1
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Delgado-Aparicio LF, VanMeter P, Barbui T, Chellai O, Wallace J, Yamazaki H, Kojima S, Almagari AF, Hurst NC, Chapman BE, McCollam KJ, Den Hartog DJ, Sarff JS, Reusch LM, Pablant N, Hill K, Bitter M, Ono M, Stratton B, Takase Y, Luethi B, Rissi M, Donath T, Hofer P, Pilet N. Multi-energy reconstructions, central electron temperature measurements, and early detection of the birth and growth of runaway electrons using a versatile soft x-ray pinhole camera at MST. Rev Sci Instrum 2021; 92:073502. [PMID: 34340413 DOI: 10.1063/5.0043672] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2021] [Accepted: 04/26/2021] [Indexed: 06/13/2023]
Abstract
A multi-energy soft x-ray pinhole camera has been designed, built, and deployed at the Madison Symmetric Torus to aid the study of particle and thermal transport, as well as MHD stability physics. This novel imaging diagnostic technique employs a pixelated x-ray detector in which the lower energy threshold for photon detection can be adjusted independently on each pixel. The detector of choice is a PILATUS3 100 K with a 450 μm thick silicon sensor and nearly 100 000 pixels sensitive to photon energies between 1.6 and 30 keV. An ensemble of cubic spline smoothing functions has been applied to the line-integrated data for each time-frame and energy-range, obtaining a reduced standard-deviation when compared to that dominated by photon-noise. The multi-energy local emissivity profiles are obtained from a 1D matrix-based Abel-inversion procedure. Central values of Te can be obtained by modeling the slope of the continuum radiation from ratios of the inverted radial emissivity profiles over multiple energy ranges with no a priori assumptions of plasma profiles, magnetic field reconstruction constraints, high-density limitations, or need of shot-to-shot reproducibility. In tokamak plasmas, a novel application has recently been tested for early detection, 1D imaging, and study of the birth, exponential growth, and saturation of runaway electrons at energies comparable to 100 × Te,0; thus, early results are also presented.
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Affiliation(s)
| | - P VanMeter
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - T Barbui
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - O Chellai
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - J Wallace
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - H Yamazaki
- National Institutes for Quantum and Radiological Science and Technology, Naka, Ibaraki 311-0193, Japan
| | - S Kojima
- Kyushu University, Kasuga-kouen 6-1, Kasuga, Japan
| | - A F Almagari
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - N C Hurst
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - B E Chapman
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - K J McCollam
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - D J Den Hartog
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - J S Sarff
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - L M Reusch
- Edgewood College, Madison, Wisconsin 53711, USA
| | - N Pablant
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - K Hill
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - M Bitter
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - M Ono
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - B Stratton
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - Y Takase
- The University of Tokyo, Kashiwa 277-8561, Japan
| | - B Luethi
- DECTRIS Ltd., 5405 Baden-Dättwil, Switzerland
| | - M Rissi
- DECTRIS Ltd., 5405 Baden-Dättwil, Switzerland
| | - T Donath
- DECTRIS Ltd., 5405 Baden-Dättwil, Switzerland
| | - P Hofer
- DECTRIS Ltd., 5405 Baden-Dättwil, Switzerland
| | - N Pilet
- DECTRIS Ltd., 5405 Baden-Dättwil, Switzerland
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2
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Nishizawa T, Almagri AF, Anderson JK, Goodman W, Pueschel MJ, Nornberg MD, Ohshima S, Sarff JS, Terry PW, Williams ZR. Direct Measurement of a Toroidally Directed Zonal Flow in a Toroidal Plasma. Phys Rev Lett 2019; 122:105001. [PMID: 30932630 DOI: 10.1103/physrevlett.122.105001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/25/2018] [Revised: 02/16/2019] [Indexed: 06/09/2023]
Abstract
Zonal flow appears in toroidal, magnetically confined plasmas as part of the self-regulated interaction of turbulence and transport processes. For toroidal plasmas having a strong toroidal magnetic field, the zonal flow is predominately poloidally directed. This Letter reports the first observation of a zonal flow that is toroidally directed. The measurements are made just inside the last closed flux surface of reversed field pinch plasmas that have a dominant poloidal magnetic field. A limit cycle oscillation between the strength of the zonal flow and the amplitude of plasma potential fluctuations is observed, which provides evidence for the self-regulation characteristic of drift-wave-type plasma turbulence. The measurements help advance understanding and gyrokinetic modeling of toroidal plasmas in the pursuit of fusion energy.
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Affiliation(s)
- T Nishizawa
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - A F Almagri
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - J K Anderson
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - W Goodman
- Electrical Engineering Department, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - M J Pueschel
- Institute for Fusion Studies, University of Texas at Austin, Austin, Texas 78712, USA
| | - M D Nornberg
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - S Ohshima
- Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - J S Sarff
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - P W Terry
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Z R Williams
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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3
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Nishizawa T, Nornberg MD, Boguski J, Den Hartog DJ, Sarff JS, Williams ZR, Xing ZA, Craig D. Measurements of Impurity Transport Due to Drift-Wave Turbulence in a Toroidal Plasma. Phys Rev Lett 2018; 121:165002. [PMID: 30387678 DOI: 10.1103/physrevlett.121.165002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 09/11/2018] [Indexed: 06/08/2023]
Abstract
The first direct measurements of an impurity particle flux driven by drift-wave turbulence in a toroidal magnetized plasma are reported. The correlation between the impurity density and radial velocity fluctuations is measured using ion Doppler spectroscopy. The small, very fast radial velocity fluctuation is resolved with the aid of a new linearized spectrum correlation analysis method that rejects uncorrelated noise as the sample size increases. The measured C^{2+} turbulent impurity flux in the edge of the plasma is directed inward and is consistent with impurity density measurements. This is also the first direct evidence for fluctuation-induced transport due to trapped-electron-mode turbulence in reversed field pinch plasmas.
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Affiliation(s)
- T Nishizawa
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - M D Nornberg
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - J Boguski
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - D J Den Hartog
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - J S Sarff
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Z R Williams
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Z A Xing
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - D Craig
- Department of Physics, Wheaton College, Wheaton, Illinois 60187, USA
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4
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Nishizawa T, Almagri AF, Goodman W, Ohshima S, Sarff JS. Development of a multi-channel capacitive probe for electric field measurements with fine spatial and high time resolution. Rev Sci Instrum 2018; 89:10J118. [PMID: 30399956 DOI: 10.1063/1.5035093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Accepted: 06/07/2018] [Indexed: 06/08/2023]
Abstract
A capacitive probe [Tan et al., Rev. Sci. Instrum. 88, 023502 (2017)] is one of a few diagnostics that is directly sensitive to the plasma potential. Using this diagnostic technique, a Multi-channel Linear Capacitive Probe (MLCP) is developed for turbulence measurements. The MLCP has 10 spatial channels and provides 9 points of radial electric field measurements simultaneously with a spatial step of 7 mm. A new readout circuit and a correction technique for low frequency attenuation are also developed to achieve the required spatial and time resolution. A performance test of the MLCP using a reversed field pinch plasma confirms that the MLCP resolves sub-centimeter structures of the equilibrium radial electric field profile and fluctuations up to 680 kHz.
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Affiliation(s)
- T Nishizawa
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - A F Almagri
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - W Goodman
- Electrical Engineering Department, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - S Ohshima
- Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - J S Sarff
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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5
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Fridström R, Chapman BE, Almagri AF, Frassinetti L, Brunsell PR, Nishizawa T, Sarff JS. Dependence of Perpendicular Viscosity on Magnetic Fluctuations in a Stochastic Topology. Phys Rev Lett 2018; 120:225002. [PMID: 29906181 DOI: 10.1103/physrevlett.120.225002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 03/21/2018] [Indexed: 06/08/2023]
Abstract
In a magnetically confined plasma with a stochastic magnetic field, the dependence of the perpendicular viscosity on the magnetic fluctuation amplitude is measured for the first time. With a controlled, ∼ tenfold variation in the fluctuation amplitude, the viscosity increases ∼100-fold, exhibiting the same fluctuation-amplitude-squared dependence as the predicted rate of stochastic field line diffusion. The absolute value of the viscosity is well predicted by a model based on momentum transport in a stochastic field, the first in-depth test of this model.
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Affiliation(s)
- R Fridström
- Department of Fusion Plasma Physics, School of Electrical Engineering, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden
| | - B E Chapman
- Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, Wisconsin 53706, USA
| | - A F Almagri
- Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, Wisconsin 53706, USA
| | - L Frassinetti
- Department of Fusion Plasma Physics, School of Electrical Engineering, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden
| | - P R Brunsell
- Department of Fusion Plasma Physics, School of Electrical Engineering, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden
| | - T Nishizawa
- Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, Wisconsin 53706, USA
| | - J S Sarff
- Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, Wisconsin 53706, USA
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6
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Anderson JK, Almagri AF, Chapman BE, Davydenko Y, Deichuli P, Den Hartog DJ, Forest CB, Fiksel G, Ivanov A, Liu D, Nornberg MD, Sarff JS, Stupishin N, Waksman J. Majority Ion Heating by Neutral Beam Injection and Confinement of Fast Ions in the Madison Symmetric Torus Reversed Field Pinch. Fusion Science and Technology 2017. [DOI: 10.13182/fst11-a11567] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
| | | | | | - y Davydenko
- Budker Institute of Nuclear Physics, Prospekt Lavrent’eva 11, Novosibirsk 630090, Russia
| | - P. Deichuli
- Budker Institute of Nuclear Physics, Prospekt Lavrent’eva 11, Novosibirsk 630090, Russia
| | | | | | - G. Fiksel
- University of Wisconsin, Madison WI 53706 USA;
- Laboratory for Laser Energetics, University of Rochester, Rochester NY 14610, USA
| | - A.A. Ivanov
- Budker Institute of Nuclear Physics, Prospekt Lavrent’eva 11, Novosibirsk 630090, Russia
| | - D. Liu
- University of Wisconsin, Madison WI 53706 USA;
| | | | - J. S. Sarff
- University of Wisconsin, Madison WI 53706 USA;
| | - N. Stupishin
- Budker Institute of Nuclear Physics, Prospekt Lavrent’eva 11, Novosibirsk 630090, Russia
| | - J. Waksman
- University of Wisconsin, Madison WI 53706 USA;
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7
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Nishizawa T, Nornberg MD, Den Hartog DJ, Sarff JS. Linearized spectrum correlation analysis for line emission measurements. Rev Sci Instrum 2017; 88:083513. [PMID: 28863643 DOI: 10.1063/1.4999450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
A new spectral analysis method, Linearized Spectrum Correlation Analysis (LSCA), for charge exchange and passive ion Doppler spectroscopy is introduced to provide a means of measuring fast spectral line shape changes associated with ion-scale micro-instabilities. This analysis method is designed to resolve the fluctuations in the emission line shape from a stationary ion-scale wave. The method linearizes the fluctuations around a time-averaged line shape (e.g., Gaussian) and subdivides the spectral output channels into two sets to reduce contributions from uncorrelated fluctuations without averaging over the fast time dynamics. In principle, small fluctuations in the parameters used for a line shape model can be measured by evaluating the cross spectrum between different channel groupings to isolate a particular fluctuating quantity. High-frequency ion velocity measurements (100-200 kHz) were made by using this method. We also conducted simulations to compare LSCA with a moment analysis technique under a low photon count condition. Both experimental and synthetic measurements demonstrate the effectiveness of LSCA.
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Affiliation(s)
- T Nishizawa
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - M D Nornberg
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - D J Den Hartog
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - J S Sarff
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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8
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Combs SK, Baylor LR, Fehling DT, Fisher PW, Foust CR, Rasmussen DA, Wilgen JB, Chapman BE, Oliva SP, Prager SC, Sarff JS, Wyman MD, Brower DL, Ding WX, Terry SD, Deng BH. New ORNL Pellet Injection System and Installation/Initial Operations on MST. Fusion Science and Technology 2017. [DOI: 10.13182/fst03-a388] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- S. K. Combs
- Oak Ridge National Laboratory, P O. Box 2009 Oak Ridge, Tennessee 37831-8071
| | - L. R. Baylor
- Oak Ridge National Laboratory, P O. Box 2009 Oak Ridge, Tennessee 37831-8071
| | - D. T. Fehling
- Oak Ridge National Laboratory, P O. Box 2009 Oak Ridge, Tennessee 37831-8071
| | - P. W. Fisher
- Oak Ridge National Laboratory, P O. Box 2009 Oak Ridge, Tennessee 37831-8071
| | - C. R. Foust
- Oak Ridge National Laboratory, P O. Box 2009 Oak Ridge, Tennessee 37831-8071
| | - D. A. Rasmussen
- Oak Ridge National Laboratory, P O. Box 2009 Oak Ridge, Tennessee 37831-8071
| | - J. B. Wilgen
- Oak Ridge National Laboratory, P O. Box 2009 Oak Ridge, Tennessee 37831-8071
| | - B. E. Chapman
- Department of Physics University of Wisconsin-Madison Madison, Wisconsin 53706
| | - S. P. Oliva
- Department of Physics University of Wisconsin-Madison Madison, Wisconsin 53706
| | - S. C. Prager
- Department of Physics University of Wisconsin-Madison Madison, Wisconsin 53706
| | - J. S. Sarff
- Department of Physics University of Wisconsin-Madison Madison, Wisconsin 53706
| | - M. D. Wyman
- Department of Physics University of Wisconsin-Madison Madison, Wisconsin 53706
| | - D. L. Brower
- Electrical Engineering Department University of California-Los Angeles Los Angeles, California 90095
| | - W. X. Ding
- Electrical Engineering Department University of California-Los Angeles Los Angeles, California 90095
| | - S. D. Terry
- Electrical Engineering Department University of California-Los Angeles Los Angeles, California 90095
| | - B. H. Deng
- Electrical Engineering Department University of California-Los Angeles Los Angeles, California 90095
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9
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VanMeter PD, Franz P, Reusch LM, Sarff JS, Den Hartog DJ. A comparison between soft x-ray and magnetic phase data on the Madison symmetric torus. Rev Sci Instrum 2016; 87:11E322. [PMID: 27910686 DOI: 10.1063/1.4960492] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The Soft X-Ray (SXR) tomography system on the Madison Symmetric Torus uses four cameras to determine the emissivity structure of the plasma. This structure should directly correspond to the structure of the magnetic field; however, there is an apparent phase difference between the emissivity reconstructions and magnetic field reconstructions when using a cylindrical approximation. The difference between the phase of the dominant rotating helical mode of the magnetic field and the motion of the brightest line of sight for each SXR camera is dependent on both the camera viewing angle and the plasma conditions. Holding these parameters fixed, this phase difference is shown to be consistent over multiple measurements when only toroidal or poloidal magnetic field components are considered. These differences emerge from physical effects of the toroidal geometry which are not captured in the cylindrical approximation.
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Affiliation(s)
- P D VanMeter
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - P Franz
- Consorzio RFX, Padova, Italy
| | - L M Reusch
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - J S Sarff
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - D J Den Hartog
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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10
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Ding WX, Lin L, Brower DL, Almagri AF, Chapman BE, Fiksel G, Den Hartog DJ, Sarff JS. Kinetic stress and intrinsic flow in a toroidal plasma. Phys Rev Lett 2013; 110:065008. [PMID: 23432267 DOI: 10.1103/physrevlett.110.065008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Indexed: 06/01/2023]
Abstract
A new mechanism for intrinsic plasma flow has been experimentally identified in a toroidal plasma. For reversed field pinch plasmas with a few percent β (ratio of plasma pressure to magnetic pressure), measurements show that parallel pressure fluctuations correlated with magnetic fluctuations create a kinetic stress that can affect momentum balance and the evolution of intrinsic plasma flow. This implies kinetic effects are important for flow generation and sustainment.
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Affiliation(s)
- W X Ding
- Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095, USA
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11
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Ding WX, Lin L, Duff JR, Brower DL, Sarff JS. Density fluctuation measurements by far-forward collective scattering in the MST reversed-field pinch. Rev Sci Instrum 2012; 83:10E302. [PMID: 23126962 DOI: 10.1063/1.4728098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The multichannel polarimeter-interferometer system on the MST reversed-field pinch can be utilized to measure far-forward collective scattering from electron density fluctuations. The collective scattering system has 11 viewing chords with ∼8 cm spacing. The source is a 432 μm (694 GHz) far infrared laser and the scattered power is measured using a heterodyne detection scheme. Collective scattering provides a line-integrated measurement of fluctuations within the divergence of the probe beam covering wavenumber range: k(⊥) < 1.3 cm(-1), corresponding k(⊥)ρ(s) < 1.3 (ρ(s) is the ion-sound Larmor radius), the region of primary interest for turbulent fluctuation-induced transport. The perpendicular wavenumber consists of toroidal, poloidal, and radial contributions, which vary with chord position. Coherent modes associated with tearing instabilities and neutral-beam driven fast particles are observed along with broadband turbulence at frequencies up to 500 kHz. Changes in frequency are consistent with a Doppler shift due to parallel plasma flow.
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Affiliation(s)
- W X Ding
- Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095, USA
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12
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Koliner JJ, Forest CB, Sarff JS, Anderson JK, Liu D, Nornberg MD, Waksman J, Lin L, Brower DL, Ding WX, Spong DA. Fast-particle-driven Alfvénic modes in a reversed field pinch. Phys Rev Lett 2012; 109:115003. [PMID: 23005639 DOI: 10.1103/physrevlett.109.115003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2012] [Revised: 06/19/2012] [Indexed: 06/01/2023]
Abstract
Alfvénic modes are observed due to neutral beam injection for the first time in a reversed field pinch plasma. Modeling of the beam deposition and slowing down shows that the velocity and radial localization are high. This allows instability drive from inverse Landau damping of a bump-on-tail in the parallel distribution function or from free energy in the fast ion density gradient. Mode switching from a lower frequency toroidal mode number n=5 mode that scales with beam injection velocity to a higher frequency n=4 mode with Alfvénic scaling is observed.
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Affiliation(s)
- J J Koliner
- Physics Department, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
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13
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Lin L, Ding WX, Brower DL, Bergerson WF, Carter TA, Yates TF, Almagri AF, Chapman BE, Sarff JS. Role of nonlinear coupling and density fluctuations in magnetic-fluctuation-induced particle transport. Phys Rev Lett 2012; 108:175001. [PMID: 22680872 DOI: 10.1103/physrevlett.108.175001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2011] [Indexed: 06/01/2023]
Abstract
Three-wave nonlinear coupling among spatial Fourier modes of density and magnetic fluctuations is directly measured in a magnetically confined toroidal plasma. Density fluctuations are observed to gain (lose) energy from (to) either equilibrium or fluctuating fields depending on the mode number. Experiments indicate that nonlinear interactions alter the phase relation between density and magnetic fluctuations, leading to strong particle transport.
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Affiliation(s)
- L Lin
- Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095, USA
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14
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Kumar STA, Den Hartog DJ, Caspary KJ, Magee RM, Mirnov VV, Chapman BE, Craig D, Fiksel G, Sarff JS. Classical impurity ion confinement in a toroidal magnetized fusion plasma. Phys Rev Lett 2012; 108:125006. [PMID: 22540593 DOI: 10.1103/physrevlett.108.125006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2011] [Indexed: 05/31/2023]
Abstract
High-resolution measurements of impurity ion dynamics provide first-time evidence of classical ion confinement in a toroidal, magnetically confined plasma. The density profile evolution of fully stripped carbon is measured in MST reversed-field pinch plasmas with reduced magnetic turbulence to assess Coulomb-collisional transport without the neoclassical enhancement from particle drift effects. The impurity density profile evolves to a hollow shape, consistent with the temperature screening mechanism of classical transport. Corroborating methane pellet injection experiments expose the sensitivity of the impurity particle confinement time to the residual magnetic fluctuation amplitude.
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Affiliation(s)
- S T A Kumar
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
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15
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Bergerson WF, Auriemma F, Chapman BE, Ding WX, Zanca P, Brower DL, Innocente P, Lin L, Lorenzini R, Martines E, Momo B, Sarff JS, Terranova D. Bifurcation to 3D helical magnetic equilibrium in an axisymmetric toroidal device. Phys Rev Lett 2011; 107:255001. [PMID: 22243082 DOI: 10.1103/physrevlett.107.255001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2011] [Indexed: 05/31/2023]
Abstract
We report the first direct measurement of the internal magnetic field structure associated with a 3D helical equilibrium generated spontaneously in the core of an axisymmetric toroidal plasma containment device. Magnetohydrodynamic equilibrium bifurcation occurs in a reversed-field pinch when the innermost resonant magnetic perturbation grows to a large amplitude, reaching up to 8% of the mean field strength. Magnetic topology evolution is determined by measuring the Faraday effect, revealing that, as the perturbation grows, toroidal symmetry is broken and a helical equilibrium is established.
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Affiliation(s)
- W F Bergerson
- Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095, USA
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16
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Paz-Soldan C, Brookhart MI, Eckhart AT, Hannum DA, Hegna CC, Sarff JS, Forest CB. Stabilization of the resistive wall mode by a rotating solid conductor. Phys Rev Lett 2011; 107:245001. [PMID: 22243004 DOI: 10.1103/physrevlett.107.245001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Indexed: 05/31/2023]
Abstract
Stabilization of the resistive wall mode (RWM) by high-speed differentially rotating conducting walls is demonstrated in the laboratory. To observe stabilization intrinsic azimuthal plasma rotation must be braked with error fields. Above a critical error field the RWM frequency discontinuously slows (locks) and fast growth subsequently occurs. Wall rotation is found to reduce the locked RWM saturated amplitude and growth rate, with both static (vacuum vessel) wall locked and slowly rotating RWMs observed depending on the alignment of wall to plasma rotation. At high wall rotation RWM onset is found to occur at larger plasma currents, thus increasing the RWM-stable operation window.
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Affiliation(s)
- C Paz-Soldan
- Physics Department, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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17
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Ren Y, Almagri AF, Fiksel G, Prager SC, Sarff JS, Terry PW. Experimental observation of anisotropic magnetic turbulence in a reversed field pinch plasma. Phys Rev Lett 2011; 107:195002. [PMID: 22181614 DOI: 10.1103/physrevlett.107.195002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2011] [Indexed: 05/31/2023]
Abstract
In this Letter we report an experimental study of fully developed anisotropic magnetic turbulence in a laboratory plasma. The turbulence has broad (narrow) spectral power in the perpendicular (parallel) direction to the local mean magnetic field extending beyond the ion cyclotron frequency. Its k[see symbol] spectrum is asymmetric in the ion and electron diamagnetic directions. The wave number scaling for the short wavelength fluctuations shows exponential falloff indicative of dissipation. A standing wave structure is found for the turbulence in the minor radial direction of the toroidal plasma.
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Affiliation(s)
- Y Ren
- Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin, USA
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18
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Nonn PD, Blair AP, McCollam KJ, Sarff JS, Stone DR. Powered oscillator using ignitron switches. Rev Sci Instrum 2011; 82:064701. [PMID: 21721714 DOI: 10.1063/1.3589266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
A 10-MVA-scale resonant oscillator, powered by a pulse-forming network and switched with a pair of commutating mercury ignitrons, was developed for the MST reversed-field pinch plasma-confinement experiment. A novel feature of this circuit is its commutation mechanism, wherein each turning on of one ignitron causes a reverse voltage transient that turns off the other. Two of these oscillators are used in oscillating-field current-drive tests, in which they are capable of nearly 1MW net input power to the plasma, with resonant frequencies of a few 100 Hz for pulse durations of a few tens of ms, being precharged for immediate full amplitude. We describe the circuit and its operation, and discuss features that allow reliable, high-current commutation of the ignitrons and exploit their low switching impedance.
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Affiliation(s)
- P D Nonn
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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19
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Fiksel G, Almagri AF, Chapman BE, Mirnov VV, Ren Y, Sarff JS, Terry PW. Mass-dependent ion heating during magnetic reconnection in a laboratory plasma. Phys Rev Lett 2009; 103:145002. [PMID: 19905576 DOI: 10.1103/physrevlett.103.145002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2009] [Indexed: 05/28/2023]
Abstract
Noncollisional ion heating in laboratory and astrophysical plasmas and the mechanism of conversion of magnetic energy to ion thermal energy are not well understood. In the Madison Symmetric Torus reversed-field pinch experiment, ions are heated rapidly during impulsive reconnection, attaining temperatures exceeding hundreds of eV, often well in excess of the electron temperature. The energy budget of the ion heating and its mass scaling in hydrogen, deuterium, and helium plasmas were determined by measuring the fraction of the released magnetic energy converted to ion thermal energy. The fraction ranges from about 10%-30% and increases approximately as the square root of the ion mass. A simple model based on stochastic ion heating is proposed that is consistent with the experimental data.
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Affiliation(s)
- G Fiksel
- Department of Physics, University of Wisconsin-Madison and Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, Madison, Wisconsin 53706, USA.
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20
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Ding WX, Brower DL, Fiksel G, Den Hartog DJ, Prager SC, Sarff JS. Magnetic-fluctuation-induced particle transport and density relaxation in a high-temperature plasma. Phys Rev Lett 2009; 103:025001. [PMID: 19659214 DOI: 10.1103/physrevlett.103.025001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2009] [Indexed: 05/28/2023]
Abstract
The first direct measurement of magnetic-fluctuation-induced particle flux in the core of a high-temperature plasma is reported. Transport occurs due to magnetic field fluctuations associated with global tearing instabilities. The electron particle flux, resulting from the correlated product of electron density and radial magnetic fluctuations, accounts for density profile relaxation during a magnetic reconnection event. The measured particle transport is much larger than that expected for ambipolar particle diffusion in a stochastic magnetic field.
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Affiliation(s)
- W X Ding
- Department of Physics, University of California Los Angeles, Los Angeles, California 90095, USA
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21
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Bergerson WF, Hannum DA, Hegna CC, Kendrick RD, Sarff JS, Forest CB. Observation of resistive and ferritic wall modes in a line-tied pinch. Phys Rev Lett 2008; 101:235005. [PMID: 19113564 DOI: 10.1103/physrevlett.101.235005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2008] [Indexed: 05/27/2023]
Abstract
The resistive wall mode is experimentally identified and characterized in a line-tied, cylindrical screw pinch when the edge safety factor is less than a critical value. Different wall materials have been used to change the wall time and show that the growth rates for the RWM scale with wall time and safety factor as expected by theory. The addition of a ferritic wall material outside the conducting shell leads to growth rates larger than the observed RWM and larger than theoretical predictions for the ferritic wall mode.
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Affiliation(s)
- W F Bergerson
- Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, Wisconsin 53706, USA
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22
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Kuritsyn A, Fiksel G, Miller MC, Almagri AF, Reyfman M, Sarff JS. Probes for measuring fluctuation-induced Maxwell and Reynolds stresses in the edge of the Madison Symmetric Torus reversed field pinch. Rev Sci Instrum 2008; 79:10F127. [PMID: 19044611 DOI: 10.1063/1.2955930] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Several probes have been constructed to measure fluctuation-induced Maxwell and Reynolds stresses in the edge of the Madison Symmetric Torus reversed field pinch (RFP). The magnetic probe is composed of six magnetic pickup coil triplets. The triplets are separated spatially, which allows for local measurements of the Maxwell stress. To measure the plasma flow components for evaluation of the Reynolds stress, we employ a combination of an optical probe [Kuritsyn et al., Rev. Sci. Indrum. 77, 10F112 (2006)] and a Mach probe. The optical probe measures the radial ion flow locally using Doppler spectroscopy. The Mach probe consists of four current collectors biased negatively with respect to a reference tip and allows for measurements of the poloidal and toroidal components of the bulk plasma flow. The stresses are observed to play an important role in the momentum balance in the RFP edge during internal reconnection events.
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Affiliation(s)
- A Kuritsyn
- Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas and Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
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23
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Ding WX, Brower DL, Craig D, Deng BH, Prager SC, Sarff JS, Svidzinski V. Nonambipolar magnetic-fluctuation-induced particle transport and plasma flow in the MST reversed-field pinch. Phys Rev Lett 2007; 99:055004. [PMID: 17930765 DOI: 10.1103/physrevlett.99.055004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2007] [Indexed: 05/25/2023]
Abstract
First direct measurements of nonambipolar magnetic fluctuation-induced charge transport in the interior of a high-temperature plasma are reported. Global resistive tearing modes drive the charge transport which is measured in the vicinity of the resonant surface for the dominant core resonant mode. Finite charge transport has two important consequences. First, it generates a potential well along with locally strong electric field and electric field shear at the resonant surface. Second, this electric field induces a spontaneous E x B driven zonal flow.
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Affiliation(s)
- W X Ding
- Department of Physics and Astronomy, University of California at Los Angeles, Los Angeles, California 90095, USA
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24
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McCollam KJ, Blair AP, Prager SC, Sarff JS. Oscillating-field current-drive experiments in a reversed field pinch. Phys Rev Lett 2006; 96:035003. [PMID: 16486717 DOI: 10.1103/physrevlett.96.035003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2005] [Indexed: 05/06/2023]
Abstract
Oscillating-field current drive (OFCD) is a steady-state magnetic helicity injection method to drive net toroidal current in a plasma by applying oscillating poloidal and toroidal loop voltages. OFCD is added to standard toroidal induction to produce about 10% of the total current in the Madison symmetric torus. The dependence of the added current on the phase between the two applied voltages is measured. Maximum current does not occur at the phase of the maximum helicity injection rate. Effects of OFCD on magnetic fluctuations and dissipated power are shown.
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Affiliation(s)
- K J McCollam
- University of Wisconsin, Madison, Wisconsin 53706, USA
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25
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Bergerson WF, Forest CB, Fiksel G, Hannum DA, Kendrick R, Sarff JS, Stambler S. Onset and saturation of the kink instability in a current-carrying line-tied plasma. Phys Rev Lett 2006; 96:015004. [PMID: 16486469 DOI: 10.1103/physrevlett.96.015004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2005] [Indexed: 05/06/2023]
Abstract
An internal kink instability is observed to grow and saturate in a line-tied screw pinch plasma. Detailed measurements show that an ideal, line-tied kink mode begins growing when the safety factor q = (4pi2r2B(z))/(mu0I(p)(r)L) drops below 1 inside the plasma; the saturated state corresponds to a rotating helical equilibrium. In addition to the ideal mode, reconnection events are observed to periodically flatten the current profile and change the magnetic topology.
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Affiliation(s)
- W F Bergerson
- Department of Physics, University of Wisconsin, 1150 University Avenue, Madison, WI 53706, USA
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26
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Ding WX, Brower DL, Craig D, Deng BH, Fiksel G, Mirnov V, Prager SC, Sarff JS, Svidzinski V. Measurement of the Hall dynamo effect during magnetic reconnection in a high-temperature plasma. Phys Rev Lett 2004; 93:045002. [PMID: 15323767 DOI: 10.1103/physrevlett.93.045002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2004] [Indexed: 05/24/2023]
Abstract
The fluctuation-induced Hall electromotive force, [deltaJ x deltaB]/nee, is experimentally measured in the high-temperature interior of a reversed-field pinch plasma by a fast Faraday rotation diagnostic. It is found that the Hall dynamo effect is significant, redistributing (flattening) the equilibrium core current near the resonant surface during a reconnection event. These results imply that effects beyond single-fluid MHD are important for the dynamo and magnetic reconnection.
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Affiliation(s)
- W X Ding
- Electrical Engineering Department, University of California at Los Angeles, Los Angeles, California 90095, USA
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27
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Biewer TM, Forest CB, Anderson JK, Fiksel G, Hudson B, Prager SC, Sarff JS, Wright JC, Brower DL, Ding WX, Terry SD. Electron heat transport measured in a stochastic magnetic field. Phys Rev Lett 2003; 91:045004. [PMID: 12906670 DOI: 10.1103/physrevlett.91.045004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2002] [Indexed: 05/24/2023]
Abstract
New profile measurements have allowed the electron thermal diffusivity profile to be estimated from power balance in the Madison Symmetric Torus where magnetic islands overlap and field lines are stochastic. The measurements show that (1) the electron energy transport is conductive not convective, (2) the measured thermal diffusivities are in good agreement with numerical simulations of stochastic transport, and (3) transport is greatly reduced near the reversal surface where magnetic diffusion is small.
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Affiliation(s)
- T M Biewer
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
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28
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O'Connell R, Den Hartog DJ, Forest CB, Anderson JK, Biewer TM, Chapman BE, Craig D, Fiksel G, Prager SC, Sarff JS, Terry SD, Harvey RW. Observation of velocity-independent electron transport in the reversed field pinch. Phys Rev Lett 2003; 91:045002. [PMID: 12906668 DOI: 10.1103/physrevlett.91.045002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2002] [Indexed: 05/24/2023]
Abstract
Confinement of runaway electrons has been observed for the first time in a reversed field pinch during improved-confinement plasmas in the Madison Symmetric Torus. Energy-resolved hard-x-ray flux measurements have been used to determine the velocity dependence of the electron diffusion coefficient, utilizing computational solutions of the Fokker-Planck transport equation. With improved-confinement, the fast electron diffusivity drops by 2 orders of magnitude and is independent of velocity. This suggests a change in the transport mechanism away from stochastic magnetic field diffusion.
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Affiliation(s)
- R O'Connell
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
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29
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Crocker NA, Fiksel G, Prager SC, Sarff JS. Measurement of the current sheet during magnetic reconnection in a toroidal plasma. Phys Rev Lett 2003; 90:035003. [PMID: 12570496 DOI: 10.1103/physrevlett.90.035003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2000] [Indexed: 05/24/2023]
Abstract
The current and magnetic-field fluctuations associated with magnetic-field-line reconnection have been measured in the reversed field pinch plasma configuration. The current sheet resulting from this reconnection has been measured. The current layer is radially broad, comparable to a magnetic-island width, as may be expected from current transport along magnetic-field lines. It is much larger than that predicted by resistive MHD for linear tearing modes and larger than prediction from two-fluid linear theory.
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Affiliation(s)
- N A Crocker
- Department of Physics, University of Wisconsin, Madison, Wisconsin 53706, USA
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30
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Ding WX, Brower DL, Terry SD, Craig D, Prager SC, Sarff JS, Wright JC. Measurement of internal magnetic field fluctuations in a reversed-field pinch by Faraday rotation. Phys Rev Lett 2003; 90:035002. [PMID: 12570495 DOI: 10.1103/physrevlett.90.035002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2002] [Indexed: 05/24/2023]
Abstract
Magnetic field fluctuations (and the associated current perturbation) have been measured in the core of a high-temperature reversed-field pinch using a newly developed fast-polarimetry system. Radial magnetic field fluctuation levels of approximately 1% are measured in standard-reversed-field pinch discharges which increase to approximately 4% during the sawtooth crash (enhanced dynamo). The fluctuation level is reduced fourfold for high-confinement plasmas where the core-resonant tearing modes are suppressed.
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Affiliation(s)
- W X Ding
- Electrical Engineering Department, University of California-Los Angeles, Los Angeles, California 90095, USA
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31
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Brower DL, Ding WX, Terry SD, Anderson JK, Biewer TM, Chapman BE, Craig D, Forest CB, Prager SC, Sarff JS. Measurement of the current-density profile and plasma dynamics in the reversed-field pinch. Phys Rev Lett 2002; 88:185005. [PMID: 12005692 DOI: 10.1103/physrevlett.88.185005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2002] [Indexed: 05/23/2023]
Abstract
First measurements of the current-density profile in the core of a high-temperature reversed-field pinch are presented. The current-density profile is observed to peak during the sawtooth cycle and broaden promptly at the crash. This change in profile can be linked to magnetic relaxation and the dynamo which is predicted to drive antiparallel current in the plasma core. For high-confinement discharges, the dynamo is suppressed and the current-density profile is observed to strongly peak.
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Affiliation(s)
- D L Brower
- Electrical Engineering Department, University of California at Los Angeles, Los Angeles, CA 90095, USA
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32
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Chapman BE, Anderson JK, Biewer TM, Brower DL, Castillo S, Chattopadhyay PK, Chiang CS, Craig D, Den Hartog DJ, Fiksel G, Fontana PW, Forest CB, Gerhardt S, Hansen AK, Holly D, Jiang Y, Lanier NE, Prager SC, Reardon JC, Sarff JS. Reduced edge instability and improved confinement in the MST reversed-field pinch. Phys Rev Lett 2001; 87:205001. [PMID: 11690477 DOI: 10.1103/physrevlett.87.205001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2001] [Indexed: 05/23/2023]
Abstract
Improved confinement has been achieved in the MST through control of the poloidal electric field, but it is now known that the improvement has been limited by bursts of an edge-resonant instability. Through refined poloidal electric field control, plus control of the toroidal electric field, we have suppressed these bursts. This has led to a total beta of 15% and a reversed-field-pinch-record estimated energy confinement time of 10 ms, a tenfold increase over the standard value which for the first time substantially exceeds the confinement scaling that has characterized most reversed-field-pinch plasmas.
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Affiliation(s)
- B E Chapman
- University of Wisconsin, Madison, Wisconsin 53706, USA.
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Hansen AK, Almagri AF, Craig D, Hegna CC, Prager SC, Sarff JS. Momentum transport from nonlinear mode coupling of magnetic fluctuations. Phys Rev Lett 2000; 85:3408-3411. [PMID: 11030908 DOI: 10.1103/physrevlett.85.3408] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2000] [Indexed: 05/23/2023]
Abstract
A cause of observed anomalous plasma momentum transport in a reversed-field pinch is determined experimentally. Magnetohydrodynamic theory predicts that nonlinear interactions involving triplets of tearing modes produce internal torques that redistribute momentum. Evidence for the nonlinear torque is acquired by detecting the correlation of momentum redistribution with the mode triplets, with the elimination of one of the modes in the triplet, and with the external driving of one of the modes.
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Affiliation(s)
- AK Hansen
- University of Wisconsin Department of Physics,1150 University Avenue, Madison, Wisconsin 53706, USA
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34
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Ji H, Yagi Y, Hattori K, Almagri AF, Prager SC, Hirano Y, Sarff JS, Shimada T, Maejima Y, Hayase K. Effect of collisionality and diamagnetism on the plasma dynamo. Phys Rev Lett 1995; 75:1086-1089. [PMID: 10060202 DOI: 10.1103/physrevlett.75.1086] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Ji H, Almagri AF, Prager SC, Sarff JS. Time-resolved observation of discrete and continuous magnetohydrodynamic dynamo in the reversed-field pinch edge. Phys Rev Lett 1994; 73:668-671. [PMID: 10057507 DOI: 10.1103/physrevlett.73.668] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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37
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Sarff JS, Hokin SA, Ji H, Prager SC, Sovinec CR. Fluctuation and transport reduction in a reversed field pinch by inductive poloidal current drive. Phys Rev Lett 1994; 72:3670-3673. [PMID: 10056260 DOI: 10.1103/physrevlett.72.3670] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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38
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Sarff JS, Assadi S, Almagri AF, Cekic M, Den Hartog DJ, Fiksel G, Hokin SA, Ji H, Prager SC, Shen W, Sidikman KL, Stoneking MR. Nonlinear coupling of tearing fluctuations in the Madison Symmetric Torus*. ACTA ACUST UNITED AC 1993. [DOI: 10.1063/1.860741] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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39
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Almagri AF, Assadi S, Prager SC, Sarff JS, Kerst DW. Locked modes and magnetic field errors in the Madison Symmetric Torus. ACTA ACUST UNITED AC 1992. [DOI: 10.1063/1.860473] [Citation(s) in RCA: 86] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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40
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Rempel TD, Almagri AF, Assadi S, Den Hartog DJ, Hokin SA, Prager SC, Sarff JS, Shen W, Sidikman KL, Spragins CW, Sprott JC, Stoneking MR, Zita EJ. Turbulent transport in the Madison Symmetric Torus reversed‐field pinch. ACTA ACUST UNITED AC 1992. [DOI: 10.1063/1.860020] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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41
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Prager SC, Almagri AF, Assadi S, Beckstead JA, Dexter RN, Den Hartog DJ, Chartas G, Hokin SA, Lovell TW, Rempel TD, Sarff JS, Shen W, Spragins CW, Sprott JC. First results from the Madison Symmetric Torus reversed field pinch. ACTA ACUST UNITED AC 1990. [DOI: 10.1063/1.859557] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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