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Experimental Tests Of Paleoclassical Transport

Description: Predictions of the recently developed paleoclassical transport model are compared with data from many toroidal plasma experiments: electron heat diffusivity in DIII-D, C-Mod and NSTX ohmic and near-ohmic plasmas; transport modeling of DIII-D ohmic-level discharges and of the RTP ECH 'stair-step' experiments with eITBs at low order rational surfaces; investigation of a strong eITB in JT-60U; H-mode Te edge pedestal properties in DIII-D; and electron heat diffusivities in non-tokamak experiments … more
Date: September 12, 2006
Creator: Callen, J. D.; Anderson, J. K.; Arlen, T. C.; Bateman, G.; Budny, R. V.; Fujita, T. et al.
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Partner: UNT Libraries Government Documents Department
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The Search for Reconnection and Helicity During Formation of a Bounded Spheromak

Description: Recent results from investigations using insertable magnetic probes at the Sustained Spheromak Physics Experiment (SSPX) [E. B. Hooper et al., Nucl. Fusion 39, 863 (1999)] are presented. Experiments were carried out during pre-programmed, constant amplitude coaxial gun current pulses, where magnetic field increases stepwise with every pulse, but eventually saturates. Magnetic traces from the probe, which is electrically isolated from the plasma and spans the flux conserver radius, indicate ther… more
Date: April 30, 2007
Creator: Romero-Talamas, C. A.; McLean, H. S.; Hooper, E. B.; Wood, R. D.; LoDestro, L. L. & Moller, J. M.
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Partner: UNT Libraries Government Documents Department
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Measurements and Phenomenological Modeling of Magnetic FluxBuildup in Spheromak Plasmas

Description: Internal magnetic field measurements and high-speed imaging at the Sustained Spheromak Physics Experiment (SSPX) [E. B. Hooper, L. D. Pearlstein, R. H. Bulmer, Nucl. Fusion 39, 863 (1999)] are used to study spheromak formation and field buildup. The measurements are analyzed in the context of a phenomenological model of magnetic helicity based on the topological constraint of minimum helicity in the open flux before reconnecting and linking closed flux. Two stages are analyzed: (1) the initial … more
Date: December 14, 2007
Creator: Romero-Talamas, C. A.; Hooper, E. B.; Jayakumar, R.; McLean, H. S.; Wood, R. D. & Moller, J. M.
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Partner: UNT Libraries Government Documents Department
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Spheromak Energy Transport Studies via Neutral Beam Injection

Description: Results from the SSPX spheromak experiment provide strong motivation to add neutral beam injection (NBI) heating. Such auxiliary heating would significantly advance the capability to study the physics of energy transport and pressure limits for the spheromak. This LDRD project develops the physics basis for using NBI to heat spheromak plasmas in SSPX. The work encompasses three activities: (1) numerical simulation to make quantitative predictions of the effect of adding beams to SSPX, (2) using… more
Date: February 11, 2008
Creator: McLean, H. S.; Hill, D. N.; Wood, R. D.; Jayakumar, J. & Pearlstein, L. D.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Comparisons Between Experimental Measurments and Numerical Simulations of Spheromak Formation in SSPX

Description: Data from a recently installed insertable magnetic probe array in the Sustained Spheromak Physics Experiment (SSPX) [E. B. Hooper et al., Nucl. Fusion 39, 863 (1999)] is compared against NIMROD [C. R. Sovinec et al., J. Comp. Phys. 195, 355 (2004)], a full 3D resistive magnetohydrodynamic code that is used to simulate SSPX plasmas. The experiment probe consists of a linear array of chip inductors arranged in clusters that are spaced every 2 cm, and spans the entire machine radius at the flux co… more
Date: March 15, 2006
Creator: Romero-Talam?s, C. A.; Hooper, E. B.; Hill, D. N.; Cohen, B. I.; McLean, H. S.; Wood, R. D. et al.
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Partner: UNT Libraries Government Documents Department
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NIMROD Resistive Magnetohydrodynamic Simulations of Spheromak Physics

Description: The physics of spheromak plasmas is addressed by time-dependent, three-dimensional, resistive magneto-hydrodynamic simulations with the NIMROD code. Included in some detail are the formation of a spheromak driven electrostatically by a coaxial plasma gun with a flux-conserver geometry and power systems that accurately model the Sustained Spheromak Physics Experiment (SSPX) (R. D. Wood, et al., Nucl. Fusion 45, 1582 (2005)). The controlled decay of the spheromak plasma over several milliseconds … more
Date: December 11, 2007
Creator: Hooper, E. B.; Cohen, B. I.; McLean, H. S.; Wood, R. D.; Romero-Talamas, C. A. & Sovinec, C. R.
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Partner: UNT Libraries Government Documents Department
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Field and Current Amplification in the SSPX Spheromak

Description: Results are presented from experiments relating to magnetic field generation and current amplification in the SSPX spheromak. The SSPX spheromak plasma is driven by DC coaxial helicity injection using a 2MJ capacitor bank. Peak toroidal plasma currents of up to 0.7MA and peak edge poloidal fields of 0.3T are produced; lower current discharges can be sustained up to 3.5msec. When edge magnetic fluctuations are reduced below 1% by driving the plasma near threshold, it is possible to produce plasm… more
Date: October 8, 2002
Creator: Hill, D. N.; Blumer, R. H.; Cohen, B. I.; Hooper, E. B.; McLean, H. S.; Moller, J. et al.
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Partner: UNT Libraries Government Documents Department
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Spheromak formation studies in SSPX

Description: We present results from the Sustained Spheromak Physics Experiment (SSPX) at LLNL, which has been built to study energy confinement in spheromak plasmas sustained for up to 2 ms by coaxial DC helicity injection. Peak toroidal currents as high as 600kA have been obtained in the 1m dia. (0.23m minor radius) device using injection currents between 200-400kA; these currents generate edge poloidal fields in the range of 0.2-0.4T. The internal field and current profiles are inferred from edge field m… more
Date: September 29, 2000
Creator: Hill, D. N.; Bulmer, R. H.; Cohen, B. L.; Hooper, E. B.; LoDestro, L. L.; Mattor, N. et al.
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Partner: UNT Libraries Government Documents Department
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Hot Electron Generation and Transport Using K(alpha) Emission

Description: We have conducted experiments on both the Vulcan and Titan laser facilities to study hot electron generation and transport in the context of fast ignition. Cu wires attached to Al cones were used to investigate the effect on coupling efficiency of plasma surround and the pre-formed plasma inside the cone. We found that with thin cones 15% of laser energy is coupled to the 40{micro}m diameter wire emulating a 40{micro}m fast ignition spot. Thick cone walls, simulating plasma in fast ignition, re… more
Date: October 15, 2009
Creator: Akli, K. U.; Stephens, R. B.; Key, M. H.; Bartal, T.; Beg, F. N.; Chawla, S. et al.
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Partner: UNT Libraries Government Documents Department
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Calculation of Neutral Beam Injection into SSPX

Description: The SSPX spheromak experiment has achieved electron temperatures of 350eV and confinement consistent with closed magnetic surfaces. In addition, there is evidence that the experiment may be up against an operational beta limit for Ohmic heating. To test this barrier, there are firm plans to add two 0.9MW Neutral Beam (NB) sources to the experiment. A question is whether the limit is due to instability. Since the deposited Ohmic power in the core is relatively small the additional power from the… more
Date: June 13, 2006
Creator: Pearlstein, L. D.; Casper, T. A.; Hill, D. N.; LoDestro, L. L. & McLean, H. S.
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Partner: UNT Libraries Government Documents Department
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Magnetic Reconnection in the Spheromak: Physics and Consequences

Description: Magnetic reconnection in the spheromak changes magnetic topology by conversion of injected toroidal flux into poloidal flux and by magnetic surface closure (or opening) in a slowly decaying spheromak. Results from the Sustained Spheromak Physics Experiment, SSPX, are compared with resistive MHD simulations using the NIMROD code. Voltage spikes on the SSPX gun during spheromak formation are interpreted as reconnection across a negative-current layer close to the mean-field x-point. Field lines a… more
Date: February 28, 2006
Creator: Hooper, E. B.; Cohen, B. I.; Hill, D. N.; LoDestro, L. L.; McLean, H. S.; Romero-Talamas, C. A. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Time-resolved Temperature Measurements in SSPX

Description: We seek to measure time-resolved electron temperatures in the SSPX plasma using soft X-rays from free-free Bremsstrahlung radiation. To increase sensitivity to changes in temperature over the range 100-300 eV, we use two photodiode detectors sensitive to different soft X-ray energies. The detectors, one with a Zr/C coating and the other with a Ti/Pd coating, view the plasma along a common line of sight tangential to the magnetic axis of the spheromak, where the electron temperature is a maximum… more
Date: August 14, 2006
Creator: Ludington, A. R.; Hill, D. N.; McLean, H. S.; Moller, J. & Wood, R. D.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Tungsten spectroscopy relevant to the diagnostics development of ITER divertor plasmas

Description: The ITER tokamak will have tungsten divertor tiles and, consequently, the divertor plasmas are expected to contain tungsten ions. The spectral emission from these ions can serve to diagnose the divertor for plasma parameters such as tungsten concentrations, densities, ion and electron temperatures, and flow velocities. The ITER divertor plasmas will likely have densities around 10{sup 14-15} cm{sup -3} and temperatures below 150 eV. These conditions are similar to the plasmas at the Sustained S… more
Date: December 1, 2009
Creator: Clementson, J.; Beiersdorfer, P.; Magee, E. W.; McLean, H. S. & Wood, R. D.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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A Dual Channel X-ray Spectrometer for Fast Ignition Research

Description: A new Dual Channel Highly Ordered Pyrolytic Graphite (DC-HOPG) x-ray spectrometer was developed to study laser-generated electron beam transport. The instrument uses a pair of graphite crystals and has the advantage of simultaneously detecting self emission from low-Z materials in first diffraction order and high-Z materials in second order. The emissions from the target are detected using a pair of parallel imaging plates positioned in a such way that the noise from background is minimized and… more
Date: April 19, 2010
Creator: Akli, K. U.; Patel, P. K.; Van Maren, R.; Stephens, R. B.; Key, M. H.; Higginson, D. P. et al.
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Partner: UNT Libraries Government Documents Department
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Sustainment of a Spheromak by DC Helicity Injection

Description: A spheromak fusion reactor would be simple and inexpensive, and might actually work. The absence of both toroidal field coil windings and central-column stack reduces complexity and means that the toroidal plasma will be simply connected and compact. Intrinsic self-organization, driven by DC edge currents, provides the means by which toroidal current becomes driven. The benefits of this engineering simplicity would be realized in the ultimate cost of a reactor. Previous spheromak experiments ha… more
Date: June 1, 2000
Creator: Woodruff, S.; Hill, D. N.; Holcomb, C. T.; Hooper, E. B.; McLean, H. S.; Stallard, B. W. et al.
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Partner: UNT Libraries Government Documents Department
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Progress in the SSPX Spheromak

Description: The spheromak, with its simply connected geometry, holds promise as a less expensive fusion reactor. It has reasonably good plasma beta and can be formed and sustained in steady state with a magnetized coaxial plasma gun. The Sustained Spheromak Physics Experiment (SSPX) shown in Fig. 1 was constructed to investigate the key issues of magnetic field generation and energy confinement. In addition to the coaxial gun, nine magnetic field coils are utilized to shape the vacuum magnetic flux. This f… more
Date: July 7, 2003
Creator: McLean, H. S.; Woodruff, S.; Hill, D. N.; Bulmer, R. H.; Cohen, B. I.; Hooper, E. B. et al.
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Partner: UNT Libraries Government Documents Department
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Final Report - Effect of Magnetic Configuration on Spheromak Performances, FY2000 - FY2001, Tracking No.00-SI-008

Description: This is the final report on LDRD SI-funded research to determine the Effect of Magnetic Field Configurations on Spheromak Performance for the years FY2000-FY2001, during which a new set of bias magnetic field coils was used to change the vacuum magnetic field configuration of the SSPX spheromak at LLNL. The USDOE Office of Fusion Energy Science funded the routine operation of the SSPX facility during FY00 and FY01. A photo of the SSPX facility as it appeared in mid-FY01, appears in this report.… more
Date: February 6, 2002
Creator: Hill, D. N.; Hooper, E. B.; McLean, H. S.; Stallard, B. W.; Woodruff, S. & Wood, R. D.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Sustainment of Spheromak Pasmas in SSPX

Description: SSPX (Sustained Spheromak Physics eXperiment) was constructed to investigate the key physics issues of buildup and sustainment of spheromak plasmas with elevated electron temperature. Long pulse buildup to high magnetic field and temperature, at modest gun current, may point the way to a potentially simpler and more compact fusion reactor. Reported here are T{sub e} measurements in new magnetic flux geometries, results from sustainment experiments with {approx}1ms pulses, and power balance mode… more
Date: June 13, 2001
Creator: Stallard, B. W.; Hill, D. N.; Holcomb, C.; Hooper, E. B.; McLean, H. S.; Wood, R. D. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Controlled and Spontaneous Magnetic Field Generation in a Gun-Driven Spheromak

Description: In the Sustained Spheromak Physics Experiment, SSPX, progress has been made in understanding the mechanisms that generate fields by helicity injection. SSPX injects helicity (linked magnetic flux) from 1-m diameter magnetized coaxial electrodes into a flux-conserving confinement region. Control of magnetic fluctuations ({delta}B/B{approx}1% on the midplane edge) yields T{sub e} profiles peaked at > 200eV. Trends indicate a limiting beta ({beta}{sub e} {approx} 4-6%), and so we have been moti… more
Date: October 1, 2004
Creator: Woodruff, S.; Cohen, B. I.; Hooper, E. B.; McLean, H. S.; Stallard, B. W.; Hill, D. N. et al.
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Partner: UNT Libraries Government Documents Department
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Route to High Temperatures by Current Amplification in the Sustained Spheromak Physics Experiment (SSPX)

Description: For the spheromak to be attractive as a reactor concept it would be necessary to sustain the configuration with a low recycling power, reflected in the current amplification factor: A{sub 1} = I{sub tor}/I{sub gun}, where I{sub tor} is the toroidal current and I{sub gun} is the gun current. It is understood that A{sub 1} needs to be around 60 for a reactor [1], although the highest obtained so far in the spheromak has been {approx}3 [2]. The spheromak is a simply connected toroidal confinement … more
Date: June 11, 2002
Creator: Woodruff, S.; Holbomb, C. T.; Stallard, B. W.; Hill, D. N.; Hooper, E. B.; McLean, H. S. et al.
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Partner: UNT Libraries Government Documents Department
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Reactor Opportunities for the Spheromak

Description: Experimental results from the Sustained Spheromak Physics Experiment, SSPX, are reviewed and applied to published reactor configurations. The results include several important features, including low fluctuation levels, (apparent) good magnetic flux surfaces, and moderate beta. Additional features needed for an attractive reactor but not yet demonstrated experimentally are identified by comparison with the reactor designs, and possible alternatives to a fully steady-state device are discussed.
Date: April 18, 2003
Creator: Hooper, E. B.; Bulmer, R. H.; Fowler, T. K.; Hill, D. N.; McLean, H. S.; Romero-Talamas, C. A. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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