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4. Ohmic energy confinement saturation and core toroidal rotation reversal in Alcator C-Mod plasmas

Author

Rice, J. E., primary, Greenwald, M. J., additional, Podpaly, Y. A., additional, Reinke, M. L., additional, Diamond, P. H., additional, Hughes, J. W., additional, Howard, N. T., additional, Ma, Y., additional, Cziegler, I., additional, Duval, B. P., additional, Ennever, P. C., additional, Ernst, D., additional, Fiore, C. L., additional, Gao, C., additional, Irby, J. H., additional, Marmar, E. S., additional, Porkolab, M., additional, Tsujii, N., additional, and Wolfe, S. M., additional

Published
2012
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7. Diagnostic Systems on Alcator C-Mod

Author

Basse, N. P., primary, Dominguez, A., additional, Edlund, E. M., additional, Fiore, C. L., additional, Granetz, R. S., additional, Hubbard, A. E., additional, Hughes, J. W., additional, Hutchinson, I. H., additional, Irby, J. H., additional, LaBombard, B., additional, Lin, L., additional, Lin, Y., additional, Lipschultz, B., additional, Liptac, J. E., additional, Marmar, E. S., additional, Mossessian, D. A., additional, Parker, R. R., additional, Porkolab, M., additional, Rice, J. E., additional, Snipes, J. A., additional, Tang, V., additional, Terry, J. L., additional, Wolfe, S. M., additional, Wukitch, S. J., additional, Zhurovich, K., additional, Bravenec, R. V., additional, Phillips, P. E., additional, Rowan, W. L., additional, Kramer, G. J., additional, Schilling, G., additional, Scott, S. D., additional, and Zweben, S. J., additional

Published
2007
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8. Internal Transport Barriers in Alcator C-Mod

Author

Fiore, C. L., primary, Ernst, D. R., additional, Rice, J. E., additional, Zhurovich, K., additional, Basse, N., additional, Bonoli, P. T., additional, Greenwald, M. J., additional, Marmar, E. S., additional, and Wukitch, S. J., additional

Published
2007
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10. Characterization of core and edge turbulence in L- and enhanced Dα H-mode Alcator C-Mod plasmas

Author

Basse, N. P., primary, Edlund, E. M., additional, Ernst, D. R., additional, Fiore, C. L., additional, Greenwald, M. J., additional, Hubbard, A. E., additional, Hughes, J. W., additional, Irby, J. H., additional, Lin, L., additional, Lin, Y., additional, Marmar, E. S., additional, Mossessian, D. A., additional, Porkolab, M., additional, Rice, J. E., additional, Snipes, J. A., additional, Stillerman, J. A., additional, Terry, J. L., additional, Wolfe, S. M., additional, Wukitch, S. J., additional, Zhurovich, K., additional, Kramer, G. J., additional, and Mikkelsen, D. R., additional

Published
2005
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11. Overview of neutron and confined escaping alpha diagnostics planned for ITER

Author

Sasao, M, primary, Krasilnikov, A V, additional, Nishitani, T, additional, Batistoni, P, additional, Zaveryaev, V, additional, Kaschuck, Yu A, additional, Popovichev, S, additional, Iguchi, T, additional, Jarvis, O N, additional, Kallne, J, additional, Fiore, C L, additional, Roquemore, L, additional, Heidbrink, W W, additional, Donne, A J H, additional, Costley, A E, additional, and Walker, C, additional

Published
2004
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12. Control of internal transport barriers on Alcator C-Mod

Author

Fiore, C. L., primary, Bonoli, P. T., additional, Ernst, D. R., additional, Hubbard, A. E., additional, Greenwald, M. J., additional, Lynn, A., additional, Marmar, E. S., additional, Phillips, P., additional, Redi, M. H., additional, Rice, J. E., additional, Wolfe, S. M., additional, Wukitch, S. J., additional, and Zhurovich, K., additional

Published
2004
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14. Internal transport barriers on Alcator C-Mod

Author

Fiore, C. L., primary, Rice, J. E., additional, Bonoli, P. T., additional, Boivin, R. L., additional, Goetz, J. A., additional, Hubbard, A. E., additional, Hutchinson, I. H., additional, Granetz, R. S., additional, Greenwald, M. J., additional, Marmar, E. S., additional, Mossessian, D., additional, Porkolab, M., additional, Taylor, G., additional, Snipes, J., additional, Wolfe, S. M., additional, and Wukitch, S. J., additional

Published
2001
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15. Analysis of ICRF-heated transport barrier experiments in Alcator C-Mod.

Author

Bonoli, P. T., Boivin, R. L., Fiore, C. L., Goetz, J., Granetz, R., Greenwald, M., Hubbard, A. E., Hutchinson, I. H., Irby, J., Davis-Lee, W., Marmar, E., Mazurenko, A., Nelson-Melby, E., Mossessian, D., Porkolab, M., Rice, J., Snipes, J., Terry, J. L., Wolfe, S. M., and Wukitch, S.J.

Subjects
CYCLOTRONS, RADIO frequency, PLASMA heating
Abstract

An internal transport barrier (ITB) mode has been produced in the Alcator C-Mod tokamak via the application of 1 - 2 MW of off-axis ICRF heating power at 4.5 T and 80 MHz. This mode is characterized by strong peaking of the electron density profile with n[sub e] (0) increasing to 6-8 × 10[sup 20] m[sup -3] while the plasma remains H-mode like outside the barrier foot (r/a ... 0.5) with n[sub e] ... 1.5 - 2.0 × 10[sup 20] m[sup -3]. Formation of the density barrier is typically accompanied by a decrease in the toroidal plasma rotation velocity from co-current to zero. Transport analysis of these discharges using the TRANSP code indicates the formation of a transport barrier in Χ[sub eff](r) at r/a ... 0.5. Heating and control of the transport barrier was successfully demonstrated by simultaneously injecting 0.6 - 1.0 MW of on-axis ICRF heating power at 70 MHz. An internal transport barrier (ITB) mode has been produced in the Alcator C-Mod tokamak via the application of 1 - 2 MW of off-axis ICRF heating power at 4.5 T and 80 MHz. This mode is characterized by strong peaking of the electron density profile with n[sub e] (0) increasing to 6-8 × 10[sup 20] m[sup -3] while the plasma remains H-mode like outside the barrier foot (r/a ... 0.5) with n[sub e] ... 1.5 - 2.0 × 10[sup 20] m[sup -3]. Formation of the density barrier is typically accompanied by a decrease in the toroidal plasma rotation velocity from co-current to zero. Transport analysis of these discharges using the TRANSP code indicates the formation of a transport barrier in Χ[sub eff](r) at r/a ... 0.5. Heating and control of the transport barrier was successfully demonstrated by simultaneously injecting 0.6 - 1.0 MW of on-axis ICRF heating power at 70 MHz. [ABSTRACT FROM AUTHOR]

Published
2001

16. Mode conversion electron heating in Alcator C-Mod: Theory and experiment

Author

Bonoli, P. T., primary, Brambilla, M., additional, Nelson-Melby, E., additional, Phillips, C. K., additional, Porkolab, M., additional, Schilling, G., additional, Taylor, G., additional, Wukitch, S. J., additional, Boivin, R. L., additional, Boswell, C. J., additional, Fiore, C. L., additional, Gangadhara, S., additional, Goetz, J., additional, Granetz, R., additional, Greenwald, M., additional, Hubbard, A. E., additional, Hutchinson, I. H., additional, In, Y., additional, Irby, J., additional, LaBombard, B., additional, Lipschultz, B., additional, Marmar, E., additional, Mazurenko, A., additional, Nachtrieb, R., additional, Pappas, D., additional, Pitcher, C. S., additional, Reardon, J., additional, Rice, J., additional, Rowan, W. L., additional, Snipes, J. A., additional, Takase, Y., additional, Terry, J., additional, and Wolfe, S. M., additional

Published
2000
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17. Electron heating via mode converted ion Bernstein waves in the Alcator C-Mod tokamak

Author

Bonoli, P. T., primary, O’Shea, P., additional, Brambilla, M., additional, Golovato, S. N., additional, Hubbard, A. E., additional, Porkolab, M., additional, Takase, Y., additional, Boivin, R. L., additional, Bombarda, F., additional, Christensen, C., additional, Fiore, C. L., additional, Garnier, D., additional, Goetz, J., additional, Granetz, R., additional, Greenwald, M., additional, Horne, S. F., additional, Hutchinson, I. H., additional, Irby, J., additional, Jablonski, D., additional, LaBombard, B., additional, Lipschultz, B., additional, Marmar, E., additional, May, M., additional, Mazurenko, A., additional, McCracken, G., additional, Nachtrieb, R., additional, Niemczewski, A., additional, Ohkawa, H., additional, Pappas, D. A., additional, Reardon, J., additional, Rice, J., additional, Rost, C., additional, Schachter, J., additional, Snipes, J. A., additional, Stek, P., additional, Takase, K., additional, Terry, J., additional, Wang, Y., additional, Watterson, R. L., additional, Welch, B., additional, and Wolfe, S. M., additional

Published
1997
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18. Particle drift effects on the Alcator C-Mod divertor

Author

Hutchinson, I H, primary, Goetz, J A, additional, Jablonski, D F, additional, LaBombard, B L, additional, Lipschultz, B, additional, McCracken, G M, additional, Snipes, J A, additional, Terry, J L, additional, Allen, A J, additional, Boivin, R L, additional, Bonoli, P T, additional, Fiore, C L, additional, Granetz, R S, additional, Greenwald, M J, additional, Hubbard, A E, additional, Marmar, E S, additional, Porkolab, M, additional, Rice, J E, additional, Takase, Y, additional, and Wolfe, S M, additional

Published
1996
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19. Survey of ICRF heating experiments and enhanced performance modes in Alcator C-Mod

Author

Takase, Y, primary, Boivin, R L, additional, Bombarda, F, additional, Bonoli, P T, additional, Fiore, C L, additional, Garnier, D, additional, Goetz, J A, additional, Golovato, S N, additional, Granetz, R S, additional, Greenwald, M J, additional, Horne, S F, additional, Hubbard, A E, additional, Hutchinson, I H, additional, Irby, J H, additional, Kimura, H, additional, Majeski, R, additional, Marmar, E S, additional, May, M, additional, Mazurenko, A, additional, O'Shea, P, additional, Pinsker, R, additional, Porkolab, M, additional, Reardon, J, additional, Rice, J E, additional, Rost, C, additional, Schachter, J, additional, Snipes, J A, additional, Stek, P, additional, Terry, J L, additional, Watterson, R L, additional, Welch, B, additional, and Wolfe, S M, additional

Published
1996
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29. Lower hybrid current drive experiments on Alcator C-Mod: Comparison with theory and simulation.

Author

Bonoli, P. T., Ko, J., Parker, R., Schmidt, A. E., Wallace, G., Wright, J. C., Fiore, C. L., Hubbard, A. E., Irby, J., Marmar, E., Porkolab, M., Terry, D., Wolfe, S. M., Wukitch, S. J., Wilson, J. R., Scott, S., Valeo, E., Phillips, C. K., and Harvey, R. W.

Subjects
RADIO frequency, DENSITY, MAGNETIC measurements, ELECTRON distribution, SPECTRUM analysis
Abstract

Lower hybrid (LH) current drive experiments have been carried out on the Alcator C-Mod tokamak [I. H. Hutchinson et al., Phys. Plasmas 1, 1511 (1994)] using a radio-frequency system at 4.6 GHz. Up to 900 kW of LH power has been coupled and driven LH currents have been inferred from magnetic measurements by extrapolating to zero loop voltage, yielding an efficiency of neILHR0/PLH≈2.5±0.2×1019 (A/W/m2). We have simulated the LH current drive in these discharges using the combined ray tracing/three-dimensional (r,v⊥,v∥) Fokker–Planck code GENRAY-CQL3D (R. W. Harvey and M. McCoy, in Proceedings of the IAEA Technical Committee Meeting on Simulation and Modeling of Thermonuclear Plasmas, Montreal, Canada, 1992) and found similar current drive efficiencies. The simulated profiles of current density from CQL3D, including both ohmic plus LH drive have been found to be in good agreement with the measured current density from a motional Stark effect diagnostic. Measurements of nonthermal x-ray emission confirm the presence of a significant fast electron population and the three-dimensional (r,v⊥,v∥) electron distribution function from CQL3D has been used in a synthetic diagnostic code to simulate the measured hard x-ray data. [ABSTRACT FROM AUTHOR]

Published
2008
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30. Compact multichannel neutral particle analyzer for measurement of energetic charge-exchanged neutrals in Alcator C-Mod.

Author

Tang, V., Liptac, J., Parker, R. R., Bonoli, P. T., Fiore, C. L., Granetz, R. S., Irby, J. H., Lin, Y., Wukitch, S. J., Frenje, J. A., Leiter, R., Mcduffee, S., and Petrasso, R. D.

Subjects
MASS spectrometry, NEUTRAL beams, SILICON diodes, HYDROGEN ions, ELECTRONIC pulse techniques
Abstract

A four-channel compact neutral particle analyzer (CNPA) based on operating small Si diode detectors in pulse-height analysis (PHA) mode is used to measure energetic hydrogen minority ions with energies between ∼50 and 350 keV stemming from ion-cyclotron range-of-frequency heated D(H) Alcator C-Mod plasmas with both active and passive charge exchange (CX). First core minority ion distribution results from Alcator C-Mod discharges and a detailed description of the diagnostic are presented. The diagnostic employs integrated electronics and fast digitization of the shaping amplifier voltage. The digitized data are stored for postshot PHA, which removes the constraints of real-time PHA and allows for improved performance via elimination of base line shift effects and potentially relieving pileup through Gaussian fitting routines. The CNPA is insensitive to the large gamma and neutron background in Alcator C-Mod discharges but is susceptible to the plasma’s soft x-ray flux. The soft x-ray flux limits the CNPA energy resolution to ∼15–20 keV. A simple model is used to interpret the active CNPA data which permits rapid estimates of the core hydrogen minority temperatures and anisotropy with a time resolution of ∼100 ms. Hydrogenlike boron is identified as an important electron donor for the CX signal. [ABSTRACT FROM AUTHOR]

Published
2006
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31. Neutron calibration techniques for comparison of tokamak results

Author

Strachan, J. D., primary, Adams, J. M., additional, Barnes, Cris W., additional, Batistoni, P., additional, Bosch, H.‐S., additional, Brzosko, J. S., additional, England, A. C., additional, Fiore, C. L., additional, Granetz, R. S., additional, Hendel, H. W., additional, Hoenen, F., additional, Jarvis, O. N., additional, Jassby, D. L., additional, Ku, L. P., additional, Liu, P., additional, Martin, G., additional, McCauley, S., additional, Motley, R. W., additional, Nishitani, T., additional, Robouch, B. V., additional, Saito, T., additional, Sasao, M., additional, Stav, R. D., additional, and Taylor, P. L., additional

Published
1990
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34. Characterization of core and edge turbulence in L- and enhanced Dα H-mode Alcator C-Mod plasmas.

Author

Basse, N. P., Edlund, E. M., Ernst, D. R., Fiore, C. L., Greenwald, M. J., Hubbard, A. E., Hughes, J. W., Irby, J. H., Lin, L., Lin, Y., Marmar, E. S., Mossessian, D. A., Porkolab, M., Rice, J. E., Snipes, J. A., Stillerman, J. A., Terry, J. L., Wolfe, S. M., Wukitch, S. J., and Zhurovich, K.

Subjects
PLASMA gases, TURBULENCE, MAGNETIC fields, MAGNETICS, PARTICLES (Nuclear physics), FLUID dynamics
Abstract

The recently upgraded phase-contrast imaging (PCI) diagnostic is used to characterize the transition from the low (L) to the enhanced Dα (EDA) high (H) confinement mode in Alcator C-Mod [I. H. Hutchinson, R. Boivin, F. Bombarda et al., Phys. Plasmas 1, 1511 (1994)] plasmas. PCI yields information on line integrated density fluctuations along vertical chords. The number of channels has been increased from 12 to 32 and the sampling rate from 1 MHz to 10 MHz. This expansion of diagnostic capabilities is used to study broadband turbulence in L and EDA H mode and to analyze the quasicoherent (QC) mode associated with EDA H mode. Changes in broadband turbulence at the transition from L to EDA H mode can be interpreted as an effect of the Doppler rotation of the bulk plasma. Additional fluctuation measurements of Dα light and the poloidal magnetic field show features correlated with PCI in two different frequency ranges at the transition. The backtransition from EDA H to L mode, the so-called enhanced neutron (EN) mode, is investigated by new high frequency (132 and 140 GHz) reflectometer channels operating in the ordinary (O) mode. This additional hardware has been installed in an effort to study localized turbulence associated with internal transport barriers (ITBs). The EN mode is a suitable candidate for this study, since an ITB exists transiently as the outer density decreases much faster than the core density in this mode. The fact that the density decays from the outside inward allows us to study fluctuations progressing towards the plasma core. Our results mark the first localized observation of the QC mode at medium density: 2.2×1020 m-3 (132 GHz). Correlating the reflectometry measurements with other fluctuating quantities provides some insight regarding the causality of the EN-mode development. [ABSTRACT FROM AUTHOR]

Published
2005
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36. Role of trapped electron mode turbulence in internal transport barrier control in the Alcator C-Mod Tokamak.

Author

Ernst, D. R., Bonoli, P. T., Catto, P. J., Doriand, W., Fiore, C. L., Granetz, R. S., Greenwald, M., Hubbard, A. E., Porkolab, M., Redi, M. H., Rice, J. E., and Zhurovich, K.

Subjects
TURBULENCE, ELECTRON transport, TOKAMAKS, PLASMA gases, PINCH effect (Physics), FUSION reactors
Abstract

Nonlinear gyrokinetic simulations of trapped electron mode (TEM) turbulence, within an internal particle transport barrier, are performed and compared with experimental data. The results provide a mechanism for transport barrier control with on-axis radio frequency heating, as demonstrated in Alcator C-Mod experiments [S. J. Wukitch et al., Phys. Plasmas 9, 2149 (2002)]. Off-axis heating produces an internal particle and energy transport barrier after the transition to enhanced D ahigh confinement mode. The barrier foot reaches the half-radius, with a peak density 2.5 times the edge density. While the density profile peaks, the temperature profile remains relatively unaffected. The peaking and concomitant impurity accumulation are controlled by applying modest central heating power late in the discharge. Gyrokinetic turbulence simulations of the barrier formation phase, using the GS2 code [W. Dorland et al., Phys. Rev. Lett. 85, 5579 (2000)] show that toroidal ion temperature gradient driven modes are suppressed inside the barrier foot, but continue to dominate in the outer half-radius. As the density gradient steepens further, trapped electron modes are driven unstable. The onset of TEM turbulence produces an outflow that strongly increases with the density gradient, upon exceeding a new nonlinear critical density gradient, which significantly exceeds the linear critical density gradient. The TEM turbulent outflow ultimately balances the inward Ware pinch, leading to steady state. Moreover, the simulated turbulent particle diffusivity matches that inferred from particle balance using measured density profile data and the calculated Ware pinch. This turbulent diffusivity exhibits a strong unfavorable temperature dependence that allows control with central heating. [ABSTRACT FROM AUTHOR]

Published
2004
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37. Double transport barrier experiments on Alcator C-Mod.

Author

Wukitch, S. J., Boivin, R. L., Bonoli, P. T., Fiore, C. L., Granetz, R. S., Greenwald, M. J., Hubbard, A. E., Hutchinson, I. H., In, Y., Irby, J., Lin, Y., Marmar, E. S., Mossessian, D., Porkolab, M., Schilling, G., Rice, J. E., Snipes, J. A., and Wolfe, S. M.

Subjects
TRANSPORT theory, SPECIFIC gravity
Abstract

Double transport barrier modes (simultaneous core and edge transport barrier) have been observed with off-axis ion cyclotron range of frequencies (ICRF) heating in the Alcator C-Mod tokamak [I. H. Hutchinson et al., Phys. Plasmas 1, 1511 (1994)]. An internal transport barrier (ITB) is routinely produced in enhanced D[sub α]H-mode (EDA) discharges where the minority ion cyclotron resonance layer is at r/a∼|0.5| during the current flat top phase of the discharge. The density profile becomes peaked without the presence of a particle source in the plasma core and continues to peak until the increased core impurity radiation arrests the improved energy confinement, ultimately leading to a barrier collapse. With the addition of moderate (0.6 MW) central ICRF heating, the double barrier mode was maintained for as long as the ICRF power was applied. Modeling shows that the internal thermal barrier was maintained throughout the discharge. The presence of sawteeth throughout most of the ITB discharge allows sawtooth-induced heat pulse analysis to be performed. This analysis indicates that there is an abrupt radial discontinuity in the heat pulse time to peak profile when an ITB is present. Furthermore, this discontinuity appears to move into the core plasma from the edge region in about 0.2 s, several confinement times. The deduced thermal diffusivity, χ[sup hp], indicates that a barrier exists in the electron thermal transport, the barrier is limited to a narrow radial region, and the transport is unaffected outside this narrow radial extent. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Published
2002

38. Observation of parametric instabilities in the lower-hybrid range of frequencies in the high-density tokamak.

Author

Takase, Y., Porkolab, M., Schuss, J. J., Watterson, R. L., Fiore, C. L., Slusher, R. E., and Surko, C. M.

Subjects
TOKAMAKS, CARBON dioxide lasers, SCATTERING (Physics)
Abstract

Parametric decay processes have been studied using rf probes and CO2 laser scattering during the lower-hybrid wave heating and current drive experiments in the Alcator C tokamak. The most important process is believed to be the nonresonant decay into ion-cyclotron quasimodes and/or that into electron-Landau quasimodes. At lower densities ω0/ωlh(0)>2 [where ω0 is the frequency of the injected pump wave and ωlh(0) is the lower-hybrid frequency evaluated at the plasma center], where efficient current drive and electron heating are obtained, parametric decay is absent or very weak. At higher densities [ω0/ωlh(0) <=2] strong parametric decay is observed which correlates well with ion tail formation near the plasma edge. Above these densities the electron tail is no longer formed and no significant heating or current drive have been obtained. Parametric decay may be responsible, at least partially, for loss of wave power near the plasma periphery. [ABSTRACT FROM AUTHOR]

Published
1985
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39. Wave-Particle Studies in the Ion Cyclotron and Lower Hybrid Ranges of Frequencies in Alcator C-Mod

Author

Bonoli, P. T., Parker, R., Wukitch, S. J., Lin, Y., Porkolab, M., Wright, J. C., Edlund, E., Graves, T., Lin, L., Liptac, J., Parisot, A., Schmidt, A. E., Tang, V., Beck, W., Childs, R., Grimes, M., Gwinn, D., Johnson, D., Irby, J., Kanojia, A., Koert, P., Marazita, S., Marmar, E., Terry, D., Vieira, R., Wallace, G., Zaks, J., Bernabei, S., Brunkhorse, C., Ellis, R., Fredd, E., Greenough, N., Hosea, J., Kung, C. C., Loesser, G. D., Rushinski, J., Schilling, G., Phillips, C. K., Wilson, J. R., Harvey, R. W., Fiore, C. L., Granetz, R., Greenwald, M., Hubbard, A. E., Hutchinson, I. H., Labombard, B., Lipschultz, B., Rice, J., Snipes, J. A., Terry, J., and Wolfe, S. M.

Abstract

AbstractThis paper reviews the physics and technology of wave-particle-interaction experiments in the ion cyclotron range of frequencies (ICRF) and the lower hybrid (LH) range of frequencies (LHRF) on the Alcator C-Mod tokamak. Operation of fixed frequency (80 MHz) and tunable (40- to 80-MHz) ICRF transmitters and the associated transmission system is described. Key fabrication issues that were solved in order to operate a four-strap ICRF antenna in the compact environment of C-Mod are discussed in some detail. ICRF heating experiments utilizing the hydrogen (H) and helium-3 (3He) minority heating schemes are described, and data are presented demonstrating an overall heating efficiency of 70 to 90% for the (H) minority scheme and somewhat lower efficiency for (3He) minority heating. Mode conversion electron heating experiments in D(3He), D(H), and H(3He) discharges are also reported as well as simulations of these experiments using an advanced ICRF full-wave solver. Measurements of mode-converted ion cyclotron waves and ion Bernstein waves using a phase contrast imaging diagnostic are presented and compared with the predictions of a synthetic diagnostic code that utilizes wave electric fields from a full-wave solver. The physics basis of the LH current profile control program on Alcator C-Mod is also presented. Computer simulations using a two-dimensional (velocity space) Fokker Planck solver indicate that ~200 kA of LH current can be driven in low-density H-mode discharges on C-Mod with ~3 MW of LHRF power. It is shown that this off-axis LH current drive can be used to create discharges with nonmonotonic profiles of the current density and reversed shear. An advanced tokamak operating regime near the ideal no-wall β limit is described for C-Mod, where ~70% of the current is driven through the bootstrap effect. The LH power is coupled to C-Mod through a waveguide launcher consisting of four rows (vertically) with 24 guides per row (toroidally). A detailed description of the LH launcher fabrication is given in this paper along with initial operation results.

Published
2007
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40. Wave-particle studies in the ion cyclotron and lower hybrid ranges of frequencies in alcator C-Mod

Author

Bonoli, P. T., Parker, R., Wukitch, S. J., Lin, Y., Porkolab, M., Wright, J. C., Edlund, E., Graves, T., Lin, L., Liptac, J., Parisot, A., Schmidt, A. E., Tang, V., Beck, W., Childs, R., Grimes, M., Gwinn, D., Johnson, D., Irby, J., Kanojia, A., Koert, P., Marazita, S., Marmar, E., Terry, D., Vieira, R., Wallace, G., Zaks, J., Bernabei, S., Brunkhorse, C., Ellis, R., Fredd, E., Greenough, N., Hosea, J., Kung, C. C., Loesser, G. D., Rushinski, J., Schilling, G., Phillips, C. K., Wilson, J. R., Harvey, R. W., Fiore, C. L., Granetz, R., Martin Greenwald, Hubbard, A. E., Hutchinson, I. H., Labombard, B., Lipschultz, B., Rice, J., Snipes, J. A., Terry, J., and Wolfe, S. M.

41. Observations of core toroidal rotation reversals in Alcator C-Mod ohmic L-mode plasmas

Author

Rice, J. E., Duval, B. P., Reinke, M. L., Podpaly, Y. A., Bortolon, A., Churchill, R. M., Cziegler, I., Diamond, P. H., Dominguez, A., Ennever, P. C., Fiore, C. L., Granetz, R. S., Greenwald, M. J., Hubbard, A. E., Hughes, J. W., Irby, J. H., Ma, Y., Marmar, E. S., McDermott, R. M., Porkolab, M., Tsujii, N., and Wolfe, S. M.

Subjects
Turbulence, Physics::Plasma Physics, Transport, Shear, No Momentum Input, Tokamaks
Abstract

Direction reversals of intrinsic toroidal rotation have been observed in Alcator C-Mod ohmic L-mode plasmas following modest electron density or toroidal magnetic field ramps. The reversal process occurs in the plasma interior, inside of the q = 3/2 surface. For low density plasmas, the rotation is in the co-current direction, and can reverse to the counter-current direction following an increase in the electron density above a certain threshold. Reversals from the co- to counter-current direction are correlated with a sharp decrease in density fluctuations with k(R) >= 2 cm(-1) and with frequencies above 70 kHz. The density at which the rotation reverses increases linearly with plasma current, and decreases with increasing magnetic field. There is a strong correlation between the reversal density and the density at which the global ohmic L-mode energy confinement changes from the linear to the saturated regime.

46. Double transport barrier plasmas in Alcator C-Mod.

Author

Rice, J. E., Bonoli, P. T., Marmar, E. S., Wukitch, S. J., Boivin, R. L., Fiore, C. L., Granetz, R. S., Greenwald, M. J., Hubbard, A. E., Hughes, J. W., Hutchinson, I. H., Irby, J. H., Lin, Y., Mossessian, D., Porkolab, M., Schilling, G., Snipes, J. A., and Wolfe, S. M.

Published
2002
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48. H mode confinement in Alcator C-Mod.

Author

Greenwald, M., Boivin, R. L., Bombarda, F., Bonoli, P. T., Fiore, C. L., Garnier, D., Goetz, J. A., Golovato, S. N., Graf, M. A., Granetz, R. S., Horne, S., Hubbard, A., Hutchinson, I. H., Irby, J. H., LaBombard, B., Lipschultz, B., Marmar, E. S., May, M. J., McCracken, G. M., and O'Shea, P.

Published
1997
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