kV Pulse Research Articles

A Hyperband Antenna to Launch and Focus Fast High-Voltage Pulses Onto Biological Targets

This paper briefly reviews the design of a prolate-spheroidal impulse-radiating hyperband antenna system to launch and focus fast (100 ps) high-voltage ( >; 100 kV) pulses onto biological targets. Design and experiments on a graded five-layer dielectric lens, designed to match the pulses into the target medium, are outlined. The design and numerical simulations of a switch system to launch high-voltage spherical TEM pulses are also presented.

Non-equilibrium plasma in liquid water: dynamics of generation and quenching

In most cases, the electric breakdown of liquids is initiated by the application of high electric field on the electrode, followed by rapid propagation and branching of plasma channels. Typically plasmas are only considered to exist through the ionization of gases and typical production of plasmas in liquids generates bubbles through heating or via cavitation and sustains the plasmas within those bubbles. The question arises: is it possible to ionize the liquid without cracking and void formation?To answer this question we used a pulsed power system with 32–220 kV pulse amplitude, 0.5–12 ns pulse duration, 150 ps rise time. The discharge cell had a point-to-plate geometry with a tip diameter of 100 µm. These parameters allowed us to observe non-equilibrium plasma generation. The measurements were performed with the help of a 4Picos ICCD camera. It was found that the discharge in liquid water forms on a picosecond time scale. The increase of emission intensity and plasma formation took 200–300 ps. The diameter of the excited region near the tip of the high-voltage electrode was ∼1 mm. After this initial stage emission rapidly decreased and the plasma region became almost invisible after 500 ps. The absence of emission during the rest of the pulse is explained by a decrease of the electrical field on the boundary of the conductive zone.Thus we have demonstrated the possibility of formation of non-equilibrium plasma in the liquid phase and investigated the dynamics of excitation and quenching of non-equilibrium plasma in liquid water.

A diffusive air plasma in bi-directional nanosecond pulsed dielectric barrier discharge

In this study, a diffuse dielectric barrier discharge in air is generated by a bi-directional nanosecond pulsed power supply using a needle–plate electrode configuration at atmospheric pressure. Time-resolved spectra of N2(C 3Πu → B 3Πg, 0–0, 337.1 nm) for both positive and negative pulse discharges are recorded under severe electromagnetic interference. It is found that the lagged time of the photocurrent pulse compared with the voltage pulse in the negative pulse discharge is about 50 times longer than that in the positive pulse discharge at 16 kV pulse peak voltage and becomes shorter with an increase in pulse peak voltage. In addition, the gas temperature of the air plasma is determined to be approximately 395 K by measuring the optical emission spectra of the first negative band of , 0–0, 391.4 nm).

X-ray emission in streamer-corona plasma

X-ray emission has been detected occasionally during the streamer-corona propagation in a wire-plate corona reactor open to ambient air. A 65 kV pulse with 15 ns rise time is applied to the wire anode superimposed on a 20 kV dc bias. The duration of the driving voltage pulse (110 ns) is less than 2.5 times the primary streamer transit time. Under this condition no arc discharge occurs between the wire and the cathode plates separated by 6 cm air. The onset of x-ray emission coincides with the initiation of the primary streamers near the wire anode. No x-rays were detected later, during or after the primary or secondary streamer development. X-ray energies ranged between 10 and 42 keV, as detected by a LaBr3 (Ce) scintillator–photomultiplier combination. Time resolved imaging of the streamer propagation highlights the different stages in the streamer discharge process. The energetic electrons originate near the anode, at the moment of streamer initialization.

Two-dimensional nanosecond electric field mapping based on cell electropermeabilization

Nanosecond, megavolt-per-meter electric pulses cause permeabilization of cells to small molecules, programmed cell death (apoptosis) in tumor cells, and are under evaluation as a treatment for skin cancer. We use nanoelectroporation and fluorescence imaging to construct two-dimensional maps of the electric field associated with delivery of 15 ns, 10 kV pulses to monolayers of the human prostate cancer cell line PC3 from three different electrode configurations: single-needle, five-needle, and flat-cut coaxial cable. Influx of the normally impermeant fluorescent dye YO-PRO-1 serves as a sensitive indicator of membrane permeabilization. The level of fluorescence emission after pulse exposure is proportional to the applied electric field strength. Spatial electric field distributions were compared in a plane normal to the center axis and 15-20 μm from the tip of the center electrode. Measurement results agree well with models for the three electrode arrangements evaluated in this study. This live-cell method for measuring a nanosecond pulsed electric field distribution provides an operationally meaningful calibration of electrode designs for biological applications and permits visualization of the relative sensitivities of different cell types to nanoelectropulse stimulation. PACS Codes: 87.85.M-

Effect of high-voltage nanosecond pulses on complex plasmas

Influence of high-voltage (1–11 kV) pulses of nanosecond (20 ns) duration on microparticles levitating in a rf plasma is studied. It is shown that the pulses produce significant influence on the plasma, causing perturbations with the relaxation time of the order of 10−4 s. This time is sufficient for the microparticle to acquire significant kinetic energy. Application of repetitive pulses leads to the vertical oscillations of the microparticles. Clusters, consisting of small number of microparticles, exhibit parametric instabilities of horizontal modes under the effect of repetitive pulses. It was shown that the parametric instability is caused by the vertical oscillations of the microparticles in the nonuniform environment of the sheath.

An ultra compact back-lighted thyratron for nanosecond switching applications

An ultra-compact back-lighted thyratron (BLT), which is also named as mini-BLT, with effective volume of 15 cm3 was developed to serve as a high voltage switch in compact transient plasma ignition systems. The mini-BLT can hold off 40 kV and was used to conduct a peak current up to 4.5 kA. A 30 ns switching delay with 2 ns jitter was achieved when triggered by a 70 mJ, 355 nm laser pulse. Delay and jitter increase as the photon energy of the trigger pulse decreases. The plasma density in the switch measured at a peak current of 3.2 kA is 9×1014cm-3. The mini-BLT was successfully used as the switch in a 100 ns, 60 kV pulse generator for generation of streamers in a plasma ignition system.

Scattered EM Field Responses of Canonical Scatterers Illuminated by an Impulse-Radiating Antenna (IRA)

This paper investigates the possibility of using the impulse-radiating antenna (IRA) as both a transmitter and receiver of electromagnetic energy for the purpose of target identification. Of specific interest is estimating the induced open-circuit voltage at the IRA's source terminals, when it is illuminated by the scattered EM field from simple conducting bodies excited by an incident field from the same IRA acting as a transmitter. In this study, several different canonical scatters are considered, including thin wires, spheres, conducting boxes, and an infinite conducting plate. For a 7 kV pulse excitation of the IRA, received peak transient voltages at the antenna ranged from a few volts to about 400 volts, depending on the scatterer.

Surface Creepage of High-Voltage Self-Breakdown Gas Switch

In this paper, the surface creepage of high-voltage self-breakdown switch which is used in 500 kV pulse modulator is analyzed in theory by employing the method of distributed element equivalent recurrent circuit. Moreover, the field distortion of the connecting ring of the switch is simulated by using software. According to the theoretical analysis, several methods to avoid surface creepage are obtained: 1) the outer housing of the switch should have high surface resistivity; 2) when the surface breakdown electric field is a constant, it is better to decrease the diameter of the electrode and to increase outer diameter and thickness of the outer housing; 3) in order to avoid field distortion, it is recommended, as far as possible, not to use metal connecting ring on the outer housing of the switch; and 4) there should be a clean environment for switch to work.

Correction of shape and energy compression of high-voltage nanosecond pulses by compact converters with a traveling wave mode

The results of investigations of converters ensuring correction of the shape and energy compression of high-voltage (∼200 kV) pulses with durations of several nanoseconds and the formation of pulses with subnanosecond rise times across a load of ∼50 Ω are described. The converters are assembled on the basis of forming and transmitting coaxial lines and a high-pressure nitrogen spark gap. Correcting devices are open-circuit strip-line stubs connected to different points of the transmitting or forming line. Depending on the stub connection point, a series or parallel discharge of the forming line and stub to the load is initiated after switching of the spark gap. As a result, the pulse may become either longer or shorter; in the latter case, its amplitude increases. The design of the stubs built into the insulating gap of the coaxial line does not increase the size of the device at all.

Enhancement of hardness and corrosion resistance of low alloy high carbon steel by plasma immersion ion implantation

Plasma immersion ion implantation (PIII) of nitrogen on low alloy high carbon steel was carried out at low energy negatively biased (−1 kV) pulses with 3˙8 kHz repetition rate for 3, 4 and 5 h of cumulative duration at a high dose of 1023 nitrogen ions per m2. Following PIII, the plasma ion implanted samples were subjected to microhardness measurements, potentiodynamic polarisation tests in 1 wt-%NaCl solution and post-corrosion microstructural studies. PIII at 500°C for 3 h seems to yield the optimum combination of increase in both hardness and resistance to corrosion.

Detection of Highly Enriched Uranium Using a Pulsed D-D Fusion Source

This paper overviews the work that has been done to date towards the development of a compact, reliable means to detect Highly Enriched Uranium (HEU) and other fissile materials utilizing a pulsed Inertial Electrostatic Confinement (IEC) D-D fusion device. To date, the UW IEC device has achieved 115 kV pulses in excess of 2 ampere, with pulsed neutron rates of 1.8x109 n/s during a 0.5 ms pulse at 10 Hz. MCNP modeling indicates that detection of samples of U-235 as small as 10 grams is achievable at current neutron production rates, and initial pulsed and steady-state HEU detection experiments have verified these results.

Compact Subnanosecond Pulse Generator Using Avalanche Transistors for Cell Electroperturbation Studies

Research on the electroperturbation effects of ultrashort high field pulses in cancer cells requires subnanosecond rise time, high voltage pulses delivered to low impedance biological loads. Here we present a compact solid-state pulse generator developed for this application. The pulse is generated by switching a chain of avalanche transistors configured as a tapered transmission line from high voltage to ground. The system features a built in 1400:1 capacitively compensated resistive voltage divider. The divider, with a 3 dB point at 910 MHz, overcomes challenges in the direct measurement of the high frequency components of the output pulse. The generator is capable of producing a 0.8 ns rise time, 1.3 ns wide, 1.1 kV pulse into a 50 Omega load at a maximum repetition rate of 200 kHz. Techniques to implement physical layouting strategies to achieve subnanosecond rise times are outlined. Problems faced in integrating the subnanosecond pulse generator with a biological load are discussed. This pulse generator will be used in experiments aimed at electromanipulation of intracellular biomolecular structures.

Energy Efficiency of Corona Discharge Reactor Driven by Inductive Energy Storage System Pulsed Power Generator

Characteristics of a pulse corona reactor driven by an inductive energy storage (IES) pulsed power generator are described in this paper with focusing on the influence of streamer-to-glow transition on NO removal efficiency. A pulsed high voltage with a short rise time of under 30 ns is employed to generate streamer discharges homogeneously in whole the discharge region. Fast recovery diodes are used as semiconductor opening switch (SOS) to shorten the rise time. The various resistors are employed as dummy load to clarify a suitable circuit parameter such as the capacitance of a primary energy storage capacitor and/or the inductance of a secondary energy storage inductor. The energy transfer efficiency of the pulsed power generator has a maximum value of 50% at 714 Omega dummy load resistance. A co-axial cylinder type discharge chamber was used as the corona discharge plasma reactor driven by the IES pulsed power generator. The pulsed power generator supplies 30 kV pulse with 300 pps repetition rate. The co-axial cylinder plasma reactor consists of 1 mm diameter tungsten wire and 19 mm i.d. copper tube with 30 cm length. NO removal from the simulated diesel engine exhaust gas (N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> :O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> =9:1, Initial NO concentration=200 ppm) increased with input energy into the reactor. The energy efficiency for NO removal was obtained to be 25 g/kWh at 30 % removal in gas flow rate of 2 L/min. However, the energy efficiency decreased to 5 g/kWh with increasing capacitance of the primary capacitor from several hundreds pF to several nF. This decrease was caused by a streamer-to-glow transition. The efficiency was affected by oxygen concentration in the gas mixture.

Design and characterization of a high-power induction module at megahertz repetition rate burst mode

The special design considerations for a unique high-power multiple-pulse induction module at megahertz repetition rate burst mode are presented and a prototype triple-pulse induction module has been constructed to verify the engineering feasibility of such a scheme. In the prototype module, three single pulses produced independently by three Marx-charged Blumlein pulse forming lines are isolated and merged by six high-voltage rectifier diodes. Experiments conducted with an iron-based metallic glass (1K101) test induction cell demonstrate that a train of three ∼250 kV pulses separated by 800 ns can be obtained in the induction gap of the cell without resetting the magnetic cores between pulses. A pulse with a rise time of 35 ns, ±1% flat top of 60 ns, and full-width at half-maximum of 120 ns was obtained when tested with a formal linear induction cell and finely tuned. It appears that nonlinear characterization of magnetic cores results in an increase in magnetization current and voltage drop pulse by pulse; the distortion of voltage waveform is not observed in the module if the voltage-seconds of the magnetic cores are sufficient. Because 1K101 metallic glass core has two times the equivalent flux swing of that of NiZn ferrite, metallic glass is advantageous for designing a compact multiple-pulse induction cell. The maximum amplitude of the voltage reversal is about 26% of that of the incident pulse when the cores are saturated.

200 ns pulse high-voltage supply for terahertz field emission

We present a method of generating 200 ns high-voltage (up to 40 kV) pulses operating at repetition rates of up to 100 kHz, which may be synchronized with laser pulses. These supplies are simple to make and were developed for ultrafast terahertz pulse generation from GaAs photoconductive antennas using a high-repetition-rate regeneratively amplified laser. We also show an improvement in signal-to-noise ratio over a continuous dc bias field and application of the supply to terahertz pulse generation.

SOSダイオードを用いたパルスパワー電源によるNOx除去におけるストリーマ&amp;mdash;グロー転移の影響

Influence of streamer-to-glow transition in NOx removal from a simulated diesel exhaust gas using pulse streamer discharge (PSD) reactor is described in this paper. A co-axial cylinder type discharge chamber was used as the PSD reactor which was driven by inductive energy storage (IES) pulse power generator with semiconductor opening switch (SOS). The pulsed power generator supplies both polarity of 30 kV pulse with 300 pps repetition rate and 25 ns pulse width. The co-axial cylinder plasma reactor consists of 1 mm diameter tungsten wire and 19 mm i.d. copper tube with 30 cm length. NO removal from the simulated gas (N2:O2=9:1, Initial NO concentration=200 ppm) increased with input energy into plasma reactor. The energy efficiency for NO removal was obtained to be 25 g/kWh at 30 % removal in gas flow rate of 2 L/min. However, the energy efficiency decreased to 4.6 g/kWh with increasing capacitance of the primary capacitor from several hundreds pF to several nF. This decrease is caused with streamer-to-glow transition.

Increase of the roughness of the stainless-steel anode surface due to the exposure to high-voltage electric pulses as revealed by atomic force microscopy

The changes of the stainless-steel electrode surface morphology occurring due to dissolution of the anode under the action of electric pulses which are commonly utilized in cell electromanipulation procedures, have been studied by using atomic force microscopy. The surface of the polished electrode was rather smooth — the average roughness was 13–17 nm and the total roughness 140–180 nm. After the treatment of the chamber filled with 154 mM NaCl solution to a series of short (about 20 μs), high-voltage (4 kV) pulses, the roughness of the surface of the anode has increased, depending on the total amount of the electric charge that has passed through the unit area of the electrode, and exceeded 400 nm for the dissolution charge of 0.24 A s/cm 2. No changes of the cathode surface were detected. Well-defined peaks with the width of 1–2 μm and the height of over 400 nm have appeared. These peaks create local enhancements of the electric field at the interface between the solution and the electrode surface which can lead to the non-homogeneity treatment of cells by electric pulses and can facilitate the occurrence of the electrical breakdown of the liquid samples.

Incident ion fluence gradients on the front and backside of flat samples

Plasma immersion ion implantation (PIII) is ideal for fast and efficient treatment into three-dimensional objects, as shown by experiments and simulations. In this presentation, a direct comparison of implantations into the front and backside of flat sample (disc, square and rectangle) at 5–15 kV pulse voltage with argon ions is performed with the spatial distribution of the incident ion fluence measured by spectroscopic ellipsometry on SiO 2/Si coupons. A strong influence of the supporting rod for the fluence distribution on the backside of the low symmetry samples, i.e. square and rectangle was observed, in contrast to no influence for the disc sample.

Nitrogen-PBII modification of ultra-high molecular weight polyethylene: Composition, structure and nanomechanical properties

Plasma based ion implantation of nitrogen was performed on mechanically polished UHMWPE model samples by applying 27.13 MHz RF energized low pressure N 2 plasma with 15–30 kV pulses and fluences up to 5 · 10 17 ions/cm 2. Surface compositional and structural alterations and nanomechanical property changes were investigated by XPS, Raman and by nano-indentation and nano-scratch techniques. The implanted N amounted up to 13–20 at.% (N/C = 0.18–0.30), while a significant amount of oxygen could also be detected on the surface. Three types of chemical states of the incorporated nitrogen were detected, related to linear sp 2 C N–C and to planar and non-planar sp 3 type C–N bonds. The applied PBII treatment led to severe dehydrogenation of the polyethylene resulting in conversion of the surface into a nitrogen-containing DLC type structure. Up to four-fold increase of the hardness at 50–100 nm depth was measured compared to the untreated samples. The scratch volume, characterising the wear resistance, decreased also significantly down to 25–35% of the original value.