Showing papers on "Plasma channel published in 2001"
TL;DR: In this article, a model of the quasineutral plasma and the transition between the plasma and dielectric wall in a Hall thruster channel is developed, where the plasma is considered using a two-dimensional hydrodynamic approximation while the sheath in front of the surface is considered to be one dimensional and collisionless.
Abstract: In this paper a model of the quasineutral plasma and the transition between the plasma and the dielectric wall in a Hall thruster channel is developed. The plasma is considered using a two-dimensional hydrodynamic approximation while the sheath in front of the dielectric surface is considered to be one dimensional and collisionless. The dielectric wall effect is taken into account by introducing an effective coefficient of the secondary electron emission (SEE), s. In order to develop a self-consistent model, the boundary parameters at the sheath edge (ion velocity and electric field) are obtained from the two-dimensional plasma bulk model. In the considered condition, i.e., ion temperature much smaller than that of electrons and significant ion acceleration in the axial direction, the presheath scale length becomes comparable to the channel width so that the plasma channel becomes an effective presheath. It is found that the radial ion velocity component at the plasma–sheath interface varies along the thr...
200 citations
Patent•
19 Mar 2001TL;DR: In this article, a plasma reactor has a capacitive electrode driven by an RF power source, and the electrode capacitance is matched at the desired plasma density and RF source frequency to the negative capacitance of the plasma, to provide an electrode plasma resonance supportive of a broad process window within which the plasma may be sustained.
Abstract: In accordance with one aspect of the invention, a plasma reactor has a capacitive electrode driven by an RF power source, and the electrode capacitance is matched at the desired plasma density and RF source frequency to the negative capacitance of the plasma, to provide an electrode plasma resonance supportive of a broad process window within which the plasma may be sustained.
170 citations
TL;DR: In this article, the triggering and guiding of leader discharges using a plasma channel created by a sub-joule ultrashort laser pulse have been studied in a megavolt large-scale electrode configuration.
Abstract: The triggering and guiding of leader discharges using a plasma channel created by a sub-joule ultrashort laser pulse have been studied in a megavolt large-scale electrode configuration (3–7 m rod-plane air gap). By focusing the laser close to the positive rod electrode it has been possible, with a 400 mJ pulse, to trigger and guide leaders over distances of 3 m, to lower the leader inception voltage by 50%, and to increase the leader velocity by a factor of 10. The dynamics of the breakdown discharges with and without the laser pulse have been analyzed by means of a streak camera and of electric field and current probes. Numerical simulations have successfully reproduced many of the experimental results obtained with and without the presence of the laser plasma channel.
129 citations
TL;DR: This model is supported by detailed experimental and numerical analysis and shows that the filament due to the self-guided propagation of an infrared femtosecond laser pulse in atmospheric-pressure air is used to trigger and guide an electric discharge.
Abstract: The filament due to the self-guided propagation of an infrared femtosecond laser pulse in atmospheric-pressure air is used to trigger and guide an electric discharge. The long low density plasma channel due to the filament is first heated by the Joule effect during an initial transient plasma stage. The heated channel of recombined gas then hydrodynamically expands radially. The onset of a discharge starts when the density depression on axis reaches the threshold discharge value. This model is supported by detailed experimental and numerical analysis.
124 citations
TL;DR: In this article, a three-dimensional envelope equation for the laser field is derived that includes nonparaxial effects such as group velocity dispersion, as well as wakefield and relativistic nonlinearities.
Abstract: To achieve multi-GeV electron energies in the laser wakefield accelerator (LWFA), it is necessary to propagate an intense laser pulse long distances in a plasma without disruption. One of the purposes of this paper is to evaluate the stability properties of intense laser pulses propagating extended distances (many tens of Rayleigh ranges) in plasma channels. A three-dimensional envelope equation for the laser field is derived that includes nonparaxial effects such as group velocity dispersion, as well as wakefield and relativistic nonlinearities. It is shown that in the broad beam, short pulse limit the nonlinear terms in the wave equation that lead to Raman and modulation instabilities cancel. This cancellation can result in pulse propagation over extended distances, limited only by dispersion. Since relativistic focusing is not effective for short pulses, the plasma channel provides the guiding necessary for long distance propagation. Long pulses (greater than several plasma wavelengths), on the other hand, experience substantial modification due to Raman and modulation instabilities. For both short and long pulses the seed for instability growth is inherently determined by the pulse shape and not by background noise. These results would indicate that the self-modulated LWFA is not the optimal configuration for achieving high energies. The standard LWFA, although having smaller accelerating fields, can provide acceleration for longer distances. It is shown that by increasing the plasma density as a function of distance, the phase velocity of the accelerating field behind the laser pulse can be made equal to the speed of light. Thus electron dephasing in the accelerating wakefield can be avoided and energy gain increased by spatially tapering the plasma channel. Depending on the tapering gradient, this luminous wakefield phase velocity is obtained several plasma wavelengths behind the laser pulse. Simulations of laser pulses propagating in a tapered plasma channel are presented. Experimental techniques for generating a tapered density in a capillary discharge are described and an example of a GeV channel guided standard LWFA is presented.
100 citations
TL;DR: In this article, the authors measured the time-dependent electrical resistance of a plasma channel created in air by a self-guiding TW femtosecond laser pulse and determined the plasma conductivity over a 200 ns time interval.
82 citations
TL;DR: A model is presented that elucidates the physics underlying the generation of an electromagnetic pulse from a femtosecond laser induced plasma channel and the induced dipole moment subsequently oscillates at the plasma frequency and radiates an electromagnetic pulses.
Abstract: We present a model that elucidates the physics underlying the generation of an electromagnetic pulse from a femtosecond laser induced plasma channel. The radiation pressure force from the laser pulse spatially separates the ionized electrons from the heavier ions and the induced dipole moment subsequently oscillates at the plasma frequency and radiates an electromagnetic pulse.
72 citations
TL;DR: In this article, the authors investigated the properties of axial standing wave patterns in the presence of a weakly damped helicon-like wave that penetrates into the bulk plasma and an electrostatic wave that can be suppressed.
Abstract: Magnetically enhanced inductively coupled plasma (MEICP) and helicon sources for materials processing are of interest because of their ability to deposit power within the volume of the plasma beyond the classical skin depth. The location and manner of power deposition can vary substantially depending on the mode of operation and reactor conditions. The coupling of electromagnetic fields to the plasma typically occurs through two channels; a weakly damped heliconlike wave that penetrates into the bulk plasma and an electrostatic wave. The electrostatic wave can often be suppressed resulting in the helicon component being responsible for the majority of the power deposition. A computational investigation was conducted to quantify this heating and determine the conditions for which power can be deposited in the downstream region of MEICP devices. For typical process conditions (10 mTorr, 1 kW ICP) and magnetic fields above 40 G, radial and axial electric fields exhibit nodal structure consistent with helicon behavior. As the magnetic fields are increased, axial standing wave patterns occur with substantial power deposition downstream. The ability to deposit power downstream with increasing B field is ultimately limited by the increasing wavelength. For example, if the plasma is significantly electronegative in the low power–high magnetic field regime, power deposition resembles conventional ICP due to the helicon wavelength exceeding the reactor.
59 citations
TL;DR: The results show that the balance between the nonlinear self-focusing of the laser beam and plasma defocusing forms a long plasma channel, which guides the laserbeam to propagate a long distance in air.
Abstract: Generation of a long plasma channel by femtosecond laser pulses is investigated. The results show that the balance between the nonlinear self-focusing of the laser beam and plasma defocusing forms a long plasma channel, which guides the laser beam to propagate a long distance in air. This phenomenon can be used to trigger lightning.
33 citations
Patent•
15 Oct 2001TL;DR: In this article, a matching circuit was proposed to match the impedance between the plasma processing chamber and the radiofrequency generator, which matches the impedance of the matching circuit with the ground potential positions which are DC-grounded.
Abstract: A plasma processing apparatus has a plasma processing chamber, a radiofrequency generator, and an matching circuit. The plasma processing chamber includes a plasma excitation electrode and a susceptor electrode for exciting a plasma. The radiofrequency generator is connected to plasma excitation electrode. The matching circuit matches the impedance between the plasma processing chamber and the radiofrequency generator. A capacitance which is 26 times a plasma electrode capacitance C e between the plasma excitation electrode and the susceptor electrode is greater than a loss capacitance C X between the plasma excitation electrode and ground potential positions which are DC-grounded.
24 citations
Patent•
19 Dec 2001
TL;DR: In this article, a full color fiber plasma display is presented, which consists of two glass plates sandwiched around a top fiber array and a bottom fiber array, with the top and bottom arrays are substantially orthogonal and define a structure of the display.
Abstract: A full color fiber plasma display device includes two glass plates sandwiched around a top fiber array and a bottom fiber array. The top and bottom fiber arrays are substantially orthogonal and define a structure of the display, with the top fiber array disposed on a side facing towards a viewer. The top fiber array includes identical top fibers, each top fiber including two sustain electrodes located near a surface of the top fiber on a side facing away from the viewer. A thin dielectric layer separates the sustain electrodes from the plasma channel formed by a bottom fiber array. The bottom fiber array includes three alternating bottom fibers, each bottom fiber including a pair of barrier ribs that define the plasma channel, an address electrode located near a surface of the plasma channel, and a phosphor layer coating on the surface of the plasma channel, wherein a luminescent color of the phosphor coating in each of the three alternating bottom fibers represents a subpixel color of the plasma display. Each subpixel is formed by a crossing of one top fiber and one corresponding bottom fiber. The plasma display is hermetically sealed with a glass frit. The sustain and address electrodes are brought out through the glass frit for direct connection to a drive control system.
TL;DR: In this paper, a brief review of ion source and plasma immersion modes is presented, and the significance of high plasma drift as a mechanism that can lead to a dc (or, at least, long-pulse) mode of ion implantation is outlined.
Abstract: The vacuum arc provides a straightforward method for the efficient production of dense metal plasma. The plasma so formed can be utilized more-or-less ‘as-is’, or with macroparticle filtering, for the deposition of films of many different kinds. More advanced techniques involve substrate pulse-biasing to achieve a metal plasma immersion processing mode, or the vacuum arc plasma source can be embodied within an ion source configuration for the formation of energetic metal ion beams for carrying out ion implantation. Not inconsequentially, the vacuum arc metal plasma has an innate high ion drift velocity (ion drift speed greater than the ion sound speed), a plasma feature that leads to some novel and important consequences — a negatively-biased substrate located in the plasma stream can maintain unexpectedly high voltages on an essentially dc basis, and an ion source with ‘conventionally poor’ extractor design can provide a kind of plasma immersion ion implantation mode of operation. As the ion source operating parameters are varied, there can in fact be a smooth transition between these two modes — a plasma immersion processing mode and an energetic ion beam processing mode. The metal ion beam mode of operation and the plasma immersion mode of operation are closely related because of the plasma drift. Here, vacuum arc generation of metal plasma is summarized, and a brief review of ion source and plasma immersion modes presented. The significance of high plasma drift as a mechanism that can lead to a dc (or, at least, long-pulse) mode of plasma immersion ion implantation is outlined.
TL;DR: The results of numerical simulations for high intensity laser pulses for plasma channel formation by the ponderomotive force of a wakefield generated by a laser pulse are in good agreement with theoretical predictions.
Abstract: A new physical effect of a plasma channel formation by the ponderomotive force of a wakefield generated by a laser pulse with a length of the order of the electron plasma wavelength is discussed. For a narrow pulse, wherein the width is less than $c/{\ensuremath{\omega}}_{\mathrm{pe}}$ ( ${\ensuremath{\omega}}_{\mathrm{pe}}$ and $c$ are the plasma frequency and light velocity, respectively), the channel has an annular form with on-axis density maximum. The depth of the channel increases with the distance from the pulse until the phase mixing arises and the wake starts to break. The linear fluid theory is used to obtain the scaling for wave-breaking conditions. The results of numerical simulations for high intensity laser pulses are in good agreement with theoretical predictions.
Patent•
01 Mar 2001
TL;DR: In this paper, an address electrode is moved from the bottom of the channel up into the barrier rib to reduce the distance between the address electrode and the sustain electrodes, thus increasing the electric field of the addressing pulse.
Abstract: The disclosure teaches using at least two orthogonal arrays of complicated shaped glass rods or very large fibers-like structures (from here in referred to as fibers) with wire electrodes to fabricate plasma displays with plasma cells larger than 0.05 mm 3 in volume. (The volume of a plasma cell is defined by the width of the plasma channel times the height of the plasma channel times the pitch of the pair of sustain electrodes.) To increase the size of the bottom fiber and keep the addressing voltage constant or to reduce the addressing voltage, the address electrode is moved from the bottom of the channel up into the barrier rib. Moving the address electrode up into the barrier rib will reduce the distance, d, between the address electrode and the sustain electrodes, thus increasing the electric field of the addressing pulse. To maintain a more uniform addressing field and build redundancy into the display an additional address electrode can be included in the barrier rib wall on the other side of the plasma channel.
TL;DR: In this paper, the electrical characteristics of a pulsed silicon "shunting plasma" are described and compared with carbon and niobium shunting plasmas, which is composed of the original chosen solid material.
Abstract: The electrical characteristics of a pulsed silicon ‘shunting plasma’ are described and compared with carbon and niobium shunting plasmas. The plasma development occurs in three phases. Initially the solid material is heated by the discharge current, followed by a surface discharge during a glow-like phase, and finally the main plasma is formed as an arc by joule heating of the chosen solid material. The time at which the surface discharge bridges over the silicon plate corresponds to an abrupt decrease in voltage across the plate. Both streamer plasma bridging and an abrupt voltage decrease initiate the arc discharges as the final phase of the plasma formation process. Observations of optical emission spectra indicate that the plasma is composed of the original chosen solid material. Ion current is extracted from the plasma to a nearby target by application of a pulsed voltage to the target. The extracted current depends on the ambient gas pressure in the target region. For a pressure of 2.7 Pa a sharp current peak occurs upon application of voltage, while for a pressure of 133 Pa a rectangular current pulse shape is formed, similar to the shape of the applied voltage pulse. This may be a result of the formation of a matrix sheath surrounding the target that is immersed in the shunting plasma.
TL;DR: In these simulations, a fully nonlinear, relativistic hydrodynamic description for the plasma wave is combined with particle-in-cell methods for the description of the bunch, and collective self-interactions within the bunch are fully taken into account.
Abstract: The dynamics of the acceleration of a short electron bunch in a strong plasma wave excited by a laser pulse in a plasma channel is studied both analytically and numerically in slab geometry. In our simulations, a fully nonlinear, relativistic hydrodynamic description for the plasma wave is combined with particle-in-cell methods for the description of the bunch. Collective self-interactions within the bunch are fully taken into account. The existence of adiabatic invariants of motion is shown to have important implications for the final beam quality. Similar to the one-dimensional case, the natural evolution of the bunch is shown to lead, under proper initial conditions, to a minimum in the relative energy spread.
TL;DR: In this article, the authors show that the Ramming instability of an intense laser pulse in a plasma channel proceeds differently than in a homogeneous plasma: the growth rate is reduced and the scaling with the laser intensity modified.
Abstract: Raman scattering instability of an intense laser pulse in a plasma channel proceeds differently than in a homogeneous plasma: The growth rate is reduced and the scaling with the laser intensity modified. These differences, significant even for shallow plasma channels, arise because of the radial shear of the plasma frequency and the existence of the weakly damped hybrid (electrostatic/electromagnetic) modes of the radially inhomogeneous plasma. The interplay of these two effects produces double-peaked spectra for the direct forward scattering in a channel.
TL;DR: In this paper, the authors examined the effect of plasma loading on the induction coil's impedance and OICR with and without a Faraday shield, and showed that coupling between the coil and the shield becomes dominant over coupling between a coil and a plasma.
Abstract: Standing waves unavoidably develop on inductively coupled plasma sources because they are mismatched transmission line systems. In addition, the electrical properties of the induction coil (or plasma source) are coupled to those of the plasma, since the coil–plasma system behaves similarly to a transformer. As a result, the input impedance, output-to-input current ratio (OICR), and electromagnetic fields symmetry of the coil are affected by the plasma conditions, which in turn influence the uniformity of plasma generation and ion flux to the wafer surface. In this article we examine the effect of plasma loading on the coil’s impedance and OICR with and without a Faraday shield. Measurements of the coil’s electrical properties without a Faraday shield showed a significant increase in the OICR with plasma conditions. Similar measurements with a Faraday shield showed that coupling between the coil and the shield becomes dominant over coupling between the coil and the plasma. Langmuir probe measurements showed that the radial profiles of ion density and electron temperature remained azimuthally symmetric for different plasma conditions with the shield.
TL;DR: In this article, the authors considered the emission of these modes from the channel end, assuming that the plasma density in the channel decreases gradually with distance from the loop, and showed that under ionospheric conditions this transmitting system can be useful for improving the antenna coupling to VLF waves of the ambient plasma.
Abstract: We study wave emission from a transmitting system consisting of a magnetic-field-aligned cylindrical plasma channel of enhanced density and a loop antenna immersed in it. An ambient medium is assumed to be a cold uniform magnetoplasma. It is found that when the plasma density in the near-antenna zone increases, the total power radiated from the antenna increases considerably due to the efficient excitation of guided modes on the channel. We consider the emission of these modes from the channel end, assuming that the plasma density in the channel decreases gradually with distance from the loop. It is shown that under ionospheric conditions this transmitting system can be useful for improving the antenna coupling to VLF waves of the ambient plasma.
TL;DR: In this paper, a simple theory is developed which describes the self-consistent nonstationary processes of the plasma formation due to impact ionization of an axially inhomogeneous gas by the beam and the beam focusing effect on the plasma.
Abstract: The plasma-assisted slow-wave oscillator (PASOTRON) is a high-power microwave source, in which the transport of an intense electron beam through an interaction region is based on the focusing effect of a beam generated plasma channel (Bennett pinch). A simple theory is developed which describes the self-consistent nonstationary processes of the plasma formation due to impact ionization of an axially inhomogeneous gas by the beam and the beam focusing effect of the plasma. The theory is illustrated by examples showing the temporal evolution of the beam transport in the process of plasma creation in PASOTRONs.
TL;DR: In this article, a multi-plasma-jet RF hollow-cathode system was developed for the deposition of alloy and composite thin films, and two primary plasma-jet channels and one secondary plasma channel were created in the volume of the reactor.
Abstract: A plasma-chemical reactor with a multi-plasma-jet RF hollow-cathode system has been developed for the deposition of alloy and composite thin films. Two primary plasma-jet channels and one secondary plasma channel were created in the volume of the reactor. High-density plasma flowing in these plasma-jet channels is generated inside the nozzles. These work simultaneously as RF hollow cathodes. An RF hollow cathode discharge is generated in these nozzles and is subsequently blown out of the reactor, creating flowing plasma jets. These jets were used for the deposition of SiGe and ZrCN thin films as an example of the deposition of alloy and composite thin films with this system. Co-sputtering or reactive co-sputtering of the nozzle material using high-density RF hollow-cathode plasma was applied for the deposition process. Control of the composition of the thin films was accomplished by setting the relative distance between the nozzle outlets without changing the plasma density inside the RF hollow cathodes. The composition of films was investigated with an electron microprobe system equipped with an X-ray microanalyser. This apparatus allowed quantitative analysis of the films. The stoichiometric homogeneity of the films was studied with this technique. Optical emission spectroscopy was used to investigate the secondary plasma-jet channel.
TL;DR: In this paper, experimental evidence of electron oscillation within the toroidal-section magnetic duct of a filtered vacuum arc plasma source was reported. But the results were limited to the case when the Bilek plate was biased.
Abstract: We report here experimental evidence of electron oscillation within the toroidal-section magnetic duct of a filtered vacuum arc plasma source. Our results clearly demonstrate that electrons can oscillate inside the duct under the combined effects of the electric and magnetic fields. In another experiment, we observe that, under the influence of the electron motion, the trajectories of the plasma ions are more or less unchanged except in the intensity when the Bilek plate is biased. Finally, our time-of-flight experiments show that the effects due to collisional scattering between plasma ions and oscillating electrons are masked by those associated with the metal plasma flow through the duct, and collisional scattering does not give rise to an increase of the mean charge state of the plasma ions. We conclude that the application of a bias voltage to the duct not only perturbs the ions but also influences the plasma electrons. Our results demonstrate that electrons at the central axis are one of the major reasons leading to improved plasma transport through the duct.
TL;DR: In this paper, the formation of plasma channels with an ultraintense laser pulse due to ponderomotive expulsion of elections and the subsequent Coulomb explosion was investigated, and the energy transmitted through the plasma increased from the few percent transmittance measured in absence of the preformed channel to almost 100% transmission with the channelling to main pulse delay at around 100 ps.
Abstract: Detailed investigations of the propagation of an ultraintense picosecond laser pulse through preformed plasmas have been carried out. An underdense plasma with peak density around 0.1nc was generated by exploding a thin foil target with an intense nanosecond laser pulse. The formation of plasma channels with an ultraintense laser pulse due to ponderomotive expulsion of elections and the subsequent Coulomb explosion were investigated. The laser transmission through underdense plasmas was measured for a picosecond pulse at intensities above 10 19 W0cm 2 with and without a plasma channel preformed with an ultraintense prepulse. The energy transmitted through the plasma increased from the few percent transmittance measured in absence of the preformed channel to almost 100% transmission with the channelling to main pulse delay at around 100 ps. The propagation of a relativistic laser pulse through overdense plasmas was also investigated. A well-characterized plasma with an electron density up to 8 nc was generated by soft X-ray irradiation of a low-density foam target. The propagation of the laser pulse was observed via X-ray imaging and monitoring the energy transmission through the plasma. Evidence of collimated laser transport was obtained.
21 May 2001-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: Schlieren et al. as discussed by the authors used a double-pulse discharge scheme to produce 40 cm long stable plasma channels with a peak discharge current of 55 kA in a 7 Torr nitrogen gas fill.
Abstract: An alternate technique for heavy ion final transport, from the driver to the target, is by the use of the self-standing Z-pinched plasma channel. Experiments conducted at the Lawrence Berkeley National Laboratory have produced 40 cm long stable plasma channels with a peak discharge current of 55 kA in a 7 Torr nitrogen gas fill. These channels are produced using a double pulse discharge scheme, namely, a pre-pulse discharge and a main capacitor bank discharge. It is postulated that the channel’s insensitivity to MHDinstabilities within the time scale relevant to beam transport is due to the wall effect the pre-pulse discharge creates. This is accomplished by leaving a gas density depression on the channel’s axis after hydrodynamic expansion. Since the pre-pulse discharge creates the initial conditions for the main bank Z-pinch, it is critical to understand how to control and engineer the pre-pulse. Here we present some of the results of ongoing experiments geared to understand the underlying physics of the LBNL Z-pinch plasma channel. Schlieren and phase contrast measurements show the radial propagation of a shock wave during the pre-pulse discharge and suggest indirectly the evidence of the on axis gas density depression, that is believed to be 5 1 10 of the original gas fill pressure. For the main bank Z-pinch, interferometry show an integrated electron line density of 1.6 � 10 17 cm � 2 for a 15 kV discharge on axis. These measurements coupled with Faraday rotation measurements will indicate ultimately the current density distribution in the channel. This data will be used to benchmark simulation codes. # 2001 Elsevier Science B.V. All rights reserved.
TL;DR: In this paper, the propagation of a 1-ps laser pulse at intensities exceeding 10 19 Wcm 22 in a low-density plasma channel was experimentally tested and the g-ray yield was studied for different channel conditions, by varying the delay between the channel forming pulse and the high intensity pulse.
Abstract: The propagation of a 1-ps laser pulse at intensities exceeding 10 19 Wcm 22 in a low-density plasma channel was experimentally tested. The channel was produced by a lower intensity preceding pulse of the same duration. Plasma electrons were accelerated during the propagation of the main pulse, and high energy g-ray detectors were used to detect their bremsstrahlung emission. The g-ray yield was studied for different channel conditions, by varying the delay between the channel forming pulse and the high intensity pulse. These results are correlated with the interferograms of the propagation region into the plasma.
TL;DR: In this article, a magnetic filter was inserted between the cathodic arc plasma source and chamber to reduce the amount of macroparticles transmitted from the plasma to the sample, and the plasma output was determined as a function of magnetic field and bias voltage, for the cases when the bias was applied to the entire duct wall or to a Bilek bias plate alone.
Abstract: A magnetic filter was inserted between the cathodic arc plasma source and chamber to reduce the amount of macroparticles transmitted from the plasma to the sample. The plasma output of the magnetic filter was determined as a function of magnetic field and bias voltage, for the cases when the bias was applied to the entire duct wall or to a Bilek bias plate alone. The factors affecting plasma diffusion in the duct were investigated. As well as collisional and inhomogeneous magnetic field effects, our computer simulation and experimental results indicate that the E×B drift results in an additional diffusion flux for the case when a Bilek bias plate is used. Hence the Bilek biasing mode results in a lower plasma output than for the case in which the entire duct is biased.
TL;DR: In this paper, the mechanism and behavior of a plasma in the presence of an external electric field with a one-dimensional fluid model was studied, and the authors used a two-fluid model, treating both electron and ion motions.
Abstract: We studied the mechanism and behavior of a plasma in the presence of an external electric field with a one-dimensional fluid model. We used a two-fluid model, treating both electron and ion motions, rather than a commonly used one-fluid model assuming the electron thermal equilibrium. In particular, we investigated the following issues: (1) the motion of plasma electrons caused by an external static electric field and the formation of a plasma potential; (2) influence of parameters on the plasma potential, which are plasma electron temperature, plasma density, and applied voltage. The plasma potential rises and reaches a value nearly equal to the anode potential in a few nanoseconds. It is higher for a higher anode potential, a higher electron temperature, and a lower plasma density.
Journal Article•
TL;DR: In this article, the authors used high speed photography and a pressure sensor to investigate the pressure characteristics of pulse discharge in water by using high speed cameras and pressure sensor, and the experiment results show that velocity of shock wave is about 1.5km/s.
Abstract: The pressure characteristics of pulse discharge in water are investigated by using high speed photography and pressure sensor.The experiment results show that velocity of shock wave is about 1.5km/s.The capacitance is 4.1μF,initial voltage is 10kV,and interelectrode gap is 7mm.The measured pressure of the first and second shock wave is 1.55MPa and 0.55MPa respectively.The pressure sensor is installed at the place of 0.3m away from the phasma channel.The corresponding calculated results are 1.0MPa and 0.38MPa respectively,which are in good agreement with the experimental measurements.The pressure in plasma channel is about 49MPa,which is taken by a scanning photo of plasma radius.The plasma radius and the velocity of channel wall are 4mm and 180m/s respectively after 30μs of discharge.
TL;DR: Using analytical and numerical techniques, the properties of electromagnetic surface waves on conducting plasma channels produced by ultrashort pulse lasers have been studied in this paper using a homogeneous slab approximation to model the conducting plasma channel, and the surface wave dispersion and wave damping for both symmetric and antisymmetric wave mode cases for both a thick and thin slab.
Abstract: Using analytical and numerical techniques, the properties of electromagnetic surface waves on conducting plasma channels produced by ultrashort pulse lasers have been studied. Using a homogeneous slab approximation to model the conducting plasma channel, we solve for the surface wave dispersion and wave damping for both the symmetric and antisymmetric wave mode cases for both a thick and thin slab. For the dense plasma case, i.e., for wave frequencies less than the electron collision frequency, it is found that surface wave damping attenuation length can be large, on the order of the laser plasma channel propagation distance, for atmospheric pressure conditions for both the thick and thin slab approximation. In addition, it is shown that large amplitude surface waves can modify the plasma channel conductivity through nonlinear effects.
17 Jun 2001
TL;DR: In this paper, a new class of semiconductor laser using these current filaments as the active region in the laser cavity is reported. But the current filament is not used for optical control of their location, shape, and timing.
Abstract: Summary form only given. At the 8th PPC (1991), we reported the first images of current filaments in high-gain photoconductive semiconductor switches (PCSS). Since then many properties of current filaments have been reported, including optical control of their location, shape, and timing. Recently, we have invented a new class of semiconductor laser using these current filaments as the active region in the laser cavity. We have fabricated current filament semiconductor lasers (CFSL) that have produced 75 nJ of 890 nm radiation in 1.5 ns (50 W peak), approximately 10 times more energy than conventional (injection-pumped) semiconductor lasers(CSL). These lasers are created from the electron-hole plasma in PCSS current filaments. In contrast to CSL, these new lasers are not based on current-injection. Instead, low-field avalanche carrier generation produces a charge-neutral plasma channel with a carrier distribution for lasing. CFSL are not limited in volume by the depth of p-n junctions (/spl sim/1 micron). Since we have observed filaments as long as 3.4 cm and 400 microns diameter, the active region in CFSL can be more than 100 times larger than in CSL. CFSL larger diameters imply higher energies and reduced divergence in diffraction-limited devices. This presentation reports lasing properties from several configurations of CFSL: high output energies, pulse compression, spectral narrowing, and lasing thresholds. The properties of e-h plasma in PCSS will be compared and contrasted with plasma properties in spark gaps. The CFSL are pulsed and optically triggered like PCSS with the exception that filaments must be created in straight lines using optical line triggers. Potential applications include: active optical sensing/imaging, optical triggers for PCSS, plasma diagnostics, micro-machining, semiconductor scribing, laser ablating, optical communication, and permanent memory.