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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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ECRH and ICRH in the TMX-U Tandem Mirror

Description: In the Tandem Mirror Experiment Upgrade (TMX-U), the formation of a thermal barrier and the potential plugging of ion end loss were achieved at central-cell densities up to 2 x 10/sup 12/ cm/sup -3/. The presence of a thermal barrier was confirmed by direct measurement, and ion axial-confinement times in the range 50 to 100 ms were measured. The ECRH in the end cells (a) initiates plasma startup, (b) generates hot, mirror-confined electrons to form thermal barriers, and (c) creates the plugging… more
Date: March 15, 1984
Creator: Stallard, B. W.; Cummins, W. F.; Molvik, A. W.; Poulsen, P.; Simonen, T. C.; Falabella, S. et al.
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Partner: UNT Libraries Government Documents Department
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Directions for possible upgrades of the Mirror Fusion Test Facility (MFTF)

Description: The Mirror Fusion Test Facility (MFTF) may be upgraded by extending the time of plasma sustenance in an approach to steady-state operation and/or by increasing the neutral-beam injection energy. Some parameter bounds for these upgrades are discussed as they relate to a definition of the required neutral-beam development.
Date: December 20, 1977
Creator: Damm, C. C.; Coensgen, F. H.; Devoto, R. S.; Molvik, A. W.; Porter, G. D.; Shearer, J. W. et al.
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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Fokker-Planck calculations of electron cyclotron resonant heating (ECRH) in mirror geometry

Description: A time dependent, bounce-averaged Fokker-Planck code, with quasi-linear diffusion at fundamental and second harmonic frequencies, has been used to study cold plasma trapping and heating of hot electrons in mirror geometry. Both electron-electron and electron-ion Coulomb collisions are included. The code can model either cavity heating (electric field throughout cavity as in EBT) or beam controlled heating (electric field spatially restricted as in the TMX-Upgrade tandem mirror). The heating met… more
Date: November 25, 1981
Creator: Stallard, B. W.; Matsuda, Y. & Nevins, W. M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Engineering design of the interaction waveguide for high-power accelerator-driven microwave free-electron lasers

Description: Linear induction accelerators (LIAs) operating at beam energies of a few million electron volts and currents of a few thousand amperes are suitable drivers for free-electron lasers (FELs). Such lasers are capable of producing gigawatts of peak power and megawatts of average power at microwave frequencies. Such devices are being studied as possible power sources for future high-gradient accelerators and are being constructed for plasma heating applications. At high power levels, the engineering … more
Date: March 16, 1989
Creator: Hopkins, D. B.; Clay, H. W.; Stallard, B. W.; Throop, A. L.; Listvinsky, G. & Makowski, M.A.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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High-average-power millimeter-wave FEL (free-electron laser) for plasma heating using the ETA-II accelerator

Description: The Microwave Tokamak Experiment (MTX) is under construction at LLNL to investigate the feasibility of intense, pulsed microwave radiation for plasma heating on future ignition tokamaks. A high-average-power free-electron laser (FEL) will use the Experimental Test Accelerator (ETA-II), a linear induction accelerator, in combination with an advanced high-field wiggler, to produce 1-2 MW of power at 1-2-mm wavelengths for periods of up to 0.5s. The design of the FEL, termed the intense microwave … more
Date: March 10, 1989
Creator: Throop, A. L.; Atkinson, D. P.; Clark, J. C.; Deis, G. A.; Jong, R. A.; Nexsen, W. E. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Changes and Developments in Electron Cyclotron Resonant Heating (ECRH) on the Tandem Mirror Experiment Upgrade (TMX-U)

Description: This paper will describe changes to the previously reported Electron Cyclotron Resonant Heating (ECRH) circular waveguide systems that deliver power to the Tandem Mirror Experiment Upgrade (TMX-U) machine. Four gyrotrons and associated waveguide systems, operating at 28-GHz and 200 kW each, helped establish electrostatic plugging in the end cells of TMX-U. A fifth gyrotron has been installed to power two resonant locations in the end plugs. This system and the pair of 10 kG heaters now use a sl… more
Date: November 14, 1985
Creator: Anderson, A. T.; Brooksby, C. A.; Calderon, M. O.; Ellis, R.; Felker, B.; Horton, R. D. et al.
Item Type: Refine your search to only Article
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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Electron Cyclotron Heating in TMX-Upgrade

Description: TMX-Upgrade, an improved tandem mirror experiment under construction at LLNL, will use electron cyclotron resonance heating (ECRH) to create thermal barriers and to increase the center cell ion confining potential. Gyrotron oscillators (200 kW, 28 GHz) supply the heating power for the potential confined electron (fundamental heating) and the mirror-confined electrons (harmonic heating) in the thermal barriers. Important issues are temperature limitation and microstability for the hot electrons.… more
Date: January 1, 1981
Creator: Stallard, B. W. & Hooper, E. B., Jr.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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ECH (electron cyclotron heating) in the Microwave Tokamak Experiment

Description: The Microwave Tokamak Experiment (MTX) at LLNL will investigate electron heating in the MTX tokamak (formerly Alcator-C) at high density (up to 6 x 10/sup 20/ m/sup -3/) and high power by using a free electron laser (FEL). Parameters of the FEL are a peak power up to 8 GW and 50 ns duration, with average power 1 to 2 MW, at a frequency of 250 GHz. The planned input driver for the FEL is a gyrotron oscillator. The FEL output will be transported quasi-optically, inside a 50 cm evacuated pipe, to … more
Date: April 28, 1987
Creator: Stallard, B. W.; Smith, G. R.; James, R. A.; Thomassen, K. I.; Kritz, A. H.; Makowski, M. et al.
Item Type: Refine your search to only Article
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.
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Partner: UNT Libraries Government Documents Department
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q Profile evolution and enhanced core confinement of high {beta}{sub p} plasmas in DIII-D

Description: In DIII-D the authors have investigated the long pulse evolution of high poloidal beta ({sub beta}{sub p}), double-null diverted H-mode discharges, which exhibit high bootstrap current fractions attractive for a reactor. At low currents I{sub p}, the current profile evolved over several seconds and the on-axis safety factor (q{sub 0}) increased. When q{sub 0} increased above {approximately}2, the MHD character changed from an m/n = 2/1 to an m/n = 3/1 internal kink mode, where m(n) are poloidal… more
Date: October 1, 1994
Creator: Stallard, B. W.; Casper, T. A. & Fenstermacher, M. E.
Item Type: Refine your search to only Article
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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Neutral beam current requirements for MX

Description: The neutral beam current required to sustain the MX plasma is calculated for the plasma modeled by (a) a flat-top radial density profile and (b) a diffuse radial profile. Estimates of the plasma length are obtained from Fokker-Planck calculations and a three-dimensional guiding-center equilibrium code. Beam trapping efficiency is calculated from a model taking into account the spatial dimensions of the beam and plasma. The sensitivity to variations of magnetic field and plasma beta is calculate… more
Date: January 14, 1977
Creator: Stallard, B. W. & Rensink, M. E.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Plasma wall charge-exchange interactions in the 2XIIB magnetic mirror experiment

Description: Plasma-wall interactions by charge-exchange wall bombardment in the 2XIIB magnetic mirror experiment are discussed. Experimental measurements are modeled with a time-dependent, radial density buildup calculation. A low-density plasma sufficient to help shield the hot interior plasma from cold-gas erosion, as required by the model, is measured.
Date: January 1, 1976
Creator: Stallard, B. W.; Coensgen, F. H.; Cummins, W. F.; Gormezano, C.; Logan, B. G.; Molvik, A. W. et al.
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Partner: UNT Libraries Government Documents Department
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Quiescent Double Barrier H-Mode Plasmas in the Diii-D Tokamak

Description: High confinement (H-mode) operation is the choice for next-step tokamak devices based either on conventional or advanced tokamak physics. This choice, however, comes at a significant cost for both the conventional and advanced tokamaks because of the effects of edge localized modes (ELMs). ELMs can produce significant erosion in the divertor and can affect the beta limit and reduced core transport regions needed for advanced tokamak operation. Experimental results from DIII-D [J.L. Luxon, et al… more
Date: November 1, 2000
Creator: Burrell, K. H.; Austin, M. E.; Brennan, D. P.; Deboo, J. C.; Doyle, E. J.; Fenzi, C. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Milestone report: Status report on high {beta}p experiments at high plasma current

Description: This report summarizes LLNL`s involvement in recent high {beta}{sub p} experiments on the DIII-D tokamak at General Atomics. These experiments were done in collaboration with several members of the DIII-D physics staff from GA and from other collaborating institutions and could not have succeeded without this joint effort. In this report, the authors summary a specific, limited set of experiments to extend high {beta}{sub p} operation with enhanced core confinement to higher plasma currents. Th… more
Date: July 1, 1995
Creator: Casper, T. A.; James, R. A.; Rice, B. W. & Stallard, B. W.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Dispersion relations for a plasma-filled helix-loaded-waveguide

Description: The propagation of waves on bounded, magnetized plasma columns arises in connection with a variety of applications. To this end dispersion relations axe developed for a variety of multi-region circularly symmetric configurations. These include, a sheath helix in free space, a plasma column in free space, a plasma filled conducting tube, a plasma filled sheath-helix in free space, a sheath helix within a conducting cylinder, a plasma filled sheath-helix within a conducting cylinder, and a plasma… more
Date: January 1, 1994
Creator: Makowski, M. A.; Hooper, E. B. & Stallard, B. W.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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