Amplitude Of High Voltage Pulses Research Articles

Ultrafast High Voltage Pulse Generator Based on Power MOSFETs Delay Push-pull Structure

In this paper, an ultrafast high voltage pulse generator based on power MOSFETs delay push-pull structure is designed. The two complementary power MOSFETs are connected in the push-pull circuit and driven by the low-power MOSFETs separately. The output ultrafast high-voltage pulse amplitude is +30 V ~ -200 V, and the front edge and back edge times of the pulse are 5 ns and 4 ns, respectively. The width and frequency of the output pulse are controlled by the external trigger input signal. The shortest output pulse width is 12 ns and the maximum operating frequency is 100 kHz while the load is 10 pF. The delay conduction method of power MOSFETs is helpful to reduce power dissipation and improve the reliability of the circuit at a high operating frequency.

Velocity of initial propagation of positive nanosecond discharge in liquid water: dependence on high voltage amplitude and water conductivity

This study deals with the effect of water conductivity and high voltage pulse amplitude on the initial velocity of nanosecond discharge in liquid water. As variable parameters, we used water solutions with three different conductivities (2 μS cm−1, 100 μS cm−1, 500 μS cm−1), and positive high voltage pulses with four different amplitudes (80 kV, 91 kV, 100 kV, 113 kV). The discharge reactor consists of metallic electrodes in a point–to–plane geometry, both immersed in liquid water. The discharge was generated by a commercial nanosecond pulse power generator with positive HV pulses of ∼6 ns pulse duration (FWHM) and ∼2.5 ns rise time. ICCD time-resolved imaging microscopy with high temporal resolution (∼ns) was utilized as a suitable diagnostic tool for the discharge dynamic propagation. It can be concluded that the discharge visual characteristics and behaviour are not significantly influenced by water conductivity and the length of the filaments increases with the increasing voltage amplitude and reaches the maximum value of ∼1.8 mm for 90 kV. The initial propagation velocity also depends on the voltage amplitude and increases with the voltage. The effect of water conductivity on the propagation velocity is negligible. As far as we know, this paper is the first to bring insight into the topic of the effect of water conductivity on the nanosecond discharge propagation in liquid water.

Generation of dual pulses of the runaway electron beam current during the subnanosecond breakdown of atomic and molecular gases

With a diaphragm placed behind the anode foil, dual runaway electron beams have been provided in helium, hydrogen, nitrogen, and air under a pressure of several torrs to several dozen torrs and a high-voltage pulse amplitude of about 250 kV. These beams consist of two pulses with commensurable amplitudes with a time interval between them of several dozen picoseconds to several hundred picoseconds. It has been shown that the breakdown of the interelectrode gap at pressures from several torrs to several dozen torrs may occur in different regimes and dual pulses of the electron beam current are registered when the initial current through the gap is below 1 kA. It has been found that a supershort avalanche electron beam that consists of one pulse is generated when the delay of breakdown equals several hundred picoseconds. It has been shown that, when the gas pressure reaches several hundred Torr, including atmospheric pressure, the runaway electrons are detected behind the foil after the termination of the supershort avalanche electron beam pulse.

A new method for compensation of the effect of charging transformer's leakage inductance on PFN voltage regulation in Klystron pulse modulators

The Line type modulators have been widely used to generate high voltage rectangular pulses to power the klystron for high power RF generation. In Line type modulator, the Pulse Forming Network (PFN) which is a cascade combination of lumped capacitors and inductors is used to store the electrical energy. The charged PFN is then discharged into a klystron by firing a high voltage Thyratron switch. This discharge generates a high voltage rectangular pulse across the klystron electrodes. The amplitude and phase of Klystron's RF output is governed by the high voltage pulse amplitude. The undesired RF amplitude and phase stability issues arises at the klystron's output due to inter-pulse and during the pulse amplitude variations. To reduce inter-pulse voltage variations, the PFN is required to be charged at the same voltage after every discharge cycle. At present, the combination of widely used resonant charging and deQing method is used to regulate the pulse to pulse PFN voltage variations but the charging transformer's leakage inductance puts an upper bound on the regulation achievable by this method. Here we have developed few insights of the deQing process and devised a new compensation method to compensate this undesired effect of charging transformer's leakage inductance on the pulse to pulse PFN voltage stability. This compensation is accomplished by the controlled partial discharging of the split PFN capacitor using a low voltage MOSFET switch. Theoretically, very high values of pulse to pulse voltage stability may be achieved using this method. This method may be used in deQing based existing modulators or in new modulators, to increase the pulse to pulse voltage stability, without having a very tight bound on charging transformer's leakage inductance. Given a stable charging power supply, this method may be used to further enhance the inter-pulse voltage stability of modulators which employ the direct charging, after replacing the direct charging with the resonant charging.

Optimization of the length of incomplete channel surface discharge at preset high-voltage pulse amplitude

We have experimentally studied the characteristics of the incomplete state of a channel surface discharge at moderate growth rates of the applied voltage. It is established that the dependence of the discharge channel length on applied voltage growth rate dU/dt at constant pulse amplitude exhibits a smooth maximum. The presence of this maximum is explained by the nonlinear dependence of the discharge propagation time on dU/dt, which allows the discharge to be optimized so as to reach its maximum length.

Design of an Electro-Optic Device for In-situ Measurement of High Voltage Pulses

Design of a Pockels cell based electro-optic device is described. The device is designed to measure the amplitude of high voltage pulses in our new Pulsed High Voltage Measurement System (PHVMS) wi...

Plasma supported combustion

Oxidation of molecular hydrogen and different hydrocarbons in stoichiometric mixtures with air and oxygen in the pulsed nanosecond discharges was studied at room temperature, and the detailed kinetics of the process has been numerically investigated. In the discharge afterglow, the reactions including electron-excited particles play a dominant role for the time up to 100 ns, ion–molecular reactions—for the time of microsecond range, and reactions including radicals mostly contribute for the time interval of several milliseconds. The principal role of processes with formation of excited components that support the development of the chain mechanism of oxidation has been shown. The spatial uniformity of the gas-mixture combustion initiated by a high-voltage nanosecond volume discharge is investigated at gas pressures of 0.3–2.4 atm and temperatures of 1000–2250 K. The self-ignition time and the time of discharge-induced ignition are determined. It is found that the discharge significantly (by 600 K) decreases the ignition temperature with very low energy in the discharge (∼10 −2 J/cm 3). The influence of gas excitation by a pulsed nanosecond discharge with a high-voltage pulse amplitude up to 25 kV on the properties of a premixed propane–air flame has been investigated over a wide range of the equivalence ratios (0.4–5). It was experimentally found that the flame’s blow-off velocity increased more than twice at a discharge energy input less than 1% of the burner power. Efficient production of active radicals under the action of a barrier discharge has been observed. The increase in the flame’s propagation velocity is explained by the production of atomic oxygen in a discharge by the quenching of electronically excited molecular nitrogen N 2 and the dissociation of molecular oxygen on electron-impact. A numerical model has been developed, which describes the influence of pulsed electric discharges on the ignition, combustion, and flame propagation.

Discharge dynamics and the production of active particles in a cathode-directed streamer

The emission spectroscopy technique is used to analyze a cathode-directed streamer discharge in air at atmospheric pressure in point-plane geometry at interelectrode distances of up to 100 mm and a high-voltage pulse amplitude of 18 kV. The densities of molecules in the N2(C3Πu, v=0), N2+(B2Σu+, v=0) and NO(A2Σ+, v=0) states are determined, and the reduced electric field in the streamer head is estimated. It is shown that the increase in the average electric field in the discharge gap substantially intensifies the production of active particles in the discharge plasma and makes the plasma more homogeneous. This effect is only related to the increase in the fraction of regions with a high electric field in the discharge gap and, as a result, the reduction of the discharge energy losses via rapidly thermalized degrees of freedom. The active particles are only produced in the streamer head, including the case in which the interelectrode gap is bridged by the streamer channel.

Pulsed power generation using open and closed ferromagnetic circuits

Results are presented of an experimental study of the generation of high-voltage and high-current pulses in generators designed as open and closed ferromagnetic circuits. Experiments were carried out using a light gas gun system. The magnetic projectiles were composed of ferromagnetic disks having 1.27- and 2.54-cm diameters. It has been shown that with velocities of the magnetic projectiles of 200-380 m/s, the peak voltage of the pulses produced by the generators reach several tens of kilovolts, peak current reaches kiloampere, and the energy delivered at the load is a few Joules. Generating modules connected in series will make it possible to produce a high-energy pulse with a peak voltage of a few hundred kilovolts. It has been shown that a closed ferromagnetic circuit generator is capable of generating not only single high-voltage pulses, but also repetitive oscillations. Data are given for the effects on the amplitude of high-voltage pulses caused by the length and velocity of the ferromagnetic projectiles and the design of the generating unit for both high-voltage and high-current modes of pulsed power generation.

Streamer discharge reactor for water treatment by pulsed power

The streamer discharges are effectively used for biological and chemical cleaning of air and water. Uniform streamer discharges were obtained in water at pulsed electric loading. The volume of these discharges exceeds 400 cm3 and the energy delivered to the discharge reached 40–400 J depending on the applied voltage. The reliable and durable reactor for water treatment by pulsed streamer discharges is designed and tested. High voltage pulse amplitude applied to the reactor requires improved electric insulation to prevent flashover along the reactor surface both in water and air. High mechanical stress due to high discharge current adds the requirements to the mechanical durability of the system. A small-size reactor with the volume of approximately 1 ℓ withstands successfully both high electrical and mechanical stresses. The reactor is designed for research purposes, however it can be upgraded to use in a high repetition-rate regime necessary for industrial applications.

The appearance of inclined discharge channels along an ionizing particle track

The formation of discharge channels inclined to the field was investigated in a 2-gap spark chamber with various amplitudes of the high-voltage pulse and with different gas fillings of the chamber. It was shown that the limiting angle for the formation of a spark channel along the chain of electrons produced by ionizing particles increases with the increase of the high-voltage pulse amplitude. The largest iimiting angle for the formation of an inclined streamer channel was observed when the chamber was filled with pure Ne and with Ne--0.5% Ar. When a particle traversed the chamber at an angle larger than 30 un. Concent 85% , distortions of the spark appeared at the electrodes. The cause of the distortions is considered. In a search for a gaseous mixture that couid reduce the memory time, positive experimental data were obtained with the chamber filled with a mixture of 90.5% Ne, 0.4% Ar and 0.1% CH/sub 4/. (A.G.W.)