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Plasma oscillation modes in a low-pressure plane positive column
Classified abstracts 7063-7072
methods and etchants used in present applications can now be optimized more effectively and appropriate etchants can be developed for new applications. J J Kelly et al, Philips Tech Rev, 44, 1988, 61-74. 35 7063. Phenomena produced by ion bombardment in plasma-assisted etching environments The emphasis of this review paper will be to summarize recent experimental results, describe and evaluate contemporary concepts in the etch:tng field, and to provide references to recent work. Harold F. Winters, J Vac Sci Technol, A6, 1988, 1997 2000.
IV. Plasma technology 40. GASEOUS D I S C H A R G E S A N D P L A S M A DEVICES 40 7064. Fluctuations during JET discharges with H-mode The appearance and disappearance of H-mode behaviour in JET Tokamak discharges is associated with characteristic instabilities detected by edge magnetic probes, arrays of soft X-ray diodes and reflectometry : edge disruptive-like modes are observed before L H transitions whereas H - L transitions are accompanied by large bursts of broad-band activity. Other observed fluctuations, shown to be resonant in the central region of the discharge, are not affected by the transitions. The importance of edge fluctuations and induced transport in a magnetic separatrix configuration is thus emphasised. M Malacarne et al, Plasma Phys Control Fusion, 29, 1987, 1675-1686. 40 + + + + 7065. O , Oz, 03 and 04 ions in Ar-O2 sputtering discharges: comments on "Oxidation mechanism in rf CO2 plasma", Vacuum, 36, 85 (1986) In this communication, we comment on a recent paper, "Oxidation mechanism in rf CO2 plasma", by J Nakano and M Suzuki, Vacuum 36, 85 (1986). Our comments concern (1) the occurrence of O +, O +, O + and O + species in 10 to torr, if-excited, Ar/O2 glow discharges and (2) Ar O2 interaction in Ar/Oz glow discharges. Carolyn Rubin Aita and Michel E Marhic, Vacuum, 38, 1988, 37 38. 40 7066. Ion emission from plasma-focus facilities Angular- and energy-distributions of ions emitted from different p l a s m ~ focus (PF) devices of energy capacity ranging from 3.6 kJ to about 200 kJ are presented. Also compared are space- and time-resolved ion signals obtained from different PF facilities. Comparative studies show some similarity features in the ion emission characteristics. M Sadowski et al, Plasma Phys Control Fusion, 30, 1988, 763-769. 40 7067. Self-similar expansions in ion beam fusion The self-similar expansion generated by an intense light ion beam pulse of energy per nucleon Eh = Eo(t/z) p and current intensity lb = Io(t/z)2p-I (0 < t < Z) impinging on a planar target, is considered. The structure of the expansion flow is analysed and profiles of beam density and velocity and density, velocity and temperature of the plasma are found from the analysis. Quantities of interest in inertial confinement fusion such as the ablation pressure and the mass ablated rate as functions of time for several values of the law time exponent p are obtained. The acceleration efficiency of thin foils, defined as the fraction of absorbed energy that goes to foil kinetic energy as a function of p, has also been calculated. A Barrero and A Fernfindez, Plasma Phys Control Fusion, 29, 1987, 1605 1613. 40 7068. Time of flight measurements of the ratio of radial diffusion coeflicient and mobility for electron swarms in helium, argon, neon and krypton at high E / N A time of flight pulse technique has been used for the measurement of the ratio of radial diffusion coefficient to mobility (Dr/#)d for electron swarms in helium, argon, neon and krypton. The experimental range for helium and argon is 56.5 < E/N < 5650 Td (where E/N is the ratio of electrical field to gas number density), whilst the experimental range for neon and krypton is 1.41 < E/N < 5650 Td. The values of (Dr/#)d increase
with increasing E/N to a maximum value and then decrease in value. The values vary from 6.52 to 21.7 V in helium, 6.40 to 16.4 V in argon, 1.23 to 28 V in neon and 5.24 to 13.3 V in krypton. The results in helium and argon show good agreement with the result of Lakshminarasimha et al obtained by using a steady-state technique over an experimental range which extended up to E/N = 1300 Td. There are no experimental results in neon and krypton for comparison. The present results have been compared with theoretical values computed by various workers using the Boltzmann and Monte Carlo technique. Good agreement can generally be obtained between selected theoretical and the experimental results for the entire E/N region. S A J AI-Amin and J Lucas, J Phys D: Appl Phys, 20, 1987, 1590-1595. 40 7069. Plasma oscillation modes in a low-pressure plane positive column The effect of the transverse non-uniformity of plane low-pressure gas discharges on LF ion-acoustic waves is investigated. The dispersion laws of the oscillation eigen-modes are found. The estimated frequency of 300 kHz for the case of an argon-laser plasma is in rough agreement with the value of 250 kHz measured by Lfithi and Seelig and Donin and coworkers. D A Shapiro, J Phys D : Appl Phys, 20, 1987, 1230-123 I. 40 7070. Striations in a gas discharge Optical instabilities in gas discharges have been known almost as long as gas discharges themselves. Fortunately, in most applications their occurrence can be avoided, often by taking external measures adapted to a particular situation. However, a universal remedy requires a better understanding of these effects. F C van den Heuvel, Philips Tech Rev, 44, 1988, 89-95. 4O 7071. Monte Carlo simulation of ion transport through rf glow-discharge sheaths The transport of ions through rf glow-discharge sheaths was simulated with a Monte Carlo method to determine the distributions of ion-bombardment energy and angle of impact. Several sheath parameters were varied and their effects examined : (1) the type of ion-molecule scattering (hard sphere, potential field interaction, charge exchange), (2) the ratio of ion and neutral masses, (3) the ratio of the sheath width to collision mean free path, (4) spatially uniform, spatially linear, and time-dependent (rf) electric fields in the sheath, and (5) the frequency of an rf component in the sheath. The results of the Monte Carlo simulations indicate that the type of elastic scattering (hard sphere or soft sphere) does not significantly change either the impact angle distributions or the scaled ion-bombardment energy distributions. Charge-exchange scattering produces a much greater ion-bombardment directionality and a different shape of the ion-bombardment energy distribution. The fully developed distributions depend only on the ion-to-neutral mass ratio, type of ion-neutral scattering, and the dc value of the electric field-to-pressure ratio at the electrode. Fully developed distributions are reached in approximately three mean free paths in spatially uniform sheath fields and in about six mean free paths for spatially linear sheath fields. The minimum ion directionality was observed when the ion-to-molecule mass ratio was approximately unity. Time-dependent (rf) variation of the sheath field produces features in the ion energy distributions which are similar for both the collisional and collisionless sheaths. Brian E Thompson et al, Jappl Phys, 63, 1988, 2241 2251.
41. OPTICAL ELECTRONICS A N D LASERS 41 7072. Electron energy distributions in oxygen microwave plasmas Knowledge of the electron energy distribution is of fundamental importance in the understanding of chemical reactions in plasmas. Many of these reactions are initiated by electron impact and their relative importance depends on the kinetic energy of the plasma electrons. The Langmuir probe is an important plasma diagnostic tool, which yields the density and potential of the plasma, as well as the electron temperature. A major shortcoming of this technique is the presumption of Maxwellian electron energy distributions. Determination of the electron energy distribution for a non-Maxwellian plasma requires a modified Langmuir probe technique developed by Druyvesteyn. We have measured distributions in microwave (915 MHz) excited O: plasmas and observed little variation 999
methods and etchants used in present applications can now be optimized more effectively and appropriate etchants can be developed for new applications. J J Kelly et al, Philips Tech Rev, 44, 1988, 61-74. 35 7063. Phenomena produced by ion bombardment in plasma-assisted etching environments The emphasis of this review paper will be to summarize recent experimental results, describe and evaluate contemporary concepts in the etch:tng field, and to provide references to recent work. Harold F. Winters, J Vac Sci Technol, A6, 1988, 1997 2000.
IV. Plasma technology 40. GASEOUS D I S C H A R G E S A N D P L A S M A DEVICES 40 7064. Fluctuations during JET discharges with H-mode The appearance and disappearance of H-mode behaviour in JET Tokamak discharges is associated with characteristic instabilities detected by edge magnetic probes, arrays of soft X-ray diodes and reflectometry : edge disruptive-like modes are observed before L H transitions whereas H - L transitions are accompanied by large bursts of broad-band activity. Other observed fluctuations, shown to be resonant in the central region of the discharge, are not affected by the transitions. The importance of edge fluctuations and induced transport in a magnetic separatrix configuration is thus emphasised. M Malacarne et al, Plasma Phys Control Fusion, 29, 1987, 1675-1686. 40 + + + + 7065. O , Oz, 03 and 04 ions in Ar-O2 sputtering discharges: comments on "Oxidation mechanism in rf CO2 plasma", Vacuum, 36, 85 (1986) In this communication, we comment on a recent paper, "Oxidation mechanism in rf CO2 plasma", by J Nakano and M Suzuki, Vacuum 36, 85 (1986). Our comments concern (1) the occurrence of O +, O +, O + and O + species in 10 to torr, if-excited, Ar/O2 glow discharges and (2) Ar O2 interaction in Ar/Oz glow discharges. Carolyn Rubin Aita and Michel E Marhic, Vacuum, 38, 1988, 37 38. 40 7066. Ion emission from plasma-focus facilities Angular- and energy-distributions of ions emitted from different p l a s m ~ focus (PF) devices of energy capacity ranging from 3.6 kJ to about 200 kJ are presented. Also compared are space- and time-resolved ion signals obtained from different PF facilities. Comparative studies show some similarity features in the ion emission characteristics. M Sadowski et al, Plasma Phys Control Fusion, 30, 1988, 763-769. 40 7067. Self-similar expansions in ion beam fusion The self-similar expansion generated by an intense light ion beam pulse of energy per nucleon Eh = Eo(t/z) p and current intensity lb = Io(t/z)2p-I (0 < t < Z) impinging on a planar target, is considered. The structure of the expansion flow is analysed and profiles of beam density and velocity and density, velocity and temperature of the plasma are found from the analysis. Quantities of interest in inertial confinement fusion such as the ablation pressure and the mass ablated rate as functions of time for several values of the law time exponent p are obtained. The acceleration efficiency of thin foils, defined as the fraction of absorbed energy that goes to foil kinetic energy as a function of p, has also been calculated. A Barrero and A Fernfindez, Plasma Phys Control Fusion, 29, 1987, 1605 1613. 40 7068. Time of flight measurements of the ratio of radial diffusion coeflicient and mobility for electron swarms in helium, argon, neon and krypton at high E / N A time of flight pulse technique has been used for the measurement of the ratio of radial diffusion coefficient to mobility (Dr/#)d for electron swarms in helium, argon, neon and krypton. The experimental range for helium and argon is 56.5 < E/N < 5650 Td (where E/N is the ratio of electrical field to gas number density), whilst the experimental range for neon and krypton is 1.41 < E/N < 5650 Td. The values of (Dr/#)d increase
with increasing E/N to a maximum value and then decrease in value. The values vary from 6.52 to 21.7 V in helium, 6.40 to 16.4 V in argon, 1.23 to 28 V in neon and 5.24 to 13.3 V in krypton. The results in helium and argon show good agreement with the result of Lakshminarasimha et al obtained by using a steady-state technique over an experimental range which extended up to E/N = 1300 Td. There are no experimental results in neon and krypton for comparison. The present results have been compared with theoretical values computed by various workers using the Boltzmann and Monte Carlo technique. Good agreement can generally be obtained between selected theoretical and the experimental results for the entire E/N region. S A J AI-Amin and J Lucas, J Phys D: Appl Phys, 20, 1987, 1590-1595. 40 7069. Plasma oscillation modes in a low-pressure plane positive column The effect of the transverse non-uniformity of plane low-pressure gas discharges on LF ion-acoustic waves is investigated. The dispersion laws of the oscillation eigen-modes are found. The estimated frequency of 300 kHz for the case of an argon-laser plasma is in rough agreement with the value of 250 kHz measured by Lfithi and Seelig and Donin and coworkers. D A Shapiro, J Phys D : Appl Phys, 20, 1987, 1230-123 I. 40 7070. Striations in a gas discharge Optical instabilities in gas discharges have been known almost as long as gas discharges themselves. Fortunately, in most applications their occurrence can be avoided, often by taking external measures adapted to a particular situation. However, a universal remedy requires a better understanding of these effects. F C van den Heuvel, Philips Tech Rev, 44, 1988, 89-95. 4O 7071. Monte Carlo simulation of ion transport through rf glow-discharge sheaths The transport of ions through rf glow-discharge sheaths was simulated with a Monte Carlo method to determine the distributions of ion-bombardment energy and angle of impact. Several sheath parameters were varied and their effects examined : (1) the type of ion-molecule scattering (hard sphere, potential field interaction, charge exchange), (2) the ratio of ion and neutral masses, (3) the ratio of the sheath width to collision mean free path, (4) spatially uniform, spatially linear, and time-dependent (rf) electric fields in the sheath, and (5) the frequency of an rf component in the sheath. The results of the Monte Carlo simulations indicate that the type of elastic scattering (hard sphere or soft sphere) does not significantly change either the impact angle distributions or the scaled ion-bombardment energy distributions. Charge-exchange scattering produces a much greater ion-bombardment directionality and a different shape of the ion-bombardment energy distribution. The fully developed distributions depend only on the ion-to-neutral mass ratio, type of ion-neutral scattering, and the dc value of the electric field-to-pressure ratio at the electrode. Fully developed distributions are reached in approximately three mean free paths in spatially uniform sheath fields and in about six mean free paths for spatially linear sheath fields. The minimum ion directionality was observed when the ion-to-molecule mass ratio was approximately unity. Time-dependent (rf) variation of the sheath field produces features in the ion energy distributions which are similar for both the collisional and collisionless sheaths. Brian E Thompson et al, Jappl Phys, 63, 1988, 2241 2251.
41. OPTICAL ELECTRONICS A N D LASERS 41 7072. Electron energy distributions in oxygen microwave plasmas Knowledge of the electron energy distribution is of fundamental importance in the understanding of chemical reactions in plasmas. Many of these reactions are initiated by electron impact and their relative importance depends on the kinetic energy of the plasma electrons. The Langmuir probe is an important plasma diagnostic tool, which yields the density and potential of the plasma, as well as the electron temperature. A major shortcoming of this technique is the presumption of Maxwellian electron energy distributions. Determination of the electron energy distribution for a non-Maxwellian plasma requires a modified Langmuir probe technique developed by Druyvesteyn. We have measured distributions in microwave (915 MHz) excited O: plasmas and observed little variation 999