High-voltage Nanosecond Pulses Research Articles

FPGA-Controlled All-Solid-State Nanosecond Pulse Generator for Biological Applications

In vivo studies of tumor-cell apoptosis induced by nanosecond pulsed electric field require high-voltage nanosecond pulses delivered to the biological tissues. In this paper, a newly developed all-solid-state nanosecond pulse generator based on the Marx generator concept is proposed for this application. The generator comprises four parts: a dc charging power, a solid-state Marx circuit using metal-oxide-semiconductor field-effect transistors, a control circuit using a field-programmable gate array, and the load. This generator has the capability of producing repetitive pulses with a voltage up to 8 kV, pulsewidth of 200-1000 ns, rise time of 35 ns, and repetition rate of 1-1000 Hz with various resistive loads and 1-kV dc input voltage. The all-solid-state design makes the generator compact and reliable. Initial experiments were carried out to verify the performances of the proposed generator.

Investigation of the electrical strength of liquid dielectrics in vacuum under the action of high-voltage nanosecond pulses

The results of an experimental study of the electrical strength of insulators that are coated with a thin liquid-dielectric layer (1–2 mm) are presented. Studies were performed in a vacuum at a pressure of 10−4–10−5 Torr and a high-voltage pulse duration of ∼100 ns on an experimental setup, which is based on a PG-1 high-voltage nanosecond generator with an output voltage of up to 500 kV at a load of up to 40 Ω. It was established that a castor or transformer oil coating on an insulator allows an increase in the amplitude of a voltage pulse, which is applied to the insulator, by a factor of at least 1.7 as compared to the clean insulator without its breakdown over the surface in vacuum.

A triggered multigap gas switch

The design, operating principles, and actual structure of a high-voltage triggered multigap gas switch (GS) that provides nanosecond switching of gigawatt-level power fluxes are considered. Its operation is based on a new model of a switching structure, in which the switching process is ensured by the overvoltage propagation along a chain of switching gaps through the mechanism of its interaction with two capacitive dividing circuits, which are formed by the GS electrodes. The GS is intended for operation in generators of high-voltage nanosecond pulses on the basis of a discharge of double coaxial-type forming lines. It is shown that the GS can be used to switch a 25-Ω forming line that is charged to a voltage of 600 kV.

Repetitive sub-gigawatt rf source based on gyromagnetic nonlinear transmission line

We demonstrate a high power repetitive rf source using gyromagnetic nonlinear transmission line to produce rf oscillations. Saturated NiZn ferrites act as active nonlinear medium first sharpening the pumping high voltage nanosecond pulse and then radiating at central frequency of about 1 GHz: shock rise time excites gyromagnetic precession in ferrites forming damping rf oscillations. The optimal length of nonlinear transmission line was found to be of about 1 m. SINUS-200 high voltage driver with Tesla transformer incorporated into pulse forming line has been designed and fabricated to produce bursts of 1000 pulses with 200 Hz repetition rate. A band-pass filter and mode-converter have been designed to extract rf pulse from low-frequency component and to form TE(11) mode of circular waveguide with linear polarization. A wide-band horn antenna has been fabricated to form Gaussian distribution of radiation pattern. The peak value of electric field strength of a radiated pulse at the distance of 3.5 m away from antenna is measured to be 160 kV/m. The corresponding rf peak power of 260 MW was achieved.

Characterization of pulsed atmospheric-pressure plasma streams (PAPS) generated by a plasma gun

An experimental study of atmospheric-pressure rare gas plasma propagation in a high-aspect-ratio capillary is reported. The plasma is generated with a plasma gun device based on a dielectric barrier discharge (DBD) reactor powered by either nanosecond or microsecond rise-time high-voltage pulses at single-shot to multi-kHz frequencies. The influence of the voltage waveform, pulse polarity, pulse repetition rate and capillary material have been studied using nanosecond intensified charge-coupled device imaging and plasma-front velocity measurements. The evolution of the plasma appearance during its propagation and the study of the role of the different experimental parameters lead us to suggest a new denomination of pulsed atmospheric-pressure plasma streams to describe all the plasma features, including the previously so-called plasma bullet. The unique properties of such non-thermal plasma launching in capillaries, far from the primary DBD plasma, are associated with a fast ionization wave travelling with velocity in the 107–108 cm s−1 range. Voltage pulse tailoring is shown to allow for a significant improvement of such plasma delivery. Thus, the plasma gun device affords unique opportunities in biomedical endoscopic applications.

Emission of cyan upon excitation of nitrogen, air, and N2-CH4 mixture by discharge pulses in an inhomogeneous electric field

We have studied spectral and amplitude-time characteristics of the emission by nitrogen, air, and the N2-CH4 mixture upon excitation by nanosecond and microsecond high-voltage discharge pulses in an inhomogeneous electric field in the pressure range of 0.01–3 atm. In the pulsed and pulse-periodic discharge regimes, we have observed emission bands of the violet system of cyan, the transition B2Σ+ → X2Σ+, which were comparable in intensity with bands of the (2+) system of nitrogen. We show that, in the pulsed regime, the highest intensity of the violet system of cyan is observed in the N2-CH4 mixture. We show that, in the pulse-periodic discharge in nitrogen with a small amount of a carbon-containing admixture, upon contracting the discharge, the efficiencies of formation and emission of the violet system of cyan considerably increase. We confirm that admixtures of oxygen to nitrogen lead to suppression of the emission of the violet system of cyan molecules.

紧凑型重复频率高压纳秒脉冲电源及其仿真模型

紧凑型重复频率高压纳秒脉冲电源及其仿真模型

Numerical simulation of the pre-ionization processes during nanosecond-pulse discharge in nitrogen

The pre-ionization of nitrogen gas by high-voltage nanosecond pulse discharges is studied using one-dimensional particle-in-cell numerical simulations. The comparison between the various mechanisms of pre-ionization, i.e., by runaway electrons, x-rays, and ultraviolet radiation, is presented. It is shown that runaway electrons produce a much higher number of electron-ion pairs than those generated by x-rays, which accompany the process of runaway electron generation. Also, results of simulations showed that among photo-ionization mechanisms the most significant gas pre-ionization is caused by x-rays generated in the process of impact ionization of the K-shell of nitrogen atoms.

Lasing from the domain of collision of ionisation waves produced due to electric field concentration at electrodes with a small radius of curvature

The characteristics of UV lasing in nitrogen and of diffusive discharge produced without an additional ionisation source were experimentally investigated in a nonuniform electric field formed by electrodes with different profiles. High-voltage nanosecond pulses were applied to the blade- and cylinder-shaped electrodes. It was determined that the gap breakdown at elevated pressure was caused by diffusive jets which propagate from the electrodes with a small radius of curvature. The electric field increasedin the intersection of counter-propagating jets, with the effect that the threshold of lasing in the C3Πu — B3Πg (λ = 337.1 nm) molecular nitrogen band was attained for low average electric fields (below 60 V cm-1 Torr-1) and at pressures of 760 Torr and above. With lowering the pressure from 760 to 20 Torr, the voltage of gap breakdown in the nonuniform electric field was observed to increase for a voltage pulse rise time of ∼300 ps and to decrease for a pulse rise timeof ∼2 ns.

Dynamics of Near-Atmospheric-Pressure Hydrogen Plasmas Driven by Pulsed High Voltages

The formation mechanism of hydrogen plasmas by nanosecond high-voltage pulses at near-atmospheric pressure was examined by particle-in-cell/Monte-Carlo-collision simulations. In the model system, plasmas were generated between parallel metal electrodes. The simulation results show the propagation of ionization fronts and the formation of non-Maxwellian electron-energy distributions. The time evolution of plasma dynamics observed in the simulations has been confirmed to be in good agreement with recent experimental results.

Nanosecond Pulsed Arrays of Microdischarges in Argon

The spatiotemporal behavior of the optical emission of an array of 25 microdischarges has been studied through fast imaging technique. The device basically consists of a metal/dielectric/metal sandwich powered by nanosecond high-voltage pulses. It is shown that all the microdischarges ignite simultaneously within an accuracy of 5 ns and that the parallel operation of all the microdischarges occurs without any ballast resistors.

Transient Plasma Fuel–Air Ignition

Transient plasma ignition, a method of fuel-air ignition involving streamer discharges produced by nanosecond high-voltage pulses, is attractive, and that it reduces ignition delay, increases the burning rate, and can ignite leaner mixtures compared with the traditional spark ignition. In this paper, images of the transient plasma discharges and subsequent flame development in a C2H4-air mixture were captured using a single-lens reflex camera and a high-speed camera, respectively.

Diffuse and Filamentary Discharges in Open Air Driven by Repetitive High-Voltage Nanosecond Pulses

Nanosecond repetitive pulsed discharge in atmospheric air has attracted significant attention due to its fast rise time and short duration in various applications. With an excitation of unipolar repetitive pulses of 25-ns rise time and 40-ns duration, diffuse discharge in open air is obtained in a tube-plane gap. The discharge photographs show the transition of the discharge forms from diffuse to filamentary discharge in response to the decrease of the air gap spacing.

Biological Cell Electroporation Using Nanosecond Electrical Pulses

Nanosecond electroporation has a range of applications including gene therapy and treatment of melanoma tumors. On applying a nanosecond high voltage pulse, potential differences are generated across the membranes of the internal organelles resulting in its electroporation. This paper investigates the effect of nanosecond high voltage pulses simulated on a biological cell placed in a conductive medium (water). The effect of cell size, shape (spherical and elliptical) and membrane thickness on electroporation is investigated. Significant difference in the field was observed indicating the importance of these factors in the success of electroporation in the event of application of external nanosecond high voltage electrical pulse.

Increase of Kinetic Energy of Dusty Cluster Particles Due to Parametric Instability Caused by Nanosecond Electric Pulses

AbstractExperimental investigations of high voltage nanosecond pulses influence on charged dust particles in low pressure rf–plasma were carried out. Application of repetitive pulses leads to the vertical oscillations of the mi‐croparticles. Evolution of the total kinetic energy for the cluster consisting of 14 particles is investigated. Flat clusters exhibit parametric instabilities of horizontal modes. In the initial phase the kinetic energy oscillates around a certain value and its amplitude grows very slowly. At a certain moment during the instability it goes into the exponential growth phase and then saturates under the effect of repetitive pulses. It is possible if the eigenfrequency is the function of height and the dust particle oscillates vertically in the non uniform electric field (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

A compact repetitive high-voltage nanosecond pulse generator for the application of gas discharge

Uniform and stable discharge plasma requires very short duration pulses with fast rise times. A repetitive high-voltage nanosecond pulse generator for the application of gas discharge is presented in this paper. It is constructed with all solid-state components. Two-stage magnetic compression is used to generate a short duration pulse. Unlike in some reported studies, common commercial fast recovery diodes instead of a semiconductor opening switch (SOS) are used in our experiment that plays the role of SOS. The SOS-like effects of four different kinds of diodes are studied experimentally to optimize the output performance. It is found that the output pulse voltage is higher with a shorter reverse recovery time, and the rise time of pulse becomes faster when the falling time of reverse recovery current is shorter. The SOS-like effect of the diodes can be adjusted by changing the external circuit parameters. Through optimization the pulse generator can provide a pulsed voltage of 40 kV with a 40 ns duration, 10 ns rise time, and pulse repetition frequency of up to 5 kHz. Diffuse plasma can be formed in air at standard atmospheric pressure using the developed pulse generator. With a light weight and small packaging the pulse generator is suitable for gas discharge application.

Targeted Tissue Ablation With Nanosecond Pulses

In-vivo porcine studies on the effect of nanosecond high voltage pulses on liver tissue have shown that cell death can be induced in well-defined tissue volumes without damaging collagen-predominant structures. Comparison of the experimental results with the results of a three-dimensional finite element model allowed us to determine the threshold electric field for cell death. For 30, 100 nanosecond long pulses this was found to be in the range from 12 to 15 kV/cm. Modelling of the temperature distribution in the tissue using Pennes' bioheat equation showed that the lethal effect of nanosecond pulses on cells is non-thermal. Muscle contractions, generally caused by high voltage pulses, were significantly reduced for the 100 nanosecond pulses compared to microsecond long pulses. The results of these studies indicate that high voltage nanosecond pulses reliably kill normal liver cells in vivo and therefore may be useful for liver tumor treatments.

The Mechanisms of Decreasing Voltage-Gated Sodium Current by Nanosecond Electric Pulses

The application of high-voltage nanosecond electric pulses (nsEP) causes the formation of nanopores in plasma membrane of mammalian cells, modifies function of voltage-gated ion channels. However, it is not known if nsEPs affect ion channels directly, or these effects are mediated in alternate method. We used the whole-cell patch-clamp technique to explore the effect of 300-nsEP on voltage-gated sodium current (INa) in NG108 neuroblastoma cells. Our data have shown that a single nsEP decreased the INa in dose-dependent manners; in parallel nsEP exposures induced a non-inactivating, voltage-sensitive inward current due to nanopore formation. At the same time, the recovery of INa after nsEP exposure took significantly longer than nanopore resealing. To check if the inflow of Na+ through nanopores was efficient enough to overcome the buffering capacity of the pipette, we measured changes of Na+ concentration in “patched” cells using the Na+-sensitive fluorescent dye (Sodium Green). These experiments showed that opening of nanopores increases the Na+ concentration in patched cells; however, the maximum increase the Na+ content, even with the most intense exposure (5.3 kV/cm), was only 2.7mM, which could unlikely cause INa inhibition. The measurement of submembrane fluorescence intensity of Sodium Green by nsEP didn’t show significant increase of submembrane Na+ concentration too. The another potential pathway of reducing the INa is increasing the intracellular Ca2+ concentration after nsEP and Ca2+ mediated inhibition of INa. Our data showed that nsEP exposure in presence of high concentration Ca2+ buffer - BAPTA (20mM) in the intracellular solution caused reduce INa in NG108 cells. Our finding suggest that decreasing of INa by nsEP was not resulted of inward Na+ leakage through nanopores, as well as Ca2+ release from intracellular stores after nsEP exposure.

纳秒脉冲下聚合物电树枝引发实验方法

纳秒脉冲下聚合物电树枝引发实验方法

Intensity of electric field radiating from high-power pulsed electromagnetic wave generator for use in biological applications

Cancer treatment is one of several new applications which use nanosecond and subnanosecond high-voltage pulses. This study focuses on the design of a compact highpower pulsed electromagnetic wave generator using a nanosecond pulsed power generator to apply a high-intensity electric field for the treatment of cancer; the pulses cause apoptosis in cancer cells. We applied an L-C inversion circuit to the pulsed power generator to obtain a voltage waveform with a single frequency, which is applied to an antenna. A water gap switch and water capacitors were used in the L-C inversion circuit to obtain a pulsed voltage with a frequency element of 250 MHz. In this experiment, an electromagnetic wave was radiated underwater by a loop antenna. A measuring double loop antenna placed 0.15 m and 0.3 m from the radiating antenna detected electric field intensities of 112 kV/m and 49 kV/m, respectively. A focusing bowl was attached to the radiating antenna to obtain a higher electric field. The electric field intensity of the radiating antenna with the focusing bowl, 300 kV/m, was 6 times higher than that without the focusing bowl. The intensity distribution of the electric field focused by the focusing bowl was measured. A measuring small loop antenna detected peak electric field intensity of 11.3 kV/cm at a focal point. Areas with electric field intensity greater than 10.8 kV/cm were approximately 5 mm square and 3 mm wide in the x-z plane and y-axis, respectively.