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We demonstrate how to construct and operate a simple and affordable apparatus for producing coherent effects in atomic vapor and for investigating their applications in time-keeping and magnetometry. The apparatus consists of a vertical cavity surface emitting diode laser directly current-modulated using a tunable microwave oscillator to produce multiple optical fields needed for the observation of coherent population trapping. This effect allows very accurate measurement of the transition frequency between two ground state hyperfine sublevels, which can be used to construct a coherent population trapping-based atomic clock. [DOI: 10.1119/1.3120262]

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.

Magnetometry is a widely used technique for clearance of areas contaminated with unexploded ordnance. The discrimination of hazardous ordnance from nonhazardous items is possible using apparent remanence if ordnance is shock demagnetized on impact with the ground. We developed a mobile device, the Magnetic Remanence Interrogation Platform (MRIP), for measuring the induced and remanent moments of steel samples. The MRIP comprises six three-component fluxgate magnetometers symmetrically distributed around a rotating sample holder. Samples are placed on the holder and are slowly spun through two complete rotations. The measurement is repeated after the sample is physically rotated by 90ddd so that the previous up direction points east. The MRIP platform was deployed to two field sites. At the first site, 76- and 90-mm projectiles were measured. Most had relatively low remanent magnetization relative to the induced, suggesting that shock demagnetization occurs. Variations in the remanent moments of different specimens of 90-mm projectiles were attributed to variations in the type of steel used. There was a strong correlation of the direction of remanent and inducing field during burial, indicating evidence of shock magnetization and/or magnetic viscosity. At the second site, intact and partial 4.2-in mortars as well as shrapnel, base plates, and cultural debris were measured. Most of the base plates and intact mortars had low remanent magnetization, whereas the shrapnel and partial mortars tended to have higher remanent magnetization. The results indicate that there is an inherent risk in using apparent remanence for discrimination as not all ordnance is demagnetized on impact. Index Terms--Magnetics, remanent, unexploded ordnance (UXO).

An inexpensive system for precision capacitance measurement is presented. The system is appropriate for undergraduate laboratories is based on a newly available capacitance-to-digital integrated circuit that can measure picofarad capacitances to six significant figures. The circuitry software for controlling the integrated circuit with a personal computer via an [I.sup.2]C interface bus are described. Examples of experiments that make use of the circuitry are discussed, including a novel hydrostatic magnetometer that uses precision capacitance measurement to determine the magnetization of a small sample.

Student-constructed magnetometers and commonly available software illustrate the use of autocorrelation functions to extract low-amplitude signals from background noise. The magnetometers are later used to measure forces at sampling rates over 50 Hz, providing data for an introduction to numerical integration. [DOI: 10.1119/1.2919741]

We demonstrate remote detection of nuclear magnetic resonance (NMR) with a microchip sensor consisting of a microfluidic channel and a microfabricated vapor cell (the heart of an atomic magnetometer). Detection occurs at zero magnetic field, which allows operation of the magnetometer in the spin-exchange relaxationfree (SERF) regime and increases the proximity of sensor and sample by eliminating the need for a solenoid to create a leading field. We achieve pulsed NMR linewidths of 26 Hz, limited, we believe, by the residence time and flow dispersion in the encoding region. In a fully optimized system, we estimate that for 1 s of integration, 7 x [10.sup.13] protons in a volume of 1 [mm.sup.3], prepolarized in a 10-kG field, can be detected with a signal-to-noise ratio of [approximately equal to]3. This level of sensitivity is competitive with that demonstrated by microcoils in 100-kG magnetic fields, without requiring superconducting magnets. microfluidics | signal-to-noise ratio | mass-limited sample

Vibration sample magnetometry (VSM) and transverse Kerr effect spectrometry (TKE) are used for studying the magnetization mechanisms in NiFe and NiFe/FeMn layered systems. The results have shown a short range order of biquadratic exchange coupling near the interface.

An autocalibration algorithm for calibration of magnetometer triads used to determine heading in small aerial vehicles is developed and its performance is analyzed. The algorithm estimates the 12 calibration parameters, which are elements of an affine transformation mapping measured, and thus, erroneous magnetometer measurements into corrected field measurements. The mapping corrects magnetometer output errors due to hard-iron biases, scale factor deviations, and nonorthogonality effects caused by soft irons or physical arrangement of the sensor axes. The correction mapping is determined by leveraging the fact that the locus of Earth's magnetic field vector as measured by a triad of magnetometers is an ellipsoid. The coefficients defining the ellipsoid are computed using a total least- squares estimator. It is shown that, generally, in such autocalibration algorithms, soft-iron errors and sensing axes nonorthogonality can result in an error mode that is unobservable. These conditions are identified and the algorithm incorporates a method for detecting them. In these instances, even though autocalibration can provide an estimate of only 9 of the 12 calibration parameters, it is shown that how external measurements from a triad of accelerometers and a global positioning system receiver can provide the information needed to estimate the unobservable error mode.

We address the problem of unexploded ordnance (UXO) detection in which data to be classified are available from multiple sensor modalities and multiple resolutions. Specifically, features are extracted from measured magnetometer and electromagnetic induction data; multiple-resolution data are manifested when the sensors are separated from the buried targets of interest by different distances (e.g., different sensor-platform heights). The proposed classification algorithm explicitly emphasizes features extracted from fine-resolution imagery over those extracted from less reliable coarse-resolution data. When fine-resolution features are unavailable (due to undeployed sensors), the algorithm analytically integrates out the missing features via an estimated conditional density function, which is conditioned on the observed features (from deployed sensors). This density function exploits the statistical relationships that exist among features at different resolutions, as well as those among features from different sensors (in the multisensor case). Experimental classification results are shown for real UXO data, on which the proposed algorithm consistently achieves better classification performance than common alternative approaches. Index Terms--Classification, incomplete data, missing data, multiresolution, multisensor, unexploded ordnance (UXO).

We discuss a comprehensive approach to the characterization of permanent magnets with the pulsed field magnetometer. The approach is based on a systematic comparison of the results obtained by this method with those from the conventional closed-circuit and open-sample methods and on the assessment of the dynamic phenomena engendered by the application of the fast exciting field pulse. Such phenomena derive from the thermal fluctuation aftereffect and the eddy currents, whose contributions to hysteresis loop swelling are brought to light and separately evaluated. We show that the quasi-static hysteresis loop can be retrieved from the dynamically obtained one by compensating for the magnetic viscosity field, found to be proportional to the coercive field, and the eddy-current counterfield. A simple analytical formulation accounts for and predicts the effect of the counterfield. Index Terms--Magnetic hysteresis loop, magnetic measurements, permanent magnets, pulsed field magnetometer.

The effects of medium-energy silver- and copper-iron irradiation on the flux pinning in the second-generation high-temperature superconductors (HTS) are discussed. Irradiation is shown to cause an enhancement of the flux pinning over a wide range of field angles.

A multichannel low transition temperature SQUID magnetometer system with integrated superconducting magnetic shielding intended for recording the magnetocardiogram (MCG) of mice in a biolaboratory environment is described.

The mutlichannel magnetocardiogram (MCG) systems of 1 magnetometer type and 2 planar gradiometer types which were fabricated to compare the MCG data measured using different pickup coil system are reported.

The studies related to the acquisition of fetal magnetocardiographic signals in various noisy environments and improvement in the signal-to-noise ratio (SNR) of weak biomagnetic signals for various noise levels and gradiometer implementations is presented.

The development of a new type of magnetocardiograph (MCG) system employing 6 high-[T.sub.C] SQUID magnetometers with high performance YBCO SQUID devices is presented.

A hybrid magnetometer system designed for application in unshielded environment which used flux quanta counting digital SQUID to operate in large environmental fields is described.

The measurements of spectroscopic linewidth and Rabi oscillation in three thin-film dc SQUID phase qubits are reported.

The effect of additional reference current on a reference junction-double relaxation oscillation SQUID (superconducting quantum interface device) (RJ-DROS) is examined. The results have shown that an input-bias current in the preamplifier detecting the outputs at the reference junctions have acted as an additional current.

A SQUID magnetometer is used to measure the irreversibility temperatures and magnetization transitions of an ITER-type internal-Sn [Nb.sub.3]Sn superconducting wire during warming and cooling cycles at a fixed magnetic field. The heat treatment condition of the ITER use wire is optimized as 675 degree Celsius/128 h, resulting in the best A15 phase composition suitable for high-field application.

The location and identification of unexploded ordnance (UXO) front magnetometer measurements have long been an area of active research interest. Ground surface methods, which are widely used for objects buried in shallow depths, become ineffective for objects deep in the soil because the object's anomalous field diminishes rapidly with distance, and interference by metal debris on the ground surface is significant. For the location and identification of deeply buried UXO, a total-field magnetometer equipped with a cone penetrometer technology (CPT) drilling system is employed in this paper. A novel inversion method is developed to extract information from individual and multiple CPT profiles. Compared with conventional inversion methods providing a single minimum as an estimate, this approach tests the likelihood distribution over the anticipated solution space, hence providing reliability. Real-world data are collected from a test site for the location and identification of a specific target. All experiments and simulations demonstrate the superior capability of this technique in solving real-world problems when only limited data points are available. Index Terms--Cone penetrometer technology (CPT), geophysical modeling/inversion, linear optimizations, magnetometer.

Fluxmetric and magnetometric demagnetizing factors N(sub f) and N(sub m) are calculated using a finite-element method for rectangular prism 2a X 2b X 2c with susceptibility x=-1 in the completely shielded state. Assuming the field is applied along the c dimension, the results are plotted and tabulated as functions of their aspect ratios c/a and b/ max [c, a].

The influence of the superconducting quantum interference device (SQUID) gradiometer baseline on the recording of magnetocardiographic measurements is analyzed. By using a first order gradiometer with an ultralong baseline of 18cm, a successful measurement of the heart signal of a fetus in real time is achieved.

An inexpensive vibrating sample magnetometer (VSM) has been developed for use in a materials physics course. An exercise using the VSM allows students to measure the magnetic properties of various materials and thus gain experience applicable to contemporary research on magnetic materials. This paper describes specific aspects of the construction of a VSM and presents measurements for two 5-mm-long Ni wires of different diameters and for floppy disk media. A 178-[micro]m-diam Ni wire served as a calibration sample for the system; the results from a 51-[micro]m-diam Ni wire set the limit of precision for this system at approximately 5 x [10.sup.-3] emu. [DOI: 10.1119/1.1572149]

Discussing the error analysis for inverse problems in superconductivity is studied. The results show that the measurement noise is more important as an error source than the numerical inaccuracies.

Byline: M. Filippelli (1), I. Romagnoli (2), F. Gigliotti (2), B. Lanini (2), M. Nerini (1), L. Stendardi (2), R. Bianchi (2), R. Duranti (1), G. Scano (1) Keywords: Respiratory muscles Chest wall Abdomen Hypoxia Hypercapnia Abstract: Abstract Chest wall compartment kinematics and respiratory muscle coordinate activity, during either hypercapnia or hypoxia, have not been comparatively assessed in healthy humans. We assessed the displacement volume of the chest wall (Vcw) in 5 normal subjects during hypoxic-normocapnic and hypercapnic-hyperoxic rebreathing by using linearized magnetometers. Vcw was divided into displacement volumes of the rib cage (Vrc) and the abdomen (Vab). Esophageal (Pes) and gastric (Pga) pressures were simultaneously recorded and transdiaphragmatic pressure (Pdi) was calculated by subtracting Pes from Pga. Pressure swings (sw) from end expiration (EE) to end inspiration (EI) were also calculated. During both hypoxia and hypercapnia, from quiet breathing to 40 L/min VE, Vrc,EI increased consistently but Vrc,EE, and Vab,EI did not. Moreover, Vab,EE decreased significantly during hypercapnia and remained unchanged during hypoxia. PesEI decreased (more negative values) and PesEE increased (less negative values) during either stimulus, while PgaEE increased with hypercapnia. Pdisw, calculated as the difference between PdiEE and PdiEI, increased significantly with both hypercapnia and hypoxia (p = 0.002 for both). On the plot of Pes vs Pga, the slope of a line from end expiratory to end inspiratory lung volume between 20 and 40 L/min VE progressively increased during hypercapnia indicating increasing rib cage muscle (RCM) contribution to inspiratory pressure swings relative to the diaphragm. From these results we conclude that in healthy man: (i) with both chemical stimuli RCM contribution accounts for increase in Vrc displacement (ii) with hypercapnia, the decrease in Vab,EE displacement indicates abdominal muscle (ABM) contribution to tidal volume (iii) RCM and ABM assist the diaphragmatic function during hypercapnic stimulation. Author Affiliation: (1) Section of Clinical Immunology, Allergology and Respiratory Disease, Department of Internal Medicine, University of Florence, Florence, Italy (2) , Don C. Gnocchi Foundation, Pozzolatico, IRCCS, Florence, Italy Article History: Accepted Date: 07/11/2002

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.

Conformable eddy current sensors with grid methods can provide an effective means for applied stress measurements and for characterization of residual stresses in steel components. This paper describes conformable MWM[R] (meandering winding magnetometer) sensors and high-resolution scanning MWM-Arrays for directional magnetic permeability measurements over a wide range of frequencies with grid methods. MWMs and MWM-Arrays are used for fatigue monitoring, crack detection, characterization of process-affected layers, including coatings, detection of surface-connected and hidden degradation, and damage characterization, e.g., detection and imaging of grinding bums. Tests have shown that these sensors can also provide the capability for residual/applied stress measurements in ferromagnetic materials, e.g., in steels. Specific examples described here illustrate this capability to estimate stresses in steels and other ferromagnetic materials from MWM measured permeability. Results of directional MWM permeability measurements, including permeability mapping, are presented here for (a) a 4340 steel specimen subjected to a series of tensile load tests with an incrementally increasing maximum load, (b) a broken 4340 tensile test specimen, (c) a shot-peened 300M steel specimen subjected to bending load tests, and (d) a shot-peened and subsequently ground high-strength steel component. Quick and inexpensive stress measurements at a point or, in a scanning mode, over a selected area are now becoming possible without permanently mounting sensors, albeit MWM sensors can be readily mounted, if needed, as well. [DOI: 10.1115/1.1491273]

The Swedish micro-satellite Astrid-2 was successfully launched into a near polar orbit in December 1998. Despite the fact that the primary science mission was auroral research, the magnetic instrument was designed to accomplish high-resolution and high-precision vector field magnetic measurements, and therefore mapping of the Earth's magnetic field was possible. The spacecraft spins about a highly stable axis in space. This fact and the globally distributed data make the magnetic measurements well suited for the estimate of a magnetic field model at the spacecraft altitude (about 1000 km). This paper describes the initial analysis of the Astrid-2 magnetic data. As a result of the study of a single day (February 7, 1999), magnetically fairly quiet, it was possible to in-flight adjust the calibration of the magnetometer and find a magnetic field model fitting the scalar component of the measurements to better than 5 n[T.sub.rms] for latitudes Equatorward of 50 [degrees]. Several methods for field modeling are discussed in this paper under the assumption that the direction of the spin axis in inertial space is nearly constant, and this assumption is corroborated by the observations. The approximate inertial orientation of the magnetometer could then be determined simultaneously with the instrument intrinsic calibration and the estimate of main field model coefficients. Hence, apart from the scientific use of the magnetic data, the attitude of the spacecraft may be estimated with high precision. Index Terms--Amorphous magnetic materials, calibration, data models, data processing, geomagnetism, geophysical inverse problems, magnetic fields, magnetic field measurement, magnetometers, measurement, modeling, satellites.

The magnetic phase diagram was constructed in small-volume high temperature superconductors using an open-flat coil magnetometer.

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

Untwisted multifilamentary superconducting tapes were measured for AC loss using a vibrating sample magnetometer.

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.

This paper presents the results of a study to evaluate the performance of a number of recently proposed semiactive control algorithms for use with multiple magnetorheological (MR) dampers. Various control algorithms used in recent semiactive control studies are considered including the Lyapunov controller, decentralized bang-bang controller, modulated homogeneous friction algorithm, and a clipped optimal controller. Each algorithm is formulated for use with the MR damper. Additionally, each algorithm uses measurements of the absolute acceleration and device displacements for determining the control action to ensure that the algorithms could be implemented on a physical structure. The performance of the algorithms is compared through a numerical example, and the advantages of each algorithm are discussed. The numerical example considers a six-story structure controlled with MR dampers on the lower two floors. In simulation, an El Centro earthquake is used to excite the system, and the reduction in the drifts, accelerations, and relative displacements throughout the structure is examined.

This article examines the geophysical methods used to investigate an archaeological site at Muweilah, United Arab Emirates. Geophysical investigations of desert sites are challenging due to mobile sand dunes and arid conditions but magnetometry was successfully used to reveal evidence of a large walled settlement from the Iron Age.

To complement the growing literature on magnetic prospection in historical archaeology, the practical aspects of magnetometer selection and survey design need to be explored. Based on a test case from the Petaluma Adobe State Historic Park in northern California, two readily-available magnetometers are compared with respect to instrument type (alkali-vapor versus proton precession), sensor configuration and number (total field versus vertical gradient), sensor height, intensity of data collection, and basestation correction procedures. These variables are then considered in light of survey speed, labor input, and monetary cost. Results indicate that the alkali-vapor gradiometer is better suited for historical archaeological research based on survey speed and efficiency, volume of data collected, temporal and spatial intensity of station readings, and sensor sensitivity. In addition, the data reconfirm the importance of sensor height, gradiometer configuration, and basestation correction in obtaining high-quality magnetic data.

Research was conducted to examine the evolutions of the uniaxial torque and magnetization with the applied magnetic field which permits a discrimination of the sources of in-plane magnetic anisotropy in amorphous ribbons. A simple model was developed for an inhomogeneous material to determine the magnetic anisotropy sources. The model was applied to explain the different behavior seen in the evolution of the uniaxial torque amplitude with the applied magnetic field of two commercial Co-based amorphous alloys.