Showing papers on "Plasma channel published in 1994"

Laser guiding in an axially nonuniform plasma channel

Abstract: A plasma channel produced by a short laser pulse is axially nonuniform due to self‐defocusing of the laser. When a delayed second laser pulse propagates through the channel, diffraction and refraction effects do not balance each other exactly, resulting in periodic beam radius variation with the distance of propagation.

Plasma-arc ignition system

Abstract: An ignition system for igniting fuel within an engine, comprising at least one ignition plug disposed in the engine, wherein the ignition plug has a pair of electrodes. A high voltage generator is connected to the ignition plug for applying a gated high voltage high frequency AC signal across the pair of electrodes so as to initiate ionization of the air/fuel mixture and create an infant plasma channel between the pair of electrodes. A plasma arc current generator is connected to the ignition plug for generating a predetermined magnitude of alternating current for a predetermined period of time so as to sustain the plasma channel and ignite the fuel, and a controller is provided for selectively enabling and disabling the high voltage generator and the plasma arc current generator at predetermined times.

Instabilities of Short-Pulse Laser Propagation through Plasma Channels.

Abstract: The stability of short laser pulses propagating through plasma channels is investigated theoretically. Perturbations to the laser pulse are shown to modify the ponderomotive pressure, which distorts the dielectric properties of the plasma channel. The channel perturbation then further distorts the laser pulse. A set of coupled mode equations is derived, and a matrix dispersion relation is obtained analytically for the special case of a quadratic radial density variation. As an example, the spatiotemporal growth of a pure dipole perturbation is evaluated in various parameter regimes. Mechanisms for suppressing the instability are discussed.

Focused injection of vacuum arc plasmas into curved magnetic filters

Abstract: Thin films of high quality can be deposited using vacuum arc plasmas when the macroparticles which are produced along with the plasma in the cathode spots are removed by curved magnetic filters (‘‘ducts’’). In order to improve the deposition efficiency of a vacuum arc plasma source coupled to a magnetic filter, the effect of a magnetically focused plasma injection into such a filter has been investigated. Maximum plasma output was found at an optimum focusing field strength of 20–40 mT with an optimum duct bias of +20 V with respect to the anode potential (ground potential). The maximum output is by a factor of 20–30 greater than without focusing field and the duct at ground potential. This significant effect at relatively low injection field strength indicates that not only the magnetic field distribution but also the plasma current distribution is essential for an efficient plasma transport.

Channel ion source

Abstract: A gas ionizable to produce a plasma is introduced into a channel within an ion source and into a hollow cathode embedded within the same ion source. A combined anode and manifold is located at a closed end of the channel and gas is introduced into the channel through the combined anode and manifold and into the hollow cathode. A heater and keeper electrode power supply is used to establish a hollow cathode and keeper electrode plasma. A discharge power supply is used to flow electrons from the hollow cathode in a predominately 180° direction to bombard the channel gas distribution and create a channel discharge plasma. A magnetic field generated by a permanent magnet circuit is concentrated by pole pieces at the open end of the channel in an orientation predominately transverse to the channel axis. Energetic electrons from the hollow cathode interact with the concentrated field to simultaneously ionize the channel gas and accelerates these ions through the open channel to form an ion beam. Simultaneously, electrons from the hollow cathode are emitted in a predominately axial direction to space-charge neutralize the ion beam.

Arc assisted CVD coating method and apparatus

Abstract: An improved vacuum arc coating apparatus is provided, having a reaction zone with a plasma channel defined within a series of aligned annular substrate holders, or between an outer wall of a chain of substrate holder blocks and the inner wall of the tube The substrate holders thus act as a liner, confining an arc within the plasma channel Carrier and plasma creating gases and the reaction species are introduced into the tube, and the deposition process may be carried out at a pressure between 10 Torr and 1000 Torr Magnetic coils may be used to create a longitudinal magnetic field which focuses the plasma column created by the arc, and to create a transverse magnetic field which is used to bias the plasma column toward the substrates Substrates can thus be placed anywhere within the reaction zone, and the transverse magnetic field can be used to direct the plasma column toward the substrate, or the tube itself can be rotated to pass the substrate through the plasma column

A preliminary study on laser‐triggered lightning

Abstract: As a preliminary study on triggering lightning with a CO2 high-power laser, we carried out laser-triggered discharge experiments to investigate the necessary conditions for initiating and guiding an electrical streamer with a CO2 laser-produced plasma channel. We found the following. (1) The necessary electric field for initiating a streamer with the plasma channel depends closely on the absorbed energy for producing the plasma channel and not on the length of the plasma channel. The higher the absorbed energy, the smaller the necessary electric field. The minimum electric field is about 200 kV/m. (2) The necessary electric field for guiding a streamer by the plasma channel is lower than that for initiating a streamer. The minimum electric field is about 170 kV/m. Furthermore, we observed the electric field at the top of a 50-m tower and the field on the ground simultaneously during 10 Japanese winter thunderstorms. The observed results agree with theoretical calculations showing that the field at the top of a 50-m tower is on average 2 orders larger than the field on the ground. We conclude that it is highly possible to trigger a lightning discharge if we shoot a CO2 laser-produced plasma channel upward through the top of a high grounded tower under conditions of high thunderstorm electric fields.

High frequency magnetron plasma apparatus

Abstract: An object of the present invention is to increase the energy efficiency of a plasma apparatus and provide a high-frequency magnetron plasma apparatus which can precisely control plasma. The plasma apparatus has a susceptor electrode, a plasma exciting electrode, magnets mounted on the plasma exciting electrode, and a magnetic shield provided around the plasma exciting electrode, all of which are arranged in a vacuum chamber. The magnetic shield has a high impedance for a high frequency. The magnetic shield is preferably earthed with a direct current, more preferably earthed through an inductance.

Measurements of potentials and sheath formation in plasma immersion ion implantation

Abstract: Collecting and emitting probes have been used to explore the distribution of potentials and the dynamic behavior of the cathodic sheath in the rf glow dischargeplasmas used for plasma immersion ion implantation (PI3). On application of a negative voltage pulse, the sheath expands rapidly but comes to a steady‐state position within a few microseconds. The potential distribution then remains stable as long as there is sufficient plasma outside the sheath region to replace the ions lost to the cathode. The various dc potentials in the plasma that arise from rectification of the rf fields are also important. At power levels up to 500 W, the plasma potential is several hundred volts above the average dc potential of the antenna. The magnitude of this voltage difference depends on the antenna geometry, its insulation from the plasma and the dc potential that can exist between it and the chamber walls. The floating potential of a typical PI3 target can vary from 50 to 300 V below the plasma potential but in all cases the difference is sufficient to ensure that there is a sheath and presheath structure around the target before the application of the high voltage pulse.

Plasma treatment method and device therefor

Abstract: PURPOSE: To provide a plasma treatment method and a device therefor in which the ununiformity of plasma density distribution in an ICP plasma treatment device is improved CONSTITUTION: A plurality of antennas for generating the plasma by IPC are arranged in a vacuum vessel 2 in which a material 10 to be treated is set, and the power distribution of the high frequency power supplied to each antenna A1 A2 is regulated, whereby the intensity distribution of the high frequency electric field induced in the vacuum vessel can be varied, and the state of plasma density distribution in the plasma generating area can be regulated Since the superposed state of the electromagnetic wave emitted from each antenna can be changed when the phase of the high frequency power supplied to each antenna A1, A2 is regulated, the in-plane uniformity of the coupling state to the induced electromagnetic filed of the plasma is enhanced, and the state of the plasma density distribution at plasma generation can be regulated

Thin Oxide MOS Damages Caused by Wafer Charging in Magnetized Helium Plasma

Abstract: The effect of nonuniform He plasma on the properties of thin Si - SiO 2 structures has been studied. The plasma reactor system used is a magnetically enhanced like reactive ion etch reactor. The damage effects in MOS structures were determined as a function of Al gate thickness (60 - 1000nm) and plasma parameters. The results indicate strong correlation between plasma induced charge build-up and Al gate thickness. The role of plasma nonuniformity as well as VUV are discussed.

Production of a large-volume plasma by a hot-cathode arc

Abstract: Probe measurements reveal that the plasma produced by a hot-cathode arc contains two groups of electrons, with temperatures ≈4 and 10 eV, with a density of 1010–1011 cm−3. These electrons are distributed uniformly over a volume of 0.2 m3. The discharge voltage is found as a function of the gas pressure and the heater current. Low-temperature regimes of the deposition of TiN coatings on metals and insulators after a plasma processing of the articles are described. The design of the discharge system is discussed.

Erosion of a relativistic electron beam propagating in a plasma channel.

Abstract: A relativistic electron beam has propagated 91 m in a laser-ionized plasma channel across applied magnetic fields much larger than the geomagnetic field. Beam currents ranged from 0.3 to 1.0 kA and transverse magnetic fields from 0.1 to 4.0 G. Beam degradation in the form of a shortening of the current pulse (erosion) was observed. The two erosion processes were inductive and magnetic erosion. Observed total erosion rates are in agreement with the theoretical inductive and magnetic erosion rates when they are summed. Magnetic erosion was enhanced when the beam radius was larger than the channel.

Plasma-assisted tube with helical slow-wave structure

Abstract: Microwave amplifiers are disclosed having a hollow helix slow-wave structure coupled directly to input and output waveguides. This helix-waveguide coupling structure couples the TEM mode of the helix to the TE10 mode of the rectangular waveguides and also defines ports communicating with the helix interior. Heating of the helix during high-power operation can be removed by cooling liquid pumped through the helix via these ports. The helix is surrounded by a cylindrical housing containing a low-pressure ionizable gas which forms a plasma channel that focuses the electron beam without the need for surrounding magnetic structures. A plasma cathode electron gun is arranged to inject an electron beam through the helix. Backflowing ions from the housing are harmlessly absorbed into the face of the plasma cathode. The microwave amplifier is converted to a backward wave oscillator by coupling a load to one of the waveguides.

Plasma cvd device and plasma cvd method

Abstract: PURPOSE: To provide the plasma CVD device and method capable of forming even a stable and high-quality conductive thin film of Ti, etc., in the plasma CVD producing plasma with the induction coupling by an RF antenna. CONSTITUTION: An RF antenna 3 is arranged at the part in contact with the plasma in a plasma producing chamber 4, and an electric field from the antenna 3 is directly impressed on the plasma 5. The surface of the antenna 3 is previously coated with a material contg. an element constituting a film forming material. Since the electric field of the antenna is not transmitted through the dielectric window of the plasma producing chamber unlike the conventional device, a decrease in the electric field strength due to the deposition of a conductive film on the dielectric window is prevented, and treatment is conducted with the constant high-density plasma.

Production of RF Plasma Using a Magnetic Line-Cusp Field

Abstract: A large-volume cylindrical rf plasma source with a magnetic line-cusp field has been developed for large-scale plasma processing. In this type of plasma source, a capacitively-coupled 13.56 MHz rf plasma is produced in the presence of a magnetic line-cusp field. Two versions of the plasma source have been designed and tested. The first version has peripheral rf electrodes placed outside the ionization chamber, and is suitable for preparing a large-volume uniform plasma. This plasma source can attain a useful area of uniform plasma over a 30-cm-diameter region within 10% nonuniformity. The second version features doughnut-shaped parallel plate electrodes which form part of the chamber wall and serve as high-current sources. The electron density in such a version is proportional to the rf power, being equal to 4×1010 cm-3 at 400 W. The measured electron-energy distribution function showed a Maxwellian distribution function due to the electron-neutral particle collisions arising from drift motion in the magnetic line-cusp field.

Characteristics of discharge induced by laser-generated plasmas in atmospheric air

Abstract: The possibility of laser-induced lightning has been investigated for the future application in the protection of electric power systems from lightning strokes. This technique induces lightning strokes artificially along a laser-produced breakdown plasma channel and conducts them to a harmless place on the ground. To clarify the plasma formation mechanism and the discharge (sparkover) induction process, sparkover induction experiments are performed for two types of long-gap electrode configurations, plate-to-rod and plate-to-plate, with a 50-J TEA CO2 laser. In the present paper, the sparkover voltage characteristics and interferometric measurement on laser-produced plasma mainly are described, together with sparkover induction for a series of metal beads arranged equidistantly which simulate a plasma channel.

Outgassing and plasma development in the early phase of dielectric surface flashover in vacuum

Abstract: Surface flashover along dielectric interfaces is the limiting factor in high voltage systems and in particle accelerator technology. The processes leading to flashover are far from being fully understood. With a high sensitivity laser beam deflection method, gradients of gas and plasma densities above the surface are measured, and correlated to high resolution current, x-ray, and luminosity signals, with a temporal resolution of better than 6 ns. Experimental results show a pre flashover phase with linearly rising current accompanied by x-ray emission during which no plasma is observed, followed by an exponential current rise associated with the build-up of a plasma channel several micrometers above the surface. Estimates of the electron drift velocity and the current density in the plasma channel point to gaseous ionization processes responsible for the plasma build-up. The results are consistent with the saturated secondary electron emission avalanche model, with electron induced outgassing as the main process causing surface flashover.

Plasma discharging cell

Abstract: PURPOSE:To equalize and stabilize plasma discharging throughout the entire length of a stripe-shape plasma channel in a plasma discharging cell. CONSTITUTION:A plasma discharging cell 2 is provided with one substrate 7, a discharging electrode 8 stripe-patterned on the surface of the substrate, the other substrate 3 connected to the substrate 7 through a certain area of space 13, and a gas that can be ionized and is sealed in the space 13. A barrier rib 11 is formed along each discharging electrode 8, and the space 13 is divided by the barrier rib 11 to form a stripe-shape plasma channel. The discharging electrode 8 has a multilayer structure containing an internal conductive layer 9 and a surface resistance layer 10. The surface resistance layer 10 functions as a load resistance, and plasma discharging is equalized and stabilized by self-bias effect. An intermediate insulator layer can be interposed between the internal conductive layer 9 and the surface resistance layer 10. The surface resistance layer 10 is electrically connected to the internal conductive layer 9 through a contact hole provided on the intermediate insulator layer.

Electric field strength in a silicon surface barrier detector with the presence of a dielectric plasma column

Abstract: The dynamic change of the electric field strength in a silicon surface barrier detector (SSBD) is studied. With the presence of a dielectric plasma column in the depletion layer of the SSBD, the electric field strength inside/outside the plasma column is suppressed/enhanced. As the length and the dielectric constant of the plasma column become shorter and smaller, the suppression and enhancement of the electric field strength become less. The electric field strength recovers the initial state, when the plasma column disappears. When the electrons and holes are inside/outside the dielectric plasma column, they have less/more electric potential than the one they have when there is no plasma column. During the movement of the electron/hole outside the plasma column to the positive/negative electrode, the enhanced electric field strength becomes smaller. Electron and hole pairs, which are the parts of the dielectric plasma column, arrive at positive and negative electrodes, having insufficient electric potential to induce the unit charge. This paper shows that the presence of a dielectric plasma column explains the main part of the residual defect in a SSBD.

Fundamental Experiments Concerning Laser Triggered Lightning

Abstract: As a huge current source, lightning has caused many disasters to human. Especially at the modern society human depend further and further on electric instruments, and hence the lightning protection will become more and more important.

Electron acceleration system

Abstract: A bore formed within a body of material storing a magnetic field at a saturation level, establishes a linear path along which an electron beam is focussed after the bore is ionized to form a plasma channel therein The driving current of the beam is sharply decreased to cause simultaneous decay of the stored magnetic field from a saturation level inducing an electric field concentrated in the plasma channel to accelerate travel of trailing electrons in the beam with a high accelerating gradient