A5069020318- Magnetic confinement fusion research
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- X-ray Diffraction in Crystallography
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- Atomic and Molecular Physics
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- Fusion materials and technologies
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- Particle Accelerators and Free-Electron Lasers
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Wheaton College - Illinois
2011-2021
University of Wisconsin–Madison
1995-2019
Princeton Plasma Physics Laboratory
2008
University of Wisconsin System
1995-2002
University of Detroit Mercy
1952
Birkbeck, University of London
1951
University College London
1951
Australian National University
1951
Atomic Energy (Canada)
1951
Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation S. J. Czyzak, D. Craig, C. E. McCain, Reynolds; Single Synthetic Cadmium Sulfide Crystals. Appl. Phys. 1 August 1952; 23 (8): 932–933. https://doi.org/10.1063/1.1702335 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Dropdown Menu...
Improved confinement has been achieved in the MST through control of poloidal electric field, but it is now known that improvement limited by bursts an edge-resonant instability. Through refined field control, plus toroidal we have suppressed these bursts. This led to a total beta 15% and reversed-field-pinch-record estimated energy time 10 ms, tenfold increase over standard value which for first substantially exceeds scaling characterized most reversed-field-pinch plasmas.
Confinement of runaway electrons has been observed for the first time in a reversed field pinch during improved-confinement plasmas Madison Symmetric Torus. Energy-resolved hard-x-ray flux measurements have used to determine velocity dependence electron diffusion coefficient, utilizing computational solutions Fokker-Planck transport equation. With improved-confinement, fast diffusivity drops by 2 orders magnitude and is independent velocity. This suggests change mechanism away from...
Blackbody levels of emission in the electron cyclotron range frequencies have been observed from an overdense (ωpe∼3ωce) Madison Symmetric Torus [Dexter et al., Fusion Technol. 19, 131 (1991)] reversed field pinch plasma, a result electrostatic Bernstein waves emitted core and mode converted into electromagnetic at extreme plasma edge. Comparison measured radiation temperature with profiles by Thomson scattering indicates that conversion efficiency can be as high ∼75%. Emission is...
By manipulating magnetic reconnection in Madison Symmetric Torus (MST) discharges, we have generated and confined for the first time a reversed-field pinch (RFP) plasma with an ion temperature >1 keV electron of 2 keV. This is achieved at toroidal current about 0.5 MA, approaching MST's present maximum. The manipulation begins intensification discrete events, causing to increase several kiloelectronvolts. then quickly suppressed inductive profile control, leading capture portion added heat...
An overview of recent results from the MST reversed field pinch programme is presented. With neutral beam injection, bursty energetic particle (EP) modes are observed. The profiles magnetic and density fluctuations associated with these EP measured using a far infrared interferometer–polarimeter. Equilibrium reconstructions quasi-single-helicity 3D helical state provided by V3FIT code that now incorporates several MST's advanced diagnostics. orientation structure controlled new resonant...
Measurements of localized ion heating during magnetic reconnection in the Madison Symmetric Torus reversed field pinch [R. N. Dexter, D. W. Kerst, T. Lovell, S. C. Prager, and J. Sprott, Fusion Technol. 19, 131 (1991)] are presented using two beam-based diagnostics: Charge exchange recombination spectroscopy Rutherford scattering. Data have been collected from three types impulsive event, which resistive tearing mode activity associated with is present either edge plasma, core or throughout...
Charge-exchange recombination spectroscopy, which is generally used to measure low-Z impurities in fusion devices, has been for measuring Al+11 and Al+13 the Madison Symmetric Torus reversed field pinch. To obtain impurity ion temperature, experimental emission spectrum fitted with a model includes fine structure atomic transition. Densities of these two ionization states, calculated from charge-exchange brightness, are combination collisional radiative estimate abundance all other charge...
Temperature evolution during magnetic reconnection has been spectroscopically measured for various ion species in a toroidal magnetized plasma. Measurements are made predominantly the direction parallel to equilibrium field. It is found that increase temperature events increases with charge-to-mass ratio of species. This trend can be understood if heating mechanism anisotropic, favoring perpendicular degree freedom, collisional relaxation multiple The derives from isotropization. result...
Impurity ion dynamics measured with simultaneously high spatial and temporal resolution reveal classical transport in the reversed-field pinch. The boron, carbon, oxygen, aluminum impurity density profiles are obtained Madison Symmetric Torus [R. N. Dexter et al., Fusion Technol. 19, 131 (1991)] using a fast, active charge-exchange-recombination-spectroscopy diagnostic. Measurements made during improved-confinement plasmas inductive control of tearing instability to mitigate stochastic...
An auxiliary poloidal inductive electric field applied to a reversed-field pinch (RFP) plasma reduces the current density gradient, slows growth of m=1 tearing fluctuations, suppresses their associated sawteeth, and doubles energy confinement time. This experiment attacks dominant RFP loss mechanism parallel streaming in stochastic magnetic field. The flattens profile fluctuation level. Since toroidal flux change linking is required generate field, drive transient avoid excessive...
Strong E×B flow shear occurs in the edge of three types enhanced confinement discharge Madison Symmetric Torus [Dexter et al., Fusion Technol. 19, 131 (1991)] reversed-field pinch. Measurements standard (low confinement) discharges indicate that global magnetic fluctuations drive particle and energy transport plasma core, while electrostatic edge. This paper explores possible contributions to reduction both and, thus, improved confinement. In one case, when is biased. Biased exhibit changes...
The first localized measurements of tearing mode flows in the core a hot plasma are presented using nonperturbing impurity ion flow. Emission from charge exchange recombination is collected by novel high optical throughput duo spectrometer providing (±1 cm) C+6 velocities resolved to <500 m/s with bandwidth (100 kHz). Poloidal Madison Symmetric Torus reversed-field pinch observed be resonant surface radial extent much broader than predicted linear magnetohydrodynamic (MHD) theory but...
High-resolution measurements of impurity ion dynamics provide first-time evidence classical confinement in a toroidal, magnetically confined plasma. The density profile evolution fully stripped carbon is measured MST reversed-field pinch plasmas with reduced magnetic turbulence to assess Coulomb-collisional transport without the neoclassical enhancement from particle drift effects. evolves hollow shape, consistent temperature screening mechanism transport. Corroborating methane pellet...
Temporally and spatially resolved measurements of carbon boron impurity density are obtained in the reversed field pinch (RFP) for first time. It is observed that, unlike tokamaks stellarators, RFP does not exhibit a centrally peaked profile either standard plasmas where lines have some degree stochasticity, or improved confinement discharges there exist well-nested flux surfaces substantial fraction plasma volume. Results from also indicate an outward convection impurities core plasma.
The connection between impurity ion heating and other physical processes in the plasma is evaluated by studying variations amount of at reconnection events Madison Symmetric Torus (MST). Correlation change temperature with individual tearing mode amplitudes indicates that edge-resonant modes are better predictors for global than core-resonant modes. There also a strong correlation current profile relaxation. Simultaneous measurements different toroidal locations reveal, first time, asymmetry...
Visible and near-infrared electron–ion bremsstrahlung measurements in fusion research devices, used to determine the effective ionic charge (Zeff), are often plagued by pollutant emission from cool-edge region. The primary sources of visible non-bremsstrahlung continuum Madison Symmetric Torus arise electron–neutral interactions, is hence directly proportional bulk neutral density. Simultaneously monitoring total at 1040 nm contaminant (via Dα emission) has enabled an extraction a...
Magnetic fluctuation-induced charge transport, resulting from particle transport that is not intrinsically ambipolar, has been measured in the high-temperature interior of a reversed-field pinch plasma. It found global resistive tearing modes and their nonlinear interactions lead to significant equivalent perpendicular Maxwell stress, vicinity resonant surface for dominant core mode during magnetic reconnection. Finite can result zonal flow associated with locally strong radial electric...
The first direct measurements of an impurity particle flux driven by drift-wave turbulence in a toroidal magnetized plasma are reported. correlation between the density and radial velocity fluctuations is measured using ion Doppler spectroscopy. small, very fast fluctuation resolved with aid new linearized spectrum analysis method that rejects uncorrelated noise as sample size increases. C^{2+} turbulent edge directed inward consistent measurements. This also evidence for fluctuation-induced...
Visco-resistive magnetohydrodynamic simulations are used to investigate the role of resistivity and viscosity in reversed field pinch sawtooth crash. Specifically, we examine temporal behavior linearly stable (m, n) = (0, 1) mode. Both volume-averaged dissipation levels region near m 0 resonance found influence characteristic time scales. Increasing causes mode rise time, fall total crash duration decrease, while increasing has opposite effect. Examination energy flow during reveals that...
We use charge exchange recombination spectroscopy to make the first localized measurements of impurity ion flow velocity profiles in reversed field pinch. Measurements improved confinement plasmas reveal an intrinsic profile that is peaked on axis and mostly parallel equilibrium magnetic field. The toroidal decreases time at off-axis locations where tearing modes are resonant, giving rise a highly sheared near axis. mode phase correlates strongly with resonant surface weakly other locations,...
The upgraded spectrometer used for charge exchange recombination spectroscopy on the Madison Symmetric Torus resolves emission fluctuations up to 400 kHz. transimpedance amplifier's cutoff frequency was increased based upon simulations comparing change in measured photon counts time-dynamic signals. We modeled each signal-processing stage of diagnostic and scanned filtering quantify uncertainty counting rate. This modeling showed that uncertainties can be calculated assuming amplification is...
Charge exchange recombination spectroscopy measurements of the poloidal component C(+6) temperature and flow in Madison Symmetric Torus have been vital advancing understanding ion dynamics reversed field pinch. Recent work has expanded diagnostic capability to include toroidal measurements. A new view overcomes a small signal-to-background ratio (5%-15%) make first localized parallel impurity core The measurement is made possible through maximal light collection optical design extensive...
An Ion Doppler Spectrometer (IDS) is used for fast measurements of C VI line emission (343.4 nm) in the Madison Symmetric Torus. Absolutely calibrated flow are difficult because IDS records data within 0.25 nm line. Commercial calibration lamps do not produce lines this narrow range. A light source using an ultraviolet LED and etalon was designed to provide a fiducial marker 0.08 wide. The coupled into at f/4, holographic diffuser increases homogeneity final image. Random systematic errors...