Magnetic Measurement System Research Articles

Extensive magnetic measurement system for TPE-RX

An extensive magnetic measurement system (MMS) which contains 1201 sensors is developed for the new large reversed-field pinch machine, TPE-RX. The system facilitates a variety of magnetic signals for axisymmetric information to obtain equilibrium profiles as well as for nonaxisymmetric information of the magnetic perturbation mode spectra. The system is now routinely in operation for physics experiments on TPE-RX. The physical quantities obtained from the system, locations and specifications of coils and loops, calibration, the method of managing large amounts of data and examples of data are reported.

Magnetic measurement system for high-field magnets.

One of the main principles in electrodynamics, the change of magnetic field flux inducing an EMF in a wire coil, is applied for magnetic measurement. A scheme and the main parameters of the magnetic measurement system are described. The system was successfully used for magnetic measurement of a 7 T superconducting wiggler for LSU CAMD; results are presented.

A temperature-compensated system for magnetic field measurements based on artificial neural networks

This paper presents a personal-computer-controlled system, assembled mainly with IEEE 488 general purpose instruments and aimed at the measurement of magnetic field intensity. The main sensor element in the system is a magnetoresistive field sensor which includes four permalloy strips connected in a Wheatstone bridge configuration. The temperature dependence of this sensor can vary almost 25% in the experimental operating temperature range (20/spl deg/C-100/spl deg/C). In order to overcome this problem, a two-terminal integrated circuit temperature transducer is connected to the system, and its temperature information is used to correct the temperature drift error of the magnetic sensor. Artificial neural networks are used for data reduction and final results show an improvement in the system's accuracy from 20% to 2%.

Magnetization Measurements under High Pressure in a Diamond-Anvil Cell Using a SQUID Vibrating Coil Magnetometer.

A magnetization measurement system has been developed for extremely small samples in a diamond-anvil cell (DAC). The system is basically a vibrating coil magnetometer, and a SQUID is used for high sensitive detection of the gradient of the magnetic flux. The system enables one to make magnetization measurements at pressures up to about 15 GPa in the temperature range from 1. 4 to 60 K. Magnetization changes as small as 10-9-10-10 emu can be detected if the temperature is limited to the range from 5 to 20K. The performance of the system is illustrated by magnetization measurements of EuTe at pressures up to about 12 GPa.

Measurement of the Gradient between the Bending Field and the Vertical Line at the SR Magnet

We developed SR compact superconducting magnets which are used for X ray lithography. If the vertical axis of the superconducting coil of SR magnet is out of the vertical line the horizontal field Bx will be appeared. The electron beam is kicked toward vertical direction by this field and this causes a large electron beam orbit distortion in the horizontal coordinate. From the beam optics, the gradient of the coil axis needs to be less than 1 mrad. We developed a magnetic field distribution measurement system of the horizontal magnetic field Bx(s) in the high bending magnetic field By0 which is 3.5T at the center of the SR (Synchrotron Radiation) magnet and measured the distribution of Bx(s) . Where, s is the beam direction. From the horizontal magnetic field Bx(s) and vertical dipole field By0(=3.5T), we can evaluate the gradient of bending field from the vertical direction. The average gradient along S direction was 0.55mrad. This value satisfies our requirement which is less than 1mrad.

Electromagnetic Noise Measurement System Using a Magnetic Field Sensing Coil Array

We developed a near-field magnetic noise measurement system using a shielded-loop-type 432 coil array. To allow measurement of magnetic noises from 1 MHz to several hundred MHz, we took account of the voltage induced by the magnetic field in the pickup coil, impedance matching at the crossing points of lead lines, and the size of ground plane. High resolution of the measurement position can be obtained by using the XY-stage.

Application of a virtual instrument concept in magnetic measurements

In the paper, the application of the virtual instrument concept for the measurement of magnetic characteristics, such as magnetisation curve, hysteresis and losses in soft magnetic materials, is described. The concept accelerates vastly the design and development phase of a magnetic measurement system, simplifies and shortens the measurements and is extremely versatile.

Soft X-ray polarization and magnetic circular dichroism measurement system

We report an apparatus for measuring polarization and magnetic circular dichroism (MCD) in the soft x-ray region of synchrotron radiation. It consists of a polarimeter and a magnetic circuit of 2.1 Tesla at the sample. The polarimeter consists of a phase shifter and an analyzer, each using V/C multilayer mirrors. We made full-polarization measurement of soft x-rays at 84.7 Å from the bending magnet. Based on this evaluation of polarization, we obtained MCD spectra of novel nitride Fe 16N 2(100) film on GaAs substrate.

Automized magnetic hysteresis measurement system

Modeling and design of magnetic components require primary data on material hysteresis properties. In this article a flexible and highly automized system is described, which is suited for the characterization of the low frequency soft magnetic behavior (≊5 Hz–2 kHz) of ferromagnetic samples. The apparatus consists of a PC with the control program, a modular data acquisition/signal generation system, and a remotely controllable power amplifier to which the sample is connected. Integration of the secondary output voltage is performed digitally. The system operates in current control mode, and the user can select from a variety of adjustable excitation functions and even complex measurement procedures. It is possible to perform stationary or transient measurements of major and minor loops, initial magnetization and commutation curves, to do automatic demagnetization, and to output specific parameters which are necessary for sample characterization or model calibration. Amplitude selection and autoscaling of the measurement sensitivity can proceed within wide dynamic ranges. Sample, signal parameter, output, and characteristic data can be printed or plotted, edited, saved, reloaded, or changed in format. A number of different options for measurement and postprocessing are available. Instead of B(H) also M(H) or μ (H) curves or time signals can be displayed. Future software versions will also support the voltage control mode (which is already provided in the amplifier), and the measurement of the anhysteretic curve. A selection of example measurements obtained for two samples and with different types of excitation signals indicates the suitability of the system for various applications.

Precise magnetization measurements under high pressures in the diamond-anvil cell

A precise magnetization measurement system for extremely small samples in the diamond-anvil cell has been developed. The system is based on position differentiating detection (PDD) combined with the use of a SQUID magnetometer. The PDD is a kind of vibrating coil magnetometer and is suitable for the case where high sensitivity detection is required for a sample around which there is little space for the detection coil. The present system enables one to make magnetization measurements at pressures up to about 12 GPa in the temperature range from 1.4 to 30 K. The sensitivity is about 10−9–10−10 emu. Three piezoelectric actuators of a bimorph type are used at liquid–helium temperature for stable vibration of the detection coil with an amplitude of 90 μm around the tips of the diamond anvils. The design and construction of the system is described in detail. The performance of the system is illustrated by magnetization measurements of EuTe under high pressures.

Methods of magnetic measurements in the RFX fusion experiment

The Magnetic Measurement System of the Reversed Field Pinch machine RFX for research on Thermonuclear Fusion is briefly presented and the main magnetic analyses performed, on the basis of experimental data, are discussed. These analyses lead to significant results for plasma physics comprehension.

A system for magnetic circular dichroism measurements with a 10 m toroidal grating monochromator

A system of remotely-controlled apertures have been installed in the Synchrotron Radiation Center 10-m toroidal grating monochromator (TGM) for production of circularly-polarized light. In addition to allowing normal operation of the beamline, the apertures can be adjusted to block any fraction of the incoming beam without excessive heating and outgassing. This selective blocking of the light produces an appreciable elliptical polarization of the incoming light. Over the energy range of the 10 m TGM high energy grating, from 200 to 800 eV, the beamline optics do not significantly affect the polarization. The 10-m instrumental energy range overlaps the binding energies of the L-shell core levels of the important transition-metal materials. Calculations have been performed to estimate the performance of the aperture system as a function of energy. The results indicate that for an aperture position transmitting 20% of the synchrotron flux, the degree of polarization should be about 85% and should be reasonably constant over the photon energy range. With the light masked, magnetic circular dichroism was observed by measuring total yield with different orientations of sample magnetization and photon spin. Thin films of magnetic materials on magnetic and non-magnetic substrates have been studied.

Magnetic inclination measurement and signal transmission system for trench wall constructions

A NdFeB permanent magnet pendulum varies the output voltage of a semiconductor Hall-effect potentiometer. The angle dependent dc-voltage is converted into a signal of variable frequency (2-15 kHz). The angle sensors, the electronic circuits, and batteries are mounted in water-proof (20 bar) and shock protected (100 g) cases on the gripper. It is operated by two steel cables which are used for the signal transmission by enclosing ring-core transformers of high initial permeability. The received angular information is decoded by a microprocessor and displayed together with the excavation depth on a screen in the operation cabin of the excavator. The measurement system provides an angular resolution of 5.10/sup -3/ degrees and an absolute accuracy of 7.10/sup -3/ degrees at /spl plusmn/2 degrees total range.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Applications of ultrasensitive magnetic measurement technologies (invited) (abstract)

The development of reliable, easy-to-use magnetic measurement systems with significantly enhanced levels of sensitivity has opened up a number of broad new areas of application for magnetic sensing. Magnetometers based on optical pumping offer sensitivities at the picotesla level, while those that utilize superconducting quantum interference devices can operate at the femtotesla level. These systems are finding applications in areas as diverse as geophysical exploration, communications, and medical diagnostics. This review briefly surveys the capabilities and application areas for a number of magnetic sensing technologies. The emphasis then focuses on the application of the most sensitive of these to the field of medical diagnostics and functional imaging. Protocols for specific applications to noninvasive presurgical planning and to the noninvasive assay of cortical dysfunction in diseases ranging from epilepsy to migraine and schizophrenia will be described in detail. Data will be presented reporting independent validation of these techniques in ten patients who subsequently underwent surgery. Routine and reliable utilization of this ultrasensitive magnetic sensing technology in the clinic is now feasible and practical.

Cryogenic and magnetic tests of the twin aperture prototype dipole in the Saclay test facility

The authors describe the test facility and the cryogenic and magnetic measurements performed on the twin aperture prototype (TAP) dipole for the CERN Large Hadron Collider (LHC). The magnet, designed by CERN and built by European industries, was tested in a facility built at CE Saclay. The focus is on the cryogenic system, which enables prototype magnets to be tested in superfluid helium; on the data acquisition systems, including a system for magnetic measurements; and on the results which were obtained during the tests. >

Design, construction, and characterization of an electromagnetic small period undulator

In this work a new concept for the construction of small period electromagnetic insertion devices is presented. The construction of a pulsed undulator with 2 mm gap and 8 mm magnetic period is described, as well as its pulser. The magnetic measurement system is presented and the obtained data is compared with the calculated field. Finally, the possible application of this device for synchrotron radiation production in LINAC’s and a future cw superconducting version for storage rings is discussed.

Status of the development of insertion devices for ELETTRA

The status of the development of insertion devices for the 1.5–2-GeV synchrotron radiation source ELETTRA is described. Recent results achieved with a prototype pure permanent magnet undulator and the construction and performance of a prototype hybrid multipole wiggler are presented. The parameters and design of the first undulator that will be constructed for ELETTRA, U12.5, are also presented, and some details are given about the magnetic measurement system.

Poloidal magnetic field measurement system in JT-60

A diagnostic system using a helium beam for local poloidal magnetic field measurements (Zeeman polarimeter system) has been constructed. The Zeeman spectrum of the helium 31P-21S line was observed in JT-60. The intensity and energy of the neutral helium beam were up to 0.6 A and 200 keV, respectively. Resolution of the Zeeman polarimeter was 0.01 nm which was realized by using a Littrow-type spectrometer. Photon counting efficiency was 0.065. Moreover, an in situ wavelength calibration could be done, using an Ar laser, within an error of 0.001 nm.

A simple digital system for ac magnetic measurements on superconductors

This article describes a simple apparatus to perform ac inductive measurements on superconductors. The ac susceptibility, the penetrated and trapped magnetic flux and the magnetization of a sample placed in an ac magnetic field are measured by processing the signal induced in a pick-up coil that surrounds the sample. The complex harmonic analysis of the signal is also performed. The setup consists of an amplifier, a three-channel recorder, and a standard desktop computer. The main advantages of the apparatus are its simple design and low cost. Its main drawback is the noise affecting the signals. Tests were performed on a high Tc superconductor.

4812761 Electrically parallel equal phase resonant loops for nuclear magnetic resonance surface coils

A nuclear magnetic resonance measurement system is disclosed which includes, in combination, means for generating an applied main magnetic field, and an array of at least two radio frequency current loops. The loops are electrically connected in parallel, and are oriented in a generally planar relationship with respect to each other. The loops are connected in phase with respect to each other so that the component of magnetization generated by the loops which orthogonal to the direction of the applied main magnetic field is in the same general direction. A capacitor is preferably electrically connected in parallel with the loops.