Magnetic Pickup Research Articles

Experimental investigation of kinetic instabilities driven by runaway electrons in the EXL-50 spherical torus

Abstract In this study, high-frequency instabilities driven by runaway electrons in the EXL-50 spherical torus have been reported using a high-frequency magnetic pickup coil. The frequency of these instabilities is found to be power function dependent on the plasma density, similar to the dispersion relation of the whistler wave. The observed instability seems to exhibit a fluctuating pattern, resembling frequency chirping behavior, which appears to align with the expected outcomes predicted by the Berk-Breizman model. Theoretically, the excitation threshold of the instability driven by runaway electrons is related to the ratio of the runaway electron density to the background plasma density, and the stability criterion is first demonstrated qualitatively in this work. The instability can be stabilized by the spontaneous rise of plasma density, consistent with the wave-particle resonance mechanism. This investigation demonstrates the excitation characteristic of chirping instabilities in a tokamak plasma and reveals new features of these instabilities, thereby advancing the understanding of the mechanisms for controlling and mitigating runaway electrons.

Instrumentation in Tractor for Evaluating Performance of a Tractor Drawn Rotavator

Performance measurement of agricultural machinery is essential for enhancing their efficiency for which they are operated. The performance related data helps the operator to select optimum operating parameters which reduce fuel consumption and increase field productivity. This study was aimed to develop various sensing units and install them on the tractor for evaluating performance of a tractor drawn rotavator. A microcontroller based embedded system was developed for continuous recording of wheel slip, actual forward speed, throttle opening, engine speed, velocity ratio, draft and power take-off (PTO) torque related data while carrying out tillage operation with rotavator. The wheel slip (from 1.5% to 35%) and actual forward speed of the tractor (up to 6 km h-1) was measured using inductive proximity sensors. For measuring throttle opening (0 to 100%), engine speed (750 to 2500 rpm), draft (65 to 350 kg) and PTO torque (up to 420 N-m) values, a potentiometer, magnetic pickup sensor, S-type loadcell and PTO torque transducer, respectively, were used. For computing velocity ratio, peripheral speed of rotavator was measured using PTO speed data received from PTO torque transducer, and actual forward speed of tractor was measured using inductive proximity sensor. The developed sensing units were calibrated under both dynamic and static conditions, and were also verified in laboratory and field conditions. Results showed that output signals received from the sensing units varied linearly with applied load. The mean absolute percentage error (MAPE) between measured and actual values was found to be below 5%. From the measured parameters, specific energy requirement and total power required for carrying out tillage operation could be computed. The power requirement was found to increase with increase in both gear and throttle settings. The specific energy requirement was minimum when rotavator was operated in L2 gear of the tractor. The minimum specific energy of 21 Wh m-3 was found at L2 gear and 75% throttle opening.

An octahedral Mach B-dot probe for 3D flows and magnetic fields in the edge of reversed field pinches.

Measurements and simulations show that plasma relaxation processes in the reversed field pinch drive and redistribute both magnetic flux and momentum. To examine this relaxation process, a new 3D Mach B-dot probe has been constructed. This probe collects ion saturation currents through six molybdenum electrodes arranged on the flattened vertices of an octahedron made of boron nitride (BN). The ion saturation current flows through configurable voltage dividers for measurement and returns through one of six selectable return electrodes equally spaced along the 12cm BN probe arm. In addition, the probe arm houses three B-dot magnetic pickup coils in the BN stalk immediately below to the octahedron, to measure the local magnetic field. Inserted in the Madison Symmetric Torus (MST) during deuterium discharges with 220kA plasma current, density of 0.8 × 1013 cm-3, the probe collects ion saturation currents with sawtooth-like peaks correlated with relaxation events. This compact octahedral design fitting six Mach electrode surfaces within a 1 cm3 cube will enable future multi-point, multi-field probes compatible with the 1.5 in. ports of MST. Such probes will allow for flow circulation, current, and canonical vorticity to be calculated in the center of the finite difference stencil formed by the measurement locations.

Influences of electric guitar pickup magnetic force on string vibrations

The design of a magnetic pickup has a significant impact on the tone of an electric guitar. In particular, the magnetic force from the pickup can influence the string vibrations and cause a beating effect, depending on the strength of the magnetic force and the amplitude of the string vibrations. To understand this behavior, we performed experiments and simulations. We measured and modeled the transversal string restoring force at various displacements from the magnetic pickup in directions both parallel and perpendicular to the guitar body. We observed that the magnetic force distribution is asymmetric in the perpendicular direction but symmetric in the parallel direction, which distorts the frequency of vibrations in opposite ways for the two directions and causes a resultant beating. This effect increases with larger string amplitudes or greater magnetic force and also varies over the duration of a plucked tone.

Magnetic pickup coil systems on the HL-3 tokamak

HL-3 is a new medium-sized copper conducting tokamak, which is dedicated to the plasma shaping control for plasma high performance and flexible operation, especially the advanced divertor configurations. According to the physics needs of the project, three types of magnetic pickup coils are designed and developed on HL-3 for magnetic field measurements. The coils emphasize different geometry sizes and array layouts. The coils are installed carefully by using high-precision positioning equipment to ensure the measurement accuracy of the system. After calibration, the magnetic field measurements are supplied for real-time equilibrium reconstruction and plasma control, e.g., with snowflake-shaped divertor configuration reconstruction. Mirnov coils satisfy the requirements for physical analysis, including determining the mode number from raw signals and detecting the magnetohydrodynamic instabilities.

The Physics of Electric Saroj Veena: A Folk Musical Instrument from India's North Eastern Region

Saroj Veena is known as a famous Folk musical Instrument in the North eastern part of India. We will discuss about the Shape and Size, Structure, body mechanism of Saroj Veena. In our lab studies, we look at the harmonic structure of standing waves in Saroj Veena strings. Using a digital oscilloscope with a Fast Fourier transform and a magnetic pickup from a Saroj Veena, the experimental data was gathered. Depending on where the string is plucked, the harmonic amplitudes in the measured signal vary, giving the sound a distinct timbre. The relative amplitudes of transverse standing waves in a string were determined from experimental data and predicted by the wave equation when the boundary and beginning circumstances matched the initial shape of the string.

Research on Grid Positioning Strategy of Coupling Mechanism in Wireless Charging System With Offset Angle Variable

The precise positioning of receiving and transmitting coils of the wireless power transmission (WPT) system is the precondition for its efficient operation, and it is necessary and indispensable in practice. The novel grid positioning model and algorithm of four pick-up coils with angles is established by adding the deflection angle of the receiving coil. The corresponding relationship between space magnetic field and pickup coil voltage is analyzed, and the method of magnetic field reconstruction is studied in this paper. Then, considering the sampling workload and effectiveness of pick-up coil voltages at grid point, the pick-up coil voltages were reconstructed and expanded based on variable slope inter-partition sampling and Kriging interpolation, to increase the positioning database. It is found that the positioning accuracy of receiving coil can be improved with the grid sampling interval density increasing, or by using variable slope sampling while the number of grid sampling is unchanged. Under the grid sampling interval of 2.5 cm, the average positioning error of the system is less than 1cm in this paper, and the experimental results are basically consistent with the theoretical results, and the validity of the proposed approach is verified.

Culture-Creating Potential of Audiovisual Technologies in the Mass Art of the Second Half of the Twentieth and Early Twenty-First Centuries

The purpose of the research is to specify and explicate the culture-creating potential of audiovisual technologies, to determine their impact on mass art in the second half of the twentieth and early twenty-first centuries. Research methodology. The article uses the following methods: cultural-historical, which identifies the main evolutionary stages of technical means and audiovisual technologies; methods of description and analysis, which made it possible to reveal the process of creating mass art products with the help of audiovisual technologies; the principle of synergy as a tool for understanding the mutual coordination and mutual influence of culture and technology during the formation of mass art in the second half of the last century. Scientific novelty. The paper first reveals and considers the cultural potential of audiovisual technologies of this period and explicates the related transformational processes in mass art. Conclusions. It has been found that the phenomenon of mass art today functions in a complex technological regime formed in the last century and continues to be developed and function at the global industrial level. It has been proved that thanks to such inventions and technologies as CDs and DVDs, personal computing, magnetic audio recording, magnetic pickup and electric guitar, CGI animation, digitalization, streaming multimedia and sound design, and others, various forms, types and independent genres of mass art (rock culture, Net Art, show programs, 3D video mapping) emerged and developed, the aesthetic and emotional experience of audiovisual product users was enhanced, as well as new professions and specialists (animator, sound engineer, producer, etc.) emerged to operate and improve audiovisual equipment to create a variety of artistic products in various formats in the future.

Virtualization of Guitar Pickups Through Circuit Inversion

A method for circuit system inversion has been recently employed to develop digital algorithms for loudspeaker virtualization. In this brief, building on such promising results, we propose an algorithm that flips the paradigm by virtualizing sensors rather than actuators. In particular, we derive direct and inverse nonlinear circuital models of guitar pickup systems by assuming string vertical excitations, and we then present a virtualization algorithm based on circuit inversion. The proposed circuital models are then implemented in the discrete-time domain in a fully explicit fashion (i.e., with no use of iterative solvers) by employing Wave Digital Filter principles. Finally, we validate and test the designed algorithm on the physical output voltage of a guitar pickup system, making it sound as if acquired by two other magnetic pickups characterized by a different nonlinear behavior.

Effective Area Measurements of Magnetic Pick-Up Coil Sensors for RFX-mod2.

A meaningful characterization of the magnetic configuration of toroidal plasmas requires the identification and estimation of the sources of error on each magnetic measurement of the overall diagnostic system. Thus, the correct characterization of magnetic pick-up coil sensors and the assessment of their reliability becomes a necessary requirement before their permanent installation in the RFX-mod2 experiment. The experimental characterization methodology developed for the three-axes magnetic pick-up coil sensors of RFX-mod2 experiment is presented here. The sensitivity of each sensor is evaluated not only by performing accurate measurements of the effective areas in a time-varying magnetic field, but also by checking the alignment of the magnetic axes through measurements of the effective areas at different rotation angles. Moreover, the effect of thermal cycles on measuring the effective area and the angle of misalignment are evaluated and analyzed.

Exploring turbulence from the Sun to the local interstellar medium: Current challenges and perspectives for future space missions

Turbulence is ubiquitous in space plasmas. It is one of the most important subjects in heliospheric physics, as it plays a fundamental role in the solar wind—local interstellar medium interaction and in controlling energetic particle transport and acceleration processes. Understanding the properties of turbulence in various regions of the heliosphere with vastly different conditions can lead to answers to many unsolved questions opened up by observations of the magnetic field, plasma, pickup ions, energetic particles, radio and UV emissions, and so on. Several space missions have helped us gain preliminary knowledge on turbulence in the outer heliosphere and the very local interstellar medium. Among the past few missions, theVoyagershave paved the way for such investigations. This paper summarizes the open challenges and voices our support for the development of future missions dedicated to the study of turbulence throughout the heliosphere and beyond.

The Simons Observatory: Magnetic Shielding Measurements for the Universal Multiplexing Module

The Simons Observatory (SO) includes four telescopes that will measure the temperature and polarization of the cosmic microwave background using over 60,000 highly sensitive transition-edge bolometers (TES). These multichroic TES bolometers are read out by a microwave RF SQUID multiplexing system with a multiplexing factor of 910. Given that both TESes and SQUIDs are susceptible to magnetic field pickup and that it is hard to predict how they will respond to such fields, it is important to characterize the magnetic response of these systems empirically. This information can then be used to limit spurious signals by informing magnetic shielding designs for the detectors and readout. This paper focuses on measurements of magnetic pickup with different magnetic shielding configurations for the SO universal multiplexing module (UMM), which contains the SQUIDs, associated resonators, and TES bias circuit. The magnetic pickup of a prototype UMM was tested under three shielding configurations: no shielding (copper packaging), aluminum packaging for the UMM, and a tin/lead-plated shield surrounding the entire dilution refrigerator 100 mK cold stage. The measurements show that the aluminum packaging outperforms the copper packaging by a shielding factor of 8-10, and adding the tin/lead-plated 1K shield further increases the relative shielding factor in the aluminum configuration by 1-2 orders of magnitude.

Mode structure measurements of ion cyclotron emission and sub-cyclotron modes on DIII-D

We report mode structure measurements of coherent ion cyclotron emission (ICE) and sub-cyclotron modes on DIII-D. Through a dedicated experiment, we aimed to characterize a variety of modes via the upgraded ICE diagnostic in both L- and H-mode plasmas. In the L-mode plasmas, autopower spectrum peaks at harmonics of the ion cyclotron frequency f ci were observed and are localized in the core of the plasma. Sub-cyclotron modes (f ∼ 0.5f ci) were also observed in L-mode plasmas when the toroidal magnetic field strength was lowered from B T = 2.17 T. In H-mode plasmas, many ICE harmonics localized to the plasma edge were observed, with some exceeding the nominal ICE diagnostic bandwidth of f ∈ [0, 100] MHz. Polarization estimates made using an orthogonal pair of vertical and horizontal magnetic pickup loops on the outer wall of the machine indicate that ICE and sub-cyclotron modes have compressional polarization at the plasma edge, the latter being consistent with simulation efforts for comparable DIII-D plasmas. For all modes, the same harmonics are observed on both the centerpost and outer wall loops, indicating that ICE is poloidally extended. Finally, toroidal mode numbers were calculated using three outer wall loops for both core ICE and sub-cyclotron modes in L-mode plasmas. The sub-cyclotron case served as a benchmark for our calculation method, with measured numbers of n ∈ [−24, −18] roughly agreeing with heuristic estimates of n ∈ [−20, −13]. Core ICE mode numbers were measured to be n ∈ [−10, 5], which is comparable to measurements made on other machines.

Real-time plasma horizontal displacement estimator based on the neural network

Plasma displacement diagnostics is one of the basic diagnostics for evaluating the plasma operating state in tokamak devices. It is related to the plasma current centroid and generally obtained by integrating and calculating the induced voltage in the displacement coils. This induced voltage is derived from the magnetic field generated by the plasma. If the induced voltage is not solely due to the plasma magnetic field, there will be an unreal deviation in the plasma displacement. In J-TEXT, this phenomenon usually occurs when the Resonant Magnetic Perturbation (RMP) coils close to the displacement coils are energized. For long pulse tokamak devices, the source of the unreal deviation may be drifting integrators or radiation-induced voltages in the magnetic pickup coils, not only the RMP coils. To solve this problem, this paper proposes a real-time non-magnetic plasma horizontal displacement measurement method using a deep fully connected neural network. The soft-X ray (SXR) diagnostic data and the plasma displacement diagnostic data are used as the training data for the network. The training and testing results show that the network obtains a satisfactory fitting effect. On the other hand, to deploy this network for real-time diagnostics, this paper has designed and developed a plasma horizontal displacement estimator based on J-TEXT real-time framework (JRTF) in J-TEXT. The experimental results show that the real-time estimator is sufficient for real-time plasma displacement diagnostics. The feasibility of establishing real-time plasma displacement diagnostics based on the SXR diagnostic system has been verified.

Plasma column position measurements using magnetic diagnostics in ADITYA-U tokamak

Due to several forces acting on the plasma column in a tokamak, the plasma column tends to move horizontally and/or vertically leading to many adverse events including termination of plasma. Precise measurement of plasma column position throughout the discharge with good temporal resolution in the real time is hence necessary in order to restrict the column movement using the stabilizing equilibrium magnetic fields. The plasma column position is measured by several magnetic diagnostics such as magnetic pick-up probe, Mirnov coil, Sine-Cosine coil along with flux loops in ADITYA Upgrade tokamak (ADITYA-U). In spite of the simplicity of the measurement principle of these probes as well as of their construction, obtaining the position of the plasma column is not very straightforward. The diversity of all these magnetic diagnostics in terms of their structures, installation location, mounting scenario etc leads to improper position estimations as these probes are being affected differently by the unwanted magnetic pick-ups. These unwanted pickups, especially those arising from vessel eddies, are successfully removed by introducing a scaling method for all the above-mentioned position probes in ADITYA-U based on the in situ calibration of these probes. The correction factors are deduced by estimating the known positions of a central current carrying conductor correctly using the probe measurements during the in situ calibration. These correction factors are used for estimating the plasma column position in the tokamak experiment along with proper nullification of magnetic fields arising from other magnets during tokamak operation. The plasma column position estimation from different magnetic probes are compared with each other and also with those estimated from diagnostics other than the magnetic ones.

Rotational Vibration Test Apparatus for Laser Vibrometer Verification

<div class="section abstract"><div class="htmlview paragraph">Prior to making rotational vibration measurements with a laser vibrometer, it is good practice to establish that the instrument is operating properly. This can be accomplished by comparative measurement of a rotational vibration source with known amplitude and frequency. This paper describes the design and development of a rotational vibration apparatus with known amplitude and frequency to be used as a reference for comparison to concurrent and co-located measurements made by a rotational laser vibrometer (RLV). The comparative measurements acquired with the apparatus are helpful to verify proper laser vibrometer operation in between regular calibration intervals, and/or whenever the functionality of the vibrometer is suspect. In the subject apparatus, a Cardan shaft with variable input speed and angle is used to provide output torsional vibration with variable frequency and amplitude. Previously derived equations of motion for Cardan joints are used to estimate operating amplitude versus speed relationship for the apparatus. To provide an independent rotational vibration measurement for comparison to the laser, a ferromagnetic toothed wheel and magnetic pickup are used. The design of the Cardan shaft and adjustable support table are described, followed by the design of the variable speed electric drive system and controller. For the finished apparatus, example operating data from the reference sensor are compared to laser vibrometer data, and to the theoretical prediction of output torsional velocity from the Cardan joint equations of motion. Finally, suggestions for future work are provided. The development and verification of rotational tuned vibration absorbers is provided as a potential additional application of the apparatus.</div></div>

Embedded digital display and warning system of velocity ratio and wheel slip for tractor operated active tillage implements

A microcontroller-based embedded digital display and warning system was developed for measuring wheel slippage, velocity ratio, PTO torque, and draft requirement of active tillage machinery. The hardware system included magnetic pickup sensor for measuring the engine speed, load cells and amplifiers to measure and amplify the sensing unit signals of the draft, proximity sensors for wheel slip, and PTO torque transducer for measuring the torque requirement. It was provided with buzzers and LEDs to warn the operator, whenever slip and velocity ratio were not in the desired range based on the algorithm, for maximum fuel efficiency and tractive performance. It measured slippage, velocity ratio, torque and draft with a maximum absolute variation of 12.90%, 7.92%, 8.99% and 11.57%, respectively. The developed system can be easily adaptable to any combination of tractor and tillage implements, and guide the operator for better soil tilth with lesser energy input.

High resolution density pedestal measurements during edge localized modes by short-pulse reflectometry in the TCV tokamak

This publication presents high spatio-temporal resolution (mm µs−1) density profile measurements of the pedestal top during type I, III, and small edge localized mode (ELM) H-mode plasmas in the tokamak à configuration variable (TCV). These measurements were performed using a novel short-pulse reflectometer. Average inter-ELM density profiles are obtained via conditional averaging using the D trace as ELM indicator. Changes to the pedestal density profile gradients prior to type-III ELMs reveal unique pedestal dynamics leading to the ELM crash which can provide important experimental data for validation of non-linear MHD ELM simulations. The small-ELM scenario is found to feature a ∼25–35 kHz quasi-coherent density fluctuation near the separatrix 0.993–1.05 not observed during a similar type-I ELM discharge. This oscillation is also found in low-field-side magnetic pick-up probes displaying a ballooning character and n = +1 toroidal mode number. This oscillation could help explain the markedly different pedestal dynamics observed in the small-ELM regime.

DESIGN OPTIMIZATION AND PERFORMANCE TEST OF MAGNETIC PICKUP FINGER SEED METERING DEVICE

As the core part of precision seeder, the performance of pickup finger seed metering device directly affects the seeding quality. Aiming at the problem that the traditional pickup finger seed metering device can be easily affected by the performance of spring material, and the reliability of spring decreases with the increase of service time, a magnetic pickup finger seed metering device is designed to open and close the pickup finger by magnetic force, so as to improve the stability of seed metering performance. Through the design and optimization of permanent magnet structure, cam structure and seed taking pickup finger structure, the magnetic force distribution of ring magnet is analysed by using ANSYS Maxwell magnetic simulation software. Under the working speed of 3.9km/h, the vibration frequency, vibration amplitude and magnetic induction intensity were selected for orthogonal test. The experimental results show that the optimal combination of factors is vibration frequency 6Hz, vibration amplitude 3.1mm and magnetic induction intensity 316.34mT. Under the condition of the combination of operation parameters, the seed arrangement performance is 91.7% of the qualified rate, 6.2% of the replant rate and 2.1% of the missed rate, which meets the requirements of the national standard for the performance of the seeder. This study can provide a reference for the optimization of the structure and the improvement of the seed metering performance of the pickup finger seed metering device.

Evaluating Emission Characteristics from Vehicles at Road Test with Different Operating Conditions.(Dept.M)

The present work aims to introduce a new method to evaluate emission characteristics from vehicles al road test condition. The technique is characterized by introducing unique factors representing the equivalent toxic effect of the exhaust species. The method depends on measuring the concentration of exhaust species and calculating a factor called 'conditioned ton taking into consideration the toxic weight of each species relative to CO. For this purpose, a series of measurements were carried out on a specified vehicle to prevent vehicle to-vehicle variation. The vehicle is equipped with an infrared gas analyzer and a magnetic pickup transducer to measure the concentration of exhaust constituents and engine rotational speed, respectively. The measurements were conducted at different vehicle speed and gearshift. The effect of spark timing and tire pressure was also examined. The results indicate that most of the carbon monoxide and unburned hydrocarbons emission appears at higher load as well as near the idling speed, which appears clearly as increase in the relative conditioned ton. The gearshift gives significant effect on the emission considering its analogy with engine load. Retarding the spark timing offers significant reduction in relative conditioned ton in spite of poor engine performance is experienced. It was found also that, the lower tire pressure exhibits significant increase in relative conditioned ton.