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Magnetocardiography (MCG) using a superconducting quantum interference device (SQUID) sensor has been known for a noninvasive, noncontact, and safe diagnostic tool to detect ischemic heart disease such as angina and myocardial infarction. The magnetic distribution generated by the electrical activation of the heart reveals the abnormality of the myocardial status. The bust depth of people in 20s and 70s are much different, and the greatest difference is up to 154 mm. The purpose of this study is to identify whether MCG signals and parameter values are changed at the different locations of the SQUID sensor assembly. It would be an important reference for the standard measurement. Four healthy male subjects (33.3 [+ or -] 6.3 years) participated in this study. The distance between the chest surface and the bottom of the sensor assembly was 20, 40, 60, and 80 mm. Recording was made using 64-channel MCG system (axial type, first-order gradiometer) developed by Korea Research Institute of Standards and Science (KRISS). MCG were recorded for 30 s in a magnetically shielded room. As the sensor location is getting away from the chest surface, the each mean amplitude of R-and T-wave peak decreases to 70 % (at 40-mm distance), 51% and 50% (at 60 mm), and 38% and 35% (at 80 mm) of the reference amplitude measured at 20-mm distance (y = -0.000002*[x.sup.3] + 0.0003* [x.sup.2] - 0.0308* x + 1.4961, [R.sup.2] = 1.00; where y = average amplitude remained after reduction}, x = distance between the chest surface and sensor location). Interindividual difference was less than 5 %. The regression equations may be used as a good reference to calculate how much strength will be decreased by the distance. In MCG parameters, most parameters decreased when the distance increased. As an example, the current moment at T-wave peak reduced to 52% (at 40-mm distance), 33% (at 60 mm), and 19% (at 80 mm). Results showed how MCG signal and parameter values decreased rapidly when the sensor assembly was located far from the signal source. The study results may be used as a useful reference to design MCG system and analysis program. Index Terms--Magnetocardiogram (MCG), sensor location, signal amplitude ratio, superconducting quantum interference device (SQUID).

Magnetocardiography (MCG) is a device to measure the weak magnetic fields generated from the heart using a superconducting quantum interference device sensor which converts magnetic flux to voltage and is the most sensitive sensor to detect magnetism. In the previous study, authors found that the values of MCG parameters of patients with non-ST-segment myocardial infarction were greater than those of age-matched controls (AMCs). In this study, we selected five different groups of patients considering their severity. We compared 10 MCG parameters recorded from 19 healthy young subjects (26.8 [+ or -] 13.4 years), 19 age-matched healthy subjects (55.4 [+ or -] 10.7), 23 stable angina patients (56.4 [+ or -] 7.6 years) with no stenosis (= 0% on coronary angiogram) and normal echocardiogram, 24 unstable angina patients (61.9 [+ or -] 9.8 years) with severe stenosis ([greater than or equal to] 70%), and 20 Q-wave myocardial infarction (QMI) patients (57.3 [+ or -] 11.2 years) with severe stenosis ([greater than or equal to] 70%). To record the magnetic signals from a heart with minimal noise, a magnetically shielded room was used. The number of abnormal parameters was counted and magnetic field map (MFM) patterns were compared. As a result, young healthy subjects showed the smallest values in all 10 MCG parameters and QMI subjects showed the greatest values. Significant difference was found from dynamics parameters such as current angle, map angle, and distance dynamics between young healthy controls and AMC groups (p < 0.05). No significant difference was found from AMC and stable angina groups even though parameter values of stable angina were slightly greater than those of AMC. Significant difference was found from five parameters between AMC and QMI subjects. These results are supportive to the previous analysis. In addition, the abnormal MCG parameters increased when the ischemic disease was worsened. Abnormal MFM patterns were easily found from QMI patients than stable angina pectoris. It is clear that abnormal MFM and parameters increase when the status of ischemic heart disease patients are getting worse. Index Terms--Ischemic heart disease, magnetocardiogram, stenosis, superconducting quantum interference device (SQUID).

In this paper, we fabricated a low-[T.sub.c] second-order superconducting quantum interference device gradiometer (SQUID) to measure magnetocardiography (MCG) in unshielded environment. The second-order gradiometer consists of the pickup coil and the SQUID. The pickup coil is formed with two single-turn coils and one double-turn coil. The three coils are connected in order of single-, double-, and single-turn coil. The coupling polarity of two single coils is opposite to the double-turn cot. The SQUID is based on double relaxation oscillation SQUID (DROS), which consists of a hysteretic signal SQUID, a reference junction, and shunted a relaxation circuit with a resistor and an inductor. The DROS has ten times larger flux-to-voltage transfer coefficient (~ 1 mV/[[PHI].sub.o]) than that of the conventional SQUID. Therefore, DROS could be operated with a simple flux-locked loop circuit. The pickup coil and the SQUID were fabricated on the independent wafers and connected superconductively using an Nb wire. The overall size of the second-order gradiometer is 94 x 12 [mm.sup.2] with a baseline of 35 mm. The average field noise was about 8 IT/[square root of (Hz)] at 100 Hz with the second-order gradiometer in shielded or unshielded environment. The noise level is low enough to measure MCG signals in the unshielded environment. Finally, we measure the MCG in shielded and unshielded environments by using the second-order gradiometer and compared the signal characteristics measured in both environments. Index Terms--Magnetocardiography (MCG), second-order gradiometer, superconducting quantum interference device (SQUID), unshielded environment.

In this paper, the effects of electromagnetic fields from the frequency band of digital wireless telephones on a superconducting quantum interference device (SQUID) were experimentally investigated. A first-order planar gradiometer based on the double relaxation oscillation SQUID (DROS) was operated without low-frequency magnetic shielding, and was exposed to radiated electromagnetic fields in the frequency range of 300 MHz-2 GHz. The experiments have been performed in a fully anechoic chamber to minimize reflected waves in the chamber. The flux-to-voltage transfer and the field sensitivity of the gradiometer have been observed under the irradiation of fields. Results show that the performance of the gradiometer was significantly affected at a typical power level of the digital wireless telephones for both horizontally and vertically polarized electromagnetic waves. The noise level of the DROS output voltage also increases as the strength of the external fields becomes higher. Index Terms--Biomagnetics, electromagnetic interference, superconducting quantum interference device (SQUID) magnetometers.

A superconducting quantum interference device (SQUID) system for nondestructive evaluation is developed using a thin-film-based Nb SQUID. This system is used to detect subsurface defects in artificially engineered aluminum plates and stainless steel weldment specimens.

The development of the first practical high Tc SQUID system for the detection of magnetic contaminants in commercial products, which consists of three SQUIDs, cooled by liquid nitrogen, a permalloy magnetic shield, a conveyer, and a magnetization unit is described.

Understanding demagnetization by hypervelocity impacts is crucial for the interpretation of planetary magnetic anomalies and remanent magnetization in meteorites. We describe an innovative approach for investigating the effects of impacts on the remanent magnetization of geologic materials. It consists of the combination of pulsed laser impacts and Superconducting Quantum Interference Device (SQUID) microscopy. Laser impacts are nondestructive, create shocks with peak pressures as high as several hundred GPa, and allow well-calibrated modeling of shock wave propagation within the impacted sampies. High-resolution SQUID microscopy quantitatively maps the magnetic field of room-temperature samples with an unprecedented spatial resolution of ~100 [micro]m. We present shock modeling and magnetic field data obtained for two laser impacts on a magnetite-bearing basalt sample. Magnetic measurements show a demagnetized area at the impact locations. We also show that high-resolution magnetic measurements combined with impact modeling provide a continuous relation between the demagnetization intensity and the peak pressure undergone by the sample. This promising technique will allow for the investigation of the demagnetization behavior of a variety of geological materials upon impacts, with implications for our understanding of the magnetization of extraterrestrial materials and of terrestrial impact structures. Keywords: impact demagnetization, SQUID microscopy, laser impact, magnetite.

Understanding demagnetization by hypervelocity impacts is crucial for the interpretation of planetary magnetic anomalies and remanent magnetization in meteorites. We describe an innovative approach for investigating the effects of impacts on the remanent magnetization of geologic materials. It consists of the combination of pulsed laser impacts and Superconducting Quantum Interference Device (SQUID) microscopy. Laser impacts are nondestructive, create shocks with peak pressures as high as several hundred GPa, and allow well-calibrated modeling of shock wave propagation within the impacted samples. High-resolution SQUID microscopy quantitatively maps the magnetic field of room-temperature samples with an unprecedented spatial resolution of ~100 [micro]m. We present shock modeling and magnetic field data obtained for two laser impacts on a magnetite-bearing basalt sample. Magnetic measurements show a demagnetized area at the impact locations. We also show that high-resolution magnetic measurements combined with impact modeling provide a continuous relation between the demagnetization intensity and the peak pressure undergone by the sample. This promising technique will allow for the investigation of the demagnetization behavior of a variety of geological materials upon impacts, with implications for our understanding of the magnetization of extraterrestrial materials and of terrestrial impact structures. Keywords: impact demagnetization, SQUID microscopy, laser impact, magnetite.

A program running on the Windows platform, which enhances the quality of two-dimensional images acquired by scanning SQUID microscope, is developed. A general description of the program and the incorporated additional digital filters for removing image artifacts in the Fourier space are discussed.

Thermally activated magnetic flux entry into a pickup coil through a flux dam in high-T(sub c) superconducting quantum interference device (SQUID) magnetometer is studied. Numerical simulation shows that circulating current can rapidly decrease much below the critical current and hence can suppress the thermally activated flux entry by using these methods.

An inverse transformation based on the fast Fourier transform can convert a two dimensional image of the normal component of magnetic field into a corresponding image of the two dimensional source currents that generated the field. Applying such a transformation to a magnetic image from a scanning Superconducting Quantum Interference Device (SQUID) microscope reveals that the spatial resolution in the current image can be over 20 times better than that found in the raw magnetic field image, and up to about 5 times smaller than the SQUID sample separation.

A superconducting quantum interference device was used to investigate the magnetization of NdBa2Cu3Oy single crystals with varying oxygen contents.

A high Tc flip-chip dc SQUID magnetometer was used in systems for geophysical prospection methods, such as the Transient Electro Magnetics method.

Measurements of flux from vortices in a field cooled wide bicrystal Yba2Cu3O7 grain boundary junction were undertaken using a superconducting thin film coils and Nb based SQUID.

The reduction of 1/f noise in ambient field to zero-field noise by rearranging antidots in HTS rf-SQUIDs is reported.

Voltage-flux properties of asymmetric dc SQUIDs of differing asymmetries were analyzed.

Resistively shunted direct coupled high Tc dc SQUID magnetometers having differing inductances were studied, and compared to unshunted devices.

The fabrication in YBa2Cu307 thin films on MgO substrates of dc SQUIDs of differing inductance values is discussed.

The use of SQUID in geophysical time domain transient electromagnetic measurements is described, and peculiarities of SQUID TEM recordings are analyzed.

The fabrication of a three axis LTS SQUID magnetometer for us as a magnetic anomaly detector on an aircraft, is described.

A high temperature superconducting SQUID magnetometer array was used to build an electronic gradiometer.

A SQUID magnetometer was used to improve a method of localization of steel needles in humans.

Research is presented describing the use of a superconducting quantum interference device (SQUID) microscope to study thin film trapped flux.

Research is presented describing the study of Cu-clad NbTi wire to monitor the changes caused by temperature fluctuation. Samples where examined by a high temperature superconducting quantum inference device (SQUID).

A study of the development of a high Tc superconducting quantum interference device (SQUID) system is presented with emphasis on its use in biological immunoassay. This magnetometer is shown to be more sensitive than conventional systems.

A study of the development of a nanoparticle detection system with a high Tc superconducting quantum interference device (SQUID) is presented with emphasis on its use in lymph node biopsy. The performance of this magnetometer is described.

A study of the designs of HTS cryogenic current comparators is presented with emphasis on their performance. The comparators, which included a flux concentrator and readout SQUID, were examined for their ability to measure charged-particle-beams.

The temperature dependence of the lower critical fields of Hc1(T) of Bi2Sr2CaCu2O8+d and YBa2Cu3O7-d single crystals was studied for both orientations of the applied fields, parallel and perpendicular to the c axis. The magnetization curves of the samples were measured by utilizing a superconducting quantum interference device. Findings indicated that the temperature dependence of the coherence length in the ab plane plays an important role.