Total Current Research Articles

Slit extraction and emittance results of a permanent magnet minimum-B quadrupole electron cyclotron resonance ion source

We present an experimental and simulation study of high charge state ion beams produced with a permanent magnet electron cyclotron resonance ion source (ECRIS) with minimum-B quadrupole magnetic field topology and slit extraction system. The unconventional topology generates fan-shaped plasma flux, favouring a rectangular aperture for beam extraction. We demonstrate successful low-energy transport of the slit beam, achieving up to 25 times higher beam currents compared to a round extraction aperture. Maximum beam intensities are 1.5 and 15 μA for argon 11＋ and 9＋, respectively. The results indicate microwave power-limited beam production. Emittance values are comparable to traditional ECRIS. Unlike in conventional ECRIS, the emittance increases monotonically with increasing charge state due to slit extraction, magnetic topology, and beam transport characteristics. The experimental transport efficiency for helium ranges from 32% to 50%, depending on the total beam current. The losses primarily occur due to the dipole magnet’s insufficient vertical aperture.

Current Tracking and Circulating Current Suppression Super-Twisting Sliding Mode Control for Parallel Operation of EAST Fast Control Power Supply

To quickly output sufficient current for plasma excitation control, parallel operation of a structure of multiple branches is adopted in the Experimental Advanced Superconducting Tokamak (EAST) fast control power supply. During the process of parallel operation of multiple branches in engineering, a larger inductance current sharing reactor is used to suppress the circulating current for the branches, which reduces the dynamic response speed of the output current and increases economic costs. In order to achieve cost savings and improve the dynamic response speed of the output current, the parallel branch current model of the EAST fast control power supply is analyzed, and the current of each branch is reconstructed into two parts: the current flowing to the load end and the circulating current flowing to other branches. Without changing the circuit structure and increasing the additional complex communication system for each branch, observation of the current flowing to the load end from each branch is achieved. Based on the observed current, a super-twisting sliding mode controller (STSMC) is designed to suppress the circulating current flowing through branches. To realize fast output of the branch current and circulating current suppression for the branches, a new STSMC with a linear term and parameter adaptive structure is designed, speeding up the convergence rate of the whole control system. The linear term and designed parameter adaptive structure based on the sliding mode system status ensure fast convergence speed and excellent control performance of the system. Simulation and experiments show that the designed control method can achieve fast output current control for each branch and that the tracking performance of the total output current is good. While reducing the inductance of the current sharing reactor, the circulating current for the branches is effectively suppressed compared with traditional control methods. The proposed method has great significance in cost savings and performance improvement in engineering practice applications.

Experimental study on beam characteristics of μHT-1 thruster under operating conditions adjustment

The micro Hall thruster μHT-1 is designed for space gravitational wave detection missions, and the beam characteristics of the thruster are studied by experiments. A Faraday probe mounted on a three-dimensional moving platform is designed for diagnosing to obtain the beam current density distribution, and the operating conditions of the discharge voltage and the mass flow rate are adjusted in the range of 700∼1200 V and 0.1–0.5 sccm, respectively. In addition, the study further analyze the variation trends of total beam current, discharge current, utilization rate, divergence angle and others. The test results indicate that the μHT-1 thruster can work stably in a wide range of operating conditions, and the beam current expresses a good axisymmetric distribution. Meanwhile, the beam current density gradually decreases along the axial direction and spreads along the radial direction. The current utilization efficiency fluctuates from 53.4 % to 67.7 % when the power is adjusted in the range of 1.45–5.76 W, and the divergence angle increases from 41.3° to 56.7°. The total beam current of the thruster shows a linear increase characteristics with the enhancing of the anode flow and the discharge voltage.

Analysis of Radial Distribution Systems by using Particle Swarm Optimization under Uncertain Conditions

Abstract: Losses in the network are one of the most important parts of a power distribution network, and work should be done to lower their value. The research used the Particle Swarm Optimisation (PSO) metaheuristic algorithm to investigate the impact of concurrently optimising phase balance and conductor size on the planning issues and objective functions of an imbalanced distribution system. These objective functions include power loss, voltage unbalance, total neutral current, and complicated power unbalance. Firstly, the optimisation process is applied to each goal function. Then, they are put together with weights to form a multi-objective optimisation problem. In this study, it was tried to find out how to minimise losses in electrical power distribution networks that aren't fair. Power flow and optimal DG placement are two PSO techniques that may be used to reduce losses. These changes may be applied to existing distribution systems using an effective load-flow method for a three-phase imbalanced radial distribution network. Knowing the node voltage, angle, branch current, actual power loss, wattles power loss, branch losses, etc. helps determine the network's true state. Simple formulae may be used to describe the relationship between the voltage at one end of the distribution system, the voltage at the other end, and the voltage drops throughout the whole system. An approach is developed to identify the relevant variables. The voltage's angle at the target is calculated with its magnitude. It's a process that requires time and effort. From the substation to each terminal node, the constant voltage of 1p.u. is considered. Voltage magnitude and phase angle are varied between repetitions, and voltage reductions are computed using the new parameters. The suggested approach has been applied to 19- and 25-node networks with unequal distribution. To demonstrate its efficacy, the recommended approach's speed requirements were compared to those of another recently developed technology. Good outcomes are achieved, and DG proves to be a viable option for reducing costs and improving performance.

Electron Dynamics in Open Quantum Systems: The Driven Liouville-von Neumann Methodology within Time-Dependent Density Functional Theory.

A first-principles approach to describe electron dynamics in open quantum systems driven far from equilibrium via external time-dependent stimuli is introduced. Within this approach, the driven Liouville-von Neumann methodology is used to impose open boundary conditions on finite model systems whose dynamics is described using time-dependent density functional theory. As a proof of concept, the developed methodology is applied to simple spin-compensated model systems, including a hydrogen chain and a graphitic molecular junction. Good agreement between steady-state total currents obtained via direct propagation and those obtained from the self-consistent solution of the corresponding Sylvester equation indicates the validity of the implementation. The capability of the new computational approach to analyze, from first principles, non-equilibrium dynamics of open quantum systems in terms of temporally and spatially resolved current densities is demonstrated. Future extensions of the approach toward the description of dynamical magnetization and decoherence effects are briefly discussed.

In situ detection with interdigitated array electrodes towards the platinum-catalyzed oxygen reduction reaction: Size effect and the reaction pathway

Platinum has long been recognized as a vital catalyst in energy conversion and utilization, particularly in oxygen reduction reaction (ORR), due to its exceptional catalytic activity. However, its exorbitant cost and scarcity have motivated researchers to explore the size-activity correlation of Pt catalysts in ORR, aiming to reduce Pt loading density while preserving high catalytic performance. In this work, we concentrate on the interdigitated-array(IDA)-electrodes-based precise detection of the influence of Pt cluster size on catalytic ability, focusing on (1) Direct synthesis of Pt catalyst onto electrodes surface, rather than offline preparation and pasting, to avoid interference from other chemicals and changes to the surface status of catalyst particles; (2) Use of IDA electrodes with largely improved sensitivity for in-situ detection of reaction intermediates (H2O2) and provide insight into the reaction pathway and electron transfer process. It indicates that the specific activity and mass activity are larger for the smaller-sized Pt cluster. Specifically, the proportion of different electron transfer pathways was analyzed with IDA results, and with the same amount of Pt catalyst loading, the smaller-sized Pt cluster produces a higher percent of H2O2; the smaller-sized Pt catalyzed ORR undergoes less proportion of 4-electron pathway than the larger-sized Pt catalyst (about 43% total catalytic current is contributed by the 4-electron pathway for the #6 Pt catalyst, and this number raises to 98% for the #1 Pt catalyst).

HTS conductor coil by in-situ winding technology for large-scale high-field magnet

High temperature superconducting (HTS) conductors have become important candidates to be used in large-scale high-field magnets, owing to its high critical current density as well as good mechanical properties. At present, there are various forms of HTS conductors proposed. In this work, we reported the fabrication of the REBCO HTS coil using in-situ winding technology. The six-layer coil with a diameter of 410 mm achieved a total current of 2562 A, and generated a central magnetic field of 7.8 mT at 77 K. The stress, deformation, and defect caused during conventional winding procedure could be significantly decreased using in-situ winding technology, indicating it has great potential for the large-scale high-field magnets in next-generation fusion reactors.

MOSFET-based HTS flux pump

We have developed a high-temperature superconducting (HTS) flux pump using high-power metal-oxide-semiconductor field-effect transistors (MOSFETs) for switching. For its primary coil, two commercial transformers are utilized, each consisting of two copper coils wound on a single iron core, which enables changing the load current over primary current ratio (101 or 194) between the primary and secondary coils. Full-wave rectification is achieved with two half-wave secondary circuits, each of them having six HTS one-turn coils to lower the resistance. Each secondary coil is composed out of nickel-reinforced BSCCO tapes, where 12 MOSFETs have been soldered in parallel straight to the tapes and controlled with analog electronics. Secondary coils are clamped to custom-made copper-stabilized HTS current leads. A support structure for keeping the HTS coils in place was 3D-printed using cryogenic-compatible composite material PETG-CF20. Resistances of the two secondary circuits were measured to be 4 and 7 at 77 K with a total critical current of 980 A. We successfully ramped up a 50 µH Conductor on Round Core solenoid at 77 K using our HTS flux pump with 50 Hz AC voltage source. We achieved a maximal load current of 900 A and exceeded the 715 A critical current of the solenoid. During the thermal runaway of the magnet, the increased load voltage limits the maximum load current supplied by the flux pump.

Realization of a filter-free wavelength image sensor and imaging system for visualization of wavelength information

In this study, we fabricated a filter-free wavelength image sensor for the two-dimensional visualization of wavelength information, in addition to light intensity, and realized an imaging system. In this sensor, the electrons generated in silicon in different distributions at each wavelength are divided into two parts by the potential peaks. The wavelength can be identified from the current ratio, and the light intensity can be determined from the total current. In the proposed structure, the pixel current is sequentially output by controlling the rows and columns. The layout was designed based on the proposed structure and was fabricated at the Toyohashi University of Technology LSI factory. An imaging system was constructed using operational amplifiers, A/D converters, and a microcontroller. The ratio and sum of the two signals obtained from the sensor responded linearly to the wavelength and light intensity. The wavelength response was independent of changes in the light intensity. Even when the spot was narrowed down, the response was obtained only at the corresponding pixel and succeeded in the simultaneous imaging of the intensity and wavelength. The above results can be applied to cell analysis, such as multiple fluorescence staining, where multiple fluorescence signals are detected simultaneously.

Mixtures of self-propelled particles interacting with asymmetric obstacles.

In the presence of an obstacle, active particles condensate into a surface "wetting" layer due to persistent motion. If the obstacle is asymmetric, a rectification current arises in addition to wetting. Asymmetric geometries are therefore commonly used to concentrate microorganisms like bacteria and sperms. However, most studies neglect the fact that biological active matter is diverse, composed of individuals with distinct self-propulsions. Using simulations, we study a mixture of "fast" and "slow" active Brownian disks in two dimensions interacting with large half-disk obstacles. With this prototypical obstacle geometry, we analyze how the stationary collective behavior depends on the degree of self-propulsion "diversity," defined as proportional to the difference between the self-propulsion speeds, while keeping the average self-propulsion speed fixed. A wetting layer rich in fast particles arises. The rectification current is amplified by speed diversity due to a superlinear dependence of rectification on self-propulsion speed, which arises from cooperative effects. Thus, the total rectification current cannot be obtained from an effective one-component active fluid with the same average self-propulsion speed, highlighting the importance of considering diversity in active matter.

Development and research of a slow-wave system for a miniature W-band multibeam traveling wave lamp

The results of the development of a meander-type slow-wave system (SS) with metal supports for a miniature high-power W-band traveling wave lamp (TWT) with two ribbon electron beams are presented. Using a three-dimensional finite element software package, the electrodynamic parameters of the GS were studied. A two-section model of a TWT amplifier with a discontinuity has been developed to prevent self-excitation. Three-dimensional modeling of electron-wave interaction was carried out. It was found that with a total beam current of 200 mA in linear mode, the gain exceeds 30 dB in the frequency band 95.4...97.75 GHz, and the output power in saturation mode reaches 120 W. A technology for manufacturing SS based on laser microprocessing of thin copper plates is proposed. Test samples of the SS were manufactured and verified using optical and scanning microscopy.

Optimization of the cathodic protection system for the main pipelines

This study investigated the multi-criteria task of optimizing the operating modes of cathodic protection stations (CPS), considering monitoring data, geological conditions at the pipeline installation site, climatic or seasonal changes, and other factors. The relevance of this research is associated with a comprehensive solution to the problem of increasing the durability and reliability of trunk pipelines to reduce accidents at their facilities by ensuring the efficiency of electrochemical protection (EChP) systems. The problems of existing EChP systems are analyzed, where the elimination of anode zones ("lack of protection") due to cathodic polarization is carried out without operational consideration of environmental conditions, as a rule, with a margin in terms of protective potential, which often leads to "overprotection", resulting in increased power consumption, gas formation on the metal surface, and detachment and wear insulation of pipelines. The aim of this research is to create a method for optimal regulation of the operation modes of the main pipelines and an adaptive electrochemical protection system that provides control and parameter management of cathodic protection stations, considering changes in external conditions on individual linear sections of main pipelines. Tasks: to develop an adjustment method for finding the effect of the CPS on the value of potentials at control points along the pipeline route; to develop a multicriteria optimization model for regulating the operation modes of the CPS; and to provide an example of testing the method of optimal regulation on the objects of the linear part of the existing main gas pipeline. The following results were obtained. A method is proposed for determining the effect of CPS operating modes on the value of potentials at control points in the mode of interrupting the protection current of other stations. An optimization model was formed according to the criterion of uniformity of the distribution of the protective potential "pipe-ground" along the pipeline route and according to the criterion of the minimum total protective current of all CPSs on a given section of the main pipeline. Conclusions. The scientific novelty of the results obtained is associated with the development of an original optimization method that allows scientifically determining the operation modes of the CPS to ensure the protection of the main pipeline both in time and length with reduced operating costs and adaptability to changes in climatic, seasonal, and geological conditions at the pipeline installation site. The effectiveness of the proposed approach is illustrated by the regulation of the parameters of the CPS based on the monitoring data of the section of the main gas pipeline of the oil and gas complex of the Republic of Kazakhstan.

MISHEMT intrinsic voltage gain under multiple channel output characteristics

In this paper the MISHEMT device (metal/Si3N4/AlGaN/AlN/GaN - metal–insulator–semiconductor high electron mobility transistor) is studied focusing mainly on the impact of the multiple conductions on the intrinsic voltage gain (A v). It is shown that the total drain current is composed of three different drain current components, whereof one is related to the MIS channel and the other two are related to high electron mobility transistor (HEMT) channels. The device output characteristics present double drain voltage saturation that gives rise to a double plateau in the saturation region of the output characteristics. This behavior relies also on the gate voltage, so the output characteristics and analog parameters extraction are bias dependent. The intrinsic voltage gain increases thanks to the early voltage increment in the second plateau where HEMT conduction is dominant. Electron concentration profiles were simulated in order to investigate the device saturation regime.

Analysis of signal cable noise currents in nuclear reactors under high neutron flux irradiation

Cables are indispensable in nuclear power plants for transmitting data measured by various types of detectors, such as self-powered neutron detectors (SPNDs). These cables will generate disturbing signals that must be accurately distinguished and eliminated. Given that the cable current is not very significant, previous research has focused on SPND, with little attention paid to cable evaluation and validation. This paper specifically focuses on the quantitative analysis of cables and proposes a theoretical model to predict cable noise. In this model, the reaction characteristics between irradiated neutrons and cables were discussed thoroughly. Based on the Monte Carlo method, a comprehensive simulation approach of neutron sensitivity was introduced and long-term irradiation experiments in a heavy water reactor (HWR) were designed to verify this model. The theoretical results of this method agree quite well with the experimental measurements, proving that the model is reliable and exhibits excellent accuracy. The experimental data also show that the cable current accounts for approximately 0.2% of the total current at the initial moment, but as the detector gradually depletes, it will contribute more than 2%, making it a non-negligible proportion of the total signal current.

Generation of the high power by a coaxial dielectric barrier discharge with a perforated electrode in atmospheric pressure air

The power is believed to play an important role in the treatment effects in both direct and indirect plasma applications. Generation of the high power has been realized by using a perforated inner electrode for a coaxial dielectric barrier discharge (DBD) in atmospheric pressure air. Compared with a non-perforated inner electrode, the perforated electrode has a 10%–20% and 10%–30% increase in the applied power and the discharge power, respectively. The strengthened local electric field of the perforated electrode in the coaxial DBD provides favorable conditions for the generation of the micro-discharge, thus increasing the power. To shed light on the reasons for the increase in the power, an extensive analysis of the optical and electrical characteristics of the DBD with the perforated electrode and the non-perforated one was carried out, including transferred charge, total current, number of discharge pulses, dielectric capacitance, gap capacitance, vibrational and rotational temperatures, and electron temperature trend.

Tolerability and blinding of high-definition transcranial direct current stimulation among older adults at intensities of up to 4 mA per electrode

BackgroundFew studies have investigated tolerability, blinding, and double-blinding of High-Definition transcranial Direct Current Stimulation (HD-tDCS) at amplitudes above 2 milliamps (mA). ObjectiveWe examined a) tolerability of HD-tDCS during stimulation sessions and b) blinding and double blinding of participants and study team members. MethodsData from a mixed neurologic sample of 292 older adults were pooled from 3046 HD-tDCS sessions (2329 active; 717 sham). Per electrode amplitudes ranged from 1 mA to 4 mA with total currents up to 10 mA. Participants completed a standardized sensation (tolerability) questionnaire after each session. Participants and study team members stated whether the participant received active or sham stimulation at the end of various sessions. Data were collapsed into the presence/absence of a symptom due to low rates of positive responding and were analyzed for both differences and bioequivalency. ResultsThere were no safety-related adverse events. HD-tDCS was well tolerated with mostly no (“none”) or “mild” sensations reported across sessions, regardless of active or sham condition and in both stimulation naïve and experienced participants. There were no significant differences in side effects between active and sham, with some achieving bioequivalence. Tingling and itching were significantly more common after lower (<2 mA) than higher (≥3 mA) amplitude active sessions, while skin redness was significantly more common after higher amplitudes. Blinding was effective at the participant and study team levels. ConclusionsHD-tDCS was well tolerated with center electrode amplitudes up to 4 mA. The bimodal ramp-up/down format of the sham was effective for blinding. These results support higher scalp-based amplitudes that enable greater brain-based current intensities in older adults.

Numerical simulation of coupling behavior in coaxial hybrid arc welding apparatus

Double-layer coaxial hybrid arcing technology has been developed based on an inner constraint arc and an outer ring arc; the heat and pressure properties of the arc source are supposed to be decoupled and leading to improved controllability of the weld pool thermal-force state. But, the coupling state between the two arcs is not uncovered, and the process window for stable hybrid arc is narrow. In this study, a numerical model of the coaxial hybrid arc system is established, the influence of the water-cooled nozzle on the arc is considered, and the model's accuracy is verified by the measured arc pressure. The physical fields, such as temperature, velocity, and current density distribution, of the hybrid arc are calculated, and the influence of the inner constraint arc current or outer ring arc current on arc pressure and the coupling state in the hybrid arc are uncovered. It was found that (1) at the center of the stable hybrid arc, the current density, magnetic flux intensity, Lorentz force, and arc pressure with a rise in constraint arc current are higher than with a rise in outer arc current; (2) given the total current, adjust the proportion of the inner or outer arc currents, the total heat input basically remains unchanged; and (3) the cause of the arc collapse phenomenon, which is challenging to explain experimentally: the non-ionized gas layer in the orifice throat is broken through.

On the Child–Langmuir law in one, two, and three dimensions

We consider the limiting current from an emitting patch whose size is much smaller than the anode–cathode spacing. The limiting current is formulated in terms of an integral equation. It is solved iteratively, first to numerically recover the classical one-dimensional Child–Langmuir law, including Jaffe's extension to a constant, nonzero electron emission velocity. We extend to two-dimensions in which electron emission is restricted to an infinitely long stripe with infinitesimally narrow stripe width so that the emitted electrons form an electron sheet. We next extend to three-dimensions in which electron emission is restricted to a square tile (or a circular patch) with an infinitesimally small tile size (or patch radius) so that the emitted electrons form a needlelike line charge. Surprisingly, for the electron needle problem, we only find the null solution for the total line charge current, regardless of the assumed initial electron velocity. For the electron sheet problem, we also find only the null solution for the total sheet current if the electron emission velocity is assumed to be zero, and the total maximum sheet current becomes a finite, nonzero value if the electron emission velocity is assumed to be nonzero. These seemingly paradoxical results are shown to be consistent with the earlier works of the Child–Langmuir law of higher dimensions. They are also consistent with, or perhaps even anticipated by, the more recent theories and simulations on thermionic cathodes that used realistic work function distributions to account for patchy, non-uniform electron emission. The mathematical subtleties are discussed.

Plasma Pressure Distribution of Ions and Electrons in the Inner Magnetosphere During CIR Driven Storms Observed During Arase Era

AbstractUsing Arase observations of the inner magnetosphere during 26 CIR‐driven geomagnetic storms with minimum Sym‐H between −33 and −86 nT, we investigated ring current pressure development of ions (H+, He+, O+) and electron during prestorm, main, early recovery and late recovery phases as a function of L‐shell and magnetic local time. It is found that during the main and early recovery phase of the storms the ion pressure is asymmetric in the inner magnetosphere, leading to a strong partial ring current. The ion pressure becomes symmetric during the late recovery phase. H+ ions with energies of ∼20–50 keV and ∼50–100 keV contribute more to the ring current pressure during the main phase and early/late recovery phase, respectively. O+ ions with energies of ∼10–20 keV contribute significantly during main and early recovery phase. These are consistent with previous studies. The electron pressure was found to be asymmetric during the main, early recovery and late recovery phase. The electron pressure peaks from midnight to the dawn sector. Electrons with energy of &lt;50 keV contribute to the ring current pressure during the main and early recovery phase of the storms. Overall, the electron contribution to the total ring current is found to be ∼11% during the main and early recovery phases. However, the electron contribution is found to be significant (∼22%) in the 03–09 MLT sector during the main and early recovery phase. The results indicate an important role of electrons in the ring current build up.

Carbonization of Corn Leaf Waste for Na-Ion Storage Application Using Water-Soluble Carboxymethyl Cellulose Binder.

Hard carbon materials are considered to be the most practical anode materials for sodium ion batteries because of the rich availability of their resources and potentially low cost. Here, the conversion of corn leaf biomass, a largely available agricultural waste, into carbonaceous materials for Na-ion storage application is reported. Thermal analysis investigation determines the presence of exothermic events occurring during the thermal treatment of the biomass. Accordingly, various temperatures of 400, 500, and 600 °C are selected to perform carbonization treatment trials, leading to the formation of various biocarbons. The materials obtained are characterized by a combination of methods, including X-ray diffraction, electron microscopy, surface evaluation, Raman spectroscopy, and electrochemical characterizations. The Na-ion storage performances of these materials are investigated using water-soluble carboxymethyl cellulose binder, highlighting the influence of the carbonization temperature on the electrochemical performance of biocarbons. Moreover, the influence of post-mechanochemical treatment on the Na-ion storage performance of biocarbons is studied through kinetic evaluations. It is confirmed that reducing the particle sizes and increasing the carbon purity of biocarbons and the formation of gel polymeric networks would improve the Na-ion storage capacity, as well as the pseudocapacitive contribution to the total current. At a high-current density of 500 mA g-1, a specific Na-ion storage capacity of 134 mAh g-1 is recorded on the biocarbon prepared at 600 °C, followed by ball-milling and washing treatment, exhibiting a reduced charge transfer resistance of 49 Ω and an improved Na-ion diffusion coefficient of 4.8 × 10-19 cm2 s-1. This article proposes a simple and effective technique for the preparation of low-cost biocarbons to be used as the anode of Na-ion batteries.