New advances in solid-state pulse generator based on magnetic switches.

The application of the nanosecond pulsed electric field (nsPEF) for biomedical treatments has gained more interest in recent decades due to the development of pulsed power technologies which provides the ability to control the electric field dose applied during tests. In this context, the proposed paper describes a new architecture of solid-state high-voltage pulse generators (SS-HVPG) designed to generate fully customised sequences of quasi-rectangular pulses. The idea is based on the combination of semiconductor switches (IGBT/MOSFET) known for their flexibility and controllability with special magnetic switches to build compact and modular generators. The proposed structure is inspired by the most known pulse generator of Marx, but mixes its two variants for negative and positive polarities. Thus, the polarity of the generated pulses can be freely selected. In addition to that, the use of IGBTs/MOSFET ensures a tunable repetition rate and pulse width. The capacitors are charged via a series of magnetic switches and a flyback DC–DC converter which provides fast and efficient charging and also an adjustable amplitude of the output pulses. The design can be easily simplified giving two other modified structures, based on the same idea, for mono-polar operating (only positive or only negative pulses) with a reduced number of switches. A SPICE simulation of the generator and results of experimental tests carried out on a three stages generator are presented. The obtained results confirm the operating principle and the claimed performances of the new structure.

A Solid-state Blumlein PFN generator using saturable pulse transformer and magnetic switch

Nanosecond and subnanosecond high-voltage pulses have used in new biological applications, such as cancer treatment using an ultrashort pulsed high electric field. For this treatment, the use of high-power pulsed electromagnetic wave has been proposed to obtain the required high electric field. This paper focuses on the design of a compact high-power pulsed electromagnetic wave generator using a nanosecond pulsed power generator for cancer treatment. We developed a pulsed power generator that continuously outputs multiple pulses via a nonlinear transmission line (NLTL) using magnetic switches. The NLTL comprises a ladder of capacitors and saturable inductors. The NLTL generates a pulse train by delaying the propagation of the pulse using the magnetic switch of each ladder. The frequency of repetition of the burst pulse is 13.8 MHz. The peak output voltage is 7 kV at the maximum input voltage of 28 kV. The number of pulses in the pulse train can be varied by the number of units of the magnetic switch.

Pulsed power is widely used for the excitation of pulsed lasers, especially the ultraviolet excimer lasers. Experiments have been carried out to demonstrate the excitation of KrF excimer laser by using pulsed power generator based on linear transformer driver (LTD) <xref ref-type="bibr" rid="ref1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[1]</xref> . In this article, the LTD system has been upgraded by replacing the semiconductor switches with silicon carbide (SiC) devices in order to increase the output current and by reshaping the output interface so that it fits better with the geometry of the laser chamber. For excimer laser application, the output current and its rise time are very important issues. These are the focus points of the system design and performance analysis for this study. The experimental test system is described in detail and the results are presented with discussions on potential applications.

基于半导体开关和磁开关的全固态脉冲电源

Summary form only given. For realizing extreme ultraviolet (EUV) lithography, a debris free EUV source with collectable radiation power of about 115 W and repetition rates exceeding 7-10 kHz will be required. Discharge produced plasma is one of the promising radiation source for achieving the required parameters. However, it has a problem of debris generation, which is due to the melting and evaporation of electrodes and a capillary caused by the excess input of heat into their surfaces and the fact that the pinching plasma interacts more strongly with the insulator surface than others. In present study, in order to overcome these difficulties and to satisfy the source requirements, a capillary Z-pinch discharge light source has been made and demonstrated. Our device is equipped with a water-cooled ceramic capillary and electrodes, and a solid state pulsed power generator. A stacked static induction thyristors are used as switching elements, which enable high repetition rate operation of pulsed power supply. A magnetic switch is connected in series, which not only assists the semiconductor switch but also provides a preionization current. It has been confirmed that the duration of preionization current can be controlled by amplitude of offset current flowing through magnetic switch and that the preionization is essential to generate a uniform and stable plasma. For mitigating debris, the gas curtain system, which is consisted of supersonic nozzle and diffuser, has been installed. The properties of the radiated EUV light will be discuss. Also, preliminary experimental results of gas curtain system will be shown.

A new type of multi-pulse generator is proposed for the generation of high power pulses with extremely short pulse repetition interval. In this system, an air-core stepup transformer is used with a magnetic switch. The pulse forming line is charged on a double resonance mode. Numerical simulations of the system have shown that 600 kV, 56 ns duration pulses, matched to a 20 /spl Omega/ impedance can be produced with a minimum pulse separation of 2.7 /spl mu/s. To demonstrate the production of double pulses experimentally, a small system was constructed. The system is constructed of two first stage capacitors (150 nF each), an air-core step-up transformer of turn ratio 1:15, magnetic switch using cobalt based material, a second stage capacitor of 1.6 nF and a load of 80 n. Double pulses of duration 100 ns, peak voltage 85 kV (first pulse) and 90 kV (second pulse) are successfully generated with interval of 3.75 /spl mu/s when initial charging voltage of the first stage capacitors were 14 kV (for first pulse) and 17 kV (for second pulse).

Summary form only given. In this study, a SPPT (Solid Propellant Pulsed Plasma Thruster) driven by a MPC (Magnetic Pulse Compression) pulse generator is presented. Electromagnetic SPPT is well-known and is one of the most simple structures for electric propulsion: it is very lightweight and reliable and its thrust force can be easily controlled by the pulse discharge characteristics. In this type of system propellants are supplied from ablation of the solid propellant by surface discharge; therefore, it is difficult to regulate the propellant supply and ensure efficient use. This causes low performance of PPT. To achieve efficient utilization of the propellant, a MPC pulse generator was used as the power source of the SPPT. The magnetic switch which was used in the MPC has a magnetic saturation characteristic. When the magnetic switch is unsaturated, discharge current is restricted by the high inductance of the magnetic switch, and propellants are fed and excited by surface discharge. Later, when the magnetic switch is saturated, high current flows through the plasma and it is accelerated by the Lorentz force. Here, a high di/dt converted the mechanism to acceleration, quickly. It was contributed to reduce the Late-Time Vaporization by low rising temperature. Also, the main discharge was formed including pre-spread plasma and it accelerates the plasma efficiently. The pulse discharge of the MPC also composes the igniter which does not require an external power supply. A co-axial electrode type MPC-SPPT was designed and operated to demonstrate the system. The igniter was put as the center electrode and driven with a MPC pulse discharge. The 18 J MPC with a thruster body has a 41.6 nF energy storage capacitor and less than 80 nH of parasitic inductance. The peak discharge current is 15 kA, and the thrust performances were evaluated by a thrust target. From experimental results the advantages and capabilities of a MPC-SPPT system are discussed.

Recently, pulsed power technologies, including pulsed electric fields (PEFs) and time-modulated plasmas, are starting to be applied actively in agriculture and food processing. In the applications, compact pulsed power generators with moderate peak power and repetitive operation are developed for controlling discharge plasmas and electric field distribution. These applications are mainly based on the biological effects of a spatially distributed electric field and the chemically active species in the plasma. The PEFs are caused by applying pulse voltage between the electrodes and contribute to form pores on the cell membrane or to change conformation of protein. When the applied voltage exceeds the discharge onset criterion, plasmas are generated through the avalanche process of electron accelerated with intense electric field in a gas or liquids medium. The plasmas produce chemically active species, UV radiation, an intense electric field in the vicinity of discharge channel and shock waves, which also have different biological effects. The agricultural applications of pulsed power can be categorized as two phases: pre-harvest and post-harvest phases. The pre-harvest phase consists of seed germination, seedling growth, plant growth and growth mode change from vegetative to reproductive. Pulsed power technologies are used to promotion of seed germination, plant growth enhancement through direct stimulation or indirect effect such as inactivation of bacteria in soil and liquid hydroponic media, and promotion of mushroom fruit body formation. The post-harvest phase consists of harvesting the agricultural produce, storing the products, transporting the products to consumers and food processing such as drying, pasteurization (sterilization of bacteria), permeabilization and fermentation. The pulsed power technologies are also used to keep freshness of agricultural produce through decontaminating airborne, inactivating bacteria and decomposition of plant hormone in the storage containers. The poration of cell membrane by PEF contributes improvement of extraction of juice, nutritional agents, and antioxidant metabolites such as polyphenols from agricultural products. In this review, at first, a basis of pulsed power system for agricultural applications and bio-effect by high-electric field exposure is outlined. After that, pre-harvest and post-harvest agricultural applications are described. The utilization of pulsed power technologies to contribute efficient food processing and improve food safety and quality is also described.

As important devices for voltage boosting and switching, respectively, pulse transformer and magnetic switch are widely used in pulsed power technology. In this paper, a new kind of transformer type magnetic switch (TTMS) with coaxial cylindrical conductors is put forward to combine the functions of voltage boosting and switching in one power device. As a compact combination device of discrete pulse transformer and magnetic switch, the compact TTMS decreases the required volume of magnetic cores in a large scale. The primary windings of the TTMS have a parallel combination structure so that the TTMS which only has 3 turns of secondary windings has a step-up ratio at 1:9. Before the magnetic core saturates, the TTMS has low unsaturated inductances of windings and good pulse response characteristics, so it can be used to substitute the Marx generator to charge the pulse forming line (PFL) at the ranges of several hundred kV and several hundred ns. After the core saturates, the cylindrical conductors can decrease the saturated inductance of the secondary windings of TTMS to a level less than 400 nH. As a result, the proposed TTMS can be used as the boosting transformer and main switch of helical Blumlein PFL to form the quasi-square voltage pulse on the 160 Ω load with a short pulse rise time only at 60 ns.

Iron-based nanocrystalline ribbon has been widely used in pulsed power devices such as transformer, magnetic switch and linear transformer driver, due to its fast response to the high-frequency pulse, high permeability and low loss of magnetization. In this paper, the ns- and μs-range insulation characteristics of iron-based nanocrystalline ribbon coated by TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> film with μm-range thickness are studied in detail. In order to evaluate the induced inter lamina voltage of the stacked ribbons, a method for withstand voltage test of the nanocrystalline ribbon is put forward under short voltage pulses. In air and transformer oil, breakdown voltages of the nanocrystalline ribbons were investigated under the conditions of different pulse widths and repetition rates. Breakdown voltages of multiple layers of the ribbon samples in stacked were also studied, and many important conclusions were revealed. The conclusions show great value on the design and manufacture of the magnetic pulsed power devices at the range of several hundred kV.

High-voltage pulsed power is nowadays a very important research field and an expanding industrial technology with major worldwide economical impact, this technology being used in different applications (food processing, medicine…). For the development of PEF technology, it is necessary to have a wide variation interval of the different pulse parameters (amplitude, pulse width, frequency …). Conventional pulse generators do not allow it, prompting the researchers to focus on the development of pulse generators to make them more versatile to be used in different applications. With the development of solid-state electronics, solid-state devices are becoming more and more suitable for pulsed power application. They could provide the pulsed power systems with compactness, reliability, high repetition rate, and long life time. The rising of pulsed power generators using solid-state devices eliminates limitations of conventional components, and promises pulsed power technology to be widely used in commercial applications. However, solid-state switching devices such as Insulated Gate Bipolar Transistor (IGBT) available now are only rated up to a few kilo Volts. Most of pulsed power systems demand much higher voltage ratings. The aim of the present work is the development of a Marx modulator which is a unique circuit intended for voltage multiplication. Its functioning is based on charging capacitors in parallel and discharging them in series into the treatment chamber. The Marx bank developed comprises four stages, was constructed using 1200 V IGBTs and 10 µF capacitors. This generator is versatile; several factors could be varied such as the voltage level up to 3.6 kV, the repetition rate and the pulse width.

Summary form given only. Pulsed power technology has been used in many applications such as control of NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> and SO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> from exhaust gases, treatment of dioxins, removal of volatile organic compounds, generation of ozone and excitation of excimer laser. Since pulse duration of applied voltage to discharge reactor has a strong influence on energy efficiency of pollutants removal, the development of short pulse generator is paramount important for practical applications. The discharge observation of the short duration pulse voltage is an essential aspect for understanding plasma physics of this new field. In the present work, the characteristics of the developed nano-seconds (ns) pulse generator, which has the pulse duration of 5 ns, and the observation results of nano-second (ns) pulsed streamer discharges in atmospheric air are presented. The developed ns pulse generator consists of a high pressure spark gap as a lower inductance self-closing switch, a triaxial Blumlein line as a pulse forming line, a coaxial energy transmission line as a connection between the Blumlein and a load, and a pulse charging source. The triaxial Blumlein line is filled up with transformer oil as insulation and dielectric medium. The ns pulse generator outputs the positive voltage, having 2 ns of rise time and 5 ns of pulse duration. The maximum output voltage reaches up to 100 kV. The propagations of the positive and the negative ns pulsed streamer discharges in a coaxial electrode were observed using a high speed gated ICCD camera and a high dynamic range streak camera. During the both polarities of ns pulsed streamer discharges, the primary and the secondary streamers propagated from inner wire to outer cylinder electrodes. This phenomenon has good agreement to the previous works which are observed in the cases of sub-frac14s pulsed streamer discharges. However, the propagation velocity of the primary streamers in the present work is approximately 6 times faster than the previous one. This is because that the velocity of primary streamers dependent on applied voltage to electrode and ns pulse generator is able to apply the higher voltage to electrode than sub-frac14s pulse generator.

In a present pulsed power generator system using semiconductor switches, saturable magnetic switches are usually connected in series to compress the output pulse because the current rise-time of semiconductor switches are generally not short enough, However, the magnetic switches are heavy and they reduce the energy transfer efficiency. So we propose a pulsed power generator system using a 5500-V static induction thyristor (SI-Thy), a Blumlein line for pulse formation, and a step-up pulse transformer. The fundamental characteristics of the generator are evaluated. From experiments using only one SI-Thy, turn-on time of several tens of nanoseconds and the maximum rise rate of the output voltage of 115-kV//spl mu/s are obtained. It is confirmed that an SI-Thy will have sufficient performance as a main switch of the pulsed power generator for the flue gas treatment and decomposition of hazardous gases when several SI-Thys are connected in series.

An all solid-state high-voltage rectangular pulse generator is proposed in this paper. This generator mainly consists of a Marx generator, a pulse forming line (PFL) and a magnetic switch (MS). As the power supply, Marx generator discharges to the PFL through an inductor. The inductance must be precisely designedly since it influences the discharging process directly and determines the volt-second product of the MS and the pre-pulse over the load. The MS saturates right the moment the discharging process finishes. Then PFL discharges to the matched resistor load through the saturated MS and a high-voltage rectangular pulse is obtained over the load. The design of Marx generator and MS are introduced in details. Experiments and PSPICE simulation are carried out. The experimental result matches well with the simulating result. A rectangular pulse with 12.5-kV voltage amplitude, 46-ns risetime, 220-ns pulsewidth was obtained over the 50-Ohm resistor load.