Conference Paper

A compact MV Marx generator

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Abstract

A compact MV Marx generator is presented. The generator employs a modular geometry designed for decreased volume, enhanced performance ease of maintenance. The generator is very well suited for the direct generation of narrow band and ultra wide band energy, as a high voltage trigger generator or as a flash X-ray source. The characteristics of the generator are discussed

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... 1. Similar capacitors, TDK-UHV-9A, have been used in the innovative Marx design of [1]. Removing some of the manufacturer epoxy encapsulation and immersing the capacitor in gas or liquid insulation, can significantly increase the overall energy density of the capacitor [2]. ...
Article
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The size of compact pulsed power generators capable of producing pulses with ~100 ns duration at Gigawatt power levels is primarily determined by the specific energy density of the utilized energy storage medium. Capacitors capable of delivering large pulsed currents at several 10 kV voltage levels have been most frequently used as the energy storage medium for portable pulse generators. To increase the specific energy density of the pulsed power generator, the capacitors are often voltage overstressed at the cost of capacitor life. However, rapid charging (milliseconds) of the capacitor immediately followed by discharging alleviates somewhat of the lifetime problem. For repetitive operation of the pulsed power generator, the charging/discharging energy loss is the more important parameter. The energy, WC, needed to charge a capacitor to a set voltage is measured along with the energy released, WR, by the capacitor under conditions corresponding to a compact Marx generator operating with ~10 Hz rep-rate into a ~20 Ohm load. For the tested capacitors with Mica as dielectric, the capacitor efficiency, eta, i.e. the ratio between WR and WC, is roughly equal to 97% and largely independent of the charging time. Also tested ceramic capacitors revealed an efficiency of ~90% for fast charging and an efficiency of ~94% for slower charging (from ~2 to 35 mus time constant).
... [4] For compact pulse generators, the Marx topology is more commonly used since it reduces sub-system count by combining the energy storage and power scaling sub-systems. [4,5] Voltage scaling is an essential function of compact pulsed power systems since the system size is strongly driven by the storage voltage. [2] Modest pulse shaping can be accomplished with Marx banks by the inclusion or reduction of inductance between stages. ...
Conference Paper
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The design of compact pulsed power systems involves the trade between size, pulse length and pulse shape. A stacked Blumlein line with high dielectric constant material can deliver a voltage flattop to a matched load with an energy density similar to capacitor banks. By imbedding nano-scale titanate particles in an epoxy matrix, a composite material with a relative permittivity in the range of 30 to 60 may be realized without the drastic loss in dielectric strength associated with large area ceramics. So called ceramic loaded polymer dielectric employed in a Blumlein line facilitates the fabrication of a compact pulse forming line potentially suitable for driving loads of several tens of Ohms in the GW power range for greater than 100 ns. This paper describes the initial efforts to fabricate and test a parallel plate Blumlein incorporating ceramic loaded polymer dielectric. Two single-stage parallel plate Blumlein lines were fabricated with different ceramic loading. The lines were designed to yield a 50 ns pulse into a 6.25 Omega load. The Blumlein lines were designed to be charged to 62.5 kV, and both fabricated units held the charge voltage in static tests. A small railgap switch was fabricated for use with the Blumlein lines. A mid-plane knife-edge electrode was used to trigger the switch. The results of the tests are presented along with projections for the future development of this technology.
... 1). Similar capacitors, TDK-UHV-9A, have been used in the innovative Marx design in [1]. Removing some of the manufacturer's epoxy encapsulation and immersing the capacitor in gas or liquid insulation can significantly increase the overall energy density of the capacitor [2]. ...
Article
Full-text available
An evaluation of the energy density and efficiency of high-voltage capacitors, from various manufacturers, at voltages above their rated level is presented. Characteristics such as decreasing capacitance, decreasing efficiency, and increasing energy density are described. Data are taken from eight capacitors; six of which are composed of varying nonlinear ceramic materials as a dielectric, and the remaining two are wound capacitors, which were chosen to exhibit their linear characteristics. Rapid (1-100 ms) charging and discharging, similar to that of a generator operation at a repetition rate of more than 10 Hz with an <sub>~</sub>100-ns pulse, were the conditions simulated in this particular test setup.
... Commercially available power supplies are generally limited to less than 100-kV, and a Marx topology, a pulse transformer, or some combination of both is used to scale the voltage above 100-kV [4]. For compact pulse generators, the Marx topology is more commonly used since it reduces sub-system count by combining the energy storage and power scaling sub-systems [4,5]. Voltage scaling is an essential function of compact pulsed power systems since the system size is strongly driven by the storage voltage [2]. ...
Conference Paper
Full-text available
Stacked Blumlein lines with solid dielectric potentially offer a compact pulsed power system for a variety of applications by combining the energy storage, voltage scaling, and pulse forming functions into a single device. By stacking the lines physically, not simply electrically, the line is made more compact because adjacent lines share electrodes. This design does not lend itself to the use of a single switch to commutate the stacked line, and multiple switches are far simpler to implement. The switch jitter and electrical characteristics strongly influence the performance of the line and the stresses on the dielectric. This paper explores the effects of switch jitter, inductance, the resistive decay during closure, and the closed-state resistance on the output pulse and dielectric stresses for stacked Blumlein lines using SPICE simulations. The impact of switch operation on the necessary dielectric strength and the quality of pulse is presented. The suitability of various switch technologies to meet the performance requirements is also discussed.
Conference Paper
Traditional uses of the Marx generator have been limited to energy storage and delivery systems, such as charging capacitors or pulse forming lines. However, low energy, high peak power Marx generators are finding applications in ultra wideband radar and high power microwave systems. This paper discusses the compact generator as well as an assortment of impulse antennas. Experimental results, including those of the Marx generator and antenna range measurements are presented and discussed.
ne Ma= Generutor As An UZpu Tidebond Source, 13" ' IEEE International Pulsed Power Conference
  • R Mayes
  • W J Carey
R. Mayes and W. J. Carey, ne Ma= Generutor As An UZpu Tidebond Source, 13" ' IEEE International Pulsed Power Conference, Las Vegas, NV, July 2001.