The Experts below are selected from a list of 189 Experts worldwide ranked by ideXlab platform

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

  • Stability analysis of Plasma Confinement by the radio frequency electromagnetic field in a toroidal device
    Plasma Physics and Controlled Fusion, 2008
    Co-Authors: Vladimir Svidzinski
    Abstract:

    Stability analysis of a recently proposed (Svidzinski 2007 Phys. Plasmas 14 102512) Plasma Confinement concept is performed. A separate calculation of the equilibrium profile of the Plasma boundary supported by a circularly polarized electromagnetic field is made in collisionless two fluid and kinetic models in slab geometry. In this concept unmagnetized Plasma is confined by electromagnetic pressure of the radio frequency (rf) field in toroidal geometry with the confining field frequency in the lower range such that the size of the device is much smaller than the vacuum wavelength. The confining magnetic field is generated by currents in the toroidal shell and by image currents on the Plasma surface which are driven by ac voltages applied to toroidal and poloidal gaps in the shell. In the present stability analysis toroidal geometry is approximated by a periodic cylinder, it is assumed that Plasma is a perfectly conducting fluid and that there is a vacuum layer between the Plasma boundary and conducting shell. In this model a dispersion equation for Plasma oscillations near equilibrium is derived. A general stability criterion is calculated when Plasma is confined by an elliptically polarized rf field. For an elliptically polarized field stable Plasma equilibria can be realized under nonrestrictive conditions for a wide range of ellipticity parameters. In particular, for circular polarization the equilibrium is stable when a 0.6b, where a is the Plasma radius and b is the radius of the cylinder. When Plasma is confined by a linearly polarized field its equilibrium is in general unstable. Stable equilibria can also be realized when polarization of the confining field is a superposition of elliptical and linear polarizations. Conclusions about Plasma stability under nonrestrictive conditions are expected to be valid in toroidal geometry from the physics consideration of the stabilizing mechanism. The up-to-date studies of the proposed Plasma Confinement concept indicate that this concept can result in a practical Plasma Confinement device.

  • Plasma Confinement by circularly polarized electromagnetic field in toroidal geometry
    Physics of Plasmas, 2007
    Co-Authors: Vladimir Svidzinski
    Abstract:

    A novel Plasma Confinement concept based on Plasma Confinement by electromagnetic pressure of circularly polarized electromagnetic fields is proposed. Practical implementation of this concept in a toroidal device is suggested. In this concept the confining field frequency is in the lower range such that the size of the device is much smaller than the vacuum wavelength. Most of the previous radio-frequency (rf) Confinement concepts of unmagnetized Plasma were related to Confinement in rf cavities which operated at high frequency for which the size of the cavity is comparable to the wavelength. Operation at lower frequencies simplifies rf design, reduces Ohmic losses in the conducting walls and probably makes application of superconductors for wall materials more feasible. It is demonstrated that circular (or nearly circular) polarization of the electromagnetic field is required for Confinement from both the equilibrium and stability considerations. Numerical analysis of Plasma Confinement for magnetohydrod...

Isao Katanuma - One of the best experts on this subject based on the ideXlab platform.

  • Plasma Confinement in the GAMMA 10 tandem mirror
    Journal of Advanced Science, 2002
    Co-Authors: Kiyoshi Yatsu, Teruji Cho, Hiroyuki Higaki, Mafumi Hirata, Hitoshi Hojo, Makoto Ichimura, Kameo Ishii, Khairul Islam, Akiyoshi Itakura, Isao Katanuma
    Abstract:

    The Plasma Confinement in the GAMMA 10 tandem mirror is studied. The mirror Confinement is much improved owing to the potential Confinement. The high density Plasma Confinement was recently attained. Relations between Confinement time and confining potential on the Plasma density have been obtained in the high density region.

  • Plasma Confinement in the GAMMA 10 tandem mirror
    Nuclear Fusion, 1999
    Co-Authors: Kiyoshi Yatsu, Teruji Cho, Mafumi Hirata, Hitoshi Hojo, Makoto Ichimura, Leonid G. Bruskin, Minoru Hamada, Keiichi Ishii, Akiyosi Itakura, Isao Katanuma
    Abstract:

    The central cell density and the diamagnetic signal were doubled as a result of plug potential formation by ECRH in hot ion mode experiments on the GAMMA 10 tandem mirror. In order to obtain these remarkable results, the axisymmetrized heating patterns of ECRH and ICRF heating were optimized. Furthermore, conducting plates were installed adjacent to the surface of the Plasma along the flat shaped magnetic flux tube located in the anchor transition regions; the plates may contribute to the reduction of some irregular electric fields produced possibly with ECRH in these thin flux tube regions. The conducting plates contributed to reducing the radial loss rate to less than 3% of the total particle losses, along with improvements in the reproducibility of the experiments and the controllability of the potential Confinement. The increases in central cell density and diamagnetism in association with the increase in plug potentials scaled well with increasing ECRH power. A plug potential of 0.6 kV and a density increase of 100% were achieved using an ECRH power of 140 kW injected into both plug regions. The Plasma Confinement was improved by an order of magnitude over a simple mirror Confinement owing to the tandem mirror potential formation.

Sakineh Meshkani - One of the best experts on this subject based on the ideXlab platform.

  • Techniques for improving Plasma Confinement in IR-T1 Tokamak
    International Journal of Hydrogen Energy, 2016
    Co-Authors: Mahmood Ghoranneviss, Sakineh Meshkani
    Abstract:

    Abstract The main goal of this paper is the investigation of different techniques for improving the Plasma Confinement in IR-T1 Tokamak. For this purpose, magnetic fluctuations determined by Mirnov coils were analyzed using singular value decomposition (SVD) and wavelet techniques. Also, electric fluctuations specified by Langmuir-Ball pen probe were studied and analyzed for calculations of Plasma potential and electron temperature. In this research, investigation was also made into influence of Resonant Helical Magnetic Field (RHF) (with both modes L = 2 and L = 3) on Plasma stability and Plasma Confinement. Results show that cold biased limiter with a positive voltage and emissive biased limiter with a negative voltage were the most effective condition on increase of Plasma stability and reduction of magnetic fluctuations. Also, the results demonstrated that RHF with mode L = 3 has an effective role in Plasma Confinement improvement.

  • Plasma Confinement Modification in IR-T1 Tokamak by Velocity Shear Stabilization
    Journal of Fusion Energy, 2014
    Co-Authors: Mahmood Ghoranneviss, Sakineh Meshkani, M. Lafouti, A. Salar Elahi
    Abstract:

    E × B velocity shear effects on the Plasma Confinement were investigated in the IR-T1 tokamak. The investigations have been done at the presence of external applied electric and Resonant Helical magnetic Fields (RHF). In this work, experimental data have been measured by using two arrays of the Langmuir probes in both the radial and poloidal directions. A velocity shear stabilization mechanism has also been proposed to be responsible for an improvement in Plasma Confinement. The results show that E_r × B drift velocity (V_E×B) reduces about 90 % due to applied biasing and RHF at edge Plasma. We have also observed that positive biasing and RHF lead to a significant decrease (>80 %) for radial turbulent transport (Γ_E×B) at edge Plasma. In this paper, the electrostatic Reynolds stress (Rs) and the shearing rate γ_E×B have been calculated. We have also compared the Rs and γ_E×B at presence of the biasing and RHF and without biasing and RHF. A good correlation between Confinement modifications and E_r × B velocity shear has been found suggesting that Confinement enhancement originates at the edge Plasma as a consequence of the formation of a particle transport barrier just inside the limiter.

  • Modification of Plasma Confinement by Applying External Resonant Fields in IR-T1 Tokamak
    2014 International Conference on Mathematics and Computers in Sciences and in Industry, 2014
    Co-Authors: M. Lafouti, M. Ghorannevis, Sakineh Meshkani
    Abstract:

    The effects of bias magnitude on electric and magnetic field, as well as poloidal and radial particle flux are investigated in this paper. Different Resonant Helical Magnetic Fields (RHF), beside different positive biasing voltages is applied to the Plasma. The effect of the helical windings radius on above parameters is investigated. Fast Fourier Transform analysis (FFT) is driven in different situations to demonstrate power spectrum of particle flux. The results show that there is a critical voltage for the ideal circumstance. It will be shown that the Plasma Confinement depends on the amount of RHF helicity. The order in which the RHF and biasing are applied is an important factor in modifying the transport.

Mahmood Ghoranneviss - One of the best experts on this subject based on the ideXlab platform.

  • Techniques for improving Plasma Confinement in IR-T1 Tokamak
    International Journal of Hydrogen Energy, 2016
    Co-Authors: Mahmood Ghoranneviss, Sakineh Meshkani
    Abstract:

    Abstract The main goal of this paper is the investigation of different techniques for improving the Plasma Confinement in IR-T1 Tokamak. For this purpose, magnetic fluctuations determined by Mirnov coils were analyzed using singular value decomposition (SVD) and wavelet techniques. Also, electric fluctuations specified by Langmuir-Ball pen probe were studied and analyzed for calculations of Plasma potential and electron temperature. In this research, investigation was also made into influence of Resonant Helical Magnetic Field (RHF) (with both modes L = 2 and L = 3) on Plasma stability and Plasma Confinement. Results show that cold biased limiter with a positive voltage and emissive biased limiter with a negative voltage were the most effective condition on increase of Plasma stability and reduction of magnetic fluctuations. Also, the results demonstrated that RHF with mode L = 3 has an effective role in Plasma Confinement improvement.

  • Plasma Confinement Modification in IR-T1 Tokamak by Velocity Shear Stabilization
    Journal of Fusion Energy, 2014
    Co-Authors: Mahmood Ghoranneviss, Sakineh Meshkani, M. Lafouti, A. Salar Elahi
    Abstract:

    E × B velocity shear effects on the Plasma Confinement were investigated in the IR-T1 tokamak. The investigations have been done at the presence of external applied electric and Resonant Helical magnetic Fields (RHF). In this work, experimental data have been measured by using two arrays of the Langmuir probes in both the radial and poloidal directions. A velocity shear stabilization mechanism has also been proposed to be responsible for an improvement in Plasma Confinement. The results show that E_r × B drift velocity (V_E×B) reduces about 90 % due to applied biasing and RHF at edge Plasma. We have also observed that positive biasing and RHF lead to a significant decrease (>80 %) for radial turbulent transport (Γ_E×B) at edge Plasma. In this paper, the electrostatic Reynolds stress (Rs) and the shearing rate γ_E×B have been calculated. We have also compared the Rs and γ_E×B at presence of the biasing and RHF and without biasing and RHF. A good correlation between Confinement modifications and E_r × B velocity shear has been found suggesting that Confinement enhancement originates at the edge Plasma as a consequence of the formation of a particle transport barrier just inside the limiter.

  • First results of movable limiter experiments and its effects on the tokamak Plasma Confinement
    Radiation Effects and Defects in Solids, 2013
    Co-Authors: Ahmad Salar Elahi, Mahmood Ghoranneviss, R. Arvin, And S. Mohammadi
    Abstract:

    Limiters play a number of roles in the tokamak operation. It serves primarily to protect the wall from the Plasma when there are disruptions, runaway electrons, or other instabilities and also the limiters localize the Plasma–surface interaction. In this research, we presented the first results of movable limiter experiments and its effects on the tokamak Plasma Confinement. For this purpose, we designed, constructed, and installed a movable localized poloidal limiter, and then measured the effects of limiter position on the time intervals of Plasma parameters such as Plasma density, temperature, and energy Confinement time. The results of effects of the movable limiter experiments on Plasma Confinement.

J. S. Hong - One of the best experts on this subject based on the ideXlab platform.

  • RF-heating and Plasma Confinement studies in the HANBIT mirror device
    Nuclear Fusion, 2003
    Co-Authors: M. Kwon, J. G. Bak, K. Choh, J. H. Choi, J.j. Choi, J. W. Choi, Kyu-sun Chung, Y.s. Chung, A.c. England, J. S. Hong
    Abstract:

    HANBIT is a magnetic mirror Confinement device. Recently, after finishing the first campaign for the basic system development, it started the second campaign for high-temperature Plasma Confinement physics study in a mirror configuration. Here, we introduce briefly the HANBIT device and report initial physics experiment results on RF-Plasma heating and Confinement in the simple mirror configuration. It appears that the discharge characteristics of HANBIT are quite different from those in other mirror devices, and an explanation is presented to clarify the difference.