Contents Return Previous Page Next Page Index


Return To: Session OV2 - Overviews 2 (Monday, 19 October)
Prev Page: Session OV2 - Overviews 2 (Monday, 19 October)
Next Page: (OV2/2) Towards high-power long-pulse operation on Tore Supra

(OV2/1) Overview of Recent Results from the Alcator C-Mod Tokamak

   
E. Marmar , P. Acedo a, O. Batishchev , R. Bengtson b, R. L. Boivin , F. Bombarda c, X. Bonnin b, P. Bonoli , C. Boswell , R. Bravenec b, N. Bretz d, C. Chang n, C. Christensen , G. Cima d, W. Dorland d, J. Drake e, E. Eisner b, G. Esser f, M. Finkenthal g, C. Fiore , K. Fournier h, T. Fredian , R. Gandy i, S. Gangadhara , K. Gentle b, J. Goetz , R. Granetz , M. Greenwald , H. Griem e, G. Hallock , J. Harker b, J. Heard i, J. Hosea d, A. Hubbard , I. Hutchinson , J. Irby , D. Johnson d, J. Ke , J. Kesner , S. Krasheninnikov , B. LaBombard , H. Lamela a, B. LeBlanc d, Y. Lin , B. Lipschultz , S. Lisgo j, R. Maqueda k, M. May g, A. Mazurenko , S. Migliuolo , E. Nelson-Melby , G. Miller , D. Mossessian , R. Nachtrieb , R. Nazikian d, R. Neu l, H. Ohkawa , P. O'Shea , T. S. Pedersen , D. Pappas , C. K. Phillips d, A. Pigarov , C. S. Pitcher , M. Porkolab , J. Ramos , J. Reardon , J. Rice , B. N. Rogers e, J. C. Rost , W. Rowan b, J. Schachter , G. Schilling d, H. Scott h, C. Skinner d, J. A. Snipes , V. Soukhanovskii g, P. Stangeby j, P. Stek , J. Stillerman , Y. Takase , G. Taylor d, J. Terry , T. Tutt , M. Umansky , W. Wampler m, A. Wan h, C. Watts i, L. Weathers , J. Weaver e, B. Welch e, J. R. Wilson d, S. Wolfe , K.-L. Wong d, A. Wootton b, S. Wukitch , G. Wurden k, Y. In , H. Yuh , S. Zweben d
 
MIT Plasma Science and Fusion Center, Cambridge, MA 02139, USA
a Carlos III University, Madrid, Spain
b U. Texas, Austin, TX, USA
c ENEA Frascati, Italy
d Princeton Plasma Physics Lab., Princeton, NJ, USA
e U. Maryland, College Park, MD, USA
f KFA Julich, Germany
g Johns Hopkins U., Baltimore, MD, USA
h Lawrence Livermore National Lab., Livermore, CA, USA
i Auburn U., Auburn, AL, USA
j U. Toronto, Toronto, Ontario, Canada
k Los Alamos National Lab., Los Alamos, NM, USA
l MPIPP, Garching, Germany
m Sandia National Lab., Albuquerque, NM, USA
n Courant Institute of Mathematical Sciences, New York University, New York, NY, USA

Abstract
Recent results from the compact, high field, Alcator C-Mod  tokamak program are summarized. H-mode  threshold studies have demonstrated that the threshold appears to be closely related to local edge plasma parameters: for fixed field and plasma current, $T_e(\psi_{95})$ takes on a density independent value at the transition. The Enhanced D-Alpha H-Mode (EDA) regime has been investigated. EDA is distinct from ELM free H mode, in that there is no accumulation of impurities, and at the same time EDA does not exhibit large discrete ELMs . The energy confinement is degraded by only about 10%, compared to ELM free. Comparisons for EDA with ELMy H-Mode database scalings indicate $\tau{EDA} \sim 1.2 \tau_{ITER97H}$. Strong toroidal rotation is observed in ICRF-only auxiliary heated plasmas; the rotation increases with plasma pressure, and decreases with increasing plasma current. The inferred radial electric field reaches the order of $\rm 30 kV/m$ near the center of the plasma. Through feedback controlled nitrogen impurity puffing , steady state detached EDA H-Modes have been achieved with $Z_{eff} < 1.5$. $\tau_E$ is reduced by about 10% in the detached case, compared to the confinement before the $\rm N_2$ puff begins. The heat load  to the divertor is reduced by a factor of 4. Volume recombination rates are measured in the divertor, using 2-d tomography of Balmer series TV movies. Volume recombination can be a significant contributor to the overall reduction in ion current to the divertor plates which occurs in detachment . Particle balance measurements indicate that the divertor and main chamber plasmas are largely isolated from one another, at least with regard to particle recycling , with most of the main chamber (core plus scrape-off) fueling coming from neutrals  in the main chamber volume. With the addition of Lower Hybrid Current Drive, C-Mod would be an ideal vehicle for investigation of advanced tokamak operation with fully relaxed current profiles. Detailed modeling indicates that discharges approaching the $\beta $ limit ( $\beta_N \sim 3.7$) with > 70% bootstrap fraction should be achievable.

                  

Read the full paper in PDF format.


IAEA 1999