Current Pulse Amplitude Research Articles

Transient Current Analysis of GaN Neutron Detector Based on the SRIM and TCAD Methods

Utilizing Technology Computer Aided Design (TCAD) software, this study determines the optimal thickness and doping concentration for the intrinsic gallium nitride (GaN) layer in a p-i-n GaN diode to improve detection efficiency and reliability. The study examines energy loss and the transient current response induced by alpha and 3H particles within the GaN p-i-n diode. Additionally, TCAD elucidates the transient current behavior arising from electron-hole pair generation, utilizing the Stopping and Range of Ions in Matter SRIM-2013 linear energy transfer distribution as a guide. The simulations disclose that the tailing effect in the transient current response results from radiation-induced hole accumulation. Elevated applied bias results in increased transient current pulse amplitude, attributed to an extended depletion region that boosts carrier collection. These insights are expected to drive advancements in GaN-based neutron detector technology, essential for advancing nuclear and space science applications in the next generation.

Measurement of pulse current during high voltage tests using Rogowski coil with non-inverting integrator

The work is devoted to the development and modelling of the system of pulse current measurement during high-voltage tests and experiments. The proposed measurement system is based on the application of Rogowski coil with non-inverting integrator. The results of numerical modelling of the developed current measurement system are compared with the results of application of a low-inductance shunt resistor, Rogowski coil with passive RC-integrator and Rogowski coil with inverting active integrator in similar measurement systems. Various standard pulse currents including steep edge pulse (1/20 µs), large amplitude current pulse (4/10 µs), lightning pulse current (8/20 µs), switching pulse current (30/80 µs), and 1-3 ms pulse currents are modelled for the comparative test. From the simulation results, it follows that the developed Rogowski coil with the proposed non-inverting integrator has sufficiently high accuracy in a wide frequency band overlapping the frequency band of standard pulse currents in high-voltage tests.

A novel design of energy absorption branch for HVDC circuit breakers

Metal oxide varistors (MOV) used for energy absorption branch in DC circuit breakers are complex enough to meet the requirements for small volume, light weight, and reliability in future high-voltage direct current (HVDC) grids. Therefore, a new energy absorption branch circuit that combines MOV and a liquid metal alloy energy absorber (LMEA) is proposed. Based on the constructed equivalent mathematical model of LMEA, the working principle and energy absorption process of MOV and LMEA in DC breaking process are analysed in PSCAD/EMTDC simulation software. Results demonstrate that LMEA, in contrast to MOV alone, absorbs 2.12 MJ of energy, constituting 35.6% of the total energy. Moreover, LMEA enhances energy dissipation density while reducing volume. Experimental analysis reveals MOV’s energy absorption mechanism via achieving residual voltage with ZnO varistor’s non-linear properties, swiftly transitioning from high to low resistance states to absorb energy. Conversely, LMEA relies on pulse current amplitude to initiate internal arcing, sharply increasing internal resistance for effective energy absorption. Experimental findings validate LMEA’s contribution of one-third of total energy absorption when pulse current amplitude reaches critical arcing threshold, consistent with simulation results. The results provide theoretical support for the engineering application of the new liquid metal alloy energy absorption in DC circuit breakers.

Investigation of recessed‐source/drain SOI feedback FET‐based integrate and fire neuron circuit with compact model of threshold switching devices

AbstractIn this article, the investigation of recessed‐source/drain (Re‐S/D) SOI feedback FET (FBFET)‐based integrate and fire (IF) neuron circuit parameters is presented using a threshold switching device compact model. FBFETs offer high ION and low SS with minimal power consumption, operating efficiently at lower voltages and currents than conventional MOSFETs. Utilizing ION/IOFF ratio and threshold voltage limits (Vt2/Vt1) of the device, a model is developed to mimic hysteresis characteristics, which is then used to implement an IF neuron circuit. Our findings show that altering the Re‐S/D thickness between 0 and 50 nm enhances the ION of the device under study while decreasing hysteresis width. We detected a significant increase in output spike frequency of 46.8% and 65.14% for input current pulse amplitudes of 5 and 20 nA, respectively. Furthermore, increasing the Re‐S/D thickness from 0 to 50 nm led to a significant 29.97% enhancement in spike amplitude. In addition, when using input current pulse amplitudes of 5 and 20 nA, we saw energy savings per spike of 3.36% and 12.7%, respectively. At the same time, there was an increase in power of 8.69% and 9.54%. These enhancements in performance metrics establish our proposed integrate and fire neuron circuit as a promising candidate for efficient neuromorphic system implementation.

The influence of magnetic fields and fluctuating currents in the complex of medical rehabilitation on the state of peripheral blood flow in the early postoperative period of breast cancer

Abstract. Taking into account the high prevalence of complications after radical surgical treatment of breast cancer, medical rehabilitation courses were developed and conducted in the early postoperative period (2–4 days after surgery) with the inclusion of physical factors: fluctuating currents, extended local magnetic therapy, general magnetic therapy, as well as physical therapy, training with biofeedback on the support reaction (balance therapy) and individual sessions with a medical psychologist. Purpose. In a comparative aspect, study the indicators of peripheral microcirculation to assess the effectiveness of various methods of magnetic therapy and fluctuarization in patients operated on for breast cancer in the early postoperative period. Material and methods. The study included 107 women operated on for breast cancer 2–4 days after surgery. Using simple randomization, the patients were divided into 3 groups, comparable in age, clinical and functional indicators; at all stages of the study, the patients underwent clinical, functional and laboratory examinations, and questionnaires. In the 1st group (n=35), in the early postoperative period, in the complex of medical rehabilitation, 10 fluctuarization procedures were carried out using an expanded technique; in the 2nd group (n=35), patients received 10 procedures of expanded magnetic therapy; in the 3rd group (n =37) patients received 10 procedures of general magnetic therapy. In addition to physiotherapy, all patients received a complex of physical therapy, balance therapy and classes with a medical psychologist. Results. In the early stages, fluctuating currents seemed more effective, which, due to chaotic changes in the frequency and amplitude of current pulses, help restore conduction along peripheral nerves and activate muscle fiber contractility, improving hemodynamics. It should be noted the effect of extended and general magnetic therapy on improving the contractility of the muscles of the upper limb and the conductivity of peripheral nerve fibers, as well as on the restoration of capillary blood flow. Early signs of the regeneration process are a restructuring of microvascular regulation, namely an increase in the contribution of nutritional blood flow, the activity of myogenic and neurogenic oscillations in hemodynamics, and an increase in blood flow activity.

Development of a pulsed magnetic field power supply for small size Betatron

In this paper, we present a new structure of capacitor-inductor discharge circuit and develop a pulsed magnetic field power supply for small size Betatron, addressing the urgent need for adjustable pulsed radiation frequencies. The proposed power supply employs insulated gate bipolar transistors (IGBTs) to control the discharge of the energy storage capacitor to the excitation winding, thus generating a pulsed current, which produces a pulsed magnetic field and accelerates the electrons. By adjusting the operating frequency of the IGBTs, the frequency of the pulsed current, and consequently the accelerator pulsed radiation frequency, can be regulated. The proposed design employs dual sustained paths, which are formed by the energy storage capacitor and the excitation winding, as well as a loss-compensation capacitor with the excitation winding. By adjusting the loss-compensation time, the problem of the pulsed current amplitude attenuation due to losses can be overcome, ensuring the stability of the pulsed magnetic field. Experimental results show that the power supply produces a pulsed current up to 220 A, which accelerates the electrons to 6.2 MeV, allowing the accelerator pulsed radiation frequency to be adjusted within a 333-Hz range. The proposed power supply makes small size Betatron suitable for a wide range of applications and provides technical knowledge for other types accelerators.

Reconfigurable spintronic logic gate utilizing precessional magnetization switching

In traditional von Neumann computing architecture, the efficiency of the system is often hindered by the data transmission bottleneck between the processor and memory. A prevalent approach to mitigate this limitation is the use of non-volatile memory for in-memory computing, with spin–orbit torque (SOT) magnetic random-access memory (MRAM) being a leading area of research. In this study, we numerically demonstrate that a precise combination of damping-like and field-like spin–orbit torques can facilitate precessional magnetization switching. This mechanism enables the binary memristivity of magnetic tunnel junctions (MTJs) through the modulation of the amplitude and width of input current pulses. Building on this foundation, we have developed a scheme for a reconfigurable spintronic logic gate capable of directly implementing Boolean functions such as AND, OR, and XOR. This work is anticipated to leverage the sub-nanosecond dynamics of SOT-MRAM cells, potentially catalyzing further experimental developments in spintronic devices for in-memory computing.

68‐2: A New PWM Micro‐LED Pixel Circuit Using LTPO TFTs with Threshold Voltage and IR‐Drop Compensations

We propose a novel pulse width modulation (PWM) micro‐LED pixel circuit utilizing LTPO TFTs. It can compensate for VTH variation, ensuring uniform micro‐LED current pulse width and amplitude. In addition, the circuit exhibits excellent IR‐drop compensation. The fabricated LTPO pixel circuit was found to perform PWM with VTH and IR‐drop compensation.

Effect of peak discharge current on the ion current density on the substrate in the short-pulse HiPIMS

The bombardment of the substrate with accelerated ions from the plasma during the magnetron sputtering process is an effective way of controlling the energy transfer to the coating. One of the ways to increase the ion flux on the substrate is to change the parameters of the discharge power supply pulses. This work investigates the effect of the discharge current pulse amplitude on the average ion current density on the substrate in short-pulse high power impulse magnetron sputtering (s-HiPIMS). During sputtering, the peak discharge current varied from 25 to 250 A with a fixed pulse duration of 6 μs and an average discharge power of 1 kW. Experimental results and theoretical calculations show that the average ion current density on the substrate increases twofold when the amplitude of the discharge current pulses is increased from 25 to 60 A. As the amplitude of the discharge current pulses is further increased, the average ion current density on the substrate stops growing and begins to decrease at currents above 150 A. The paper discusses the reasons for the nonlinear dependence of the average ion current density on the substrate on the amplitude of the discharge current pulses.

Experimental study of liquid aluminum droplet breakup characteristics based on a Drop-on-demand (DOD) magnetohydrodynamic actuation

In magnetohydrodynamic (MHD) drop-on-demand (DOD) actuation, Lorentz force generated in different excitation stages are exerted on the liquid metal jet to form a "push-pull" mechanism, which is crucial for generating accurate and repeatable metal droplets. In this study, the important parameters of the excitation current waveform in the magnetohydrodynamic (MHD) process, including the influence of the excitation voltage pulse width ratio and current amplitude on the velocity, energy, volume, and breakup length of aluminum droplets are studied. The conversion process of surface energy and kinetic energy during the formation and fall stage of liquid droplets is analyzed. The results show that the negative and positive excitation voltage pulse width ratio of the MHD pump has a significant effect on the droplet velocity, breakup time, size, and sphericity. The amplitude of the excitation current and Hartmann number has a significant impact on the generation of stable droplets. The results show that the single droplet ejection state can be achieved within the Ha number between 319.5 and 391.1. As the Ha number increases, the volume, length, kinetic energy and surface energy of the droplets at breakup time also increase. The size of droplets can be adjusted by changing the amplitude of excitation waveform.

Numerical study of transient supercooling performance and thermal stress analysis of segmented annular thermoelectric cooler

A multiphysics-coupled numerical simulation of a segmental annular thermoelectric cooler (SATEC) was performed using a three-dimensional finite element method. A coupling model of the temperature, stress, and electric fields was established based on the three-dimensional transient states. Moreover, the effects of different pulse width (τ), pulse current amplitude (Pa), pulse current shape parameter (m), heat transfer coefficient (h), angle (θ), and length (H) of the thermoelectric leg on the SATEC transient properties and von Mises stress were studied. The results show that τ and Pa are the key influencing factors of SATEC. The larger the h, the more optimized the heat transfer effect of the SATEC hot end. However, when h increased to a certain value, the changes in the transient performance were insignificant. The optimal pulse can be achieved when the input pulse current Iop = 6.47 A and pulse width τ = 20 s. When the length of the thermoelectric leg H4 was 3 mm and the thermoelectric leg angle θ2 was 7°, the performance of SATEC was optimal, with Tc,min being 249.57 K, Tc,max being 279.50 K, thold being 5.5 s, and the maximum von Mises stress being 37.48 MPa. The results show that different supercooling indices and von Mises stresses could be obtained for different pulse current shapes. Geometric optimization of SATEC can improve the cooling performance and reduce the von Mises stress, thereby providing a theoretical reference for practical engineering applications and thermoelectric cooling research.

Experimental and numerical study on atmospheric‐pressure air dielectric barrier discharge via 50 Hz/5000 Hz dual‐frequency excitation

AbstractA dual‐frequency (DF) dielectric barrier discharge, excited by the superposition of a 50 Hz low frequency (LF) and a 5000 Hz intermediate frequency (IF), is proposed to enhance discharge. The effect of the LF voltage component on the breakdown behaviour of the DF discharge during different periods has been studied both experimentally and numerically. The number of high‐current pulses rises as the LF voltage increases. The statistical analysis shows that the number of the current pulse amplitude above 80 mA in the DF discharge reaches nearly 6 times that in the IF discharge. Additionally, the total discharge energy in the DF discharge is significantly higher than that in the IF discharge. The simulation reproduces the temporal variation of the breakdown behaviours in the DF discharge. The simulated results reveal that the maximal electric field strength of the breakdown process is greater in the DF discharge compared to the IF discharge during a half‐period of DF. Finally, the comparison between the IF and DF discharges exhibits that the LF voltage regulates the accumulation of residual charged species on the dielectric surface after the breakdown by modulating the residual voltage between the air gap.

Simulation of lighting characteristics of pulse discharge in cesium vapor

Mathematical modeling of characteristics of intense light source on the basis of high pressure pulse discharge in cesium vapor is performed. The investigated discharge is realized in a long ceramic tube from Al2O3 with an internal diameter of 5 mm. The amount of cesium in the discharge is determined by the value of the saturation pressure at the cold end of the tube. A current pulse with amplitude of 40 A to 250 A is periodically passed through the discharge plasma, with a frequency of 400- 1700 Hz. In the work, a mathematical model based on the equations of radiation gas dynamics is used to simulate discharge. When calculating heat exchange by radiation in plasma and light characteristics of discharge, direct integration of the radiation transfer equation is performed. The model takes into account two mechanisms for heating the walls of the gas discharge tube. Firstly, it is the molecular thermal conductivity of the near wall plasma and secondly, it is the absorption of discharge plasma radiation by walls. As a result of the simulation, the dependencies of plasma pressure and temperature, luminous flux and luminous efficacy of the discharge on the temperature of the cold tube end were investigated for different values of amplitudes of current pulses. It is shown that at all current amplitudes there is a pronounced maximum of luminous efficacy. In all studied modes of discharge combustion color rendering index exceeds Ra > 95. It is shown in particular that if the power embedded per unit of discharge length increases to 400 W/cm, the luminous flux reaches 36000 lm/cm.

Failure behavior of dielectric films for peaking capacitor subjected to surface flashover under nanosecond pulses

The flashover failure and damage of polypropylene (PP) and polyester (PET) films under nanosecond current pulses were experimentally investigated. A nanosecond pulse current test platform was established to study the flashover characteristics, performance degradation, and structural damage of dielectric films under repeated nanosecond current pulses. The accumulation and emission of surface charge influenced by field distortion and trap distribution were analyzed to clarify the mechanism by which the flashover voltage increases linearly with gas pressure at low pressure and saturates at high pressure. The significant effects of pulse energy, gas pressure, and discharge gap on film damage behavior were investigated. The damage pattern of PP and PET films includes surface deformation, reduced flash-voltage tolerance, molecular chain breakage, and group shedding. The damage of PP films is manifested as fine furrows, while PET corresponds to mountainous bumps. With the increasing number of discharges, the breakdown voltage of PP films decreased significantly, while the flash tolerance performance of PET films was more stable. Under the conditions of high pulse current amplitude, small discharge gap, and low air pressure, the damage degree of the film intensifies, which is characterized by severe destruction to the molecular structure and a significant decrease in flashover withstand voltage. Polymer films, flashover, nanosecond current pulses; performance degradation; microstructural damage.

Field-Free Spin-Orbit Torque-Induced Magnetization Switching in the IrMn/CoTb Bilayers with a Spontaneous In-Plane Exchange Bias.

Spin-orbit torque (SOT)-induced magnetization switching in ferrimagnetic materials is promising for application in a new generation of information storage devices. Here, we demonstrate SOT-induced field-free magnetization switching of the perpendicularly magnetized CoTb ferrimagnet layer in the IrMn/CoTb bilayer, in which the in-plane magnetic inversion symmetry is broken by a spontaneous in-plane exchange bias (IEB) established by isothermal crystallization of the IrMn layer. We obtain a significant SOT effective field acting on the CoTb layer and a large effective spin Hall angle in this system, derived by the second harmonic voltage measurement method. Moreover, the IrMn/CoTb bilayer demonstrates multistate magnetic switching behavior with different amplitudes of current pulses at zero field, which can mimic the synaptic weight updates in the neuromorphic network. These findings make the IrMn/CoTb bilayer with spontaneous IEB a promising candidate for potential applications in multilevel storage and neuromorphic computing.

Calibration of terahertz sampling detectors for intense unipolar picosecond current pulses in waveguides

Terahertz pulses are nowadays commonly used in many areas of condensed matter physics to access material properties and explore transport phenomena at fast timescales. However, little work has been devoted to the full characterization of such pulses when confined in waveguides. In this work, we fabricate terahertz photoconductive switch detectors, located at various points along a coplanar waveguide, and sample the electrical pulses that pass by the detectors. Two different but consistent methods were developed to calibrate the pulse amplitude. Notably, we synchronize a commercial pulse generator with the laser in order to sample nanosecond-wide pulses with the photoswitch detectors, effectively turning the setup into an on-chip high-frequency sampling oscilloscope. Both methods give identical results on pulse current, voltage, and field amplitudes and enable an absolute characterization of the electrical pulse propagation along the waveguide. These techniques constitute a reliable tool to explore (non-linear) phenomena such as current or field induced magnetization switching or phase transitions, which take place at high THz intensities.

The Variation of Electrical Pulse Duration Elicits Reliable Network-Mediated Responses of Retinal Ganglion Cells in Normal, Not in Degenerate Primate Retinas.

This study aims to investigate the efficacy of electrical stimulation by comparing network-mediated RGC responses in normal and degenerate retinas using a N-methyl-N-nitrosourea (MNU)-induced non-human primate (NHPs) retinitis pigmentosa (RP) model. Adult cynomolgus monkeys were used for normal and outer retinal degeneration (RD) induced by MNU. The network-mediated RGC responses were recorded from the peripheral retina mounted on an 8 × 8 multielectrode array (MEA). The amplitude and duration of biphasic current pulses were modulated from 1 to 50 μA and 500 to 4000 μs, respectively. The threshold charge density for eliciting a network-mediated RGC response was higher in the RD monkeys than in the normal monkeys (1.47 ± 0.13 mC/cm2 vs. 1.06 ± 0.09 mC/cm2, p < 0.05) at a 500 μs pulse duration. The monkeys required a higher charge density than rodents among the RD models (monkeys; 1.47 ± 0.13 mC/cm2, mouse; 1.04 ± 0.09 mC/cm2, and rat; 1.16 ± 0.16 mC/cm2, p < 0.01). Increasing the pulse amplitude and pulse duration elicited more RGC spikes in the normal primate retinas. However, only pulse amplitude variation elicited more RGC spikes in degenerate primate retinas. Therefore, the pulse strategy for primate RD retinas should be optimized, eventually contributing to retinal prosthetics. Given that RD NHP RGCs are not sensitive to pulse duration, using shorter pulses may potentially be a more charge-effective approach for retinal prosthetics.

Nonuniform Current-Driven Formation and Displacement of the Magnetic Compensation Point in Variable-Width Nanoscale Ferrimagnets.

Nano- and microstructures based on ferrimagnets can demonstrate high efficiency and dynamics of current-induced magnetization switching combined with high stability of spin textures such as bubble domains and skyrmions, which are of practical importance for the development of spintronics and spin-orbitronics. This set of features is usually associated with magnetic momentum or angular momentum compensation states. Here, we experimentally show that the compensation state can be realized locally using nonuniform Joule heating. This effect is observed in the variable-width current guide made of the ferrimagnetic W/Co76Tb24/Ru thin films, where the position of a region heated to the compensation temperature depends linearly on the current pulse amplitude. This approach makes it possible to observe the simultaneous coexistence of Co-dominant and Tb-dominant regions, where current pulses induce spin-orbit torques in opposite directions, leading to local magnetization switching. It is found that the position of a Néel domain wall constraining the switched region lies in the vicinity of the coordinate corresponding to the compensation point but does not coincide with it due to high mobility under the action of spin current. Our findings open an alternative approach for engineering of ferrimagnetic nanodevices with advanced properties for future applications in spintronics, spin-orbitronics, and nanoelectronics.

Direct density modulation of photo-assisted field emission from an RF cold cathode

This paper explores direct density modulation of high-current electron beam emission from an RF cold cathode using optical excitation. We theoretically study the photo-assisted field emission of periodically bunched electron beams of various pulse shapes under the combined excitation of an RF field and an optical field, using an exact quantum model. Both continuous-wave (CW) and pulsed optical fields are considered. The emission current pulse amplitude, pulse width, electron number density per pulse, as well as pulse shape and its harmonic contents are investigated in detail. For CW photon sources in the UV to NIR range (i.e., 200–1200 nm), increasing the optical intensity under an RF bias tends to change the current pulse from a Gaussian to sinusoidal-like shape, thus offering strong flexibility to control the frequency components in beam current emission. Pulsed photon sources combined with an RF field can produce sharp, high-current electron bunches with pulse duration comparable with or even less than that of the optical pulse. A contour map of the density modulation depth is constructed for different combinations of RF and laser fields. The results provide insight into unlocking new opportunities to achieve direct density modulation during electron current emission by optical means.

The characteristics of positive corona discharge at different altitudes

With the vigorous growth of UHV transmission projects, transmission lines crossing high-altitude areas are inevitable, and the degree of corona discharge in high-altitude areas is more intense. The electromagnetic environmental problems caused by corona discharge have gradually become one of the key technical problems restricting UHV transmission in high-altitude areas. To investigate how height affects the positive polarity corona’s corona characteristics, using the movable small corona cage to carry out experiments at four altitude points in the range of 1120 m–4320 m, and measures the corona current pulse and radio interference level of 0.8 mm diameter fine copper wire under different positive voltages. Several conclusions can be drawn from the data analysis, including the following: The average current pulse amplitude grows with altitude, first before decreasing, and the current pulse repetition frequency rises along with altitude. The major conclusions of this essay can serve as a starting point for the study of the corona effect.