays. The analyzer has been applied to assay biomarkers in human plasma associated with Alzheimer's disease (AD) and Parkinson's disease (PD). The involved assay methodology is the so-called immunomagnetic reduction (IMR). Such an analyzer has been approved for clinical use in Taiwan and Europe. The mass production of the analyzer is needed for clinical utilities. The issue of exploring analyzer-to-analyzer variations in the performances becomes critical. Unfortunately, there is no standard characterization to determine the variations in performances among analyzers. In this study, key characterizations, such as output signal stability, signal-to-noise ratio, measured concentrations of a control sample, etc., are proposed. In total, three analyzers are characterized in this work. The detected biomarkers include amyloid peptides, total tau protein, phosphorylated tau protein, and α-synuclein protein for AD and PD. Through one-way ANOVA for any of the characterizations among the three analyzers, it was found that there was no significant difference in any of these characterizations among the analyzers (p > 0.05). Furthermore, the three analyzers are applied to assay biomolecules for AD and PD in reference samples. High correlations (r > 0.8) in measured concentrations of any of these biomarkers in reference samples were obtained among the three analyzers. The results demonstrate that the proposed characterizations are feasible for achieving consistent performance among high-Tc SQUID-based AC magnetosusceptometers for assaying biomolecules.

Automatic coregistration of MRI and on-scalp MEG

BackgroundRecent progress in optically pumped magnetometers (OPMs) and high-temperature superconducting quantum interference devices (SQUIDs) has facilitated the development of an on-scalp magnetoencephalography (MEG) system that offers high signal intensity and flexibility at a lower cost. While the on-scalp sensor array has high flexibility, it brings new challenges to accurate sensor-to-brain coregistration, which is essential for MEG source localization. New methodA novel automatic filtering algorithm based on plane segmentation was proposed to locate on-scalp MEG sensors in 3D images reconstructed from optical scanning. Global image registration was employed for the automatic alignment of anatomical images and sensor positions. ResultsSeventy-one sensor dummies on the scalp were located and registered to brain anatomical images. The deviations of the sensor location and orientation from the averaged result of 10 measurements were less than 1 mm and 0.6°, respectively. The entire process could be completed in less than 4 min. Comparison with existing methodsCompared with existing methods that involve various manual procedures, such as moving digitizers to fiducials and repeatedly pulling out sensors, our proposed coregistration method is more efficient and accurate. ConclusionAn automatic method for the coregistration of anatomical structure and on-scalp sensors that will have a large impact on the practical use of on-scalp MEG is developed.

Detection of interictal epileptiform discharges: A comparison of on-scalp MEG and conventional MEG measurements

ObjectiveConventional MEG provides an unsurpassed ability to, non-invasively, detect epileptic activity. However, highly resolved information on small neuronal populations required in epilepsy diagnostics is lost and can be detected only intracranially. Next-generation on-scalp magnetencephalography (MEG) sensors aim to retrieve information unavailable to conventional non-invasive brain imaging techniques. To evaluate the benefits of on-scalp MEG in epilepsy, we performed the first-ever such measurement on an epilepsy patient. MethodsConducted as a benchmarking study focusing on interictal epileptiform discharge (IED) detectability, an on-scalp high-temperature superconducting quantum interference device magnetometer (high-Tc SQUID) system was compared to a conventional, low-temperature SQUID system. Co-registration of electroencephalopraphy (EEG) was performed. A novel machine learning-based IED-detection algorithm was developed to aid identification of on-scalp MEG unique IEDs. ResultsConventional MEG contained 24 IEDs. On-scalp MEG revealed 47 IEDs (16 co-registered by EEG, 31 unique to the on-scalp MEG recording). ConclusionOur results indicate that on-scalp MEG might capture IEDs not seen by other non-invasive modalities. SignificanceOn-scalp MEG has the potential of improving non-invasive epilepsy evaluation.

Dynamic Range Expansion Method of Three-component HTc SQUIDs Magnetometer

In view of the small dynamic range of the three-component high-temperature superconducting quantum interference device (HTc SQUID) magnetometer and it is easy to exceed the measurement range when working in the field without magnetic shielding environment. A dynamic range expansion method based on step compensation is proposed. By setting a magnetic compensation coil on each axis of the three-component HTc SQUIDs magnetometer probe, a current is passed to generate a magnetic field opposite to the direction of the external magnetic field to offset most of the magnetic field to be measured. The measured values are calculated and processed to obtain the magnetic field value to be measured. The test results show that the method can greatly improve the dynamic range without reducing the sensitivity of the magnetometer, which can work stably in a non-magnetic shielding environment and meet the requirements of field geophysical magnetic exploration.

Portable Cryostat With Temperature Control Function for Operation of HTS-SQUID at a Higher Slew Rate

We examined a portable cryostat utilizing liquid nitrogen with temperature control function for operation of high-temperature superconducting quantum interference devices (HTS-SQUIDs) to have a higher slew rate. To operate a non-destructive evaluation system with HTS-SQUID in city areas with serious environmental electromagnetic noise, we often need a higher slew rate. A glass Dewar is installed in an outer case made of aluminum, which is sealed hermetically. The temperature of liquid nitrogen is controlled by using a vacuum pump connected to a feedback circuit, which monitors the temperature of liquid nitrogen. The temperature of liquid nitrogen could be controlled in the range between 73 and 77.2 K with a 0.1 K step. For example, the temperature was kept at 75 K with precision of ±0.05 K for 9 hs and SQUID was operated stably for this period. The ΔV and the slew rate of a test SQUID were increased from 22 μV and 3.2 mT/s at 77.2 K to 37 μV and 5.9 mT/s at 73 K, respectively. The white noise was also improved from 48 fT/√Hz at 77.2 K to 32 fT/√Hz at 74 K. We believe that this technology is useful to extend application of HTS-SQUIDs in the fields.

High-pressure neutron diffraction study of Pd3Fe

High-pressure neutron diffraction data from powder and single-crystal samples of atomically disordered (Fm3¯m) and ordered (Pm3¯m) Pd3Fe were collected up to pressures of 15 GPa, and high-pressure SQUID magnetometry data were collected up to 6 GPa. The data show a subtle decrease in the magnetic moment with applied pressure, resulting in a transition to a paramagnetic state by approximately 8 GPa at 300 K. Diffraction results have been used to determine the equation of state, resulting in a bulk modulus of 176.78(9) GPa for the disordered powder and 187.96(7) GPa for the ordered single-crystal samples, approximately 20% more compressible than previously reported from X-ray measurements. High-temperature superconducting quantum interference device magnetometry was used to confirm the ambient pressure Curie temperature of the sample (545 K), which was further investigated using high-temperature single-crystal neutron diffraction at ambient pressure.

Development of HTS-SQUID System for a Monitoring System of CO2 Enhanced Oil Recovery

We have tried to develop an induction logging system for oil fields utilizing a high-temperature superconducting quantum interference device (HTS-SQUID). Enhanced oil recovery (EOR) technology utilizing carbon dioxide (CO2 ) is a promising technique for efficient production of petroleum. To control the EOR, it is important to improve the accuracy of monitoring technique of CO2 injected into the oil reservoir. The HTS-SQUID has a potential to monitor CO2 behavior in crude oil reservoir because of its high sensitivity in a wide frequency range from dc to over 1 MHz. As the first step of the developments, we prepared a vessel for SQUID system by using carbon fiber reinforced plastic with pressure tightness of 70 MPa and thermal durability of 200 °C. By using the SQUID system placed at a depth of about 300 m in a steel-cased borehole filled with water, magnetic signals from a transmitter coil in another borehole were successfully measured.

Ultra-low field MRI food inspection system prototype

We develop an ultra-low field (ULF) magnetic resonance imaging (MRI) system using a high-temperature superconducting quantum interference device (HTS-SQUID) for food inspection. A two-dimensional (2D)-MR image is reconstructed from the grid processing raw data using the 2D fast Fourier transform method. In a previous study, we combined an LC resonator with the ULF-MRI system to improve the detection area of the HTS-SQUID. The sensitivity was improved, but since the experiments were performed in a semi-open magnetically shielded room (MSR), external noise was a problem. In this study, we develop a compact magnetically shielded box (CMSB), which has a small open window for transfer of a pre-polarized sample. Experiments were performed in the CMSB and 2D-MR images were compared with images taken in the semi-open MSR. A clear image of a disk-shaped water sample is obtained, with an outer dimension closer to that of the real sample than in the image taken in the semi-open MSR. Furthermore, the 2D-MR image of a multiple cell water sample is clearly reconstructed. These results show the applicability of the ULF-MRI system in food inspection.

Magnetorelaxometry of few Fe3O4 nanoparticles at 77 K employing a self-compensated SQUID magnetometer

Magnetic nanoparticles (MNPs) are of great interest for industrial and medical applications. Therefore, the properties of the particles have to be well controlled. Several magnetic measurement schemes have been developed in order to determine particle parameters such as size distribution and structural properties. In general, systems are designed either for the analysis of large amounts of MNP (≫1000) or for single particle investigation. Up to now, the region in between has been less studied. However, small and well defined amounts of MNPs are of high interest, e.g. for the systematic investigation of particle–particle interactions. In this paper, we present a method using electron beam lithographic preparation of small amounts of MNPs directly on a self-compensating high-temperature superconducting quantum interference device (SQUID) with micrometer dimensions which is insensitive to homogeneous fields and first order gradients but very sensitive to internal magnetic dipole fields. Magnetorelaxometry (MRX) measurements were carried out at 77K sample temperature in a magnetically shielded room in order to analyze the dynamic behavior of MNP samples and to evaluate the detection limit of our SQUID sensors. Calculations based on the magnetic moment superposition model (MSM) and finite element simulations (FEM) indicate that the MNP samples can be fabricated in a well-defined way by the presented method. Based on MRX measurements of a sample with 200 single-core magnetite MNPs with core diameters of 12nm, we estimate the detection limit of our SQUID MRX setup as 70 MNPs.

Numerical Simulation of DC SQUID Taking Into Account Quantum Characteristic of Josephson Junction

High-temperature superconducting quantum interference devices (HTS SQUIDs) have been developed as an extremely sensitive magnetic sensor. The HTS SQUIDs are required to have high robustness with respect to the magnetic noise for stable operation in an unshielded environment and also reduced cost to widen the application range. It is, therefore, necessary to clarify the quantum magnetic behavior of the HTS SQUID. However, a simulation tool, which can consider the quantum magnetic behavior, has not been developed yet. In this paper, an equivalent circuit of a Josephson junction comprising the HTS SQUID is more properly considered to represent the quantum behavior. It can consider the ac and dc Josephson effect. The obtained results are compared with an ordinary simulation using a simplified circuit model, and the results agree well with each other. Using the proposed simulation method instead of the ordinary simulation, the current path is more accurately simulated, so this new method will be used to evaluate the robustness of the SQUID.

Development of Non-destructive Evaluation System Using an HTS-SQUID Gradiometer with an External Pickup Coil

We are developing a new eddy-current non-destructive evaluation (NDE) system using a high-temperature superconducting quantum interference device (HTS-SQUID) gradiometer with the aim of applying it to power plants. Electric power facilities such as ducts and vessels are generally untransportable because of their size, and thus it is difficult to apply a conventional SQUID NDE system. The new NDE system employs an external Cu pickup coil which is supposed to be driven flexibly by a robot arm at room temperature and an HTS-SQUID chip which is placed in a magnetically shielded vessel. In the present research, we investigated the performance of an HTS-SQUID sensor connected with external pickup coils before mounting them to a robot arm. By varying the Cu coil conditions such as their sizes, the number of turns, and the diameter of wire, we qualitatively evaluated the frequency dependence of the effective area and the cutoff frequency.

Noise properties of HTS-SQUID gradiometer in an elevated magnetic field

Abstract Stability of a high-temperature superconducting quantum interference device (HTS-SQUID) gradiometer with ramp-edge Josephson junctions against application of magnetic fields was investigated. The gradiometer with a SQUID inductor having a 5-μm-wide line and pickup coils of 0.5x1.5 mm for one side was used. Noise spectra were measured for the gradiometer in zero field after cooled in dc magnetic fields up to 300 μT. no increase in noise level was observed until 95 T, being higher than the earth field. Noise spectra in elevated magnetic fields up to 320 μT were also measured for the gradiometer cooled in zero field. No appreciable increase in noise was observed until 150 μT. By decreasing the applied field from 320 μT to zero, the gradiometer recovered the original low noise level. These results indicated that the examined gradiometer had a good durability against magnetic fields and could be used without a magnetic shield for various applications.

A Superconducting Magnetic Tensor Gradiometer for Underwater UXO Detection

Magnetic surveys are routinely used for detection of discrete magnetic targets, such as unexploded ordnance (UXO). Gradient tensor measurements have a number of benefits over measuring total field intensity or its vector gradient: they provide detailed information about a target in a single pass, without necessarily passing directly over the target; they determine the location of the target using a direct method, rather than the indirect inversion method required with other measurements; and they determine directly the magnitude and orientation of the magnetic moment, as well as the location of the target, aiding discrimination between sources and characterization of the munitions. The CSIRO is building a magnetic tensor gradiometer, designed for underwater deployment, based on high temperature superconducting quantum interference devices (SQUIDs). Technical challenges for the project include: designing a high temperature SQUID device that can achieve the required gradient sensitivity in motion; developing a gradiometer housing that can deal with the boil-off gas from the liquid nitrogen cryogen while underwater; identification and removal of wave-induced magnetic noise; compensation for magnetic noise caused by motion and the platform itself; and developing a dipole-tracking algorithm for gradient tensor measurements that is both robust and computationally undemanding. This paper presents the progress to date on this project including an evaluation of gradiometer performance in laboratory conditions, and describes some simple methods for localization and characterization of compact magnetic sources using gradient tensor measurements.

Metallic Contaminant Detection using a High-Temperature Superconducting Quantum Interference Devices Gradiometer

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 × 50 μm2 on the electrode of a lithium ion battery could be clearly detected. This detection level is difficult to achieve when using other methods.

Application of SQUID to magnetic contaminant detection

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 8mm in width and compared its detection width with that of a conventional small sensor 3mm wide. We found that the effective detection width of the 8mm sensor was 11.6mm. 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 50μm×50μm on the electrode of a lithium ion battery could be detected clearly.

The need for stable, mono-dispersed, and biofunctional magnetic nanoparticles for one-step magnetic immunoassays

We have developed a magnetic immunoassay system (MIA) using magnetic nanoparticle markers for biomolecule detection. We have magnetically characterized multi-core magnetic nanoparticles (MNPs) containing single-domain crystals of Fe3O4 and CoFe2O4 with our system using a high temperature superconducting quantum interference device as detector. We use a Helmholtz coil to excite the MNPs and study the AC-susceptibility. The data is fit to a model and information about the particle size distribution of the MNP system is extracted. We observe high stability of the unfunctionalized MNPs. However, our MIA measurements require stable functionalized MNPs. We have found a significant increase in hydrodynamic size of the functionalized MNP systems in the course of just a few days caused by agglomeration behaviour. Separate measurements performed at Imego AB with their AC-Susceptometer, DynoMAG®, confirm these findings. Without stable, functionalized MNPs MIAs of this kind are impossible.

Analysis of the possibility to amplify an RF signal with a superconducting quantum interference filter

A laboratory prototype RF amplifier for the frequency range 1–10 GHz is designed, created, and tested. The device is based on high-temperature superconducting quantum interference filters (SQUIFs) and the technology of bicrystalline substrates. The main characteristics of the prototype SQUIF amplifier are numerically simulated and measured.

Sensitivity and resolution of using magneto-telluric gradient method for detecting buried objects

The feasibility of using magneto-telluric gradient measurements at the surface of the earth for detecting buried objects is examined. A modified quasi-static version of the finite-difference time-domain method is used to examine the sensitivity and resolution of this approach. Buried objects with varying sizes, conductivities and depths were simulated. The use of high temperature superconducting quantum interference devices (SQUID) for carrying out this magneto-telluric measurement is discussed.

Resonance phenomena in asymmetric superconducting quantum interference devices

The theory of self-induced resonances in asymmetric two-junction interferometer device is presented. In real devices, it is impossible to have an ideal interferometer free of imperfections. Thus, we extended previous theoretical approaches, introducing a model that contains several asymmetries: Josephson current $ϵ$, capacitances $\ensuremath{\chi}$, and dissipation $\ensuremath{\rho}$ presented in an equivalent circuit. Moreover, nonconventional symmetry of the order parameter in high temperature superconducting quantum interference devices forced us to include phase asymmetries. Therefore, the model has been extended to the case of $\ensuremath{\pi}$-shift interferometers, where a phase shift is present in one of the junctions.

Magnetophoresis and cytometry with magnetic microparticles

Abstract We are developing a bioassay technique utilizing superparamagnetic and ferromagnetic microparticles, with the aim of using these in biological labeling. The technique uses two independent pieces of instrumentation; a magnetophoresis instrument and a magnetic flow cytometer. The former consists of a microfluidic sorting chamber that incorporates standard flow techniques and a permanent magnet. The particles are deflected into different outlet collection bins, with the degree of deflection determined by the particle's magnetic moment. We report on microparticle sorting and discuss the hydrodynamics of the chamber in relation to reproducibility. Once the microparticles have been sorted, the different populations will then be sequentially analyzed both optically and magnetically (while in flow). The magnetic analysis is presently performed with the aid of a LN 2 -cooled high temperature superconducting quantum interference device (HTS SQUID) array. We are currently also evaluating the use of giant magnetoresistive (GMR) sensors. In this paper we will discuss the sorting and resorting of microparticles and present preliminary results for the magnetic detection of the microparticles both with HTS SQUID and GMR sensors.