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ECH propagation and absorption experiments at 140 GHz in MTX

Description: Single pass absorption experiments using fundamental, O-mode ECH waves have been performed in the Microwave Tokamak Experiment (MTX) and found to be consistent with linear absorption theory, as predicted for the ECH source which is a 140 GHz, 400 kW CW gyrotron. These experiments provide the basis for comparison with future Free Electron Laser (FEL) experiments in which the absorption is predicted to be in the non-linear regime for P{sub FEL} {ge} 1 GW. The gyrotron power is coupled into a quas… more
Date: August 1, 1991
Creator: Fenstermacher, M. E.; Allen, S. L.; Casper, T. A.; Foote, J. H.; Hooper, E. B.; Johnston, S. et al.
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Partner: UNT Libraries Government Documents Department
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MTX (Microwave Tokamak Experiment) diagnostic and auxiliary systems for confinement, transport, and plasma physics studies

Description: This note describes the diagnostics and auxiliary systems on the Microwave Tokamak Experiment (MTX) for confinement, transport, and other plasma physics studies. It is intended as a reference on the installed and planned hardware on the machine for those who need more familiarity with this equipment. Combined with the tokamak itself, these systems define the opportunities and capabilities for experiments in the MTX facility. We also illustrate how these instruments and equipment are to be used … more
Date: July 28, 1989
Creator: Hooper, E. B.; Allen, S. L.; Casper, T. A. & Thomassen, K. I.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Control of gas input and background pressure in the end plug regions of the TMX-U thermal barrier experiment

Description: Rate equations for the plasma species in a thermal barrier end plug establish an upper bound on the neutral pressure (P) external to the plasma. For the Tandem Mirror Experiment-Upgrade (TMX-U), this bound is P less than or equal to 0.5 - 1.0 x 10/sup -6/ Torr. Initially TMX-U did not satisfy this criterion, and axial end plugging of plasma losses seemed limited by the excessive pressure. Subsequently, we modified the machine to improve the vacuum conditions, decreasing P to the desired range. … more
Date: October 26, 1983
Creator: Turner, W. C.; Nexsen, W. E.; Allen, S. L.; Hooper, E. B.; Hunt, A. L.; Lang, D. D. 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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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.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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ECH on the MTX (Microwave Tokamak Experiment)

Description: The Microwave Tokamak Experiment (MTX) at LLNL is investigating the heating of high density Tokamak plasmas using an intense pulse FEL. Our first experiments, now beginning, will study the absorption and plasma heating of single FEL pulses (20 ns pulse length and peak power up to 2 GW) at a frequency of 140 GHz. A later phase of experiments also at 140 GHz will study FEL heating at 5 kHz rate for a pulse train up to 50 pulses (35 ns pulse length and peak power up to 4 GW). Future operations are… more
Date: April 1, 1989
Creator: Stallard, B. W.; Byers, J. A.; Hooper, E. B.; Makowski, M. A.; Meassick, S.; Rice, B. W. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Use of polarimetry to measure the current profile in MTX

Description: It is possible in principle to measure the poloidal magnetic field profile, and hence, the profile of the plasma current measuring the change in the polarization of a sequence of microwave beams that pass through the plasma. Actual measurements of the plasma current profile would be very interesting in connection with Lower-Hybrid (or EC) current drive experiments since this would provide direct information on modification of the current profile by the application of rf power. A microwave polar… more
Date: July 14, 1987
Creator: Nevins, W. M.; Hooper, E. B. & Bernstein, I. B.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Preparation for propagation and absorption experiments in MTX

Description: Preparatory calculations of microwave transmission through the MTX access duct, propagation of the waves through the plasma and the resulting power deposition profile on a calorimeter located on the tokamak inside wall have been performed. The microwave transmission calculations include the relative phase slippage of waveguide modes in the duct to determine the spatial structure of the wavefront at the duct exist. Ray-tracing calculations show substantial spreading of the beam in the poloidal d… more
Date: April 1, 1989
Creator: Byers, J. A.; Cohen, R. H.; Fenstermacher, M. E.; Hooper, E. B.; Meassick, S.; Rognlien, T. D. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Characterization of disruptions in the Microwave Tokamak Experiment, MTX

Description: The Microwave Tokamak Experiment (MTX) has a substantial number of fast diagnostics, especially for electrons, as part of its mission for pulsed, high-power electron cyclotron heating. As part of its contribution to ITER R D, these diagnostics are being used to characterize disruptions in MTX. This report is the first of two, with the second planned for submittal in September 1990, at the end of the ITER conceptual design activity. Here, we analyze the characteristics of disruptions during norm… more
Date: March 30, 1990
Creator: Hooper, E. B. & Makowski, M. A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Anatomy of a disruption in MTX (Microwave Tokamak Experiment)

Description: Disruptions are observed in the Microwave Tokamak Experiment, MTX (nee Alcator C), over a wide range of plasma parameters. Indeed, disruptions often occur far from the boundaries of the operating space as defined by Hugill and l{sub i}-q plots. Despite this, the general behavior during the disruptive process is generally similar whatever the operating parameters. This report will describe one disruption in detail in order to provide a detailed anatomy of the event.
Date: October 15, 1990
Creator: Hooper, E. B.; Casper, T. A.; Lasnier, C. J.; Makowski, M. A.; Meyer, W. H.; Moller, J. M. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Free-electron laser experiments in the microwave tokamak experiment

Description: Microwave pulses have been injected from a free electron-laser (FEL) into the Microwave Tokamak Experiment (MTX) at up to 0.2 GW at 140 GHz in short pulses (10-ns duration) with O-mode polarization. The power transmitted through the plasma was measured in a first experimental study of high power pulse propagation in the plasma; no nonlinear effects were found at this power level. Calculations indicate that nonlinear effects may be found at the higher power densities expected in future experimen… more
Date: August 1, 1990
Creator: Allen, S. L.; Brown, M. D.; Byers, J. A.; Casper, T. A.; Cohen, B. I.; Cohen, R. H. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Optimization of neutron source

Description: I consider here the optimization of the two component neutron source, allowing beam species and energy to vary. A simple model is developed, based on the earlier publications, that permits the optimum to be obtained simply. The two component plasma, with one species of hot ion (D{sup +} or T{sup +}) and the complementary species of cold ion, is easy to analyze in the case of a spatially uniform cold plasma, as to good approximation the total number of hot ions is important but not their spatial… more
Date: November 9, 1993
Creator: Hooper, E. B.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Modeling results for a linear simulator of a divertor

Description: A divertor simulator, IDEAL, has been proposed by S. Cohen to study the difficult power-handling requirements of the tokamak program in general and the ITER program in particular. Projections of the power density in the ITER divertor reach {approximately} 1 Gw/m{sup 2} along the magnetic fieldlines and > 10 MW/m{sup 2} on a surface inclined at a shallow angle to the fieldlines. These power densities are substantially greater than can be handled reliably on the surface, so new techniques are req… more
Date: June 23, 1993
Creator: Hooper, E. B.; Brown, M. D.; Byers, J. A.; Casper, T. A.; Cohen, B. I.; Cohen, R. H. et al.
Item Type: Refine your search to only Report
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.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Experiments on nonlinear absorption of ECH waves in MTX and a comparison with theory

Description: Intense pulse electron cyclotron heating (ECH) experiments have been carried out on the MTX tokamak. Rf pulses at 140 GHz, peak power of 1--2 GW, and 25 ns pulse length were generated by the ETA-III/IMP FEL and transported quasi-optically to MTX for o-mode launch. Because of the intense rf electric fields ({approximately}250 keV/cm), reduction of plasma absorption by nonlinear effects were expected and several rf beam geometries (k{sub {parallel}} gradient) were investigated to study their effe… more
Date: July 1, 1993
Creator: Stallard, B. W.; Allen, S. L.; Byers, J. A.; Casper, T. A.; Cohen, B. I.; Cohen, R. H. et al.
Item Type: Refine your search to only Article
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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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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Particle Control in the Sustained Spheromak Physics Experiment

Description: In this paper we report on density and impurity measurements in the Sustained Spheromak Physics Experiment (SSPX) which has recently started operation. The SSPX spheromak plasma is sustained by coaxial helicity injection for a duration of 2msec with peak toroidal currents of up to 0.5MA. The plasma-facing components consist of tungsten-coated copper to minimize sputtering. The surfaces are conditioned by a combination of baking at 150 C, glow discharge cleaning, Titanium gettering, and pulse-di… more
Date: May 1, 2000
Creator: Wood, R. D.; Hill, D. N.; Hooper, E. B.; Buchenauer, D.; McLean, H.; Wang, Z. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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The Microwave Tokamak Experiment (MTX)

Description: A new experimental facility is being assembled at the Lawrence Livermore National Laboratory (LLNL) for studying microwave propagation and absorption in high density plasmas. A unique feature of the facility is the free electron laser (FEL) used to generate high peak power microwaves at 250 GHz, at a repetition rate so as to produce up to 2 MW of average power for up to 30 s. Called the Microwave Tokamak Experiment (MTX), the facility will be used for studies of plasma heating, current drive, a… more
Date: October 2, 1987
Creator: Thomassen, K. I.; Cohen, B. I.; Hooper, E. B.; Lang, D. D. & Nevins, W. M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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