Steep Pulse Research Articles

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.

High-frequency irreversible electroporation ablation for the prostate in Beagle dogs.

Ablation procedures have garnered significant attention as a minimally invasive treatment of prostate diseases. However, the feasibility and safety of applying high-frequency irreversible electroporation (H-FIRE) to ablate the Beagle prostate for benign prostatic hyperplasia (BPH) treatment have not been thoroughly explored, the appropriate range of parameters has not been determined. In order to ensure the feasibility and safety of prostate ablation surgery, we conducted a study using Beagle dogs as subjects to investigate prostate tissue. We utilized a composite steep pulse therapy device to perform ablations on 26 lateral lobes of the prostate in 13 Beagles, employing various parameters for different needle distances. The effectiveness of this device was assessed through the observation of the ablation area, intraoperative muscle tremors, postoperative hematological examination, and gross inspection. The findings of our study revealed that 1,000 to 2,000 v/cm in electric field strength, combined with 5 µs pulse width and pulse number 100, is a safe parameter range for ablation of prostate tissue. At the same time, the large electric field strength (2,000 v/cm) has the best ablation effect with the biggest continuous and thorough ablation area. All parameters of H-FIRE were safe for Beagles. H-FIRE ablation for prostate is safe and effective in dogs, which has the potential to be a useful addition to the range of minimally invasive treatments available for the treatment of BPH against this backdrop of increasing surgical practice.

Preventing partial discharge in liquid metal polymer composites under steep voltage pulses

Liquid metal polymer composites (LMPCs) offer viable solutions for deformable electronics, including sensors and actuators. To ensure the longevity of the deformable technologies, partial discharge (PD) must be mitigated as it causes premature material aging and device failure. While studies on the dielectric properties of LMPCs have mainly focused on AC voltage, a large number of deformable applications will inevitably involve power electronics for higher efficiency and power density. Consequently, addressing PD in LMPCs under repetitive steep voltage pulses generated by power electronic switches becomes important. This study employs an electric field cancellation technique using electrets to reduce the PD magnitude and increase the partial discharge inception voltage (PDIV) of LMPCs under steep square voltage waves. We placed either a non-electret or electret thin film on top of LMPC samples and conducted PD experiments in flat and bent test coupon arrangements. The results show that electrets can reduce PD magnitude and increase PDIV in both test arrangements. Furthermore, the study provides deeper insights into the experimental results by conducting the electric field analysis of the LMPC experiments through numerical models.

Noninvasive and Accurate Measuring Method of the MMC and HVDC Circuit Breaker Action Moment Based on Transient E-Field Pulse

This article introduces the measurement and analysis of the transient electric field (E-field) derived from the switching operation of the modular multilevel converter (MMC) and the high voltage direct current (HVdc) circuit breaker (CB) in a 200 kV converter station constructed in the Zhoushan Islands, China. It is revealed that the switching transient E-field in the converter station is a quasi-static field. Although the switching E-field pulse is a kind of electromagnetic interference to the secondary electronic circuit of the converter station, it can be used to accurately monitor the action moment of the MMC and the CB. The action moment of the MMC and the CB can be measured with an error of less than 0.005 ms based on the steep pulse front of the switching E-field pulse. This result, which is far more accurate compared to the measurement using the voltage recording system that comes with the converter station. This is of significance to the relay protection of the HVdc transmission system whose fault rapidly develops. Additionally, this method has the advantage of being noninvasive, flexible, and low cost. It has potential application value in the condition monitoring of the MMC and the HVdc CB.

Development of Non-invasive Endoscope System with Magnetic Anchored Ablation Electrode for Early Cancer of Digestive Tract

This study introduces a non-invasive gastrointestinal early cancer magnetic anchor ablation electrode endoscopy system, including a magnetic anchor module and ablation electrode module. The magnetic anchoring module is composed of an external guide magnet and an internal magnet, made of permanent magnet material NdFeB; the ablation electrode module is based on the modification of the front end lens hood of the existing endoscope (CMD-90D LED electronic upper gastrointestinal endoscope). The new endoscope system not only includes all the functions of the original endoscope, but also introduces magnetic anchoring to enable the ablation electrode to be accurately positioned and controllable in the process of treating tumors, avoiding the phenomenon of gastric perforation; the introduction of steep pulse electric field ablation electrodes realizes the purpose of non-invasive treatment. Its clinical application will become a new method to treat early cancer of the digestive tract.

Development Status of Irreversible Electric Perforated Tumor Ablation Device

This study firstly introduced the mechanism, benefits and applications of irreversible electroporation(IRE) for tumor ablation. In addition, this study also introduced the most advanced IRE systems cleared by FDA or CFDA and IRE research equipment. The clinically licensed IRE systems include the Nanoknife 3.0 of Angiodynamics, the DophiTM N3000's steep pulse therapy system of Sanoway, and compound steep pulse therapy equipment of Reeves Technology IRE research equipment include the BTX and Bio-Rad electroporation devices.

CYCLOGRAMS OF THE ST-25 HALL THRUSTER STARTING

The results of the start sequence diagram selection and experimental tests of the ST-25 Hall thruster intended for using on small spacecraft are presented. In order to reduce the mass and dimensions of the power processing unit of the propulsion system, it is proposed to exclude the hollow cathode keeper power supply from the structure of the power processing unit. The exclusion of the keeper power supply from the power processing unit made it necessary to select the thruster start sequence diagram. Four start sequence diagrams of the ST-25 Hall thruster start-up are considered: a) using a separate high voltage power supply for the hollow cathode keeper; b) using a separate low voltage power supply for the hollow cathode keeper; c) using a discharge power supply connected to the keeper through a high-resistance resistor to the hollow cathode keeper; d) connecting the keeper of the hollow cathode to the discharge power supply through an electronic switch with the possibility of adjusting the duration of the keeper connection to the discharge power supply. The graphs of changes in the thruster’s currents and voltages for various power supply circuits of the hollow cathode keeper are presented. The results of the choice of the start sequence diagram for the Hall engine ST-25 and the experimental studies carried out have shown that the use of an electronic switch with a steep pulse front makes it possible to obtain a reliable thruster start-up when a separate power supply for the keeper is excluded from the power processing unit of the propulsion system. As a result of the work carried out, it became possible to place the power processing unit for a propulsion system based on the ST-25 thruster in a volume of 2U. The possibility of using ST-25 thruster on spacecraft, the onboard electrical power of which is limited up to 200 W were confirmed.

Features of Operation of Transistor Switches in a Half-Bridge Circuit for the Formation of Steep High-Voltage Rectangular Pulses

Features of Operation of Transistor Switches in a Half-Bridge Circuit for the Formation of Steep High-Voltage Rectangular Pulses

Optimization Design of a 40-kJ HTSPPT Module for Inductive Pulsed Power Supply

The topology category based on high-temperature superconducting pulse power transformer (HTSPPT) is an important branch of inductive pulse power supply (IPPS) for rail guns. Optimization design of the HTSPPT can improve the overall performance of the IPPS system. The purpose of this article is to design a 40-kJ air-core HTSPPT module with a high-temperature superconducting (HTS) primary winding and a normally conducting secondary winding. According to the application characteristics of the HTSPPT, under the constraints of the three main performance indicators of critical current, stored energy, and coupling coefficient, the amount of HTS tapes and the volume of the entire HTSPPT are reduced as much as possible. The design of the secondary winding combines the electromagnetic launch requirements for the current pulse in the approximate flat waveform and steep pulse rising edge. With this optimized design, a 43-kJ HTSPPT module with a primary inductance of 79.4 mH, a secondary inductance of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$255.4~\mu \text{H}$ </tex-math></inline-formula> , and a coupling coefficient of 0.97 was obtained. Finally, the maximum stress and strain of the designed HTSPPT in the energy storage state are analyzed through the electromagnetic (EM) structure coupling field.

Infraschall aus technischen Anlagen. Wissenschaftliche Grundlagen für eine Bewertung gesundheitlicher Risiken

Infrasound from technical installations: Scientific basis for an assessment of health risks Background: The pathogenic potential of infrasound from technical sources is significantly underestimated by the public and politicians. Wind turbines are the most common emitters and their rapid rollout means that an increasing number of residents are affected by far reaching pressure pulses. Methods: Research findings relating to causal mechanisms of infrasound are compiled and examined for indications of adverse effects on health. Results: Infrasound is perceived as a stressor and is met with adaptive and defensive responses. Points of attack for toxic effects can be identified a) at cellular level, where membrane processes react with particular sensitivity. This leads to disruption of the microcirculation, muscle contraction and neuronal signal transmission. b) In the cardiovascular system, the effects mentioned in a) cause a reduction in the efficiency of the myocardial muscle coupled with centrally mediated bradycardia, hypertension and reduced cardiac output. c) The signal receptors for the balance system receive infrasound as interference and produce a clinical picture similar to motion sickness. d) In the brain, infrasound is unconsciously perceived in areas that are involved in the control of autonomic functions (incl. respiratory frequency and blood pressure) and in emotional control. Conclusions: The findings available today substantiate a fundamental health risk for people exposed to infrasound. The steep pressure pulses of actual emissions have been disregarded by government-initiated studies of wind turbines to date. There is a need for adequate safety margins and further research in order to establish dose (energy)-response curves for the cardinal symptoms. Keywords: infrasound – wind turbine – pressure pulse – adverse effects on health

Generating ultrashort flat-top optical pulses with a fiber-loop time-lens system

For generating short flat-top optical pulses, traditional methods are either bandwidth limited or have low controllability (in pulse width and shape). We propose a fiber-loop based time-lens system to realize ps-level flat-top pulses, and theoretically study their features under various parameter circumstances. This time-lens system, functioning as many stacked time-lenses, introduces great controllability for the generated pulse’s characteristics through tuning both the phase modulation device and the dispersion-compensating setup. To achieve high-quality narrow flat-top pulses (with steep pulse edges), several factors including phase modulation function, modulation strength and dispersion compensating status must be optimized simultaneously. In simulation, after 50 loops of parabolic phase modulation and chirp compensation, the flat-top pulse’s duration can be narrowed to 2.8 ps with edge widths of 1.7 ps. This kind of ps-scale flat-top pulse is very desirable for application in various areas.

Efficacy and mechanism of steep pulse irreversible electroporation technology on xenograft model of nude mice: a preclinical study

BackgroundSteep pulse therapy can irreversible electrically brackdown of tumor membrance and cause cell death. In previous studies, we investigated the effect of steep pulsed electroporation on the killing of large cell lung cancer cell line L981- in vitro, and determined the best parameters for killing lung cancer cells by steep pulse technology. But the optimal parameters and the mechanisms of steep pulse irreversible electroporation technology on nude mouse tumor model are unclear.MethodsThree settings of steep pulse therapy parameters were applied to the nude mouse model. An in vivo imaging system was employed to observe the effect of different parameters on the mouse model. The pathological changes of the tumor tissue and immunofluorescence data on Caspase-3 protein expression were recorded.ResultsUnder the in vivo imaging system, the steep pulse had an obvious inhibitory effect on the transplanted tumor in the nude mouse model. Pathological tests showed that occurrence of necrosis and apoptosis and expression of Caspase-3 protein in the tumor tissue were increased compared to those in the normal tissue.ConclusionsSteep pulse irreversible electroporation technology showed a promising antitumor effect in the nude mouse tumor model. With splint-type electrode, the best treatment parameters determined for the nude mouse tumor model were voltage amplitude 2000 V/cm, pulse width 100 μs, pulse frequency 1 Hz, pulse number 60, and repeat time 3. Moreover, steep pulse induced coagulative necrosis of tumor tissue by cell apoptosis.

OH density measured by PLIF in a nanosecond atmospheric pressure diffuse discharge in humid air under steep high voltage pulses

The spatiotemporal distributions of the OH radical density are measured using planar laser induced fluorescence in the afterglow of a nanosecond diffuse discharge at atmospheric pressure in humid air. The diffuse discharge is generated between a pin and a grounded plate electrodes within a gap of 18 mm. The high voltage pulse applied to the pin ranges from 65 to 85 kV with a rise time of 2 ns. The specific electrical energy transferred to the gas ranges from 5 to 40 J l−1. The influence of H2O concentration is studied from 0.5% to 1.5%. An absolute calibration of OH density is performed using a six-level transient rate equation model to simulate the dynamics of OH excitation by the laser, taking into account collisional processes during the optical pumping and the fluorescence. Rayleigh scattering measurements are used to achieve the geometrical part of the calibration. A local maximum of OH density is found in the pin area whatever the operating conditions. For 85 kV and 1% of H2O, this peak reaches a value of 2.0 × 1016 cm−3 corresponding to 8% of H2O dissociation. The temporal decay of the spatially averaged OH density is found to be similar as in the afterglow of a homogeneous photo-triggered discharge for which a self-consistent modeling is done. These tools are then used to bring discussion elements on OH kinetics.

Discharge mode transition and temporal-spatial evolution of an air-water plasma jet generated by pulsating DC power

In this paper, pulsating direct current air-water plasma jet, which can increase the production of •OH and decrease the temperature, is studied. The results show that the discharge mode changes in one cycle from corona discharge with steep Trichel current pulse to glow-like discharge. It is unknown whether the different discharge modes and water ratio have an effect on the transient process of the excited O and •OH production and the mechanism of plasma propagation. So, a series of experiments are done in this paper. The results show that the changing rules of both the excited state O and the discharge current reach their two peak values synchronously. And its maximum appears at the time of the first peak current value in corona mode. However, the change of the excited state •OH is different. It increases to its maximum at the time of the second peak current value in glow-like mode. Besides, the intensified charge coupled device photographs show that the luminous intensity of the discharge zone at the first peak current value in corona mode is stronger than the second peak current value in glow-like mode. At the same time, the discharge area of the former is larger than the latter. Nevertheless, with the increase in water ratio, the discharge area change reversed. Additionally, the air plasma plume propagation depends on the gas flow. The initial propagation velocity decreases with the increase in water ratio.

Transition from symmetric discharge to asymmetric discharge in a short gap helium dielectric barrier discharge

The discharge dynamics of a 2.08 mm gap helium dielectric barrier discharge (DBD) are studied with a one-dimensional fluid model. By increasing the amplitude of a sinusoidal voltage source, it is observed that the discharge is symmetric at first and abruptly turns into an asymmetric state after passing a certain critical value. Compared with former publications dealing with relatively larger gap-distance DBD, our simulation results indicate some new discoveries. First, in both the symmetric and asymmetric states, every discharge event is fully developed from Townsend discharge to glow discharge, and the discharge current appears as a steep narrow pulse. Second, the residual positive column is always completely dissipated before the next break down; therefore, its influence on the symmetric-to-asymmetric transition can be eliminated. It is further revealed that the symmetric-to-asymmetric transition in the short-gap DBD is more delicate. A subtle phase shift is observed before the transition process. When the phase shift is further promoted with voltage rising, a discordance of the evolution paces between electron and ions occurs, which consequently leads to the formation of discharge asymmetry.

Effect of piecewise linear current waveforms on surge arrester residual voltage

The object of research is the magnitude and shape of the residual voltage that arises between the terminals of the surge arrester models when they are subjected to current and voltage pulses of a piecewise linear waveform. One of the most problematic places in this problem is the approximation of current switching pulses with a short duration and also steep front current pulses. With the help of the well-known double-exponential pulse, it is impossible to describe a pulse whose time-to-half duration is twice bigger the time-to-crest duration . At the same time, current pulses in the manufacturer catalogs of the surge arresters have exactly this ratio (1/2, 30/60 or 45/90 ). With the help of piecewise linear approximation, it is possible, bypassing complex calculations, to describe pulses of almost any shape, including switching current pulses and steep front current pulses. By means of evaluation version of Micro-Cap 11 circuit simulator the residual voltage on the surge arrester terminals is computed during a passage of the current pulses with different amplitude and wave shape. Current sources used in this research represent sources of simplified triangular (piecewise linear) current pulses. It is considered that the current wave rises linearly to its maximum value, and then also decays linearly to half its amplitude value. Comparison of the results suggests that proposed simplification of discharge current waveform has no significant effect on relative calculation error of residual voltage on surge arrester. If it is necessary to estimate only maximum value of residual voltage on surge arrester, it is possible to use piecewise linear approximation of switching and lightning currents with any amplitude and shape without loss of accuracy.

Study of surge arrester model under influence of various current pulses

The model of surge arrester, which consists of two nonlinear resistors, connected with each other via two inductive and a resistive element is studied. To determine the model parameters are only required by the data given in the catalogs of surge arresters manufacturers. Until now, in the simulation of surge arresters insufficiently investigated the effect of currents typical for lightning surges. It is shown that the model of surge arrester can be investigated by comparing the results of computer simulation with the data given in the catalogs of surge arresters. The study will use the following data, specific both switching and lightning surges: the residual voltage at switching impulse current, the residual voltage at lightning impulse current, as well as the residual voltage at steep current pulse. Residual voltages corresponding to the 250-2000 A standard switching current pulses, 1.5-20.0 kA standard lightning current pulses and 10.0 kA steep current pulses were defined using Micro-Cap model of surge arrester. Residual voltages obtained in the simulation were compared with the corresponding values given in catalogs of surge arresters. It is shown that the smallest error takes place under the influence of lightning current pulses on the model of surge arrester. The model of surge arrester in Micro-Cap program allows high accuracy determination of the residual voltage on the surge arrester during the flow of discharge pulses, which are typical for lightning surges. The model also allows to calculate the transients during the flow of the lightning currents, which are composed with several successive pulses, which can pose a significant danger to the surge arresters. The results of the research can specify the parameters of substation protection against different overvoltages and, thus, reduce economic losses due to possible faults.

Sub-nanosecond time resolved light emission study for diffuse discharges in air under steep high voltage pulses

Pin-to-plane discharges in centimetre air gaps and standard conditions of pressure and temperature are generated under very high positive nanosecond scale voltage pulses. The experimental study is based on recordings of sub-nanosecond time resolved and Abel-processed light emission profiles and their complete correlation to electrical current waveforms. The effects of the voltage pulse features (amplitude between 20 and 90 kV, rise time between 2 and 5.2 ns, and time rate between 4 and 40 kV · ns−1) and the electrode configuration (gap distance between 10 and 30 mm, pin radius between 10 and 200 µm, copper, molybdenum or tungsten pin material) are described. A three time period development can be found: a glow-like structure with monotonic light profiles during the first 1.5 ns whose size depends on time voltage rate, a shell-like structure with bimodal profiles whose duration and extension in space depends on rise time, and either diffuse or multi-channel regime for the connection to the cathode plane according to gap distance. The transition of the light from monotonic to bimodal patterns reveals the relative effects and dynamics of streamer space charge and external laplacian field. A classical 2D-fluid model for streamer propagation has been used and adapted for very high and steep voltage pulses. It shows the formation of a strong space charge (streamer) very close to the pin, but also a continuity of emission between the pin and the streamer, and electric fields higher than the critical ionization field (28 kV · cm−1 in air) almost in the whole gap and very early in the discharge propagation.

Bipolar Steep Pulse Current Source for Highly Inductive Load

A bipolar pulse current source is proposed for a highly inductive load. The current source exploits a noninductive capacitor to store or release the energy back to and from inductive load during switching on or off of power inverter. A boost module is designed at the dc side of inverter to supplement the required energy gap so that edge steepness of the load current can be improved. The capacitor and boost elements are configured based on the analysis of capacitor impact on the load current and boost inductor current. The stability of load current can be guaranteed by the multiple driving pulses generated from closed-loop control of boost switch, regardless of load changes or initial pulse width offset. An experiment prototype is built to generate a flat-top 20 A current with the 200 μs rise/fall time for an inductive load of 2 mH or higher. Due to the steep rising and falling edges, the inductive load can realize high-frequency pulse currents. Moreover, the steep pulse current source can excite strong magnetic field, which make it especially useful for the inductive coils of high-power geophysical transient electromagnetic method (TEM) transmitter.

3D PIC modeling of laser acceleration of electrons from two-dimensional inhomogeneous plasma corona

This paper presents the results of three-dimensional (3D3V) particle-in-cell modeling of the interaction of a femtosecond laser pulse with a two-dimensional inhomogeneous plasma corona of subcritical density. It was shown that in the presence of sufficiently steep temporal pulse edge the excitation of plasma waves, electron trapping and generation of collimated beams of accelerated electrons with energy of about 0.2-0.5 MeV may occur. The simulation results are compared with experiments on the generation of collimated beams of accelerated electrons from metal targets irradiated by intense femtosecond laser radiation.