The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform

Tatsuo Shoji - One of the best experts on this subject based on the ideXlab platform.

  • Whistler wave Plasma Production in CHS
    2004
    Co-Authors: Tatsuo Shoji, Y. Sakawa, C. Suzuki, K. Toi, Ryosuke Ikeda, Masaki Takeuchi, G. Matsunaga
    Abstract:

    Rf Plasma Production in Whistler waves range of frequency f/fci >1 is applied on the compact helical system (CHS) in a steady state operation with low toroidal magnetic field strength, where f and fci are rf and ion cyclotron frequencies, respectively. Maximum rf power and pulse width are is170kW and 10 msec at 9MHz, respectively. The line averaged Plasma density as high as 2x10^18 m-3 (He Plasma) is produced in the region of toroidal magnetic field strength on magnetic axis B=100G~1.5kG and the electron temperature measured at Plasma periphery is about 20eV. The wave magnetic field strength measured at the Plasma periphery showed the evidence of the toroidal eigen modes of the Whistler waves. The additional long pulse microwave heating of 2.45GHz (>200msec) is applied and it sustains the Plasmas while the microwave itself can not ignite Plasmas when B

  • High-Density Hydrogen Plasma Production in a Simple Torus using Helicon Waves
    AIP Conference Proceedings, 2003
    Co-Authors: Youichi Sakawa, Tatsuo Shoji
    Abstract:

    High‐density hydrogen Plasma Production in a simple torus using helicon waves has been investigated. The measured Plasma density versus external magnetic field peaks at a condition close to the lower‐hybrid resonance. The measured dispersion relation of helicon waves in the high‐density region shows deviation from that of the m = +1 mode derived using the uniform Plasma assumption and agrees relatively well with that using the parabolic density profile. The difference in the dispersion relation of the m = +1 mode between the uniform and non‐uniform Plasma models is explained by adding the vacuum region in the calculation of the boundary condition.

  • Plasma Production by helicon and slow waves in HF/VHF bands of rf
    2001
    Co-Authors: Youichi Sakawa, Hideki Kikuchi, Hiroyuki Kunimatsu, Tatsuo Shoji
    Abstract:

    Plasma Production by helicon and slow waves in HF (f = 13.56 MHz) and VHF (f = 50 and 144 MHz) bands of rf is studied. The experiments are conducted at rf power Prf < 4.5 kW, Ar gas pressure P = 3.5 mTorr, and a static magnetic field of B0 = 1.0 kG. The rf is applied to an antenna surrounding a Pyrex discharge tube (length = 90 cm, diameter = 5 cm) which is mounted on one end of a stainless steel vacuum chamber (length = 150 cm, diameter = 36 cm). A capacitive antenna, in which only rf voltage is applied, and an inductive antenna are used to excite the m = 0 mode of helicon wave and slow wave. By increasing Prf from ≈1 W to ≈1 kW, transition of discharge mode, slow-wave, capacitivelycoupled (E), and helicon-wave discharges, are observed. Radial and axial profiles of oscillating magnetic field and potential are measured and compared with analytic and two-dimensional wave code calculations.

  • Plasma Production by m = 0 Standing Helicon Waves
    Japanese Journal of Applied Physics, 2000
    Co-Authors: Mudtorlep Nisoa, Youichi Sakawa, Tatsuo Shoji
    Abstract:

    m=0 standing helicon waves (SHWs) are used to produce high-density Ar Plasmas, of the order of 1013 cm-3, in a bounded cylindrical Plasma column. Axial mode number N=1, 3, and 5 (N is the number of half-wavelengths in the Plasma column) SHWs are strongly excited for Plasma length L=10–26 cm with the rf power Prf≤3.5 kW and external static magnetic field B0=237 G. Hollow and parabolic density profiles that depend on the axial mode of SHW are observed. The standing wave ratio decreases with L, and travelling helicon waves dominate the Plasma Production for L>26 cm. The measured results are compared with a two-dimensional wave calculation.

  • Characteristics of the high density Plasma Production by m=0 helicon wave
    Applied Physics Letters, 1996
    Co-Authors: Y. Sakawa, N. Koshikawa, Tatsuo Shoji
    Abstract:

    The characteristics of the high density Plasma Production by the m = 0 azimuthal mode helicon wave is investigated. By varying the power of the applied radio frequency Prf two discharge modes exist; one is the low density mode (Plasma density np

Haruo Shindo - One of the best experts on this subject based on the ideXlab platform.

  • A New Method of Line Plasma Production by Microwave in a Narrowed Rectangular Waveguide
    Applied Physics Express, 2009
    Co-Authors: Y. Kimura, Masakazu Furukawa, Hideki Kawaguchi, Shin Kagami, Haruo Shindo
    Abstract:

    A newly proposed method of large-scaled line Plasma Production is studied with the microwave of 2.45 GHz. In this method, the narrowed rectangular waveguide of 62.0 mm in width, which is close to the cutoff condition for TE10 mode, is examined to produce 1.1 m line Plasma. The Ar Plasma thus produced becomes a very high density, as high as more than 6 times larger than the cutoff density, and its axial uniformity is within 5% in the entire Plasma. It is also found that the short plunger equipped at the end of waveguide produces a standing wave.

  • Large-scaled line Plasma Production by evanescent microwave in a narrowed rectangular waveguide
    2008
    Co-Authors: Haruo Shindo, Y. Kimura, N. Sato, M. Suzuki
    Abstract:

    Long line-shaped Plasmas are inevitable in material processing in manufacturing industries, such as flat panel displays (FPDs) and surface modification of large-area thin films. In this work, we studied a newly proposed method of large-scaled line Plasma generation. In this method, microwave power of frequency of 2.45 GHz in a narrowed and flattened rectangular waveguide is employed to produce a long uniform line Plasma. Since the width of waveguide is very close to the cutoff condition, the wavelength of microwave inside the guide is very much lengthened, providing a condition of long uniform line Plasma generation. The narrowed rectangular waveguides of 1.0 and 1.5 m in length and 5 mm in height were examined. The width of the waveguide could be varied from 59 to 61 mm. The waveguide has a long slot of 5 mm width on the top surface to launch the microwave into the discharge Plasma chamber. The Plasmas of Ar nad He at the pressures of 100 mTorr were generated by employing an extremely long microwave wavelength. It was observed that the microwave electric field became more uniform as the wave guide width was narrowed, indicating that the Plasma Production is due to the mechanism expected. The optical emission line measurements in Ar and He Plasmas also confirmed that the uniform Plasma was produced in the entire region of 1 m and 1.5 m. Thus we conclude that the present method of Plasma Production is quite advantageous for large area processing. Plasma extraction was also successfully tested and further long line Plasma of 2 meter is now under consideration.

  • Radio-Frequency Downstream Plasma Production by Surface-Wave in a Very High-Permittivity Material Discharge Tube
    Japanese Journal of Applied Physics, 2005
    Co-Authors: Kazuya Fujiwara, Michihiko Yanagisawa, Masakatsu Endo, Ikeda Yasushi, Tsutomu Suzuki, Haruo Shindo
    Abstract:

    A novel method of radio-frequency surface-wave Plasma Production is proposed, with a particular interest in use of a very high permittivity material discharge tube. A discharge tube of TiCa-TiMg composite, which has the permittivity of 140, is employed to produce SF6 Plasma by the 13.56 MHz radio-frequency power. The axial distribution of optical emission lines of fluorine shows a rapid decay, more than 5 times faster than that in quartz tube. This is because the speed of the surface-wave is reduced in a condition of very high permittivity. It is concluded that the method is innovative in use of radio-frequency power to produce downstream Plasma with a very high permittivity discharge tube.

  • Surface Wave Plasma Production Employing High-Permittivity Discharge Tube for Material Processing
    Japanese Journal of Applied Physics, 2003
    Co-Authors: Kazuya Fujiwara, Tadayoshi Okuya, Michihiko Yanagisawa, Haruo Shindo
    Abstract:

    As a novel method of Plasma Production, microwave-sustained discharge was studied, particularly focusing on the permittivity effect on the axial distributions of the Plasma in the discharge column with the two discharge tube materials. In the alumina discharge tube with a high permittivity, the axial distribution of electron density showed to be very localized in the upstream, nearby the microwave launcher, while in the quartz with a low permittivity a higher density region appeared further downstream. This difference in the axial distribution of the electron density could be explained by the behavior of the surface wave. It was stressed that this property could be one of the biggest advantages in its application to material processing on the industrial level, particularly in achieving a low-damage Plasma process, such as low-damage silicon etching.

  • Surface Wave Plasma Production Employing High-Permittivity Material for Microwave Window
    Japanese Journal of Applied Physics, 2001
    Co-Authors: Kouta Kusaba, Keisuke Shinagawa, Masakazu Furukawa, Katsufumi Kawamura, Haruo Shindo
    Abstract:

    As a novel method of large-diameter Plasma Production for ultralarge-scale integrated (ULSI) circuit processes, microwave Plasma Production employing a high-permittivity material window is proposed. A systematic Plasma density enhancement is found to occur in conjunction with increase in the permittivity value of the dielectric window material. The results are shown to be due to the surface wave, and the microwave power consumption mainly occurs near the window in the high permittivity. This Plasma Production can provide a good downstream Plasma with a large diameter for ULSI processes.

Youichi Sakawa - One of the best experts on this subject based on the ideXlab platform.

  • High-density hydrogen-Plasma Production in a simple torus using helicon waves
    Physics of Plasmas, 2003
    Co-Authors: Youichi Sakawa, M. Ohshima, Y. Ohta, T. Shoji
    Abstract:

    High-density hydrogen-Plasma Production in a simple torus using the m=+1 azimuthal mode of helicon waves is investigated. The measured dispersion relation of helicon waves in the high-density region shows deviation from that of the m=+1 mode derived using a uniform-Plasma dispersion relation. The dispersion relation is calculated for the parabolic, modified-parabolic density profiles, and for a uniform Plasma with a vacuum region.

  • High-Density Hydrogen Plasma Production in a Simple Torus using Helicon Waves
    AIP Conference Proceedings, 2003
    Co-Authors: Youichi Sakawa, Tatsuo Shoji
    Abstract:

    High‐density hydrogen Plasma Production in a simple torus using helicon waves has been investigated. The measured Plasma density versus external magnetic field peaks at a condition close to the lower‐hybrid resonance. The measured dispersion relation of helicon waves in the high‐density region shows deviation from that of the m = +1 mode derived using the uniform Plasma assumption and agrees relatively well with that using the parabolic density profile. The difference in the dispersion relation of the m = +1 mode between the uniform and non‐uniform Plasma models is explained by adding the vacuum region in the calculation of the boundary condition.

  • Plasma Production by helicon and slow waves in HF/VHF bands of rf
    2001
    Co-Authors: Youichi Sakawa, Hideki Kikuchi, Hiroyuki Kunimatsu, Tatsuo Shoji
    Abstract:

    Plasma Production by helicon and slow waves in HF (f = 13.56 MHz) and VHF (f = 50 and 144 MHz) bands of rf is studied. The experiments are conducted at rf power Prf < 4.5 kW, Ar gas pressure P = 3.5 mTorr, and a static magnetic field of B0 = 1.0 kG. The rf is applied to an antenna surrounding a Pyrex discharge tube (length = 90 cm, diameter = 5 cm) which is mounted on one end of a stainless steel vacuum chamber (length = 150 cm, diameter = 36 cm). A capacitive antenna, in which only rf voltage is applied, and an inductive antenna are used to excite the m = 0 mode of helicon wave and slow wave. By increasing Prf from ≈1 W to ≈1 kW, transition of discharge mode, slow-wave, capacitivelycoupled (E), and helicon-wave discharges, are observed. Radial and axial profiles of oscillating magnetic field and potential are measured and compared with analytic and two-dimensional wave code calculations.

  • Plasma Production by m = 0 Standing Helicon Waves
    Japanese Journal of Applied Physics, 2000
    Co-Authors: Mudtorlep Nisoa, Youichi Sakawa, Tatsuo Shoji
    Abstract:

    m=0 standing helicon waves (SHWs) are used to produce high-density Ar Plasmas, of the order of 1013 cm-3, in a bounded cylindrical Plasma column. Axial mode number N=1, 3, and 5 (N is the number of half-wavelengths in the Plasma column) SHWs are strongly excited for Plasma length L=10–26 cm with the rf power Prf≤3.5 kW and external static magnetic field B0=237 G. Hollow and parabolic density profiles that depend on the axial mode of SHW are observed. The standing wave ratio decreases with L, and travelling helicon waves dominate the Plasma Production for L>26 cm. The measured results are compared with a two-dimensional wave calculation.

  • Control of antenna coupling in high-density Plasma Production by m=0 helicon waves
    Applied Physics Letters, 1998
    Co-Authors: Youichi Sakawa, T. Takino, T. Shoji
    Abstract:

    Antenna coupling has been controlled in high-density Plasma Production by m=0 helicon waves using multiple-loop antennas and varying the phase and the distance between antennas. When two single-loop antennas are connected in series with the phase between the two being zero, threshold power for the density jump Pth is reduced by a factor of 2–3 compared with that of the one-turn loop antenna. This reduction in Pth is caused by the increase in antenna coupling at the lower Plasma density. The observed differences in antenna coupling among different antennas have been examined by using a two-dimensional wave code.

T. Shoji - One of the best experts on this subject based on the ideXlab platform.

  • Improvement of Plasma Production for Large Area Multi‐antenna RF Ion Source
    2011
    Co-Authors: Y. Oka, T. Shoji
    Abstract:

    A multi‐antenna RF ion source for negative ions has been studied. In a previous experiment, basic characteristics of a Faraday‐shielded multi‐antenna RF ion source with a high RF power up to 300 kW at 9 MHz for 10 msec pulse duration were studied. Present studies are focused on a study of the Plasma Production and/or an improvement of the RF power efficiency with hydrogen. Plasma parameters of Te, Npl, and Vpl were measured with Langmuir probes along with their dependence on the net RF power and the gas pressure. The parameters are calculated also by a simple transport model. On the basis of comparative discussions of two results and the experimental ones, a new Faraday‐shielded multi‐antenna system with a close coupling configuration is designed and tested for the improvement of Plasma Production. In a preliminary test of the new multi‐antenna system, the positive ion saturation current density of over several amperes per cm2 is achieved at ∼30 kW of the net RF power. Correspondingly the power efficiency...

  • High-density hydrogen-Plasma Production in a simple torus using helicon waves
    Physics of Plasmas, 2003
    Co-Authors: Youichi Sakawa, M. Ohshima, Y. Ohta, T. Shoji
    Abstract:

    High-density hydrogen-Plasma Production in a simple torus using the m=+1 azimuthal mode of helicon waves is investigated. The measured dispersion relation of helicon waves in the high-density region shows deviation from that of the m=+1 mode derived using a uniform-Plasma dispersion relation. The dispersion relation is calculated for the parabolic, modified-parabolic density profiles, and for a uniform Plasma with a vacuum region.

  • Control of antenna coupling in high-density Plasma Production by m=0 helicon waves
    Applied Physics Letters, 1998
    Co-Authors: Youichi Sakawa, T. Takino, T. Shoji
    Abstract:

    Antenna coupling has been controlled in high-density Plasma Production by m=0 helicon waves using multiple-loop antennas and varying the phase and the distance between antennas. When two single-loop antennas are connected in series with the phase between the two being zero, threshold power for the density jump Pth is reduced by a factor of 2–3 compared with that of the one-turn loop antenna. This reduction in Pth is caused by the increase in antenna coupling at the lower Plasma density. The observed differences in antenna coupling among different antennas have been examined by using a two-dimensional wave code.

Vladimir E. Moiseenko - One of the best experts on this subject based on the ideXlab platform.

  • RF Plasma Production and heating below ion-cyclotron frequencies in Uragan torsatrons
    Nuclear Fusion, 2011
    Co-Authors: Vladimir E. Moiseenko, V.l. Berezhnyj, V.n. Bondarenko, P. Ya. Burchenko, Francisco Castejón, V.v. Chechkin, V. Ya. Chernyshenko, M. Dreval, Igor E. Garkusha, G.p. Glazunov
    Abstract:

    In the IPP-Kharkiv there are two torsatrons (stellarators) in operation, and in both of them Alfven resonance heating under high-k∥ conditions is used. This method of heating is advantageous for small-size devices, since in contrast to the minority and second-harmonic heating it can be realized at lower Plasma densities. A series of experiments has been performed at the Uragan-3M torsatron with an aim to investigate the features of the discharge with a three-half-turn antenna. Electron temperatures in the range are achieved at Plasma densities . The Plasma energy content has increased by a factor of 2 with respect to the Plasma produced with the frame antenna. A new four-strap shielded antenna has been manufactured and installed in the Uragan-2M. A high-frequency discharge for wall conditioning is introduced in the Uragan-2M torsatron. The discharge is sustained by a specially designed small frame antenna, and efficient hydrogen dissociation is achieved. A self-consistent model has been developed for simulation of Plasma Production in ICRF. The model includes a set of particle and energy-balance equations for the electrons, and the boundary problem for the Maxwell equations. The first calculation results on RF Plasma Production in the Uragan-2M stellarator with the frame-type antenna are presented.

  • RF Plasma Production in Uragan‐2M Torsatron
    AIP Conference Proceedings, 2007
    Co-Authors: Vladimir E. Moiseenko, Yu. S. Stadnik, O. M. Schvets, K. N. Stepanov, E.d. Volkov, V.i. Tereshin
    Abstract:

    A single frame antenna is used for Plasma Production below the cyclotron frequency at the medium‐size Uragan‐2M torsatron which has started operation at the end of year 2006. Its sizes and the regime of Plasma Production are chosen using the numerical modeling. In the numerical analysis, time‐harmonic Maxwell's equations are solved and the power deposition to the electrons is calculated. In the calculations the Plasma density is varied in the range np∼108–1013 cm−3. The single frame antenna provides the core power deposition at the low densities. With increase of the Plasma density the power deposition per particle decreases and the power deposition profile worsens since more power is delivered to the Plasma periphery. The first experimental results on Plasma Production in the Uragan‐2M torsatron are presented and discussed.

  • Analysis of ICRE (ω ⩽ ωci) Plasma Production in large scale tokamaks
    Nuclear Fusion, 1992
    Co-Authors: A.i. Lysojvan, Vladimir E. Moiseenko, O.m. Shvets, K. N. Stepanov
    Abstract:

    The authors study the possibility of target Plasma radiofrequency (RF) Production in the ion cyclotron range of frequencies (ICRF) (ω ≤ ωci) in large scale tokamaks before the startup of an Ohmic discharge. A number of experimental and theoretical studies on dense Plasma Production in the ICRF in toroidal magnetic devices are reviewed. The criteria for optimal development of the RF discharge stages are analysed, i.e., for RF breakdown of the neutral fill gas in the vicinity of the antenna (non-wave stage, ne