Plasma Erosion Opening Switch Research Articles

Narrow band vacuum ultraviolet radiation, produced by fast conical discharge

The article presents the experimental study of discharges in a conical cavity, filled with Ar at pressure 80 Pa. The electrical current driver (inductive storage with plasma erosion opening switch) supplies to the load electrical current pulse with growth rate about 1012 A s−1 and maximal value 30–40 kA. The convergent conical shock wave starts from the inner surface of the discharge cavity and collapses in ‘zippering’ mode. The pin hole camera imaging with MCP detector (time resolution 5 ns) have demonstrated the appearance of effectively fast moving compact plasma with visible velocity v = (1.5 ± 0.14) × 107 cm s−1. Plasma emits narrow band radiation in the spectral range of Rydberg series transitions of Ar VII, Ar VIII with quantum number up to n = 9 (wavelength about 11 nm). The intensity of radiation is comparable with the total plasma emission in the range 10–50 nm. Charge exchange between multiply charged Ar ions and cold Ar atoms of working gas is proposed as the possible mechanism of the origin of the radiation.

Plasma instability in fast spherical discharge induced by a preionization

As it was shown earlier, fast discharge (dI/dt ∼ 1012 A/s and Imax ≈ 40 kA) in a spherical cavity (Al2O3, inner diameter 11 mm, 4 mm apertures for the current supply) filled with working gas (Ar and Xe, pressure 80 Pa), results in the formation of a plasma with the form close to spherical. The physical mechanism can be the cumulation of a convergent shock wave, which was originated near the inner surface of the discharge cavity. It was also shown for the cylindrical fast discharge that the preionization influences the dynamics of the cylindrical convergent shock wave, its evolutions becomes faster. The present work is devoted to the study of the influence of the preionization on the plasma formation in the fast discharge with spherical geometry (Ar, 80 Pa). The inductive storage with plasma erosion opening switch was used as a current driver. The spatial structure of the discharge plasma was studied by means of a pin-hole camera with the microchannel plate (MCP) detector with time gate of 5 ns. The extreme ultra violet spectra were studied by means of the grazing incidence spectrometer with the same MCP detector with time gate of 20 ns. Beside the expected effects (reduction of the spherical plasma formation time and some increase of the electron temperature), the preionization of the discharge by the current 500 A results also in the development of the plasma instabilities and destruction of the compact plasma ball in several tens of nanoseconds. Possible mechanism of the instability is discussed.

Fast discharge in a spherical cavity

The work is devoted to the study of the plasma, created by a fast discharge in a spherical cavity. The discharge was driven by an inductive storage with plasma erosion opening switch (dI/dt ∼1012 A/s). The plasma was produced in a spherical cavity (alumina, 11 mm diameter). Xe, Ar, and He at the pressure 80 Pa were used as working gases. The time evolution of the spatial structure and of extreme ultraviolet (EUV) spectra of the discharge plasma was studied by means of micro channel plate detector. The discharges with Xe and Ar resulted in the stable appearance of the spherically shaped plasma with the diameter about 1–3 mm. The plasma emission in the EUV region lasts ∼500 ns. The EUV spectrum of Ar discharge at the moment of maximum of the electron temperature Te contains the lines of Ar X (ionization potential 478.7 eV), that indicates a value of Te in the range 50–100 eV. The mechanism of plasma appearance can be the cumulation of the convergent spherical shock wave, generated by fast heat deposition and magnetic pressure in working media near the inner surface of the discharge volume.

Dynamics of VUV spectra in fast capillary discharge

The temporal behavior of VUV spectra of capillary discharge with a rate of a current rise on the order of 1012 A/s is studied. The current is generated using an inductive storage unit with a plasma-erosion opening switch. This discharge is accompanied by the generation of a shock wave on an inner wall of a capillary and by its subsequent cumulation on the discharge axis. The capillary is prefilled with argon at a pressure of 80 Pa. Radiation spectra are obtained using an off-Rowland spectrograph based on a concave grating with optimal focusing in the wavelength range of 20 nm. The radiation is recorded with a detector based on a microchannel plate with a time resolution of 20 ns, which makes it possible to separate the spectra of two phases of the discharge, i.e., the cumulation phase of the shock wave in argon that fills the capillary (T e ∼ 20–30 eV) and the phase of subsequent discharge in a substance desorbed from the capillary wall T e ∼ 50 eV).

Plasma erosion opening switch for fast discharges with current growth rate about 1012 A/s1

The article presents the construction of a plasma erosion opening switch, capable of creating the discharge with electrical current of several tens kiloamperes and a growth rate up to 1012 A/s in the circuit with the inductive load up to 100 nH. The results of test experiments with imitator of load are presented. The discharge circuit under consideration will be used for the experiments for creation of shock waves in plasma.

Pulsed gas lasers pumped by generators with inductive energy storage

A new method of pumping electric-discharge gas lasers and excimer lamps is proposed on the basis of generators with inductive energy storage and opening switches of various types (exploding wires, gas-discharge low-pressure devices, plasma erosion opening switches, and semiconductor SOS diodes). It is shown that the inductive energy storage provides a convenient way of varying the pump pulse parameters (primarily, the pulse duration and the input power) and obtaining optimal excitation pulses for various types of lasers. The potential of using generators with inductive energy storage for pumping gas lasers is demonstrated.

Mathematical modeling of plasma opening switches

This article investigates Plasma Opening Switches with the help of an implicit code. The plasma is described using a collisional bifluid model, where the low ratio of electronic and ionic masses allows us to drop inertial terms from the electronic momentum equation. This asymptotic model filters plasma oscillations from the equations and the scheme is stable for time steps exceeding the electron plasma period. However, an implicit coupling of fluid and Maxwell's equations is considered because of the presence of a damped mode, whose characteristic time scale restricts the time steps of explicit schemes to small values compared to the simulation requirements. The stability of the scheme is illustrated by simulating certain operating phases of the Plasma Erosion Opening Switch.

Observation of ASE effect for Ne-like Ar in a capillary discharge driven by inductive storage with plasma erosion opening switch

Inductive storage with plasma erosion opening switch was used as a current driver for capillary discharge. A discharge current of 40-50 kA was reached with current time derivative higher than 10 12 A/sec. At the moment 50 - 60 nsec from beginning of a discharge time gated off-axis VUV imaging of a plasma has shown an appearance of a bright spot corresponding to the position of a center of a far end of a capillary. Simultaneously an enhanced intensity of 469 A line of 3p-3s transition of Ar IX was detected. We consider these observations as a proof of an effect of amplified stimulated emission (ASE).

A two-stage exploding-foil/plasma erosion opening switch conditioning system

When a load requiring a very fast rising current is fed from a flux-compression generator, it is necessary to introduce a conditioning circuit in order to reduce the rise time of the generator output current substantially. The final stage of this circuit will include a plasma erosion opening switch, which is the fastest known opening switch for use at the current levels involved. This paper presents results obtained during the development of a novel two-stage conditioning circuit and compares the experimental performance of the circuit with results provided by a computer simulation. A time compression of the rise time of the currents from microseconds to less than 100 ns was obtained, representing a 40-fold increase in the corresponding signals.

Plasma X-Ray Radiation Source

This paper gives the results of studies on a plasma x-ray source, which enables one to obtain a 2.5-krad radiation dose per pulse over an area of 100 cm2in the quantum energy range from 20 to 500 keV. Pulse duration is 100 ns. Spectral radiation distributions from a diode under various operation conditions of a plasma are obtained. A Marx generator served as an initial energy source of 120 kJ with a discharge time ofT/4 = 10−6s. A short electromagnetic pulse (10−7s) was shaped using plasma erosion opening switches.

Plasma X-Ray Radiation Source

This paper gives the results of studies on a plasma x-ray source, which enables one to obtain a 2.5-krad radiation dose per pulse over an area of 100 cm2 in the quantum energy range from 20 to 500 keV. Pulse duration is 100 ns. Spectral radiation distributions from a diode under various operation conditions of a plasma are obtained. A Marx generator served as an initial energy source of 120 kJ with a discharge time of T/4 = 10-6 s. A short electromagnetic pulse (10-7 s) was shaped using plasma erosion opening switches.

Plasma erosion opening switch using laser-produced plasma

In order to construct a practical inductive energy storage pulsed power generator, an opening switch which can repeatedly conduct a large current and then rapidly interrupt this current is necessary. Though the plasma erosion opening switch (PEOS) can interrupt a large current rapidly, the effective number of switch operations is limited because of the decrease of the carbon sprayed on the insulator with each shot. A PEOS using a laser-produced plasma, which can possibly be operated for hundreds of thousands of shots without maintenance, is proposed, and its operation as an opening switch is confirmed experimentally.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Compact pulsed power generator using an inductive energy storage system with two-staged opening switches

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. >

A conduction model for PEOS operation incorporating simplified cathode sheath effects

An extension of the US Naval Research Laboratories' model for plasma erosion opening switch (PEOS) operation is proposed (see P.F. Ottinger, et al., 1984). This model differs from previous models in that it includes a simplified 1-D plasma sheath at the cathode to allow for an additional mechanism for opening: the onset of enhanced erosion in this sheath region. Switching currents based on this model are compared with those observed in PEOS experiments on FALCON at the Physics International Company and on OMNI II at Cornell University.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Current channel migration and magnetic field penetration in a perfectly conducting plasma with emitting, conducting boundaries

In collisionless simulations of the plasma erosion opening switch, a highly conductive plasma allows magnetic field penetration through the entire length of the plasma, to depths almost two orders of magnitude greater than the collisionless skin depth, c/ωpe. Field penetration is accomplished by a narrow (skin-depth-like) current channel that migrates through the plasma. The plasma behind the current channel is unable to shield the rising magnetic field from the body of the plasma and allows it to penetrate almost instantly and completely through the plasma up to the current channel. The migration of the channel and the penetration of the field appear to occur in the absence of both Coulomb collisions and instabilities. These unusual features are permitted by the electric field structure in the plasma behind the current channel and the presence of conducting boundaries that can emit electrons.

Plasma erosion opening switches experiments

The authors describe experiments that have contributed to the understanding of the physics of PEOS (plasma erosion opening switches). A theoretical switch model was studied and it was in agreement with experimental results. A power multiplication of 2.6 and pulse compression of 5 were obtained on the SIDONIX I generator. A PEOS system will be tested on the AGLAE II pinch diode to enhance plasma homogeneity. It is concluded that the PEOS system can improve and extend the operation of existing pulse power devices. >

Investigation of collisional effects in the plasma erosion opening switch

During the conduction phase of the plasma erosion opening switch (PEOS), magnetic field has been observed experimentally to penetrate completely through plasmas up to 30 cm long. Current channels in the main body of the plasma have been observed that are more than 10 cm (or more than about 60 collisionless skin depths) wide. In addition, the maximum current carried by the switch before opening (the conduction current) seems to scale roughly linearly with plasma density n and switch length l. Collisionless pic code simulations of the plasma switch show current conducted in skin-depth-like channels, with the conduction current scaling close to l 2/5 and n1/4. In this paper, the effect of collisions on the behavior of the PEOS is investigated and is shown to bring the pic simulations and experimental results in closer agreement. In collisional simulations, current channels as wide as those in experiments are observed, and the conduction current scales linearly with l and as n1/2 in the anode-dominated case. In the cathode-dominated case, linear scaling with both length and density can be inferred from the cathode penetration distance versus time.

Analysis of anomalous resistivity during the conduction phase of the plasma erosion opening switch

During the conduction phase of the plasma erosion opening switch, the current channel width, in the body of the plasma away from the electrodes, has been observed to be many times wider than the collisionless skin depth. Anomalous collisions have been invoked to explain this discrepancy. Here the problem is analyzed using an electrostatic Vlasov approach, and an unstable ion acoustic mode is identified. The derived growth rate is fast enough and the nonlinear saturation level is high enough to explain the observed magnetic field penetration.

Plasma Erosion Opening Switch Research at NRL

This paper is a review of plasma erosion opening switch (PEOS) research performed at the Naval Research Laboratory (NRL). Several experimental and theoretical results are described to illustrate the present level of understanding and the best switching results obtained to date. Significant power multiplication has been achieved on the Gamble II generator, producing 3.5 TW with less than 10-ns rise time. Switching after nearly 1-μs conduction time has been demonstrated on Pawn, producing a 0.2-TW 100-ns pulse. Scaling the switch to higher current, power, and conduction time should be possible based on theoretical analysis and the favorable results of scaling experiments performed thus far.

Plasma Erosion Opening Switch in the Double-Pulse Operation Mode of a High-Current Electron Accelerator

This paper reports the results of investigations of the operation of a fast current opening switch, with a 1013-1016 plasma density produced either by dielectric surface flashover or by explosive emission of graphite. A series of two pulses was applied to two diodes in parallel. The first pulse produced plasma in the first diode which closed that diode gap by the arrival time of the second pulse. The first, shorted, diode then acted as an erosion switch for the second pulse. A factor of 2.5-3 power multiplication was obtained under optimum conditions. The opening-switch resistance during the magnetic insulation phase, neglecting the electron losses between the switch and the generating diode, exceeded 100 Ω. The duration of the rapid opening phase was less than 5 ns under optimum conditions. This method of plasma production does not require external plasma sources, and permits a wide variation of plasma density, which in turn allows high inductor currents and stored energies.