Showing papers on "Marx generator published in 2005"

Demonstration of a desk-top size high repetition rate soft x-ray laser.

Abstract: We have demonstrated a new type of high repetition rate 46.9 nm capillary discharge laser that fits on top of a small desk and that it does not require a Marx generator for its excitation. The relatively low voltage required for its operation allows a reduction of nearly one order of magnitude in the size of the pulsed power unit relative to previous capillary discharge lasers. Laser pulses with an energy of ~ 13 microJ are generated at repetition rates up to 12 Hz. About (2-3) x 10 4 laser shots can be generated with a single capillary. This new type of portable laser is an easily accessible source of intense short wavelength laser light for applications.

X‐ray bursts produced by laboratory sparks in air

Abstract: [1] X-ray observations were made during fourteen 1.5 to 2.0 m high-voltage discharges in air produced by a 1.5 MV Marx circuit. All 14 discharges generated x-rays in the ∼30 to 150 keV range. The x-rays, which arrived in discrete bursts, less than 0.5 microseconds in duration, occurred from both positive and negative polarity rod-to-plane discharges as well as from small, 5–10 cm series spark gaps within the Marx generator. The x-ray bursts usually occurred when either the voltages across the gaps were the largest or were in the process of collapsing. The bursts are remarkably similar to the x-ray bursts previously observed from lightning. These results should allow for the detailed laboratory study of runaway breakdown, a mechanism that may play a role in thunderstorm electrification, lightning initiation and propagation, and terrestrial gamma-ray flashes (TGFs).

Novel dual Marx Generator for microplasma applications

Abstract: Micrometer size plasmas, or microplasmas, find applications in pollution control, reduction, and prevention. The required nonthermal plasmas can be generated by either an electron beam or an electric discharge. The pulse widths and voltages necessary to generate these nonthermal plasmas are 10/sup -10/-10/sup -8/ s, and 10/sup 3/-10/sup 4/ V, respectively, depending on the application. The required energy is typically in the low 10/sup -3/ J range. This paper presents a novel circuit design to generate high-voltage pulses with variable pulse widths and pulse rise and fall times in the low 10/sup -9/ s regime. The circuit employs two parallel Marx Generators utilizing bipolar junction transistors (BJTs) as closing switches. The BJTs are operated in the avalanche mode to yield fast rise times. The design allows for positive or negative polarity pulses, and can easily be changed to yield higher or lower output voltage.

Solid state Marx Generator using series-connected IGBTs

Abstract: This paper describes a newly developed novel repetitive impulse voltage generator using a boost converter array. To solve problems such as short life time, low operating frequency, and the fixed pulse width of conventional generators, the proposed generator is designed with a boost converter array that employs series-connected capacitors and insulated gate bipolar transistors. The circuit can easily obtain a high-voltage pulse without any high-voltage direct current source and pulse transformer. Thus, the proposed circuit not only allows elimination of the expensive high-frequency transformer but also allows operation at a frequency up to several kilohertz with high reliability and longer life span. To validate the proposed circuit, two pulse generators rated at 1.8 kV, 40 A and 20 kV, 300 A are implemented and tested.

High voltage pulse generator

Abstract: A high voltage pulse generator (11) utilizes an even number of Marx cells (13) using L-C inversion topology. Each Marx cell is associated with an individual inverter transformer (T1 and T2) having a primary winding connected to the output o an ac power supply such as a series resonant inverter (12). The secondary of each inverter transformer is half-wave rectified to charge the energy storage capacitors in each Marx cell. A distributed voltage-sensing scheme can be provided for accurate feedback to the inverter's controller. An inductive element can be used to achieve a magnetic diode effect in the L-C inversion circuit to reduce component stress and improve efficiency. A transformer-coupled floating gate drive circuit can be used as one method of providing local power conditioning and trigger timing for discharge of the energy storage capacitors.

Design and optimization of a compact, repetitive, high-power microwave system

Abstract: The electrical characteristics and design features of a low inductance, compact, 500 kV, 500 J, 10 Hz repetition rate Marx generator for driving an high-power microwave (HPM) source are discussed. Benefiting from the large energy density of mica capacitors, four mica capacitors were utilized in parallel per stage, keeping the parasitic inductance per stage low. Including the spark-gap switches, a stage inductance of 55 nH was measured, which translates with 100 nF capacitance per stage to ∼18.5Ω characteristic Marx impedance. Using solely inductors, ∼1mH each, as charging elements instead of resistors enabled charging the Marx within less than 100 ms with little charging losses. The pulse width of the Marx into a matched resistive load is about 200 ns with 50 ns rise time. Repetitive HPM generation with the Marx directly driving a small virtual cathode oscilator (Vircator) has been verified. The Marx is fitted into a tube with 30 cm diameter and a total length of 0.7 m. We discuss the Marx operation at up...

Triggered Marx generators for the industrial-scale electroporation of sugar beets

Abstract: Electroporation is a method to induce pores in the membranes of biological cells by applying an electric field. During the last few years, some research and development has been done for sugar beets to transfer this method from the laboratory into the industrial scale in order to replace the thermal denaturation process. High-efficiency pulsed electric fields with short pulse durations are applied to the beets as a whole. This paper deals with some aspects concerning the electrode geometry and a new trigger concept for the Marx generators used to create the required electric fields.

High voltage pulse power supply using Marx generator & solid-state switches

Abstract: High voltage pulse power supply using Marx generator and solid-state switches is proposed in this study. The Marx generator is composed of 12 stages and each stage is made of IGBT stack, two diode stacks, and capacitor. To charge the capacitors of each stage in parallel, inductive charging method is used and this method results in high efficiency and high repetition rates. It can generate the pulse voltage with the following parameters: voltage: up to 120 kV, rising time: sub /spl mu/S, pulse width: up to 10 /spl mu/S, pulse repetition rate: 1000 pps. The proposed pulsed power generator uses IGBT stack with a simple driver and has modular design. So this system structure gives compactness and easiness to implement total system. Some experimental results are included to verify the system performances in this paper.

A 10-GW Pulsed Power Supply for HPM Sources

Abstract: A research activity involving the detailed consideration of novel high voltage transformers (HVTs) for pulsed-power applications has recently begun at Loughborough University (LU). Although the main goal is the demonstration of a compact and lightweight unit employing magnetic self insulation under vacuum conditions, the initial stage of the work is directed towards the development of a conventional air-cored HVT as a main component in a compact power supply for HPM sources. In cooperation with the Swedish Defence Research Agency (FOI), the power supply has been tested with a HPM source of the vircator type. The power source for the system uses a 70 kJ/25 kV capacitor bank and an exploding wire array to generate a 150 kV voltage pulse in the primary circuit of the HVT. A pressurised SF6 spark gap in the secondary circuit sharpens the high-voltage output, so that pulses approaching 500 kV and with a rise time below 100 ns are generated on a 20 Omega high-power resistor. The peak power produced by the power supply is in excess of 10 GW. Measurements provided by various diagnostic techniques are analysed with the aid of a detailed numerical code. Experimental results are presented from final testing of the system, where a reflex triode vircator replaces the 20 Omega resistor. Measurements made of the microwave emission using free-field sensors are presented for various electrode configurations. Comments are made with the microwave emission from the same vircator powered by a Marx generator at FOI.

A Compact, Repetitive, 500kV, 500 J, Marx Generator

Abstract: The electrical characteristics and design features of a low inductance, compact, 500 kV, 500 J, 10 Hz repetition rate, Marx generator are discussed. While benefiting from the large energy density of mica capacitors, 4 mica capacitors were utilized in parallel per stage, keeping the parasitic inductance per stage low. Including the spark- gap switches, a stage inductance of 55 nH was measured, which translates with 100 nF capacitance per stage to ~18.5 Omega characteristic Marx impedance. Using solely inductors, ~1 mH each, as charging elements instead of resistors enabled charging the Marx within less than 100 ms with little charging losses. The pulse width of the Marx into a matched resistive load is about 200 ns with 50 ns rise-time. Repetitive HPM generation with the Marx directly driving a small Vircator has been verified. The Marx is fitted into a tube with 30 cm diameter and a total length of 0.7 m. We discuss the Marx operation at up to 21 kV charging voltage per stage, with repetition rates of up to 10 Hz in burst mode primarily into resistive loads. A lumped circuit description of the Marx is also given, closely matching the experimental results.

All Silicon Marx-bank Topology for High-voltage, High-frequency Rectangular Pulses

Abstract: This paper discusses the operation of a fully integrated solid-state Marx generator circuit, which has been developed for high-frequency (kHz), high-voltage (kV) applications needing rectangular pulses. The conventional Marx generator, used for high-voltage pulsed applications, uses inductors, or resistors, to supply the charging capacitors voltage, which has the disadvantages of size, power loss and frequency limitation. The proposed circuit takes advantage of the intensive use of power semiconductor switches, replacing the passive elements in the conventional circuit, to increase the performance, strongly reducing losses and increasing the pulse repetition frequency. Also, the proposed topology enables the use of typical half-bridge semiconductor structures, while ensuring that the maximum voltage blocked by the semiconductors is the voltage of each capacitor (i.e. the power supply voltage), even with mismatches in the synchronized switching, and with fault conditions. A laboratory prototype with five stages, 5 kW peak power, of this all silicon Marx generator circuit, was constructed using 1200 V IGBTs and diodes, operating with 1000 V d-c input voltage and 10 kHz frequency, giving 5 kV pulses, with 10 mus width and 50 ns rise time

High-voltage high-frequency Marx-bank type pulse generator using integrated power semiconductor half-bridges

Abstract: This paper discusses the operation of an all silicon-based solution for the conventional Marx generator circuit, which has been developed for high-frequency (kHz), high-voltage (kV) applications needing rectangular pulses The conventional Marx generator, for high-voltage pulsed applications, uses passive power components (inductors or resistors), to supply the energy storage capacitors This solution has the disadvantages of cost, size, power losses and limited frequency operation In the proposed circuit, the bulky passive power elements are replaced by power semiconductor switches, increasing the performance of the classical circuit, strongly reducing costs, losses and increasing the pulse repetition frequency Also, the proposed topology enables the use of typical half-bridge semiconductor structures, and ensures that the maximum voltage blocked by the semiconductors equals the power supply voltage (ie the voltage of each capacitor), even with mismatches in the synchronized switching, and in fault conditions A laboratory prototype with five stages, 5 kW peak power, of the proposed silicon-based Marx generator circuit, was constructed using 1200 V IGBTs and diodes, operating with 1000 V d-c input voltage and 10 kHz frequency, giving 5 kV/1 A pulses, with 10 mus width and 50 ns rise time

Status of the 10 MV, 120 kA RITS-6 Inductive Voltage Adder

Abstract: The six-cell RITS-6 accelerator is an upgrade of the existing RITS-3 accelerator and is next in the sequence of Sandia IVA accelerators built to investigate/validate critical accelerator and radiographic diode issues for scaling to the Radiographic Integrated Test Stand (RITS) (nominally 16 MV, 156 kA, and 70 ns). In the RITS-6 upgrade to RITS-3 the number of cells/cavities, PFLs, laser triggered gas switches and intermediate stores is being doubled. A rebuilt single 61-nF Marx generator will charge the two intermediate storage capacitors. The RITS-3 experiments have demonstrated a MITL configuration matched to the PFL/induction cell impedance and a higher impedance MITL. RITS-6 is designed to utilize the higher impedance MITL providing a 10.5-MV, 123-kA output. The three years of pulsed power performance data from RITS-3 will be summarized and the design improvements being incorporated into RITS-6 will be outlined. The predicted output voltage and current for RITS-6 as a function of diode impedance will be shown. Particle-in-cell simulations of the vacuum power flow from the cell to the load for a range of diode impedances from matched to ~ 40 Ohms will be shown and compared with the re-trapped parapotential flow predictions. The status of the component fabrication and system integration will be given. Another potential upgrade under consideration is RITS-62. In this case the RITS-6 Marx, intermediate stores, gas switches, and PFLs would be duplicated and a tee would replace the elbow that now connects a single PFL to a cell thereby allowing two PFLs to be connected to one cell. The output of RITS-62 matched to the cell/PFL impedance would then be 8 MV, 312 kA or 25.6 ohms. The predicted operating curves for RITS-62 with other non-matched MITLs will be shown. The power delivered to a radiographic diode can be maximized by the correct choice of MITL impedance given the cell/PFL and radiographic diode impedances. If the radiated output for a given diode has a stronger than linear voltage dependence this dependence can also be included in the correct choice of MITL impedance. The optimizations and trade-offs will be shown for RITS-6 and RITS-62 for diode impedances characteristic of radiographic diodes.

Rapid Capacitor Charger for 10 HZ Operation of a Low-Inductance Compact Marx Generator

Abstract: We designed and build a rapid capacitor charger for 10 Hz, 500 J/shot operation of a low-inductance, compact Marx generator. The charger uses a hard-switched IGBT H-Bridge Inverter, which drives a 30 kHz, nano- crystalline step-up transformer. The transformer, in addition to the high-voltage rectifier and a trigger- transformer are contained in a section which is filled with transformer oil. The main circuit board also contains a solid-state Marx generator to trigger the main Marx generator. We also implemented a self-powered HV-feedback sensor to stop the charge process precisely at the target voltage. This new sensor greatly enhanced the rep-rated performance of the Marx by preventing pre-fires, since it enabled us to charge aggressively without overshooting the target voltage and have more time for spark-gap recovery.

Characteristics of pulsed power generator by versatile inductive voltage adder

Abstract: A pulsed power generator by inductive voltage adder, versatile inductive voltage adder (VIVA-I), which features a high average potential gradient (2.5 MV/m), was designed and is currently in operation,. It was designed to produce an output pulse of 4 MV/60 ns by adding 2 MV pulses in two-stages of induction cells, where amorphous cores are installed. As a pulse forming line, we used a Blumlein line with the switching reversed, where cores are automatically biased due to the presence of prepulse. Good reproducibility was obtained even in the absence of the reset pulse. Within ∼40% of full charge voltage, pulsed power characteristics of Marx generator, pulse forming line (PFL), transmission line (TL), and induction cells were tested for three types of loads; open-circuit, dummy load of liquid (CuSO4) resistor, and electron beam diode. In the open-circuit test, ∼2.0 MV of output voltage was obtained with good reproducibility. Dependences of output voltage on diode impedances were evaluated by using various dummy loads, and the results were found as expected. An electron-beam diode was operated successfully, and ∼18 kA of beam current was obtained at the diode voltage of ∼1 MV.

ZR Marx capacitor vendor evaluation and lifetime test results

Abstract: The Z machine at Sandia National Laboratories (SNL) is the world's largest and most powerful laboratory X-ray source. The Z Refurbishment Project (ZR) is presently underway to provide an improved precision, more shot capacity, and a higher current capability. The ZR upgrade has a total output current requirement of at least 26 MA for a 100-ns standard Z-pinch load. To accomplish this with minimal impact on the surrounding hardware, the 60 high-energy discharge capacitors in each of the existing 36 Marx generators must be replaced with identical size units but with twice the capacitance. Before the six-month shut down and transition from Z to ZR occurs, 2500 of these capacitors will be delivered. We chose to undertake an ambitious vendor qualification program to reduce the risk of not meeting ZR performance goals, to encourage the pulsed-power industry to revisit the design and development of high- energy discharge capacitors, and to meet the cost and delivery schedule within the ZR project plans. Five manufacturers were willing to fabricate and sell SNL samples of six capacitors each to be evaluated. The 8000-shot qualification test phase of the evaluation effort is now complete. This paper summarizes how the 0.279/spl times/0.356/spl times/0.635-m (11/spl times/14/spl times/25-in) stainless steel can, Scyllac-style insulator bushing, 2.65-/spl mu/F, <30-nH, 100-kV, 35%-reversal capacitor lifetime specifications were determined, briefly describes the nominal 260-kJ test facility configuration, presents the test results of the most successful candidates, and discusses acceptance testing protocols that balance available resources against performance, cost, and schedule risk. We also summarize the results of our accelerated lifetime testing of the selected General Atomics P/N 32896 capacitor. We have completed lifetime tests with twelve capacitors at 100 kV and with fourteen capacitors at 110-kV charge voltage. The means of the fitted Weibull distributions for these two cases are about 17 000 and 10 000 shots, respectively. As a result of this effort plus the rigorous vendor testing prior to shipping, we are confident in the high reliability of these capacitors and have acquired information pertaining to their lifetime dependence on the operating voltage. One result of the analysis is that, for these capacitors, lifetime scales inversely with voltage to the 6.28/spl plusmn/0.91 power, over this 100 to 110-kV voltage range. Accepting the assumptions leading to this outcome allows us to predict the overall ZR system Marx generator capacitor reliability at the expected lower operating voltage of about 85 kV.

A Compact, Low Jitter, 1 kHz Pulse Repetition Rate Gas-Switched Pulse Generator System

Abstract: We present the results of an experimental research effort focused on developing a compact, low jitter, command triggered, high peak power, high pulse repetition rate (PRR), gas-switched pulse generator system. The pulse generator is command triggered by a single TTL level pulse generated by a control system implemented using software and a computer interface card. The TTL trigger pulse fires a solid-state trigger pulser that closes the first stage switch in a modular Marx-like pulse generator. The control system also sets the charge voltage of a 2500 J/s high voltage capacitor charging power supply and inhibits capacitor charging during firing of the pulse generator. The individual Marx stages are compact and stackable and utilize surface mount multilayer ceramic chip capacitors and field enhanced spark gap switches. The stage capacitors are charged in parallel through mutually coupled inductors in series with resistors. This charging scheme allows for high PRR operation limited only by the stage switch recovery time and the power of the capacitor charging power supply. The stage switches are optically coupled to aid in Marx erection and to minimize system jitter. The Marx generator is housed in a pressure vessel and operated in a low pressure dry air environment. The design exhibits a low inductance which is estimated to be <20 nH based on the measured output voltage rise time and load resistance. The pulse generator system has been operated in a burst mode at a PRR in excess of 1 kHz with good output voltage regulation. The jitter of the Marx generator, characterized independent of the trigger pulse, was measured and found to be ~500 ps.

Influence of peaking capacitors in reducing rise times of high-voltage nanosecond pulses

Abstract: High-voltage (a few hundred kilovolt), short pulses (microseconds to to nanoseconds) have been found to be effective for various biological decontamination applications, such as cleaning of water with bacteria/algae. Marx generators are most commonly used for this purpose. A serious disadvantage of Marx generators is the increase in rise times due to series inductance. To alleviate this effect, peaking capacitors have been used to produce early time, fast-rising pulses that the Marx generators otherwise cannot supply due to their relatively high series inductance. This paper presents the results of the design and development of a 600-kV, 50-ns-rise-time, and /spl sim/250-ns-duration pulse generator using a peaking capacitor. A 132-kV condenser-type bushing of 650-kV BIL and 230-pF capacitance was used as a peaking capacitor to reduce rise time. The effect of the peaking capacitor was also studied employing circuit modeling of the generator and the influence of various parameters was investigated. There is a good correlation between the experimental and the numerical results.

Current Radiographic Pulsed Power Machines at AWE

Abstract: The Hydrodynamics Department at AWE has built up an impressive suite of X-ray machines over the last four decades. The machines cover a voltage range from 800 kV to 9.5 MV which caters for a broad range of experiments. The service radiographic machines are fielded in pairs which gives the added bonus that two images can be gained from each experiment. All the machines are built on the same principles. A Marx generator charges a Blumlein which is discharged by a self closing switch. The output pulse passes through an insulator stack (X-ray tube) into a magnetically insulated transmission line (MITL) and on to the e-beam diode. The Hydrodynamics Department is developing higher resolution X-ray sources for its future facilities. To develop these sources the department has three research machines, Eros for low impedance diodes like the rod pinch and self pinch, EMU for high impedance diodes such as the paraxial and immersed Bz and PIM (an IVA based machine) for 1-3 MV X-ray machine and diode research.

Autonomous RF Radiation Package for Various Applications

Abstract: The development of an autonomous RF radiation package for various applications is presented. This work is a coordinated effort to develop a tightly integrated unit, including the batteries, power supply, Marx generator, and plug and play antennas for various applications. ARC technology has designed the Marx generator and its associated high voltage antennas for this effort. Previous work by ARC has demonstrated 75 mm diameter, 700 mm length diameter Marx generators capable of delivering 200 kV pulses into 50 Omega coaxial cable with sub-nanosecond risetimes, enabling it to drive an antenna and generate high power microwaves. This technology has been re-designed into a reduced length geometry and augmented by inductive charging to permit pulse repetition rates. The antenna is incorporated directly onto the Marx output for efficient energy transfer and for compactness. This package has demonstrated peak electric field strengths up to 4700 V/m at 10 m. Texas Tech University has worked closely with ARC in developing a rapid charging power supply to meet stringent package constraints and still permit high pulse repetition rates. This system has already demonstrated the ability to charge a 50 nF capacitance up to 40 kV with a repetition frequency of 100 Hz, delivering an average power of 4 kW. This paper details the present status of the project, which will be completed in July, 2005. The cylindrical geometry of the final package has a diameter of 155 mm, a length of approximately 1500 mm without the antenna, and a mass of approximately 35 kg, depending upon the chosen antenna implementation. Results of preliminary tests are included.

Fast discharge energy storage development for advanced X-ray simulators

Abstract: Design studies have been completed to investigate the impact of improvements in fast energy storage systems on the designs of: larger future simulators (such as a 15-MA plasma radiation source (PRS) simulator), simulator upgrades of operational machines (such as Double-EAGLE), and for very compact, smaller simulators. The fast energy storage system that has been investigated and is presently under development is a fast Marx generator (FMG) with inductance capacitance (LC) 1/2=200 ns and LC 1/2=300 ns, depending on the capacitance per stage. This new fast Marx energy storage system uses newly developed, low-inductance rail switches and low-inductance capacitors. These components are configured in a low-inductance FMG stage and then stacked in series to form a unit for the voltage required and a number of units in parallel for the required system inductance and stored energy. A four-stage fast Marx prototype has been demonstrated with a total of 60-kJ energy stored and an output voltage of 680 kV. This new FMG technology will provide the capability to build X-ray machines in a significantly more compact configuration. The new FMG technology minimizes or eliminates the need for storing the energy in a large water transfer capacitor. A design sketch of a 15-MA PRS machine driven by a fast Marx will be presented. This generator would consist of 48 eight-stage FMG units and would drive the PRS directly without further pulse compression. We will also present the concept of a high voltage (2-3 MV), compact X-ray machine that uses a nine-stage fast Marx module to directly charge a vacuum inductive store. A plasma opening switch (POS) is used to switch the inductive store and deliver the electron beam to the load.

Compact, repetitive Marx generator and HPM generation with the Vircator

Abstract: ii ACKNOWLEDGEMENTS I would like to thank my committee for the support they gave me throughout the project's length. I would especially like to thank Dr. Neuber for his guidance and serving as the chairman for the committee. Also, I would like to thank Dr. Mankowski for the help that he has given me especially with the Vircator testing and for being a part of my thesis committee. Special thanks goes out to and the pulse power staff who made the completion of this project possible. I would also like to extend my gratitude to all my colleagues in the Center of Pulse Power and Power Electronics whose friendship and assistance has proven invaluable in this projects accomplishment. Additional thanks goes to my parents, Kuo-Tsai and Suh-Jen Chen who have supported me through out my years and raised me to be the person that I am. I would also like to thank Khuyen Do for her love a support through out the project. Finally, I thank God for watching and protecting my every step in this journey.

A Fast, 3MV Marx Generator for Megavolt Oil Switch Testing with an Integrated Abramyan Network Design

Abstract: The University of Missouri-Columbia has a new test facility online to study oil breakdown of enhanced and uniform gaps. The test facility includes a 3 MV Marx generator consisting of 30 stages with a total capacitance of 1.6 nF. With an inductance of 4.6 muH, the pulser is designed to deliver the 3 MV output pulse with a risetime (10-90%) of < 10 ns with a peaking gap. The output polarity of the pulser can be easily reversed for switch and dielectric testing. The configurations tested include a large electrode gap spacing with point-ball electrodes. The test results from these experiments will be reported along with a conceptual design for a simple modification which will allow a rectangular pulse to be applied to the sample under test. The conceptual design for the pulser includes an Abramyan network designed to extend the output at 1-1.5 MV to a pulse width of 1 mus. By reverse-discharging a fraction of the stages in parallel with an inductor of an optimized value, the pulse width increases dramatically at a minimal cost to the pulse amplitude. The cost-effective addition of a single inductor will be compared to the efficiencies of traditional pulse-forming networks. This paper will also discuss the Abramyan network versatility with respect to altering pulse amplitude and width using a simple modification to the inductor. Benefits for switch testing will be discussed along with test results.

Intense nanosecond duration source of 10–250 keV x rays suitable for imaging projectile-induced cavitation in human cadaver tissue

Abstract: The design, fabrication, and performance of a repetitive nanosecond x-ray source having a pumped field-emission x-ray tube are described. A compact Marx generator, 61 cm in length and storing 12 J energy, directly drives the field-emission tube with voltage pulses >380kV and with <4ns rise time from an equivalent generator impedance of 52Ω. The x-ray dose is 520 μSv at a distance of 30.5 cm. A numerical simulation model is used in which the x-ray tube’s cathode width and anode-cathode gap spacing are permitted to change with time, while electron flow between the cathode and anode is space charge limited and nonrelativistic. The x-ray tube model is coupled to an equivalent circuit representation of the Marx generator that includes the capacitance variation with charging voltage of the BaTiO3 capacitors. The capabilities of the x-ray source for flash radiography have been demonstrated by the study of the evolution of cavitation in human cadaver legs induced by high-velocity projectiles.

Long-Term Test of a Triggered Marx-Generator in Repetitive Operation

Abstract: For the industrial-scale electroporation of sugar beets the use of a set of synchronized, hence triggered, Marx-generators promises an energy-efficient processing. Such generators need to operate during a seasonal campaign of 100 days without interruption. In order to obtain some experience in the possible problems of the design, a long- term test is performed. The following issues are considered to be critical: the wear of the spark gaps, the jitter of the switching time (important for the synchronization), and the durability of the over-voltage trigger circuit directly switched into the charging current's path. The paper deals with some aspects of the test.

Development of a 300-kV Marx generator and its application to drive a relativistic electron beam

Abstract: We have indigenously developed a twenty-stage vertical structure type Marx generator. At a matched load of 90–100 Ω, for 25 kV DC charging, an output voltage pulse of 230 kV, and duration 150 ns is obtained. This voltage pulse is applied to a relativistic electron beam (REB) planar diode. For a cathodeanode gap of 7.5 mm, an REB having beam voltage 160kV and duration 150ns is obtained. Brass as well as aluminum explosive electron emission-type cathodes have been used

Bipolar Marx generators with a switching turret for industrial gas processing uses directly triggered impulse generators

Abstract: The bipolar Marx generator used for gas conditioning processes uses two impulse generators [IG2,IG3] in a switching turret. One of these is synchronised with positive voltage amplitude signals and the other with negative amplitude signals. These are coupled to the reactor process [R]. The operation is provided by direct triggering using electrostatic or magnetic lenses.

Performance of an Advanced Repetitively Pulsed Electron Beam Pumped KrF Laser Driver

Abstract: Electa is a repetitively pulsed, electron beam pumped krypton fluoride (KrF) gas laser that is a step in developing the technologies that meet the Inertial Fusion Energy (IFE) requirements for durability, efficiency, repetition rate, and cost. The technologies to be developed in the Electa system are to be directly scalable to a full size fusion power plant beam line. We have fielded an advanced pulsed power driver for the KrF preamplifier in the Electa system which serves two roles: it completes the laser system and serves as a demonstrator for the advanced pulsed power topology that can meet the IFE requirements. The initial system employs a gas switched Marx with improved reliability and maintenance schedule. The Marx will later be retrofitted (circa 2006) with advanced solid state switches, presently under development in the Electa program. The output of the pulsed power driver, delivered to counter-streaming electron beam diodes, is 20/40/30 ns (trise/flattop/tfall), 150-175 kV, and 60-80 kA per side with a 1.1 ohm nominal impedance. The pulser operates in single-shot, burst, and continuous modes at up to 5 Hz, with 1 ns (1 sigma) or less absolute timing jitter. A single pulsed power driver is coupled to the opposing electron guns via four liquid-filled TTI's (transit time isolators). These TTI's are necessarily compound (oil/water/oil) in order to balance their electrical lengths against unequal mechanical lengths. The Marx is gas-insulated and charges a 1.1-ohm water PFL in less than 100 ns. An output magnetic switch with a saturated inductance of less than 14 nH using Metglasreg cores discharges the pulse forming line (PFL) into the four parallel compound TTI's. A set of four (2 each side) inverted Z-stack bushings provide the interface between the TTI's and the vacuum chambers and diodes. The pulsed power driver design for this preamplifier has been described previously.

Design of a Vacuum Coaxial Line for Astérix to Study the Behavior of a MITL at High Voltage

Abstract: AT PEM (Polygone d'Experimentation de Moronvilliers), the CEA will build a flash x-ray generator based on LTD technology. In this machine, the electrical energy is transmitted to the X-ray diode by a MITL (magnetically insulated transmission line). To study the behavior of this kind of high voltage line and the energy fed to the diode, the CEA has undertaken to install a new coaxial line on the Marx generator ASTERIX, located at the CEG (Centre d'Etudes de Gramat). This modification will associate to the present vacuum line, a new element that will increase the radius of the internal conductor and decrease the radius of the external conductor to the dimensions of the future LTD generator line. Also it will increase the length of the line to study with more details the MITL behavior. To design this new element and optimize the different dimensions, PIC simulations with the LSP code were used. They permit to control magnetic insulation by taking into account the electronic current flow along the internal conductor and to show the effects of this addition on the Marx bank. In this paper, the design of this additional element and the different simulation results are presented. Also, the different diagnostics needed to characterize the power transmission and the magnetically insulation are specified.

A 5-Megavolt, 600-Kiloampere Laser-Triggered Gas Switch for use on Z-R: Comparison of Experiments and Simulations

Abstract: The Z refurbishment project is designed to increase the peak current to the load on Z to ~26 MA in a 100-ns wide power pulse. This current is achieved by summing the current from 36 independent pulse-power modules. To meet these requirements, we have designed and constructed an SF6-insulated gas switch that can hold off 5.5 MV and conduct a peak current of 600 kA for over a hundred shots. The gas switch is charged by a Marx generator in ~1 microsecond and transfers about 200- kilojoules of energy and 0.25 Coulombs of charge to a pulse-forming line in a ~150-ns-wide power pulse peaking at 2.5 TW. The gas switch consists of a laser- triggered section holding off 15% of the voltage followed by 25 self-breakdown gaps. The self-breaking gaps are designed to provide multiple breakdown arcs in order to lower the overall inductance of the switch. The gas switch is submerged in transformer oil during operation. In this work, we show how simulation and experiment have worked together, first to verify proper operation of the switch, and then to solve problems with the switch design that arose during testing.