A variant of the laboratory work “Investigation of the axial magnetic induction of the solenoid” is given for the case when the solenoid is located in a separate block and its parameters are unknown. ...The results of calculations of axial induction of a solenoid with a different ratio of the length of the solenoid to the diameter are given. It is shown that the maximum of the derivative of axial induction in relative length corresponds to the physical end of the solenoid with sufficient accuracy for practice.An algorithm for determining the parameters of a solenoid based on experimental data on measuring the axial induction of the solenoid is described. Laboratory work has a character that orients students to independent research. Processing of digital data is carried out using the Excel program.
•Bismuth hall sensors with 100 nm are developed for HL-2A.•Calibration accuracy is better than ±1 % for magnetic fields greater than 3 mT.•Using the magnetron sputtering and SiO2 substrate can reduce ...the thickness error.•The housing and mounting position of the bismuth hall sensor is designed.
100 nm bismuth-based Hall sensors have been developed on the HL-2A tokamak recently. This paper reviews the process of manufacturing a Hall sensor with high sensitivity, including material selection, craft optimization, and platform testing. Magnetron sputtering and SiO2 glass substrate are proposed to reduce the thickness error. The sensitivity of the sensor is obtained by linear fitting, and the calibration accuracy is better than ±1 % when the magnetic field range is greater than 3 mT. The housing and mounting position of the Hall sensor are designed so that they can be compared with the pick-up coils in the upcoming discharge experiment.
Nanobiosensors contribute to point-of-care (POC) efforts to make routine biodiagnostics more accessible to patients with respect to both expense and convenience. However, devices whose operation is ...based on magnetic phenomena appear delayed in their progress toward POC commercialization despite their promise of better sensitivity, as compared to devices based on optical, mechanical, or electrochemical phenomena. This review aims to elucidate the technical challenges preventing magnetic nanobiosensors from reaching market readiness. The following types of magnetic nanobiosensor operation are reviewed: giant magnetic impedance (GMI), superconducting quantum interference device (SQUID), anisotropic magnetoresistance, giant magnetoresistance (GMR), resonant coil, Hall effect, and microcantilever. In particular, a careful comparison of each type in terms of their advantages, disadvantages, recently overcome challenges, and sensitivities will be presented. For example, a disadvantage of GMI sensors, and certain others reviewed here, is the fact that ferromagnetic materials used in their construction directly impact the biosensing event since magnetic nanoparticle (MNP) labels are involved in the strategy. Other challenges associated with use of MNP labels will be addressed. Furthermore, some of the more interesting state-of-the-art magnetic nanobiosensor efforts will be discussed in order to provide an overview of target analytes and sample media under consideration. This review identifies GMR sensors as poised to dominate the market owing to their good sensitivity and ease of use. On the other hand, SQUID sensors, at their current stage of development, are revealed as unsuitable for POC applications due to their high operational cost and unwieldy instrumentation. Magnetics experts endeavoring to progress the field toward commercialization will find this review indispensable.
The successful assembly of heterostructures consisting of several layers of different 2D materials in arbitrary order by exploiting van der Waals forces has truly been a game changer in the field of ...low-dimensional physics. For instance, the encapsulation of graphene or MoS2 between atomically flat hexagonal boron nitride (hBN) layers with strong affinity and graphitic gates that screen charge impurity disorder provided access to a plethora of interesting physical phenomena by drastically boosting the device quality. The encapsulation is accompanied by a self-cleansing effect at the interfaces. The otherwise predominant charged impurity disorder is minimized, and random strain fluctuations ultimately constitute the main source of residual disorder. Despite these advances, the fabricated heterostructures still vary notably in their performance. Although some achieve record mobilities, others only possess mediocre quality. Here, we report a reliable method to improve fully completed van der Waals heterostructure devices with a straightforward postprocessing surface treatment based on thermal annealing and contact mode atomic force microscopy (AFM). The impact is demonstrated by comparing magnetotransport measurements before and after the AFM treatment on one and the same device as well as on a larger set of treated and untreated devices to collect device statistics. Both the low-temperature properties and the room temperature electrical characteristics, as relevant for applications, improve on average substantially. We surmise that the main beneficial effect arises from reducing nanometer scale corrugations at the interfaces, that is, the detrimental impact of random strain fluctuations.
•A new method for M-H loop determination in thin films is presented.•The method is based on Hall sensor measurements.•In addition, MR measurements validate magnetic anisotropy in soft magnetic thin ...films.
In this paper, a new method and technology to determine magnetization loops in thin films is demonstrated. The method is based on Hall sensor measurements set parallel to the thin film, which is magnetized using a Helmholtz pair coil set-up. The magnetic lines out of the thin films are measured by a Hall sensor, set parallel to the thin film. Provided that the shape of the thin film under test, preferably in the form of rectangle or circle, is well known with a length or diameter at least 100 times larger than its thickness, the precise determination of the magnetization loop of the film is possible with acceptable uncertainty, by means of calibrating the Hall sensor response with respect to the comparison with a standard method.
•A new type of 3D Hall sensor for magnetic field measurements was designed and a prototype was fabricated.•The sensor consists of six specially designed and assembled 1D Hall sensors to form a ...miniature sub-mm active volume.•Ability for precise magnetic field measurements at the same point at the same time.•Planar Hall voltage reduction by more than 35 times.
The measurement of all three components of a magnetic field, simultaneously to high precision with Hall sensors, remains a challenge. Given the high precision of state-of-the-art conventional uniaxial Hall sensors, this is disappointing. Currently, three-axis Hall sensors suffer from either, or a combination, of the following: large spatial distribution between active areas; high signal noise; cross-sensitivity between measurement axes due to angular errors or the planar Hall effect; the inability to measure at a single point in space and time. A new type of three-axis Hall sensor is proposed, consisting of three sets of uniaxial Hall sensors in a small active volume. The feasibility of the proposed sensor has been proven in a prototype with an active volume as small as 200μm×200μm×200μm. Due to its unique configuration, the new sensor addresses current three-axis Hall sensor limitations: it provides a high spatial resolution of 30μm×30μm×1μm for each field component; full field vector measurements practically at a single point in space and time; and a reduction of the planar Hall effect by a factor of 35. Angular errors between the individual Hall sensors in the prototype lie between 0.1° and 0.5°, above the tolerable error for non-corrected measurements. However, once understood they can be taken into account. With proper calibration, this type of three-axis Hall sensor has great potential for high-accuracy three-axis magnetic field measurements and is particularly suitable for field mapping of magnets.
With the global trend to develop digital substation automation systems, measurement devices are required to be reliable, of small size and light weight and of acceptable accuracy in a wide frequency ...band. This article presents a combined high voltage direct current measurement method which comprises the above-mentioned features that makes it suitable for smart grids protection and control applications. The proposed measurement method utilizes Hall sensor array for dc current measurement. DC voltage is measured using a voltage divider circuit while the harmonic currents are measured using a square Rogowski coil made of four straight bars along with a high precision digital integration algorithm. A four-spectral line interpolation fast Fourier transform algorithm based on trapezoidal convolution window is proposed to improve the extraction accuracy of the dc and harmonic components from the measured signal. Experimental results show that the error variation of the proposed method is less than 0.098% for voltage measurement while it is less than 0.104% for current measurement. The harmonic measurement ratio error is less than 0.2% and the angle error is less than 8'.
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