High Current Mode Research Articles

CONTROL OF REDUCED ELECTRIC FIELD IN THE POSITIVE COLUMN OF A PULSED DISCHARGE IN CO2

The electric field strength in the positive column of dc and bipolar pulsed discharges in carbon dioxide was determined by the method of moving electrodes. It is shown that an increase in the frequency of the pulse voltage leads to the electric field strength increase. The following values of the reduced electric field E/p for a gas pressure of 0.5 Torr were obtained: 22.5 V/(cmTorr) for dc discharge, 30 V/(cmTorr) for pulsed discharge at 20 kHz for lowcurrent mode and 32 V/(cmTorr) for high-current mode, and 36.6 V/(cmTorr) for 75 kHz. We see that in the dc discharge, the reduced electric field is weak, due to which the exchange of vibrational energy between CO2 molecules dominates the conversion process. The increase of the electric field strength in the positive column of a pulsed discharge, especially under conditions of gas heating, allows obtaining E/N > 100 Td when the process of direct dissociation of CO2 molecules by fast electrons makes the main contribution to the conversion process.

High Gain, Low Noise, Low Voltage, and Low Power Current Mode Up-Conversion Mixer for 5G Applications

A high conversion gain, low noise up-conversion mixer for 5G New Radio band (850 MHz) Internet of Thing (IoT) applications implemented in UMC 0.18 μm standard CMOS technology is presented. The proposed mixer is based on the Flipped voltage follower current mirror with a passive switching circuit. The proposed up-conversion mixer achieves a noise figure (NF) of 4.4 dB, maximum Conversion Gain (CG) of 33.85 dB, maximum input third-order intercept point (IIP3) of 33.16 dBm, and output third-order intercept point (OIP3) of 11.89 dBm. It has a total power consumption of 23.58 mW with a 1.2 V supply voltage. The overall chip area of the design is 26.5 µm × 54.9 µm.

Plasma hysteresis caused by high-voltage breakdown in gridded microwave discharge ion thruster μ10

A cluster of gridded microwave discharge ion thrusters μ10 contributed to the success of the deep space exploration missions of the Japanese asteroid explorers Hayabusa and Hayabusa2. To meet the demands of the next mission DESTINY+, the maximum ion beam current was increased to 200 mA from the 170 mA used in Hayabusa2 by redesigning the magnetic field and grid configuration. However, this thruster exhibited the plasma hysteresis caused by a high-voltage breakdown. Specifically, the ion beam current (i.e. thrust) has two modes at a given propellant flow rate, namely high- and low-current modes. In nominal operation, the thruster operates in high-current mode. However, once a high-voltage breakdown occurs, the ion beam current transitions to and remains in low-current mode, which significantly decreases thrust efficiency. In this paper, based on an investigation of the physical mechanism that causes the hysteresis, we proposed a recovery method to return the thruster operation to high-current mode. In the investigation, we focused on the plasma mode transition, where plasma is generated inside the waveguide. We experimentally investigated the hysteresis by varying the grid configuration and the waveguide geometries while maintaining the magnetic field. The results show that the neutral density and plasma conditions inside the waveguide are strongly related to the hysteresis, which indicates that the main cause of the hysteresis is plasma generation inside the waveguide.

Optimizing the Opening Velocity for a Vacuum Circuit Breaker With Cup-Type Axial Magnetic Field Contacts

This article extends the quantitative method of optimizing the opening velocities for a vacuum circuit breaker (VCB) with cup-type axial magnetic field (AMF) contacts. The material of the AMF contact is Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">50</sub> Cr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">50</sub> . We define v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> as the initial opening velocity over half the full contact gap and v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> as the average velocity over the full contact gap of 20 mm. We optimize v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> and v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> using the transition of anode-discharging modes, of which we combine the footpoint mode and anode spot mode into a large-gap high-current (LGHC) mode. The experiment shows that v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> should be higher than a threshold velocity v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1_th</sub> , which corresponds to a peak critical contact gap d <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1_th</sub> for the transitions of an intense arc mode into a diffuse arc mode, in high-current interruption. The higher v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> is than v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1_th</sub> , the faster the intense arc mode evolves into the diffuse arc mode. This helps successfully interrupt the short-circuit current in a short arcing time. Another threshold velocity, v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2_th</sub> , corresponds to the maximum critical contact d <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">II_th</sub> for the formation of an LGHC mode in the second arc current half-wave. A high v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> design needs v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> to be lower than v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2_th</sub> . The lower v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> is than v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2_th</sub> , the better the VCB avoids the LGHC mode in high-current interruption. This helps interruption over a long arcing time. We propose an intelligent opening and breaking operation for VCBs with cup-type AMF contacts, whereby the VCB opens with different opening velocities according to the short-circuit current level.

Radiation Power of a High-Current Vacuum Arc Stabilized by an Axial Magnetic Field in the Visible and UV Ranges of the Spectrum

Using a silicon photodiode, we have performed measurements of the power emitted by a vacuum arc in the UV and visible spectral ranges. Measurements have been carried out upon stabilizing the arc by an axial magnetic field in high-current modes with developed anodic activity. The power of radiation emerging from the arc through the side surface is measured. The results obtained show that, when analyzing the energy balance of a high-current vacuum arc, the radiation must be taken into account.

A data-driven complex network approach for planning sustainable and inclusive urban mobility hubs and services

New mobility services that facilitate multimodal options are important for strategic urban transport systems planning. Part of this strategy is municipal investment in urban mobility hubs to increase access to mobility services. We present a new evaluation framework and algorthim to locate and assess the sustainability and equity impacts of hubs in cities. Scenarios are used to evaluate hub investment strategies in different cities that prioritize (1) current mode split, (2) high transit capacity, and (3) multimodal services. From an equity perspective, high transit capacity and multimodal hub strategies include more low-income areas than current mode split, which covers middle-income areas most. Travel times to access the nearest hub in Portland by low-income households is ∼20–40 min compared to high-income households requiring ∼25–30 min. Seattle and Vancouver perform better requiring ∼15–20 min for low-income compared to ∼25–35 min for high-income households. Multimodal hubs are the most efficient requiring ∼15–20 minutes to reach compared to ∼15–30 minutes for high capacity and current mode split scenarios. From a sustainability perspective, ∼10%–50% of the population cannot reach a hub within 30 minutes by public transit compared to &lt;10% by car, and travel time to reach the nearest hub in all three cities by car is &lt;20 min compared to ∼20–40 min by public transit. Between all cities, low-income households representing ∼2%–15% of the total population have no access to a hub by public transit within 30 min compared to high-income households representing ∼1%–3% of the total population. Only in Portland are there low-income households not able to reach a hub by car, and in each city, all high-income households can reach at least one hub by car within 30 min. Our results show how municipalities can strategically invest in public transit and multimodal options to increase the frequency, quality, and overall mobility for low- and medium-income households and improve access to essential amenities for more vulnerable citizens. Municipalities can use our hub evaluation framework to explore alternative transport investment scenarios and spatially locate urban hubs to meet future travel demand, increase adoption of multimodal services, and improve equitable access for all citizens.

BURNING MODES OF A BIPOLAR PULSED DISCHARGE IN CO2

We have studied the burning modes of the bipolar pulsed discharge in CO2 within the frequency range between 20 and 300 kHz and the duty cycle of 11...97 %. The current and voltage waveforms within the pressure range between 0.1 to 1 Torr were registered. We have established that the duty cycle values may affect the axial structure of the discharge considerably causing the voltage drop redistribution across the electrodes. The bipolar pulsed discharge may burn in a high-current mode (with cathode sheaths near every electrode) as well as in a low-current one (with a low discharge current and weak glow). The transition between these modes may be observed at high duty cycle values. We have found that one may make a shift of the complete oscilloscope voltage pattern higher or lower along the voltage axis and produce a self-bias constant voltage the value and sign of which depend on the duty cycle, amplitude and frequency of the applied voltage.

Fault diagnosis with synchrosqueezing transform and optimized deep convolutional neural network: An application in modular multilevel converters

High voltage direct current (HVDC) transmission mode with modular multilevel converters (MMC) topology is the future direction of transmission engineering, and security is their fundamental issue. Submodule fault of MMC in HVDC is the most common problem, nevertheless, traditional time–frequency based diagnosis technology can’t achieve high accuracy. To solve this pain spot, a new diagnosis strategy based on the synchrosqueezing transform (SST) and genetic algorithm optimized deep convolution neural network (GA-DCNN) is proposed in this paper. Firstly, the time–frequency representations (TFRs) of the raw signals which is synthesized by ac current and inner circulating current of the MMC are calculated with SST. Then, DCNN is introduced to learn the underlying features from the TFRs, and its key hyperparameters are optimized with genetic algorithm. Meanwhile, batch normalization, dropout and data augment technologies are explored to prevent DCNN model from overfitting and improve model performance. Compared to traditional SVM and BP-based algorithms, SST-GA-DCNN achieve high diagnosis accuracy. The experimental results show the feasibility and applicability of the proposed fault diagnosis framework.

Parameters of the Ion Flow of the Pulsed Vacuum Flashover Discharge

The plasma flow parameters of nanosecond vacuum flashover were examined in detail. It was found that high-velocity ion flow could be obtained using significantly more compact and cheap equipment than that used earlier. These new results will be useful to the design of new type compact plasma thrusters. It was proven that the plasma charge composition is formed at the low-voltage phase of vacuum discharge. After the analysis of experimental data, there was not found any clear dependence of the ion spectra and the degree of ionization on the flashover amplitude. The ion flow propagates in wide solid angle (up to 60°) and the ion-energy spectra contain several local maxima. The maxima positions coincide for different charge states of ions. The coincidence can be explained by the formation of plasma waves in the ion flow. The strong dependence of maximum and average ion energies on an ion charge was found. When the short interelectrode gap was used in the vacuum arc, discharge occurred at high-current discharge mode (>200 A), leading to a metal electrode consumption. A plasma acceleration model based on the occurrence of ion-acoustic shock waves was proposed.

A Comparative Study of Silicon Carbide Merged PiN Schottky Diodes with Electrical-Thermal Coupled Considerations.

A comparative study of surge current reliability of 1200 V/5 A 4H-SiC (silicon carbide) MPS (Merged PiN Schottky) diodes with different technologies is presented. The influences of device designs in terms of electrical and thermal aspects on the forward conduction performance and surge current capability were studied. Device forward characteristics were simulated and measured. Standard single-pulse surge current tests and thermal impedance measurements were carried to show their surge capability and thermal design differences. An advanced thermal RC (thermal resistance-capacitance) model, with the consideration of current distribution non-uniformity effects, is proposed to accurately calculate the device junction temperature during surge events. It was found that a thinner substrate and a hexagonal layout design are beneficial to the improvement of the bipolar conduction performance in high current mode, as well as the surge current capability. The thinner substrate design also has advantages on thermal aspects, as it presents the lowest thermal resistance. The calculated failure temperature during the surge tests is consistent with the aluminum melting phenomenon, which is regarded as the failure mechanism. It was demonstrated that, for a SiC MPS diode, higher bipolar conduction performance is conducive to restraining the joule heat, and a lower thermal resistance design is able to accelerate the heat dissipation and limit the junction temperature during surge events. In this way, the MPS diode using a thinner substrate and advanced layout design technology is able to achieve 60% higher surge current density capability compared to the other technologies.

Trifold Frequency Multiplier by using Triode for the Feedback System of BEPC II

In BEPC II(Upgrade of Beijing Electron-Position Collider), multi-bunches and high current operation mode is usually used. Due to the influence of high frequency cavity structure or resistance impedance, the beam will be unstable. If the beam is unstable, the luminosity and brightness of the accelerator will be decreased. In order to improve the beam current and brightness of accelerator and the collider luminosity, the beam feedback system is needed to suppress the instability.&#x0D; The trifold frequency multiplier by using triode is simple to operate, and it has good performance. In the experiments, the 500MHz signal was passed through the Triode Frequency Multiplier to get the 1.5GHz signal, and its output amplitude stability is 1.7mV, and its synchronization stability is 3.46ps compared with the 500MHz input signal.

A Novel High Frequency Low Voltage Low Power Current Mode Analog to Digital Converter Pipeline

This paper introduces a novel structure for the realization of a low voltage, low power current-mode analog to the digital converter (ADC) pipeline (12 bits). The proposed structure of the ADC is based on a novel design of a current comparator and Digital to Analog Converter (DAC) structure. This modification allows us to reach a higher speed, lower voltage, and lower power dissipation. ELDO simulators using 0.18 μm, CMOS and TSMC parameters are performed to confirm the workability of this architecture. The proposed ADC is powered with a 1 V supply voltage. It is characterized by wide conversion frequency (350 MHz) and low power consumption that is 2.76 mW.

Comparison of plasma parameters and optical emission in DC, HIPIMS and hybrid DC+HIPIMS modes of magnetron sputtering

Experimental studies of the parameters of the plasma of a magnetron discharge and optical radiation from plasma in the regime of direct current (DC), high-current mode (HIPIMS), and hybrid (DC+HIPIMS) mode for a copper cathode 100 mm in diameter were carried out. The hybrid mode of operation of the magnetron sputtering system was carried out by means of a matching unit of two power supplies APEL-M-5HIPIMS and APEL-M-5PDC. The results of the experiments showed that the plasma concentration at a distance of 120 mm from the cathode has maximum values (5.6·1011 cm−3) in the HIPIMS regime at a frequency of 500 Hz. Measurement of the optical emission spectra for a copper cathode in an argon plasma showed, that at the same average discharge power (500 W), the intensity of the copper ion lines in the high-current and hybrid modes is 3 and 1.5 times, respectively, more than in the DC regime.

Ion source based on a circular anode layer plasma thruster.

A new version of pulsed ion source based on plasma thruster technology has been developed and tested. The ion source design uses a circular anode layer geometry in which the ion beam is extracted radially from the full circumference. The source has been tested for operation in argon, nitrogen, and air at a gas flow rate of up to 20 SCCM with discharge current and voltage measurements in low- and high-current modes. The source, having a simple design and open acceleration gap geometry for observation and photography, is suitable for the treatment of the inner surfaces of pipes and tubes.

Plasma Source for Bipolar Electron-Optical System

The paper presents the experimental study of pulsed plasma source with hollow cathode intended for bipolar electron-optical system with open-boundary plasma. The proposed configuration of the plasma source includes two ring-shaped discharge cells based on plasma thruster technology. The plasma source can operate both in a low-current high-voltage mode and a high-current low-voltage mode. The main attention is paid to the highcurrent mode which is similar to the glow discharge positive column. It is found that along with the discharge in closed electron drift the ignition of additional, non-self-sustained hollow cathode discharge with electron oscillation is possible, thus considerably reducing the voltage of the closed-drift discharge. Current–voltage characteristics of the high-current discharge are measured for these conditions. Using the double probe technique, the local plasma parameters are measured together with their spatial distribution in the discharge region. The maximum plasma density along the plasma source axis is (6.5–6.8)•1012 сm–3.

Effects of gas pressure and discharge current on beam composition in a magnetron discharge ion source.

The magnetron discharge plasma is commonly used in thin film deposition processes, but it can also be utilized for ion beam production. We have developed and investigated an ion source based on planar magnetron discharge. We show that under certain conditions, the discharge, running in a high current pulsed mode, effectively produces plasmas with a high fraction of ions formed from the magnetron target material. The ion beam extracted from the discharge plasma and its composition were studied using a time-of-flight method. The plasma electron temperature was measured by using a double Langmuir probe. We find that the increased working gas pressure and discharge current lower the electron temperature, leading to an increased fraction of target material ions in the plasma and therefore also in the extracted ion beam due to their lower ionization potential compared to that of the working gas.

Plasma source based on ring-shaped anode layer thruster for a bipolar electron-optical system

The conceptual design of pulsed plasma source for plasma-optic application and materials modification are investigated. The source is based on plasma thruster’s technology, that were developed by Goncharov’s group in Institute of Physics (Kiev, Ukraine). The plasma device with its two modified closed-drift anode layer thrusters can operate in low-current high-voltage mode and in high-current plasma mode. Most attention in the paper is focused on the latter mode being similar to a glow discharge with a positive column. The study shows that under certain conditions, the discharge with closed electron drift can be accompanied by non-self-sustained hollow-cathode discharges with oscillating electrons which greatly decrease the auxiliary discharge voltage. Presented in the paper the current–voltage characteristics of this type of high-current discharge and the spatial distributions of plasma parameters are measured in the discharge region with double Langmuir probe techniques. The maximum plasma densities on the central cathode axis are (6.5÷6.8)×1012 cm–3.

Observation of multiply charged states ions in a high-power pulsed reflex discharge

Time-resolved optical emission spectroscopy studies have been made to investigate the elemental/charge composition of the plasma ionic component at pulsed reflex discharge. The discharge plasma has are registered spectral lines neutral atoms and ions of the working gas Ar, Ar1+, Ar2+, and also of the cathode material: Zr, Zr1+, Zr2+, Zr3+. The presence of zirconium in the spectrum attests to the entry of cathode material into the plasma and its subsequent ionization. The variation of spectral line intensity with time in the early stage of the discharge and in the stage of dense plasma existence (time interval from the onset of the discharge up to 4 ms) correlates with the dynamics of plasma parameters. Characteristic times of appearance of excited atoms and ions in the plasma have been determined. The time of appearance of excited Zr* atoms is by the order of magnitude longer than that of Ar*. The stage of high-voltage mode exhibits the lines of excited Ar*, Zr* atoms and Ar+*, Zr+* ions, with the intensity of which sharply increasing during the transition to the high-current mode. The excited Ar2+*, Zr2+*, Zr3+* ions appear later, when the discharge has already gone into the high-current mode.

Resistive random-access memory with an a-Si/SiNx double-layer

Resistive random-access memory (RRAM) with a Ni/SiNx/a-Si/p+-Si structure is presented. In contrast to RRAM devices based on high-k materials, the proposed Si-based device is more attractive and promising because the SiNx and a-Si layers have full compatibility with conventional complementary metal-oxidesemiconductor technology. The proposed device is compared to a control device with a single layer of SiNx. A conduction path containing Si dangling bonds (traps) can be generated in both the SiNx and a-Si layers. The conduction path in each layer can be controlled by the compliance current during the forming process. For high compliance current mode, the double-layer device has a higher ON/OFF ratio (∼104) and lower leakage current (∼10-9 A) than the single-layer device. For low compliance current mode, better non-linearity (∼103) can be obtained when a 1/2 read bias scheme is applied to the cross-point array.

First resolution test results of the Atomki nuclear nanoprobe

In this work we report about the layout, assembly and the first resolution tests of the nuclear nanoprobe at MTA Atomki, Debrecen, Hungary. The nanoprobe setup was installed on the recently inaugurated 2 MV Tandetron accelerator manufactured by High Voltage Engineering Europa B.V. (HVEE). Although the complete Tandetron Laboratory was planned at the first project proposal stage, due to funding limitations the major components were purchased step by step, and so the present layout is only temporary. The necessary building reconstruction was also performed in phases. We present the preliminary experimental results and compare them what to expect in the final configuration using WinTRAX calculations. These calculations include focusing at different working distances, the performance at the planned final length (object distance), as well as scanning simulations using ‘dog-leg’ scan. At the present status it is already worth reporting that the preliminary nanoprobe setup has reached a satisfactory experimental performance of around 200 nm spot size for low current mode, and below 600 nm for high current mode.