Showing papers on "Marx generator published in 1991"
Patent•
14 Jun 1991
TL;DR: In this paper, the authors describe a high voltage, very short pulse, microwave radiating source using low-cost components, and capable of operating at high pulse repetition frequencies (prf).
Abstract: This invention describes a high voltage, very short pulse, microwave radiating source using low-cost components, and capable of operating at high pulse repetition frequencies (prf). The source is activated by an ordinary video trigger commensurate with driving TTL logic. A trigger will cause a chain of N (where N may be 12 or greater) avalanche transistors connected in a Marx generator configuration to threshold resulting in a 1,200 volt or greater baseband pulse having a rise time of less than 100 ps and a duration of about 3 ns driving the input port of a dipole antenna. The dipole is excited by a balun. This invention achieves very short pulse duration broadband microwave radiation at pulse repetition frequencies as high as 30 kHz or greater.
57 citations
TL;DR: In this paper, the Marx and the Pulse forming section can be integrated into a single unit, and the stray capacitance present in each stage acts as a peaking capacitor, which can be used to increase the rise time of the output pulse.
Abstract: This article relates to the development of an ultrafast (nanoseconds–picoseconds time scale) compact system(s) readily applicable to the field of EMP/radiation, x‐ray‐induced nondestructive testing, plasma fusion (energy) experiments, bioelectromagnetic (food‐drug) sterilization, drivers for x‐ray preionized XeCl laser and similar applications. The present work shows that the Marx and the Pulse forming section can be integrated into a single unit. The stray capacitance present in each stage acts as a peaking capacitor. For a charging voltage per stage of <40 kV, the rise time of the output pulse is below 50 ps at 200 kV into a 100‐Ω load. Work is in progress to extend the voltage amplitude to 1.6 MV while maintaining the relative pulse waveform. With a contemporary optical diagnostic technique it is believed that the present concept may achieve 1–10 ps rise‐time pulses at a megavolt level in ‘‘smart gas mixtures.’’ In addition a solution for the classical peaking circuit has been obtained and presented in...
38 citations
TL;DR: The ASO-I as mentioned in this paper is a two-staged opening switch, consisting of fuses in water and a plasma erosion opening switch and can be operated hundreds of times a day at an output power of 230 kV and 35 kA.
Abstract: The pulsed power generator, named ASO-I, is extremely compact and light in comparison with a conventional pulsed power generator, which consists of a Marx bank and a water pulse forming line. The ASO-I has a two-staged opening switch, consisting of fuses in water and a plasma erosion opening switch, and can be operated hundreds of times a day at an output power of 230 kV and 35 kA. The parallel fuses are effective for power multiplication, and small differences in length of the parallel fuses do not influence the output power. The risetime of current through the short-circuit load decreases with the increase of the gap length of the spark gap, which is placed between the fuses and the load. The plasma erosion opening switch can be operated as a second opening switch, and the risetime of the current through the short-circuit load decreases from 250 to 10 ns. The maximum resistance of the plasma erosion opening switch is 3.5 Omega with an open-circuit load. >
30 citations
TL;DR: In this article, a fast cavity dumper for picosecond glass laser has been made, which is described in terms of optical and electrical characterization, and the contrast ratio of 1000 is obtained after a double pass through an amplifier.
Abstract: A fast cavity dumper for picosecond glass laser has been made. The optical and electrical characterization of the cavity dumper is described. An avalanche transistor Marx bank generator drives the cavity dumper. Up to 5 kV peak amplitude and 1.5 ns fall time negative polarity step pulses are generated by the Marx bank circuit. With a capacitive load like Pockels cell the pulse fall time increases to 4 ns. Optical switching times as fast as 2 ns (10%–90%) are experimentally measured. The contrast ratio of 1000 is obtained after a double pass through an amplifier. Single picosecond pulses are produced with an energy jitter of 10%.
29 citations
Patent•
23 Jul 1991TL;DR: In this paper, an electric propulsion engine for sustained space travel is described, where a gas is discharged against an inductor comprising a series of parallel coils arranged in a spiral fashion, each coil consists of four separate electrically connected coil sections.
Abstract: This invention discloses an engine for use in sustained space travel. The engine is of an electric type powered by a nuclear reactor. The electric engine includes a pulsed inductive magnetic thruster. A gas is discharged against an inductor comprising a series of parallel coils arranged in a spiral fashion. Each coil consists of four separate electrically connected coil sections. Each coil section traverses one-quarter of the distance around the inductor from an outer perimeter to an inner perimeter to form a single closed loop. A capacitor is electrically connected to two outer perimeter connector points for each coil forming a Marx Bank arrangement. All capacitors are charged to full charge and discharged simultaneously by a trigger generator immediately after a puff of propellant gas reaches the inductor. The high induced EMF in the inductor caused by the multiple capacitors in series in a single loop creates a rapidly rising magnetic field which ionizes the propellant gas. The current and magnetic field in the ionized gas drives the gas away from the coil creating the thrust which drives the spaceship.
18 citations
16 Jun 1991
TL;DR: The characteristics of the Blumlein pulse power sources developed at the University of Texas at Dallas are reviewed in this article, where the authors show that relatively low charging voltages are multiplied to give the desired discharge voltage without the need for complex Marx bank circuitry.
Abstract: In this report we review the characteristics of the Blumlein pulse power sources developed at the University of Texas at Dallas. These devices consist of several triaxial Blumleins stacked in series at one end. The lines are charged in parallel and synchronously commuted with a single thyratron at the other end. In this way relatively low charging voltages are multiplied to give the desired discharge voltage without the need for complex Marx bank circuitry. Progress in the scaling of these Blumlein pulse generators to obtain open circuit voltages in excess of 0.5 MV is described. Application of these devices to produce high power x-ray pulses is discussed.
11 citations
TL;DR: In this paper, a virtual cathode reflex triode was operated using a lowvoltage (∼100 kV), low-impedance Marx generator, thus maintaining a low electron reflex frequency.
Abstract: A virtual cathode reflex triode was operated using a low‐voltage (∼100 kV), low‐impedance Marx generator, thus maintaining a low electron reflex frequency. The electron current density was increased from ∼80 A/cm2 to ∼3.2 kA/cm2 by changing the shape of the cathode. The observed frequency at peak power increase from 2 to 20 GHz along with an increase in the electron current density, being in good agreement with the frequency of the calculated values of virtual cathode oscillations. The highest peak power (approximately 100 MW) in the 5‐GHz band was generated from the virtual cathode in the triode, measured by a crystal detector and the calorimeter of a graphite sheet absorber. Readings taken at a distance of 37 cm from the side of the triode resulted in microwave power measurements of 60 kW received by the waveguide of 5 GHz.
8 citations
01 May 1991-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this article, the authors described the progress in construction and characterization of pulse-power generators capable of discharging at high repetition rates, which consist of several triaxial Blumleins stacked in series at one end with a single thyratron at the other end.
Abstract: Described here is the progress in construction and characterization of pulse-power generators capable of discharging at high repetition rates. These devices consist of several triaxial Blumleins stacked in series at one end. The lines are charged in parallel and synchronously commuted with a single thyratron at the other end. In this way relatively low charging voltages are multiplied to give the desired discharge voltage without the need for complex Marx bank circuitry. Scaling of these stacked Blumlein generators to obtain open circuit voltages in excess of 0.5 MV is reported. Peak power generated by discharging into an X-ray diode exceeds 10 7 R/s and high repetition rates allow for an average emitted X-ray exposure rate of 25 R/s from a sequence of 40 ns pulses.
8 citations
16 Jun 1991
TL;DR: In this paper, the applicability of photoconductive semiconductor switches (PCSS) for use as output switches in sub-nanosecond pulse for EMP simulators was evaluated in a 50 ohm tri-plate transmission line geometry.
Abstract: Experiments were performed to determine the applicability of photoconductive semiconductor switches (PCSS) for use as output switches in subnanosecond pulse for EMP simulators. Lateral switches made of both Gallium Arsenide and Silicon with 1.5 cm long insulating regions immersed in Fluorinert were tested in a 50 ohm tri-plate transmission line geometry. Mode locked and Q- switched lasers were used to trigger both a gas switched Marx generator which pulse-charged the transmission line in 100- 150 ns and to illuminate the PCSS via an optical delay line. Illuminating beam energies and electric field strengths at switchout were varied to determine minimum risetimes and light energies required for triggering. The GaAs switches were operated in the high gain (lock- on) mode. Risetimes as fast as 600 ps were observed using a mode locked laser and 700 ps using a Q-switched laser. The minimum light energy required to trigger GaAs was 22/spl mu/J and the highest switched fields for both GaAs and Si is about 60 kV/ cm.
7 citations
TL;DR: In this article, a concept for compact, megavolt Marx generators has been developed, resulting in several designs which are approximately half the diameter and half the height of conventional units.
Abstract: A concept for compact, megavolt Marx generators has been developed, resulting in several designs which are approximately half the diameter and half the height of conventional units. The customized Marx capacitor assemblies utilize multiple windings incorporated into a single common capacitor case. Spark gap switch electrodes extend directly from the external capacitor terminals, eliminating the need for additional buswork. In order to construct the Marx generator, two capacitor assemblies are positioned opposite each other so that the electrodes line up in a vertical column between the two assemblies. Because the entire assembly is housed inside a pressurized (207 kPa of SF/sub 6/) gas vessel, the need for individual switch housings is eliminated. A four-stage, 400-kV-output Marx generator has been tested, operating at a repetition rate of 2-3 pps (power supply limited) continuously for over 5000 discharge cycles at 85-kV stage charging voltage. A second design has been fabricated and tested, utilizing 16 Marx stages to develop a 1.5-MV (open circuit) output voltage, and is contained in a cylindrical gas vessel 76.2 cm in diameter and 55.9 cm in height, weighing approximately 72.6 kg. Experimental measurements indicate a stage inductance of approximately 45 nH per 100-kV Marx stage. >
7 citations
16 Jun 1991
TL;DR: In this paper, a five-stage Marx bank was constructed using surface-mount capacitors and NPN transistors, achieving an output pulse rise time of two nanoseconds with a pulse duration of five nano-conds at a continuous repetition rate of 40 kHz and a worst case peak power of 6.5 kW.
Abstract: A five-stage Marx bank was constructed using surface-mount capacitors and NPN transistors . An output pulse rise time of two nanoseconds with a pulse duration of five nanoseconds at a continuous repetition rate of 40 kHz and a worst case peak power of 6.5 kW was achieved. The two-nanosecond rise time for the Marx bank was accomplished by biasing the transistors in the avalanche mode. The emphasis in the design was on miniatarization and reliability since the unit was to be submerged down a well hole to a depth of 500 meters. To increase the output power for another application, three solid-state Marx banks were connected in parallel. Synchronization for the parallel firings of the Marx banks was the critical design issue. A third application required that two of the avalanche circuits be triggered at precisely-controlled time differences.
Patent•
21 Feb 1991
TL;DR: In this paper, a high voltage power supply having energy storage, charging and switching elements and using an interruptible switch as the switching element for efficient, compact and safe operation is presented.
Abstract: A high voltage power supply having energy storage, charging and switching elements and using an interruptible switch as the switching element for efficient, compact and safe operation. In a specific embodiment, the interruptible switch is implemented with at least one cold cathode grid-controlled, crossed field plasma switch and associated control circuit. The charging element is a Marx bank which can be capacitive or inductive. Embodiments with a single master-slave control arrangement, a pulse-forming network providing high voltage regulation, an inductive implementation with a plurality of switching elements in a single envelope with the cathode of at least one switching element being the anode of the next switching element are disclosed. A current amplifier and voltage regulator implemented with a cold cathode grid-controlled, crossed field plasma switch having a cathode, an anode and a control grid therebetween are disclosed.
01 Jan 1991
TL;DR: The Particle Beam Fusion Accelerator II (PBFA II) as discussed by the authors uses 36 separate modules, each module includes a Marx generator, a water-insulated energy store, a laser-triggered 5-MV switch, a 5MV charge water pulse-forming line, and multiple self-breakdown megavolt water pulse sharpening switches.
Abstract: The design and construction of accelerators in the 100-terawatt class have significantly increased the demands placed on gas and liquid switching.1 The 100-terawatt PBFA II (Particle Beam Fusion Accelerator) uses 36 separate modules. Each module includes a Marx generator, a water-insulated energy store, a laser-triggered 5-MV switch, a 5-MV charge water pulse-forming line, and multiple self-breakdown megavolt water pulse sharpening switches. The resultant electrical pulse formed by PBFA II has subnanosecond syncronization in the main diode. During the analysis of the PBFA switching data, a scaling law was found that has implications for switch research and development.
07 Apr 1991
TL;DR: In this article, the highvoltage pulses excitation of a glow-discharge electron beam source has been experimentally investigated, and the beam source was driven at voltages ranging from tens of kilovolts to values in excess of 100 kV by means of either a capacitor discharge circuit or a Marx generator.
Abstract: The high-voltage pulses excitation of a glow-discharge electron beam source has been experimentally investigated. A solid aluminum cathode 2.5 cm in diameter with a concave front face was employed. The beam source was driven at voltages ranging from tens of kilovolts to values in excess of 100 kV by means of either a capacitor discharge circuit or a Marx generator. It has been possible to extract beams whose currents vary from the tens to the hundreds of amperes in helium at pressures of 50 mtorr to 15 torr. The pulsewidths ranged from 30 ns to 300 ns, and beam generation efficiencies between 14% and 57% were obtained. It has been found that the maximum peak beam current and the corresponding beam generation efficiency occur at an optimal gas pressure which is a function of the discharge voltage. The beam generation efficiency itself is seen to be primarily a function of the discharge current. >
16 Jun 1991
TL;DR: In this article, the authors designed and constructed a facility to analyze the phenomena associated with high voltage surface flashover of insulators in the low earth orbit environment, which was used to test the validity of models which extend laboratory vacuum-based design principles to include the Earth's upper atmosphere environment.
Abstract: A facility has been designed and constructed to analyze the phenomena associated with high voltage surface flashover of insulators in the low earth orbit environment. The facility incorporates a 10/sup -4/ Torr background vacuum, a low energy plasma, and ultraviolet radiation to simulate the effects of insulator and electrode charging, which are believed to be the main causes of most exterior spacecraft surface flashover problems. Experiments are being conducted to test the validity of models which extend laboratory vacuum-based design principles to include the Earth's upper atmosphere environment. The design and performance of the various sub-systems, including a Marx generator, plasma source, diagnostics, and data acquisition, are discussed in this paper. In addition, the facility's capabilities are presented, with a summary of some of the results generated to date, and an outline of the topics to be investigated in the near future.
03 Jun 1991
TL;DR: Thor as discussed by the authors is a long pulse electron beam generator based on a 4 MV, 27 stage resistive-capacitively coupled (hybrid) Marx bank, with a variable pulselength from 250 ns to 2 microsecond.
Abstract: : Thor is a long pulse electron beam generator. The pulse generator portion of the machine is based on a 4 MV, 27 stage resistive-capacitively coupled (hybrid) Marx bank. The total Mar:'capacitance is 24 nH. When the Marx erects, the full voltage IS applied to a 1.29 muH inductance and 21 omega resistance in series with the load. In parallel with the resistor and load is a capacitive filter stack. In parallel with the load is a resistive voltage divider/monitor, and a triggerable crowbar switch. The pulse generator is capable of supplying 4 MV, 10 kA, for a variable pulselength from 250 ns to 2 microsecond. The overshoot on this pulse is approximately 15% with a droop of 5% over 1 microseceond into a 400 omega resistive load.
01 Jul 1991
TL;DR: In this article, the authors report successful operation of a Raman-type free electron laser situated at the University of Twente, which is based on a Marx generator, and uses a transmission line to produce a flat ( ΔV V ≤ 2% ) 500 kV voltage pulse of 100 ns duration.
Abstract: We report successful operation of a Raman-type free electron laser situated at the University of Twente. It is based on a Marx generator, and uses a transmission line to produce a flat ( ΔV V ≤ 2% ) 500 kV voltage pulse of 100 ns duration. The parameters of the bifilar helical undulator are λu = 3 cm, 0 ≤ Bu ≤ 0.25 T. The field emission diode and the undulator are immersed in an axial guiding field. The radiation is guided using a circular waveguide with 8 mm inner radius. We estimate the spontaneous power level, and give the calculated growth factor for a TE11 mode.
16 Jun 1991
TL;DR: In this article, a gas-puff z-pinch switch was proposed to interrupt high current rapidly in a pulsed power generator with an inductive energy storage system, which can be operated not only as an opening switch but also as a triggered closing switch.
Abstract: The pulsed power generator with an inductive energy storage system is very attractive because of its size and weight, as compared with the conventional pulsed power generator which consists of a Marx bank and a water capacitor. However, there are few experiments being conducted now of applications using the inductive storage system because a repetitive opening switch which can interrupt high current rapidly has not been developed. Here, a repetitive opening switch using a gas-puff z-pinch is proposed and studied. After a capacitor (the primary energy storage device) is charged, an annular puff of Ar gas is injected between two electrodes. The annular gas starts to discharge when the pressure between the electrodes reaches a threshold pressure. The inductance of the plasma then increases due to both the pinch phenomena occurring in the plasma and the MHD instability of pinched plasmas, and soon the rapid interruption of current occurs. The gas-puff z-pInch can be operated not only as an opening switch but also as a triggered closing switch.
16 Jun 1991
TL;DR: In this article, a pre-bulk breakdown apparatus, in vacuum, was constructed to study commercially available samples of polycarbonate, acrylic, and polyacetal, and the system consisted of a Marx generator, inductor, high voltage vacuum bushing, and a needle-plane electrode geometry.
Abstract: In our laboratory we have constructed a pre-bulk breakdown apparatus, in vacuum, in which to study commercially available samples of polycarbonate, acrylic, and polyacetal. The system consists of a Marx generator, inductor, high voltage vacuum bushing, and a needle-plane electrode geometry. Through the use of the inductor and needle, fields in excess of 1 MV/cm can be obtained. Detection of the microscopic precursors to puncture in the samples requires a highly sensitive diagnostic. Laser induced fluorescence using fluorescent probes will locate and characterize the precursors.
16 Jun 1991
TL;DR: FALCON as mentioned in this paper is a fast Marx bank which stores 1.1 MJ at an output voltage of 720kV and produces currents of 2.2 MA with a quarter period of 1.5 /spl mu/s into a diode short.
Abstract: FALCON is a fast Marx bank which stores 1.1 MJ at an output voltage of 720kV. For the experiments described here, FALCON produced currents of 2.2 MA with a quarter period of 1.5 /spl mu/s into a diode short. Up to 61 kJ have been coupled into a bremsstrahlung diode in a 140-ns pulse. X-ray measurements corroborated the electrical measurements of the diode energy. The opening switch impedance has been the basis for circuit simulations of the DECADE generator.