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Numerical Study of Field-reversed Configurations: The Formation and Ion Spin-up

Description: Results of three-dimensional numerical simulations of field-reversed configurations (FRCs) are presented. Emphasis of this work is on the nonlinear evolution of magnetohydrodynamic (MHD) instabilities in kinetic FRCs, and the new FRC formation method by counter-helicity spheromak merging. Kinetic simulations show nonlinear saturation of the n = 1 tilt mode, where n is the toroidal mode number. The n = 2 and n = 3 rotational modes are observed to grow during the nonlinear phase of the tilt insta… more
Date: June 6, 2005
Creator: Belova, E. V.; Davidson, R. C.; Ji, H.; Yamada, M.; Cothran, C. D.; Brown, M. R. et al.
Partner: UNT Libraries Government Documents Department
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The effect of collisionality and diamagnetism on the plasma dynamo

Description: Fluctuation-induced dynamo forces are measured over a wide range of electron collisionality in the edge of TPE-1RM20 Reversed-Field Pinch (RFP). In the collisionless region the Magnetohydrodynamic (MHD) dynamo alone can sustain the parallel current, while in the collisional region a new dynamo mechanism resulting from the fluctuations in the electron diamagnetic drift becomes dominant. A comprehensive picture of the RFP dynamo emerges by combining with earlier results from MST and REPUTE RFPs.
Date: April 28, 1995
Creator: Ji, H.; Yagi, Y.; Hattori, K.; Hirano, Y.; Shimada, T.; Maejima, Y. et al.
Partner: UNT Libraries Government Documents Department
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Reversed-field pinch studies in the Madison Symmetric Torus

Description: Studies of large-size (R = 1.5 m, a = 0.5 m), moderate current (I < 750 kA) reversed-field pinch (RFP) plasmas are carried out in the Madison Symmetric Torus in order to evaluate and improve RFP confinement, study general toroidal plasma MHD issues, determine the mechanism of the RFP dynamo, and measure fluctuation-induced transport and anomalous ion heating. MST confinement has been improved by reduction of magnetic field errors with correction coils in the primary circuit and reduction of imp… more
Date: April 3, 1993
Creator: Hokin, S.; Almagri, A.; Cekic, M.; Chapman, B.; Crocker, N.; Den Hartog, D.J. et al.
Partner: UNT Libraries Government Documents Department
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Nonlinear coupling of tearing fluctuations in the Madison Symmetric Torus

Description: 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 linearl… more
Date: November 1, 1992
Creator: Sarff, J. S.; Almagri, A. F.; Cekic, M.; Den Hartog, D. J.; Fiksel, G.; Hokin, S. A. et al.
Partner: UNT Libraries Government Documents Department
open access

Reversed-field pinch studies in the Madison Symmetric Torus

Description: Studies of large-size (R = 1.5 m, a = 0.5 m), moderate current (I < 750 kA) reversed-field pinch (RFP) plasmas are carried out in the Madison Symmetric Torus in order to evaluate and improve RFP confinement, study general toroidal plasma MHD issues, determine the mechanism of the RFP dynamo, and measure fluctuation-induced transport and anomalous ion heating. MST confinement has been improved by reduction of magnetic field errors with correction coils in the primary circuit and reduction of imp… more
Date: April 3, 1993
Creator: Hokin, S.; Almagri, A.; Cekic, M.; Chapman, B.; Crocker, N.; Den Hartog, D. J. et al.
Partner: UNT Libraries Government Documents Department
open access

Nonlinear Coupling of Tearing Fluctuations in the Madison Symmetric Torus

Description: 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 … more
Date: November 1, 1992
Creator: Sarff, J. S.; Almagri, A. F.; Cekic, M.; Den Hartog, D. J.; Fiksel, G.; Hokin, S. A. et al.
Partner: UNT Libraries Government Documents Department
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Identification of Y-shaped and O-shaped diffusion regions during magnetic reconnection in a laboratory plasma

Description: Two strikingly different shapes of diffusion regions are identified during magnetic reconnection in a magnetohydrodynamic laboratory plasma. The shapes depend on the third vector component of the reconnecting magnetic fields. Without the third component (anti-parallel or null-helicity reconnection), a thin double-Y shaped diffusion region is identified. In this case, the neutral sheet current profile is accurately measured to be as narrow as the order of the ion gyro-radius. In the presence of … more
Date: April 1, 1997
Creator: Yamada, Masaaki; Ji, H.; Hsu, S.; Carter, T.; Kulsrud, R.; Ono, Yasushi et al.
Partner: UNT Libraries Government Documents Department
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Study of driven magnetic reconnection in a laboratory plasma

Description: The Magnetic Reconnection Experiment (MRX) has been constructed to investigate the fundamental physics of magnetic reconnection in a well controlled laboratory setting. This device creates an environment satisfying the criteria for a magnetohydrodynamic (MHD) plasma (S {much_gt} 1, {rho}{sub i} {much_lt} L). The boundary conditions can be controlled externally, and experiments with fully three-dimensional reconnection are now possible. In the initial experiments, the effects of the third vector… more
Date: December 31, 1998
Creator: Yamada, Masaaki; Ji, H.; Hsu, S.; Carter, T.; Kulsrud, R.; Bretz, N. et al.
Partner: UNT Libraries Government Documents Department
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Current density fluctuations, nonlinear coupling, and transport in MST

Description: New information on magnetic fluctuations and transport in toroidal devices has been obtained in the MST reversed field pinch through measurement of nonlinear coupling of three waves in k-space, and measurement of current density fluctuations. Measurements of nonlinear coupling of magnetic fluctuations reveals that (1) two poloidal mode number m = 1 modes couple strongly to an m = 2 mode, (2) toroidal mode coupling is broad extending up to n = 20, (3) these features agree with predictions for te… more
Date: September 1, 1992
Creator: Prager, S. C.; Almagri, A. F.; Assadi, S.; Cekic, M.; Chapman, B. E.; Crocker, N. et al.
Partner: UNT Libraries Government Documents Department
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Current density fluctuations, nonlinear coupling, and transport in MST

Description: New information on magnetic fluctuations and transport in toroidal devices has been obtained in the MST reversed field pinch through measurement of nonlinear coupling of three waves in k-space, and measurement of current density fluctuations. Measurements of nonlinear coupling of magnetic fluctuations reveals that (1) two poloidal mode number m = 1 modes couple strongly to an m = 2 mode, (2) toroidal mode coupling is broad extending up to n = 20, (3) these features agree with predictions for te… more
Date: September 1, 1992
Creator: Prager, S. C.; Almagri, A. F.; Assadi, S.; Cekic, M.; Chapman, B. E.; Crocker, N. et al.
Partner: UNT Libraries Government Documents Department
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Initial Results from Coaxial Helicity Injection Experiments in NSTX

Description: Coaxial Helicity Injection (CHI) has been investigated on the National Spherical Torus Experiment (NSTX). Initial experiments produced 130 kA of toroidal current without the use of the central solenoid. The corresponding injector current was 20 kA. Discharges with pulse lengths up to 130 ms have been produced.
Date: May 10, 2001
Creator: Raman, R.; Jarboe, T. R.; Mueller, D.; Schaffer, M. J.; Maqueda, R.; Nelson, B. A. et al.
Partner: UNT Libraries Government Documents Department
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Noninductive Current Generation in NSTX using Coaxial Helicity Injection

Description: Coaxial Helicity Injection (CHI) on the National Spherical Torus Experiment (NSTX) has produced 240 kA of toroidal current without the use of the central solenoid. Values of the current multiplication ratio (CHI produced toroidal current/injector current) up to 10 were obtained, in agreement with predictions. The discharges which lasted for up to 200 ms, limited only by the programmed waveform, are more than an order of magnitude longer in duration that any CHI discharges previously produced in… more
Date: May 10, 2001
Creator: Raman, R.; Jarboe, T. R.; Mueller, D.; Schaffer, M. J.; Maqueda, R.; Nelson, B. A. et al.
Partner: UNT Libraries Government Documents Department
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Results of NSTX Heating Experiments

Description: The National Spherical Torus Experiment (NSTX) at Princeton is designed to assess the potential of the low-aspect-ratio spherical torus concept for magnetic plasma confinement. The plasma has been heated by up to 5 MW of neutral beam injection, NBI, at an injection energy of 90 keV and up to 6 MW of high harmonic fast wave, HHFW, at 30 MHz. NSTX has achieved beta T of 32%. A variety of MHD phenomena have been observed to limit eta. NSTX has now begun addressing E scaling, eta limits and current… more
Date: June 18, 2002
Creator: Mueller, D.; Ono, M.; Bell, M. G.; Bell, R. E.; Bitter, M.; Bourdelle, C. et al.
Partner: UNT Libraries Government Documents Department
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High Performance Plasmas on the National Spherical Torus Experiment

Description: The National Spherical Torus Experiment (NSTX) has produced toroidal plasmas at low aspect ratio (A = R/a = 0.86 m/0.68 m approximately equal to 1.3, where R is the major radius and a is the minor radius of the torus) with plasma currents of 1.4 MA. The rapid development of the machine has led to very exciting physics results during the first full year of physics operation. Pulse lengths in excess of 0.5 sec have been obtained with inductive current drive. Up to 4 MW of High Harmonic Fast Wave … more
Date: July 10, 2001
Creator: Gates, D. A.; Bell, M. G.; Bell, R. E.; Bialek, J.; Bigelow, T.; Bitter, M. et al.
Partner: UNT Libraries Government Documents Department
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Recent Progress on the National Spherical Torus Experiment (NSTX)

Description: Recent upgrades to the NSTX facility have led to improved plasma performance. Using 5MW of neutral beam injection, plasmas with toroidal {beta}{sub T} (= 2{micro}{sub 0}&lt;p&gt;/B{sub T}{sup 2} where B{sub T} is the vacuum toroidal field at the plasma geometric center) &gt; 30% have been achieved with normalized {beta}{sub N} (= {beta}{sub T}aB{sub I}/I{sub p}) {approx} 6% {center_dot} m {center_dot} T/MA.. The highest {beta} discharge exceeded the calculated no-wall {beta} limit for several w… more
Date: July 2, 2002
Creator: Gates, D. A.; Bell, M. G.; Bell, R. E.; Bialek, J.; Bigelow, T.; Bitter, M. et al.
Partner: UNT Libraries Government Documents Department
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The National Spherical Torus Experiment (NSTX) Research Program and Progress Towards High Beta, Long Pulse Operating Scenarios

Description: A major research goal of the National Spherical Torus Experiment is establishing long-pulse, high-beta, high-confinement operation and its physics basis. This research has been enabled by facility capabilities developed over the last two years, including neutral-beam (up to 7 MW) and high-harmonic fast-wave heating (up to 6 MW), toroidal fields up to 6 kG, plasma currents up to 1.5 MA, flexible shape control, and wall preparation techniques. These capabilities have enabled the generation of pla… more
Date: October 15, 2002
Creator: Synakowski, E. J.; Bell, M. G.; Bell, R. E.; Bigelow, T.; Bitter, M.; Blanchard, W. et al.
Partner: UNT Libraries Government Documents Department
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Progress Towards High Performance, Steady-state Spherical Torus

Description: Research on the Spherical Torus (or Spherical Tokamak) is being pursued to explore the scientific benefits of modifying the field line structure from that in more moderate aspect-ratio devices, such as the conventional tokamak. The Spherical Tours (ST) experiments are being conducted in various U.S. research facilities including the MA-class National Spherical Torus Experiment (NSTX) at Princeton, and three medium-size ST research facilities: Pegasus at University of Wisconsin, HIT-II at Univer… more
Date: October 2, 2003
Creator: Ono, M.; Bell, M. G.; Bell, R. E.; Bigelow, T.; Bitter, M.; Blanchard, W. et al.
Partner: UNT Libraries Government Documents Department
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