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The Japan Aerospace Exploration Agency has developed a power processing unit for a 6 kW Hall thruster, a candidate for propulsion systems for geostationary satellites. Hall thrusters have a discharge instability of tens of kHz, which may damage thrusters, power processing units, and satellite systems. This paper proposes our system for detecting discharge current amplitudes that exceed the specified limit of the thruster. The discharge current is converted into a voltage by the current sensor and is output to a digital controller through an AD converter. The system's innovation includes a frequency prediction model and a damping correction algorithm, which allow the system to accurately detect the peak amplitude of the discharge current without testing to measure the frequency characters of the Hall thruster. The design of the amplitude detection system considers the frequencies of the ionization oscillation and the switching frequency of the power processing unit. The frequency prediction model estimates the frequency of discharge current oscillations from simple parameters: the output voltage of the discharge power supply and the thruster dimensions. The amplitude of the discharge current is damped slightly by the frequency characteristics of the system, but the algorithm corrects this. The results of the frequency prediction model agreed well with the actual measurements. The predicted value was 13.2 kHz, while the actual measurement was 8–15 kHz. The integration test showed that the amplitude detection system identified 36 peaks exceeding the specified limit of 80% peak-to-peak during a 100 ms segment, although the actual number was 34. This difference is acceptable. The proposed amplitude detection system can accurately count the peaks in the discharge current that exceed specifications. • An amplitude detection system detects discharge current oscillations that exceed the specifications for protecting satellites. • The algorithm and frequency response of the system are designed considering the frequency of ionization oscillations. • The frequency is estimated by a simple model with only the output voltage of the discharge power supply and thruster dimensions. • The system detected the amplitude of the discharge current oscillations with an error of 5.8%. [ABSTRACT FROM AUTHOR]

The adoption of the brushless DC motor in the electric drive vehicle industry continues to grow due to its robustness and ability to meet torque–speed requirements. This work presents the implementation of a fault-tolerant control (FTC) for a BLDC motor designed for electric vehicles. This paper focuses on studying the defect in the Ha sensor and its signal reconstruction, assuming possible cases, but the same principle is applied to the other two sensors (Hb and Hc). In this case, the fault diagnosis allows for the correction and reconstruction of the signal in order to compel the system to work despite the presence of a fault. Indeed, several robust control systems are used within the work to regulate the speed of the motor properly, such as control via fuzzy logic and control via a neural network. This paper presents three BLDC control configurations for EVs, PID, fuzzy logic (FL), and an artificial neural network (ANN), discusses the pros and cons, and develops corresponding mathematical models to enhance a fault-tolerant control strategy which is analyzed and studied using MATLAB-based simulations (by discussing the two cases, the steady state and the transient state), allowing for a novel design based on the analytical models developed. The results obtained from the simulation of this system improved the speed controlled by the neural network compared to the fuzzy logic controller. At the same time, the sensor failure had no effect on the system's operation due to the efficiency of the FTC control. [ABSTRACT FROM AUTHOR]

In an ATON-type Hall effect thruster, a ring-shaped anode and a cusped magnetic field intersect the match between the anode shape and the field topology thus must be clarified to optimize the electron transport to the anode and consequently the design of a high-efficiency thruster. By changing the match pattern with both the change in the length of the anode ring and the axial displacement of the cusp magnetic field, this study experimentally investigated the influence of the match pattern on the discharge characteristics of an ATON-type thruster—P100—under the condition of a moderate discharge voltage. The experimental results show that there is a match pattern that always optimizes the performance of the P100 thruster. At the rated operation parameters (300 V of discharge voltage and 5 mg/s of propellant mass flow rate) and the rated magnetic field strength, the observed improvements on thrust (∼79 mN to ∼85 mN) and anode efficiency (∼46% to ∼55%) are significant. Through further theoretical analysis, this study revealed that the change in the characteristics of electron momentum and energy transfer in the near-anode region, induced by the change of the match pattern, is the basic reason. The findings of this work are instructive for both understanding the electron motion in a cusp magnetic field and guiding the design of the anode ring intersecting with a cusp magnetic field in an ATON-type Hall effect thruster. [ABSTRACT FROM AUTHOR]

Beam splitters are widely used in various optical systems, but traditional beam splitters are bulky and heavy, which are not conducive to the integrated utilization of optical devices. Metamaterials have attracted extensive attention as a kind of miniature artificial materials, and there have been many works on the design of metasurface beam splitters. Using metasurfaces, multiple functions of traditional beam splitters can be achieved. Meanwhile, metasurface beam splitters have the advantages of small size, easy integration, flexible design of beam-splitting performance, and tunable functions. This review surveys the current work on metasurface beam splitters and provides a classification and introduction to metasurface beam splitters. Metasurface beam splitters are expected to play a huge role in interferometers, multiplexing, multi-beam communications, and more. [ABSTRACT FROM AUTHOR]

Ophthalmic anesthesia plays a crucial role in eye surgery. However, the conventional practice of this process is a blind procedure, in which a needle is inserted blindly into the cadaver. This paper introduces a needle tip tracking system for ophthalmic anesthesia training focusing on the Retrobulbar block procedure. The study presents a development in a prototyped system using Hall effect sensor arrays to track a 5D magnetized needle tip (X, Y, Z, $\boldsymbol{\theta }$ , $\boldsymbol{\varphi }$ ). The orbital structure is fabricated with embedded Hall effect sensors. The extended Kalman filter and least square method are developed to select the observation model from multiple training sets and to estimate the needle tip coordinates. The robotic manipulator (ABB YUMI) is used to model the training set between the distance and the initial angle of the magnetized needle. The developed system provides the needle tip position with an RMS of Euclidean distance error up to 1.7398 ± 0.5288 mm. As a result, the system is capable of providing the needle tip positions with an acceptable error comparing the system’s accuracy with the size of the retrobulbar target space and important anatomies.

The Japan Aerospace Exploration Agency (JAXA) has developed a power processing unit (PPU) for a 6 kW Hall thruster system. The PPU is a candidate for future mission applications, such as all-electric satellites, exploration vehicles, and orbital transfer services. The PPU has to be small and still provide a wide output range of outputs, consider the in orbit and launch environments, and manage any instability in the Hall thruster's discharge. Specifically, the four converters that make up the anode power supply of the PPU is digitally controlled to reduce the size of the control circuit. It must operate stably despite small output capacitors and long dead times. This article clarifies the design criteria for the power supply, focusing on the size of capacitors and the PI control parameters to solve these problems. The result is a compact, high-performance PPU for the 6 kW Hall thruster. The power supply meets stringent design criteria and operates the thruster stably with an output voltage that can be varied between 200 and 730 V, provide a maximum power of 5.9 kW, and offer a maximum efficiency of 96.1% in the coupling test for the 6 kW Hall thruster. The proposed PPU, including the anode power supply, achieves a power density of 0.3 kW/kg, significantly higher than that of comparable PPUs. [ABSTRACT FROM AUTHOR]

Hall thrusters are very efficient and competitive electric propulsion devices for satellites and are currently in use in a number of telecommunications and government spacecraft. Their power spans from 100W to 20 kW, with thrust between a few mN and 1N and specific impulse values between 1000 and 3000 s. The basic idea of Hall thrusters consists in generating a large local electric field in a plasma by using a transverse magnetic field to reduce the electron conductivity. This electric field can extract positive ions from the plasma and accelerate them to high velocity without extracting grids, providing the thrust. These principles are simple in appearance but the physics of Hall thrusters is very intricate and non-linear because of the complex electron transport across the magnetic field and its coupling with the electric field and the neutral atom density. This paper describes the basic physics of Hall thrusters and gives a (non-exhaustive) summary of the research efforts that have been devoted to the modelling and understanding of these devices in the last 20 years. Although the predictive capabilities of the models are still not sufficient for a full computer aided design of Hall thrusters, significant progress has been made in the qualitative and quantitative understanding of these devices. [ABSTRACT FROM AUTHOR]

The spin orbital torques in Ta/CoFeB/MgO structures are experimentally investigated utilizing the planar Hall effect and magnetoresistance measurement. By angular field characterization of the planar Hall resistance at ±current, the differential resistance which is directly related to the spin orbital torques is derived. Upon curve fitting of the analytical formulas over the experimental results, it is found that the anti-damping torque, also known as spin Hall effect, is sizable while a negligible fieldlike torque is observed. A spin Hall angle of about 18±0.6% is obtained for the Ta layer. Temperature dependent study of the spin orbital torques is also performed. It is found that temperature does not significantly modify the spin Hall angle. By cooling down the sample down to 100K, the obtained spin Hall angle has a maximum value of about 20.5±0.43%. [ABSTRACT FROM AUTHOR]

Accurately sensing AC magnetic field signatures poses a series of challenges to commonly used Hall-effect sensors. In particular, induced voltage and lack of high-frequency spinning methods are bottlenecks in the measurement of AC magnetic fields. We describe a magnetic field measurement technique that can be implemented in two ways: 1) the current driving the Hall-effect sensor is oscillating at the same frequency as the magnetic field, and the signal is measured at the second harmonic of the magnetic field frequency, and 2) the frequency of the driving current is preset, and the measured frequency is the magnetic field frequency plus the frequency of the current. This method has potential advantages over traditional means of measuring AC magnetic fields used in power systems (e.g., motors, inverters), as it can reduce the components needed (subsequently reducing the overall cost and size) and is not frequency bandwidth limited by current spinning. The sensing technique produces no induced voltage and results in a low offset, thus preserving accuracy and precision in measurements. Experimentally, we have shown offset voltage values between 8 and $27 ~\mu \text{T}$ at frequencies ranging from 100 Hz to 1 kHz, validating the potential of this technique in both cases. [ABSTRACT FROM AUTHOR]

The dependence of the measured DC voltage on the non-magnetic material (NM) in NM/CoFeB and CoFeB/NM bilayers is studied under ferromagnetic resonance conditions in a TE011 resonant cavity. The directional change of the inverse spin Hall effect (ISHE) voltage VISHE for the stacking order of the bilayer can separate the pure VISHE and the anomalous Hall effect (AHE) voltage VAHE utilizing the method of addition and subtraction. The Ta and Ti NMs show a broad deviation of the spin Hall angle θISH, which originates from the AHE in accordance with the high resistivity of NMs. However, the Pt and Pd NMs show that the kinds of NMs with low resistivity are consistent with the previously reported θISH values. Therefore, the characteristics that NM should simultaneously satisfy to obtain a reasonable VISHE value in bilayer systems are large θISH and low resistivity. [ABSTRACT FROM AUTHOR]

A recent experiment in CuBi alloys obtained a large spin Hall angle (SHA) of -0.24 (Niimi et al., Phys. Rev. Lett. 109, 156602 (2012)). We find that the SHA can be dramatically enhanced by Bi impurities close to the Cu surface. The mechanisms of this enhancement are two-fold. One is that the localized impurity state on surface has a decreased hybridization and combined with Coulomb correlation effect. The other comes from the low-dimensional state of conduction electrons on surface, which results in a further enhancement of skew scattering by impurities. Furthermore, we note that a discrepancy in sign of SHA between the experiment and previous theories is simply caused by different definitions of SHA. This re-establishes skew scattering as the essential mechanism underlying the spin Hall effect in CuBi alloys. [ABSTRACT FROM AUTHOR]

This paper deals with the modeling of sensitivity of epitaxial graphene Hall bars, from submicrometer to micrometer size, to the stray field generated by a magnetic microbead. To demonstrate experiment feasibility, the model is first validated by comparison to measurement results, considering an ac-dc detection scheme. Then, a comprehensive numerical analysis is performed to investigate signal detriment caused by sensor material heterogeneities, saturation of bead magnetization at high fields, increment of bead distance from sensor surface, and device width increase. [ABSTRACT FROM AUTHOR]

The authors report experimental investigations on Hall sensors based on AlGaN/GaN heterojunctions grown on silicon 111 (Si 111) substrates. Realisation of two‐dimensional electron gas‐based Hall sensors on Si substrates can have the advantages of low cost and integrability with complementary metal‐oxide semiconductor circuits. Design and fabrication of such Hall sensors and their characterisation over a wide temperature range of 75 to 500 K are reported. The authors experimentally investigate the temperature dependence of the transresistances, sheet resistance and current‐related sensitivity (or gain) of such Hall sensors. The current‐related sensitivity is shown to be reasonably constant over the complete temperature range and certain inevitable variations in current‐related sensitivity can easily be compensated. The temperature dependence of the transresistance can be used for such compensation. The variation of the geometrical correction factor of the Hall sensor with the applied magnetic field strength and the operating temperature is also studied. The authors also demonstrate the possibility of realising Hall sensors with a high geometrical correction factor (≈0.97), which is practically insensitive to variations in temperature (≃2% from 75 to 500 K) and applied magnetic field, for applications such as in electromechanical devices. [ABSTRACT FROM AUTHOR]

This paper proposes a detection method of open-circuit fault of insulated-gate bipolar transistor in the voltage source inverters. The magnetic field signal at the DC bus of the inverter is collected and analysed to detect the fault. First, the simulation is developed for a voltage source inverter-fed induction machine drive which operates in healthy state and single switch open-circuit conditions. The faulty characteristic frequencies in the spectrum of DC-link current signal are derived on the basis of the power balance analysis through the inverter. Second, laboratory tests are implemented with a test bed of voltage source inverter-based induction machine drive in which a Hall sensor suited for the geometry complexity of the DC bus structure is utilized for measuring the magnetic field signal, which can be considered as an image of the simulated DC-link current. The fast Fourier transform of the magnetic field signal shows sharp increases in spectrum amplitude at the fundamental, second-order and third-order harmonics that they can be used as the indication to detect the fault. The approach using proposed signal offers several advantages such as single-sensor requirement, non-invasive and less costly device. [ABSTRACT FROM AUTHOR]

The Hall resistance of small Hall sensors and its nonlinear dependence on magnetic field B were investigated at the temperature of 4.2 K. The sensors were four-terminal crosses fabricated by etching AlGaAs/InGaAs/GaAs δ-doped heterostructures. While large sensors exhibit good linearity of the Hall voltage on magnetic field, in sensors smaller than 5 μm we detected pronounced nonlinearities for magnetic fields between 0 and 2 T. We attribute the latter to ballistic corrections to the classical Hall effect, and we model the Hall and the bend resistances at low temperature using Monte Carlo simulation. We also carried out temperature studies of the Hall sensors. We show that the nonlinearities persist up to room temperature. The effect of nonlinearities on the performance of Hall sensors is discussed. [ABSTRACT FROM AUTHOR]

Hall sensors with cross width of ∼1 μm were fabricated from InAs/AlSb quantum well semiconductor heterostructures containing two-dimensional electron gas. The room-temperature device characteristics were examined by Hall effect and electronic noise measurements along with analytical calculations. In the low-frequency range, from 20 Hz to 1.6 kHz, the noise-equivalent magnetic field resolution was found to be limited by 1/f and generation-recombination noise from 22 to 3.5 μT/Hz. The corresponding noise-equivalent magnetic moment resolution reached 106μB/Hz at ∼700 Hz and was even lower at higher frequencies. Using a phase-sensitive measurement technique, detection of a single 1.2 μm diameter bead, suitable for biological applications, was achieved with a signal to noise ratio of ∼33.3 dB, as well as detection of six 250 nm beads with a signal to noise of ∼2.3 dB per bead. The work demonstrates the efficacy of InAs quantum well Hall devices for application in high sensitivity detection of single magnetic biomolecular labels. [ABSTRACT FROM AUTHOR]

A semiempirical time-dependent thermal model of Hall effect thrusters was developed to compute evolution of the thruster channel wall temperature during a transient regime. The model accounts for heat conduction through dielectric walls and radiative transfer as the channel is considered as a thermal enclosure. The graybody view factors are experimentally determined during the cooling period that follows a power shutdown. The model permits the assessment of the amount of power delivered to walls by fitting calculated temperature profiles to experimental profiles obtained by means of calibrated infrared imaging. Plasma-surface interactions are examined in this contribution for three types of thrusters, namely, SPT100-ML, PPS®1350-G, and the 5-kW-class PPSX000-ML. The electrical input power range that is probed stretches out from 500 W to 5 kW. The energy flux passed to the discharge chamber dielectric walls varies between 0.1 and 2 W/cm2. The overall amount of power delivered to the external and internal walls is found to vary linearly with the applied power. It is in favor of an energy loss mechanism driven by ion bombardment. A departure from the linear trend is observed at high discharge voltage. Production of multiply charged ion species could be an explanation. The impact of thruster design and wall material on power losses inside the thruster channel is also investigated from both a technological and a physics standpoint. [ABSTRACT FROM AUTHOR]

The response of a mesoscopic Hall cross to a local potential barrier is calculated from which we derive two-dimensional resistance maps. At zero magnetic field a double butterfly Hall resistance pattern arises in the Hall cross that is attributed to barrier-induced inhomogeneous current flow. Small, i.e., nonquantizing magnetic fields smoothen out the two wings of the butterfly into a single elongated feature. The longitudinal resistance pattern shows the strongest changes in the current leads leading to two well separated (by the cross area) bumps. Symmetry properties are found for the resistance maps (Hall and longitudinal) with respect to the position of the local introduced potential barrier. [ABSTRACT FROM AUTHOR]

We have investigated the consequences of a modified design of modulation doping pseudomorphic AlGaAs/InGaAs/GaAs and we propose a quantum well structure for a Hall device with the goal of improving its performances. From self-consistent calculations we find that the electron concentration ns in the interface region is increased. This implies that one can have a wider spacer layer and still have the same ns with the result that the mobility is improved. This result should be valuable for many types of devices. We specifically consider Hall sensors, where it is desirable to have a low electron concentration and a high mobility. [ABSTRACT FROM AUTHOR]

We report on AlGaN/GaN heterojunction structures for use in Hall effect sensors working over a wide range of temperatures. Room temperature current-related magnetic sensitivity of 55 V/AT at a sheet resistance below 300 Ω/sq and very low temperature cross sensitivity of 103 ppm/°C up to 300 °C were obtained for a square-shaped Hall effect sensor. The active layer of the Hall effect sensor is the two-dimensional electron gas formed at the Al0.3Ga0.7N and GaN heterointerface caused by the gradient in the total polarization between the AlGaN barrier and the GaN buffer layer, which results in the positive polarization induced interface charge attracting free electrons. The temperature-dependent transport properties of the heterojunction were analyzed by Hall measurement. The drop of its electron mobility from room temperature to 300 °C is mainly due to the enhanced polar optical scattering, while the very stable sheet carrier density contributes to the excellent temperature cross sensitivity of the Hall effect sensor. [ABSTRACT FROM AUTHOR]

Carrier-concentration and mobility profiles formed in Si by BF2 implantation and by subsequent rapid thermal annealing (RTA) have been examined by differential Hall-effect measurements. B-concentration profiles are measured before and after RTA by a secondary-ion-mass spectroscopic technique. It is shown that a significant amount of B atoms, over 40% of an effective implant dose, is lost during RTA if the substrate is dipped in a dilute HF solution prior to annealing. The loss of B atoms gives rise to the increase in sheet resistivity of the formed p-type layers. It is revealed that an approximately 1.3–1.5-nm-thick, native oxide layer acts as an encapsulant and depresses the loss of implanted B atoms from the substrate during RTA at/above 950 °C, resulting in the formation of an electrical profile with a long tail. The redistribution of B atoms during RTA is suppressed in the sample from which the native oxide has been stripped. Also, an approximately 25-nm-thick, p+ layer with a maximum carrier concentration of 1×1020/cm3 is formed by 3-keV BF2 implantation and subsequent RTA at 1000 °C. Experimental data indicate that the HF dipping effect is negligibly small if BF2 implantation is carried out above 40 keV. [ABSTRACT FROM AUTHOR]

A stationary, macroscopic model [E. Ahedo, J. Gallardo, and M. Martínez-Sánchez, Phys. Plasmas 10, 3397 (2003)] is used to carry out parametric investigations on the effects of (i) the discharge voltage, (ii) the gas flow rate, (iii) the axial gradient of the magnetic field, and (iv) the chamber length on the Hall thruster performances and the axial structure of the plasma discharge. The high-thrust and high-specific-impulse modes for dual-mode thrusters are compared too. The results of the simulations agree well with the main tendencies observed in different experiments. The interaction among the several physical phenomena is discussed and useful scaling laws are proposed. Special attention is paid to understand (i) the adjustment of the magnetic field strength with the discharge voltage for optimum operation, (ii) the effect of the magnetic field shape, (iii) the dimensions of the different regions of the discharge, and (iv) the parameter trends needed to increment the propulsive and ionization efficiencies (the product of which determines the thrust efficiency). [ABSTRACT FROM AUTHOR]

Scaling methods are a straightforward way to design new thrusters at different power levels. Based on the general equations, this work derives the scaling rules from those equations and presents a model for thruster with anode layer (TAL) and stationary plasma thrusters (SPTs) that encompass the scaling methods described until now. With the exception of the magnetic field, the scaling rules derived can be used for both TAL and SPT. In addition, this model is used to study the impact of the different scaling methods in the performance of the thruster. In particular, how the total thruster efficiency is affected through the current efficiency and the influence of this efficiency loss in the thrust. Accordingly, using the rules derived from the general equations for the magnetic field, the possible conflicts with the electron confinement given by the Larmor Radius for both SPT and TAL thrusters are studied. Finally, it is shown how the selected scaling method strongly affects the expected lifetime of the thruster. In this aspect, the strict scaling results to be the most rigorous method, whereas the length extension method allows for further improvement of the lifetime. [ABSTRACT FROM AUTHOR]

Tailoring of the magnetic field was attempted for performance improvement in a 500-W class small Hall thruster (KmHT-60). Two different tailored magnetic field configurations, both having field lines convex toward the anode but with different curvatures, resulted in different thrusts, anode specific impulses, and anode efficiencies; the corresponding values were 20.7 mN, 2150 s, and 51.5% at an anode power of 423 W in the case of the better aligned magnetic field, which were 27%, 21%, and 54% higher than those in the other magnetic field configuration, respectively. Efficiency analysis using far-field plume measurements showed that the difference in the thruster performance is mostly due to the enhancements in the current utilization efficiency caused by the suppression of the electron leakage current and the high propellant utilization efficiency due to the increased ion current. [ABSTRACT FROM AUTHOR]

Magnetic sensors are widely used in automotive and industrial applications to measure linear or angular movements. Although the measurement of the magnetic field vector offers the opportunity to estimate all mechanical degrees of freedom, previous approaches could not be applied in these environments. This paper presents an improved method for sensing a magnetic source’s position and orientation with six degrees of freedom. To solve the underlying inverse magnetostatic problem, an Unscented Kalman Filter in combination with an analytical model of the magnetic source’s field is used. The performance of the method is demonstrated on the basis of a novel multi-axis input device. It comprises a cuboid magnet and a CMOS (Complementary metal-oxide-semiconductor) Hall-Sensor array with up to 36 elements. The localization algorithm and the measurement model are implemented in an efficient way to achieve real-time capability and sampling rates up to 80Hz on embedded hardware. This outperforms known methods significantly and allows for a wide application of multi-degree of freedom sensors. Moreover, an absolute position and orientation accuracy of 71 $\mu \text{m}$ and 1.4° are achieved. The work describes the basis for advanced input devices but can also be transferred to other kinds of magnetic localization problems. [ABSTRACT FROM AUTHOR]

Brushless direct current motors with Hall sensors have been widely used in myriad industrial and commercial applications due to their simplicity and low cost. Meanwhile, the fault tolerant control (FTC) of Hall sensor drives has attracted renewed research attention. During FTC, the motor drives need to diagnose the Hall-sensor fault(s) and reconstruct the faulty signal(s). In this context, we propose an innovative fast fault diagnosis (FFD) method for analyzing different fault cases and diagnosing faulty signal(s) in the shortest possible time. Compared with established fault diagnosis methods, the FFD method does not require complicated vector-tracking observers, and it is capable of handling up to two simultaneous faults while greatly improving the diagnostic speed. Our simulation and experimental results verify the effectiveness of the proposed method and demonstrate its advantages over established methods particularly during transient operations. Due to the simplicity of diagnostic algorithm, the proposed FFD method can be readily implemented in conventional drive systems, either through extra coding within existing controllers or as an auxiliary circuit. [ABSTRACT FROM AUTHOR]

The principal difficulty in large magnetic systems having an extensive flux-return yoke is to characterize the magnetic flux distribution in the yoke steel blocks. Continuous measurements of the magnetic flux density in the return yoke are not possible and the usual practice uses software modeling of the magnetic system with special 3-D computer programs. The 10 000 t flux-return yoke of the Compact Muon Solenoid (CMS) magnet encloses a 3.8 T superconducting solenoid with a 6 m diameter by 12.5 m length free bore and consists of five dodecagonal three-layered barrel wheels around the coil and four endcap disks at each end. The yoke steel blocks, up to 620 mm thick, serve as the absorber plates of the muon detection system. A magnetostatic 3-D model of the CMS magnet has been developed to describe the magnetic field outside the solenoid volume, which was measured with a field-mapping machine. To verify the magnetic flux distribution calculated in the yoke steel blocks, direct measurements of the magnetic flux density with 22 flux loops installed in the selected regions of the yoke were performed during the CMS magnet test in 2006 when four “fast” discharges of the CMS coil (190 s time constant) were triggered manually to test the magnet protection system. No fast discharge of the CMS magnet from its operational current of 18.2 kA, which corresponds to a central magnetic flux density of 3.8 T, has been performed at that time. For the first time, in this paper, we present measurements of the magnetic flux density in the steel blocks of the return yoke based on the several standard linear discharges of the CMS magnet from the operational magnet current of 18.2 kA. To provide these measurements, the voltages induced in the flux loops (with amplitudes of 20–250 mV) have been measured with six 16 bit data acquisition modules and integrated offline over time. The results of the measurements during magnet linear ramps performed with a current rate as low as 1–1.5 A/s are presented and discussed. [ABSTRACT FROM AUTHOR]

A quest for a quantitative and noninvasive method for the measurement of local magnetic fields with high spatial and field resolution at variable temperatures calls for a selection of suitable magnetic sensor and appropriate scanning system. Scanning Hall probe microscopy (SHPM) is one of the choices as it addresses the stated issues and complements the other magnetic imaging methods. Compatibility of Si-Hall sensor fabrication with standard CMOS fabrication process and controllability of silicon characteristics parameters make them more suitable, for Hall probe applications, over other compound semiconductors (AlGaAs/GaAs, InSb, and AlGaN/GaN). However, the effect of Si-Hall sensor's device thickness, applied bias current, and impediments in its use at variable temperatures SHPM application need to be investigated. In this article, a systematic study on the optimization of performance parameters of silicon-on-insulator micro-Hall sensors for their dedicated application in SHPM system is presented. Si ∼0.7μm×0.7μm Hall sensors have been fabricated using monolithic device fabrication steps. These Hall sensors have been investigated based on the electrical, magnetic and noise characteristics to study the effect of thickness of the active layer (300-550 nm) and temperature (25-150∘C). Formation of trapping centers and defects have been observed due to device layer thinning, which not only limit the working temperature, bias current but also the minimum thickness of the device layer to be 300 nm. This compromise in Si-Hall sensor characteristics due to surface morphology of thinned films can be removed by growing the device layer on SiO2 instead of thinning the device layer. [ABSTRACT FROM AUTHOR]

Abstract: The causes and mechanisms of variation in the quantum efficiency and other characteristics of InGaN/GaN heterostructures are actively investigated in various operating modes. The results are presented from an experimental study of the variation in the external quantum efficiency of low-power InGaN/GaN green light-emitting diodes with and without a quantum well in the space-charge region (SCR) of the heterostructure in the accelerated test mode. It is found that after 8 hours of testing at a temperature of 300 K in the pulse mode with a pulse amplitude of 0.5 A, a pulse duration of 100 µs, and a duty cycle of 100, the external quantum efficiency grows for all LEDs without a quantum well in the SCR and diminishes for LEDs with a quantum well throughout the range of operating currents. It is shown that at a low level of injection, the intensity of emission of light emitting diodes without a quantum well in the SCR is determined by recombination processes according to the Shockley-Read-Hall mechanism, while that of LEDs with a quantum well is determined by tunneling-recombination processes. Current training of green LEDs based on InGaN/GaN heterostructures in the forced pulse mode for 4 hours can be used as a technological operation for stabilizing their lighting characteristics, and for identifying potentially unreliable products under conditions of mass production. [ABSTRACT FROM AUTHOR]

Many modern electronic devices utilize linear Hall sensors to measure current and the magnetic field, as well as to perform switching and latching operations. Smartphones, laptops, and e-readers all work with very low (sub-milliampere) currents. To perform a switching function in low-power devices, however, Hall sensors must work in the microampere regime. This paper demonstrates, for the first time, the ability of a standard Hall detector to work linearly in the microampere regime between 0 and 0.7 Tesla. To do so, we developed a current source with RMS noise on the order of 10–100 pA/ Hz . An optimized electronic circuit with minimal connections feeds current to the Hall sensor, and the Hall voltage is measured with an industrial nanovoltmeter. After cooling this system down to temperatures as low as 77 K, we found mostly 1/f noise. In this regime the thermal noise was negligible. We demonstrate the capabilities of this system by precisely measuring the slope of the Hall effect with a four-point probe at current intensities of 100, 10, and 1 μA. We expect that our system can work as a microampere Hall sensor using external voltage detectors. [ABSTRACT FROM AUTHOR]

Large induction motors used in variable speed industrial applications (digging, traction, etc.) undergo dynamic stresses at high power levels. Their lifetime is reduced as compared with constant speed motors and downtime costs are very high. To monitor the condition of such motors, advanced sensor instrumentation is considered, including installation of Hall effect flux sensors inside the motor airgap. Such an advanced instrumentation enables continuous measurement of the airgap flux in both time and space domains simultaneously. This allows for advanced fault detection algorithms. This paper presents a method for early diagnosis of stator turn-to-turn faults and static eccentricity, and differentiation between these two conditions. The paper demonstrates that the proposed method detects, localizes, and quantifies both faults with high accuracy and sensitivity. Furthermore, each fault can be detected at an incipient stage and its development can be predicted. The results of the presented study have been supported by both simulation and experimental results obtained on a laboratory scale induction motor. Based on the results presented in the paper, a real-time condition monitoring system has been developed. [ABSTRACT FROM AUTHOR]

We demonstrate a six-axis scanning imaging apparatus using piezo bending actuators with a large scan range. The six axes of motion of the bending actuators together with the coupling mechanism to the translation stage allow complete control of the sensor position and orientation over the scanning surface, which is ideal for the use of planar sensors such as Hall devices. In particular, the design allows for in situ correction of the probe tilt angle so that the sensor distance to sample surface can be minimized. We investigate the impact of this alignment on the quality of the measured data using an InSb Hall sensor and a magnetic sample. We also demonstrate a synchronous commutation setup that can greatly enhance the magnetic image by reducing the Hall signal offset. [ABSTRACT FROM AUTHOR]

In this study, Ga 0.6 Sb 0.4 thin films were grown on quartz and Ge(100) 1° off-axis substrates by RF magnetron sputtering at 500 °C. Ga 0.6 Sb 0.4 /Ge(100) shows n -type conductivity at room temperature (RT) and p -type conductivity at low temperatures, whereas undoped GaSb thin films exhibit p -type conductivity, irrespective of their growth methods and conditions. Their electrical properties were determined by rapid thermal annealing, which revealed that Ga 0.6 Sb 0.4 /Ge(100) contains two types of acceptors and two types of donors. The acceptors are considered to be Ga Sb and electrically active sites on dislocations originating at the Ga 0.6 Sb 0.4 /Ge(100) interface, while donors are believed to be Ga i and electrically active sites originating at the Ga 0.6 Sb 0.4 /Ge(100) interface. In these acceptors and donors, the shallow donor concentration is higher than the shallow acceptor concentration, and the shallow donor level is deeper than the shallow acceptor level. Thus, we concluded that Ga 0.6 Sb 0.4 /Ge(100) shows n -type conductivity at RT due to electrically active sites originating at the Ga 0.6 Sb 0.4 /Ge(100) interface and native defects originating from excess Ga. [ABSTRACT FROM AUTHOR]

Most of the existing electrical techniques of condition monitoring and fault diagnosis are based on frequency analysis of signals measured externally to the motor. In this paper, it is proposed to add the space dimension to the measured signals by using an array of Hall effect flux sensors installed inside the motor air gap, and to explore the advantages brought by such an instrumentation. The paper presents analytical models of air gap flux density expressed in terms of time and space, for a healthy motor and for a motor with rotor bar faults and mixed eccentricity. Based on these models, the paper proposes a new technique for early detection of rotor bar faults and mixed eccentricity, and for discrimination between them. The paper demonstrates that, with the help of the proposed technique, the severity of each fault and its location relative to rotor or stator can be accurately established. The results of the presented study are supported by simulations and validated by experiments on a laboratory scale induction motor. The formulated fault diagnosis algorithm is suitable for real-time implementation. [ABSTRACT FROM PUBLISHER]

A recent improvement of the design of the ITER outer vessel steady-state magnetic field sensors (OVSS) is presented. OVSS features a pair of Hall sensors with a sensing layer made of bismuth. Sixty OVSS will be installed on the ITER vacuum vessel outer skin to perform an absolute measurement of magnetic field. The bismuth Hall sensor measurement is temperature dependent, and the maximum allowed OVSS error of 4-mT limits the error of the measurement of the Hall sensor temperature by an on-board thermocouple to be less than 0.28 °C. This error consists of the temperature difference between the thermocouple and Hall sensors, thermocouple calibration error, and thermocouple measurement error. The improved design of the sensor housing reduces the temperature difference between the thermocouple and the Hall sensors bellow 0.04 °C. Procedures of the calibration prior installation and in situ calibration will allow calibrating the on-board thermocouple with the error less than 0.06 °C. The thermocouple measurement error limit was determined as 0.27 °C in which case OVSS meets the maximum allowed error. [ABSTRACT FROM AUTHOR]

We examine the creation and design of a plasma thruster based on the converting of radial and circumferential momentum of the plasma flow into the axial direction. The acceleration effect is formed by the azimuthal electric field which comes about as a variation of an external, axial magnetic flux. Simultaneously, the azimuthal electron and ion flows interact with the radial magnetic field via the Lorentz force. Owing to this process, the transformation of azimuthal momentum transfers into axial momentum. As a result, the electron and ion flows are accelerated in one axial direction. Estimations specifying the admissible range of parameters of this device and the plasma flow are derived. [ABSTRACT FROM AUTHOR]

Several ZnO:Al thin films have been successfully deposited on glass substrates at different substrate temperatures by RF (radio frequency) magnetron sputtering method. Effects of the substrate temperatures on the optical and electrical properties of these ZnO:Al thin films were investigated. The UV–VIS–NIR spectra of the ZnO:Al thin films revealed that the average optical transmittances in the visible range are very high, up to 88%. X-ray diffraction results showed that crystallization of these films was improved at higher substrate temperature. The band gaps of ZnO:Al thin films deposited at 25 ℃, 150 ℃, 200 ℃, and 250 ℃ are 3.59 eV, 3.55 eV, 3.53 eV, and 3.48 eV, respectively. The Hall-effect measurement demonstrated that the electrical resistivity of the films decreased with the increase of the substrate temperature and the electrical resistivity reached 1.990×10 −3 Ω cm at 250 ℃. [ABSTRACT FROM AUTHOR]

Aluminum doped zinc oxide (AZO) films are synthesized on glass substrates using different number of coatings (6, 12, 18 and 24) by the sol-gel dip-coating technique. The effects of thickness on structural, morphological, electrical optical and waveguiding properties of the prepared films are studied through X-ray diffraction (XRD), Raman spectroscopy (RS), scanning electron microscopy (SEM), atomic force microscopy (AFM), Hall effect measurements, UV–Visible–NIR spectrophotometer and m-lines spectroscopy (MLS). XRD analysis shows that all AZO films exhibit the hexagonal wurtzite crystal structure with a preferential growth orientation along the c -axis. The intensity of the (002) diffraction peak and crystallite size tend to increase with increase in the thickness indicating an improvement in the crystallinity of the films. Furthermore, the observation of the high-frequency E 2 mode in the Raman spectra supports the hexagonal wurtzite structure of ZnO in the films. SEM and AFM images indicate that microstructure parameters, such as grain size and surface roughness depend sensitively on the thickness of the film. The electrical resistivity and carrier concentration are found to increase and decrease, respectively, as the film thickness increased. Optical transmittance spectra demonstrate that all the films exhibit high average transmittance (86.8–89.1%) in the visible spectral range. Moreover, the band gap energy shows a red-shift with the film thickness. MLS measurements at a 632.8 nm wavelength put into evidence that AZO planar waveguides support single and multi-well confined guided modes for both transverse electric (TE) and transverse magnetic (TM) polarizations. Both TE and TM refractive indexes are found to increase with thickness and reach saturation values when the number of coatings is greater than 18. Moreover, the thickest AZO planar waveguide demonstrates a propagation loss lower than 1 dB/cm. [ABSTRACT FROM AUTHOR]

In this paper the authors discuss a low-cost distributed monitoring system for structural crack monitoring in monumental architecture. The proposed solution is suitable for monitoring widely extended areas like the Siena’s ancient city walls. The prototype sensing system, based on Hall sensor technology, has been developed and characterized to reach a displacement resolution in the order of tens of micrometers. The distributed measures are transmitted to a server using a wireless communication network based on a mesh topology. The server receives, collects, post-processes and stores the data in a database. [ABSTRACT FROM AUTHOR]

Tin sulfide thin films were deposited on different substrates by thermal evaporation technique. The effect of substrate on the growth of SnS thin films has been studied thoroughly. X-Ray Diffractrometry pattern shows that the deposited films are showing (111) orientation having primitive type orthorhombic structure and those deposited on glass/ZnO:Al has better crystallinity and less dislocation density than the others. Small cracks are visible on the surface and that may be due to the higher dislocation density or strain exerted on the surface. Different types of substrate also shifts the absorption edge of the films deposited on different substrates. Electrical characteristics obtained from Hall Effect measurements show the films deposited on glass/ZnO:Al has better mobility and less resistivity than the films deposited on other substrates. Electric potential-current characteristics shows ohmic and rectifying behavior as the substrate is changed. [ABSTRACT FROM AUTHOR]

We numerically investigate the effects of disorder on the quantum Hall effect (QHE) and the quantum phase transitions in silicene based on a lattice model. It is shown that for a clean sample, silicene exhibits an unconventional QHE near the band center, with plateaus developing at v = 0; ±2; ±6; : : : ; and a conventional QHE near the band edges. In the presence of disorder, the Hall plateaus can be destroyed through the float-up of extended levels toward the band center, in which higher plateaus disappear first. However, the center v = 0 Hall plateau is more sensitive to disorder and disappears at a relatively weak disorder strength. Moreover, the combination of an electric field and the intrinsic spin-orbit interaction (SOI) can lead to quantum phase transitions from a topological insulator to a band insulator at the charge neutrality point (CNP), accompanied by additional quantum Hall conductivity plateaus. [ABSTRACT FROM AUTHOR]

The band structure of many semiconducting monolayer transition metal dichalcogenides (TMDs) possesses two degenerate valleys with equal and opposite Berry curvature. It has been predicted that, when illuminated with circularly polarized light, interband transitions generate an unbalanced nonequilibrium population of electrons and holes in these valleys, resulting in a finite Hall voltage at zero magnetic field when a current flows through the system. This is the so-called valley Hall effect that has recently been observed experimentally. Here, we show that this effect is mediated by photogenerated neutral excitons and charged trions and not by interband transitions generating independent electrons and holes. We further demonstrate an experimental strategy, based on wavelength dependent spatial mapping of the Hall voltage, which allows the exciton and trion contributions to the valley Hall effect to be discriminated in the measurement. These results represent a significant step forward in our understanding of the microscopic origin of photoinduced valley Hall effect in semiconducting transition metal dichalcogenides and demonstrate experimentally that composite quasi-particles, such as trions, can also possess a finite Berry curvature. [ABSTRACT FROM AUTHOR]

A linear galvanic isolator was developed, using a compact and high sensitivity Quantum Well Hall Effect (QWHE) sensor. This sensor is based on a GaAs-InGaAs-AlGaAs heterostructure, with a maximum capacitance of 5.5 pF and a 3 dB bandwidth of 40.2 MHz. As part of this work, a printed transmitter coil was also designed as part of this QWHE galvanic isolator. A linear relationship between input current and output voltage, at each frequency of the isolation device, were observed ( R 2 ≈ 1.0). The relative errors of frequency response between 0 and 100 kHz were ≤5.4%. Two gain temperature coefficients were also obtained at low and high temperatures, α 1 and α 2 , with a temperature of 280 K being the boundary between the two regions. The mean values of α 1 and α 2 were (7.09 ± 0.27) × 10 −4 K −1 and (3.22 ± 0.17) × 10 −4 K −1 respectively. The controlling mechanisms for the amplitudes of α 1 and α 2 are suggested to be due to the temperature variation of the two-dimensional electron gas (2DEG) electron mobility, arising from the heterostructure nature of the QWHE sensor used. The QWHE isolator has high accuracy, large bandwidth, high frequency-gain linearity and thermal stability. Compared with commercial optical isolators, Silicon Hall sensor-based isolators and coil isolators, this QWHE isolator does not require any external light sensor transistor or ferrite toroid to enhance its sensitivity. As such, it is not affected by any nonlinear transistor behaviour, B - H curve or magnetic retention. The results indicate that this high sensitivity, highly linear QWHE isolator is suitable for use as a low cost, high efficiency, linear galvanic isolation device. [ABSTRACT FROM AUTHOR]

In the previous investigations, an intermode exchange was used to demonstrate the transfer of energy and momentum into using different kinematic degrees of freedom. This paper examines using a hydrodynamic approach using a cold, neutral flow in a rotating cylindrical plasma column using crossed magnetic fields. Results show that the twirling plasma flow in a cylindrical vortex can be accelerated in an axial direction, thereby resulting an energy/momentum transfer in the axial direction. These results are analogous to the creation of a plasma thruster using this effect. [ABSTRACT FROM PUBLISHER]

We have studied collective excitation almost all of the filling fraction, in the Jain series of positive flux attachment states. In this article we have presented excitation spectrum of all positive flux attachment states for a real two dimensional electron system to get the complete scenario. The fundamental roton energy becomes zero at the filling fractions associated with four pair of magnetic flux quanta attachment composite fermion, which suggest that there is a limitation of flux attachment to the electron to form a composite fermion in fractional quantum Hall effect. The roton energy and energy gap become zero at filling fraction ν = 1 / 2 , which shows that the gapless state ν = 1 / 2 can be naturally obtained as an extrapolation of the collective excitation of the incompressible gaped states. [ABSTRACT FROM AUTHOR]

Stimulated by the recent implementation of a three-port Hall-effect microwave circulator of Mahoney et al. (MEA), we present model studies of the performance of this device. Our calculations are based on the capacitive-coupling model of Viola and DiVincenzo (VD). Based on conductance data from a typical Hall-bar device obtained from a two-dimensional electron gas (2DEG) in a magnetic field, we numerically solve the coupled field-circuit equations to calculate the expected performance of the circulator, as determined by the S parameters of the device when coupled to 50Ω ports, as a function of frequency and magnetic field. Above magnetic fields of 1.5 T, for which a typical 2DEG enters the quantum Hall regime (corresponding to a Landau-level filling fraction ν of 20), the Hall angle $\theta_{H}=\tan^{-1}\sigma_{xy}/\sigma_{xx}$ always remains close to 90°, and the S parameters are close to the analytic predictions of VD for $\theta_{H}=\pi/2$ . As anticipated by VD, MEA find the device to have rather high (kΩ) impedance, and thus to be extremely mismatched to 50Ω, requiring the use of impedance matching. We incorporate the lumped matching circuits of MEA in our modeling and confirm that they can produce excellent circulation, although confined to a very small bandwidth. We predict that this bandwidth is significantly improved by working at lower magnetic field when the Landau index is high, e.g. $\nu=20$ , and the impedance mismatch is correspondingly less extreme. Our modeling also confirms the observation of MEA that parasitic port-to-port capacitance can produce very interesting countercirculation effects. [ABSTRACT FROM AUTHOR]