Edge Fluctuations In The Mst Madison Symmetric Torus Reversed Field Pinch
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Edge Fluctuations In The Mst Madison Symmetric Torus Reversed Field Pinch
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Author :
language : en
Publisher:
Release Date : 1990
Edge Fluctuations In The Mst Madison Symmetric Torus Reversed Field Pinch written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1990 with categories.
Edge magnetic and electrostatic fluctuations are measured in the Madison Symmetric Torus (MST) reversed field pinch. At low frequency (25 kHz), the mode number spectra of magnetic fluctuations agree very well with theoretical prediction for nonlinearly saturated tearing fluctuations resonant in the core. At high frequency (50 kHz to 100 kHz) the magnetic spectra broaden and the modes become resonant in the reversal region. Nonlinear phenomena are under experimental investigation. The low frequency fluctuations phase-lock together to produce a rotating localized disturbance. Bi-spectral analysis in frequency also reveals nonlinear three-wave mode-coupling at low frequency. Electrostatic fluctuations are substantial and do not appear to obey a Boltzmann relation (i.e. e{tilde {phi}}/kT{sub e} {tilde p}{sub e}/p{sub e} where {tilde {phi}} and {tilde p}{sub e} are the fluctuating potential and pressure, respectively). From measurements of the fluctuating density, temperature, and potential we infer that the electrostatic fluctuation induced transport of particles and energy can be substantial. 13 refs., 11 figs.
Confinement And Fluctuations In The Mst Madison Symmetric Torus Reversed Field Pinch
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Author : J.C. SPROTT
language : en
Publisher:
Release Date : 1990
Confinement And Fluctuations In The Mst Madison Symmetric Torus Reversed Field Pinch written by J.C. SPROTT and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1990 with categories.
Measurement Of Magnetic Turbulence Structure And Nonlinear Mode Coupling Of Tearing Fluctuations In The Madison Symmetric Torus Reversed Field Pinch Edge
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Author : Saeed Assadi
language : en
Publisher:
Release Date : 1994
Measurement Of Magnetic Turbulence Structure And Nonlinear Mode Coupling Of Tearing Fluctuations In The Madison Symmetric Torus Reversed Field Pinch Edge written by Saeed Assadi and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1994 with categories.
Turbulent Transport In The Mst Reversed Field Pinch
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Author :
language : en
Publisher:
Release Date : 1991
Turbulent Transport In The Mst Reversed Field Pinch written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1991 with categories.
Measurement Of Magnetic Turbulence Structure And Nonlinear Mode Coupling Of Tearing Fluctuations In The Madison Symmetric Torus Reversed Field Pinch Edge
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Author :
language : en
Publisher:
Release Date : 1994
Measurement Of Magnetic Turbulence Structure And Nonlinear Mode Coupling Of Tearing Fluctuations In The Madison Symmetric Torus Reversed Field Pinch Edge written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1994 with categories.
Linear and nonlinear magnetohydrodynamic (MHD) stability of current-driven modes are studied in the MST reversed field pinch. Measured low frequency (f
Controlling Fluctuations And Transport In The Reversed Field Pinch With Edge Current Drive And Plasma Biasing
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Author :
language : en
Publisher:
Release Date : 1998
Controlling Fluctuations And Transport In The Reversed Field Pinch With Edge Current Drive And Plasma Biasing written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1998 with categories.
Two techniques are employed in the Madison Symmetric Torus (MST) to test and control different aspects of fluctuation induced transport in the Reversed Field Pinch (RFP). Auxiliary edge currents are driven along the magnetic field to modify magnetic fluctuations, and the particle and energy transport associated with them. In addition, strong edge flows are produced by plasma biasing. Their effect on electrostatic fluctuations and the associated particle losses is studied. Both techniques are accomplished using miniature insertable plasma sources that are biased negatively to inject electrons. This type of emissive electrode is shown to reliably produce intense, directional current without significant contamination by impurities. The two most important conclusions derived from these studies are that the collective modes resonant at the reversal surface play a role in global plasma confinement, and that these modes can be controlled by modifying the parallel current profile outside of the reversal surface. This confirms predictions based on magnetohydrodynamic (MHD) simulations that auxiliary current drive in the sense to flatten the parallel current profile can be successful in controlling magnetic fluctuations in the RFP. However, these studies expand the group of magnetic modes believed to cause transport in MST and suggest that current profile control efforts need to address both the core resonant magnetic modes and those resonant at the reversal surface. The core resonant modes are not significantly altered in these experiments; however, the distribution and/or amplitude of the injected current is probably not optimal for affecting these modes. Plasma biasing generates strong edge flows with shear and particle confinement likely improves in these discharges. These experiments resemble biased H modes in other magnetic configurations in many ways. The similarities are likely due to the common role of electrostatic fluctuations in edge transport.
Nonlinear Coupling Of Tearing Fluctuations In The Madison Symmetric Torus
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Author :
language : en
Publisher:
Release Date : 1992
Nonlinear Coupling Of Tearing Fluctuations In The Madison Symmetric Torus written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1992 with categories.
Three-wave, nonlinear, tearing mode coupling has been measured in the Madison Symmetric Torus (MST) reversed-field pinch (RFP) [Fusion Technol. 19, 131 (1991)] using bispectral analysis of edge magnetic fluctuations resolved in k-space. The strength of nonlinear three-wave interactions satisfying the sum rules m[sub 1] + m[sub 2] = m[sub 3] and n[sub 1] + n[sub 2] = n[sub 3] is measured by the bicoherency. In the RFP, m=l, n[approximately]2R/a (6 for MST) internally resonant modes are linearly unstable and grow to large amplitude. Large values of bicoherency occur for two m=l modes coupled to an m=2 mode and the coupling of intermediate toroidal modes, e.g., n=6 and 7 coupled to n=13. These experimental bispectral features agree with predicted bispectral features derived from MHD computation. However, in the experiment, enhanced coupling occurs in the crash'' phase of a sawtooth oscillation concomitant with a broadened mode spectrum suggesting the onset of a nonlinear cascade.
Origin Of Tearing Mode Excitation In The Mst Reversed Field Pinch
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Author : Seung-Ho Choi
language : en
Publisher:
Release Date : 2006
Origin Of Tearing Mode Excitation In The Mst Reversed Field Pinch written by Seung-Ho Choi and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006 with categories.
Scientific And Technical Aerospace Reports
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Author :
language : en
Publisher:
Release Date : 1991
Scientific And Technical Aerospace Reports written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1991 with Aeronautics categories.
Improved Confinement And Beta In An Rfp With Reduced Turbulence
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Author :
language : en
Publisher:
Release Date : 2001
Improved Confinement And Beta In An Rfp With Reduced Turbulence written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2001 with categories.
Improved confinement has been obtained in the Madison Symmetric Torus (MST) reversed field pinch (RFP) (1) by application of current profile control, (2) spontaneously, subject to constraints on toroidal field-reversal and plasma density, and (3) by application of electrostatic biasing. In all three cases, either or both magnetic and electrostatic fluctuations are reduced. Improved confinement coinciding with reduced turbulence in the RFP is expected, since magnetic fluctuations have been measured to produce large particle and energy transport in the RFP core (roughly defined interior to the reversal surface), while electrostatic fluctuations produce large particle transport in the edge. (The cause of energy transport in the edge remains unidentified.) Here we briefly describe the important observations for each of these three cases of improved confinement in MST.
