Overview of MAST results

Autor: M.R. O'Brien, K. Imada, I. Klimek, S. Saarelma, A.J. Thornton, Matthew Carr, John Caughman, A. R. Field, L. V. Wyk, N. Thomas-Davies, M. Cox, D. Muir, Stanislas Pamela, E.D. Fredrickson, David Dickinson, James W. Bradley, J. R. Harrison, S. Lisgo, Vladimir Shevchenko, J. Chorley, B. Huang, R. O. Dendy, A. W. Morris, G. Naylor, Stanley Kaye, M. Kocan, M. Romanelli, J. Brunner, K. G. McClements, T.S. Bigelow, Alexander Schekochihin, Simon Freethy, Clive Michael, C. M. Roach, N. J. Conway, W. A. Peebles, E. Havlickova, Bogdan Hnat, S. S. Henderson, William Dorland, Takuma Yamada, Volker Naulin, C. Gurl, M. Peng, R. V. Perez, Benjamin Daniel Dudson, J. Storrs, S. Zoletnik, Mario Podesta, V. A. Rozhansky, P. Cahyna, W. Guttenfelder, C. Ham, Gen Motojima, Yuichi Takase, S. A. Silburn, G. Taylor, R. J. Akers, H. Leggate, Hajime Tanaka, K. J. Gibson, Bruce Lipschultz, N. Ben Ayed, O. M. Jones, J. Horacek, Romualdo Martín, Neal Crocker, A. V. Danilov, R. Scannell, D. L. Keeling, Eric Nardon, C. D. Challis, Matthew Lilley, S. D. Pinches, M. Price, L. Appel, John Howard, Daniel Thomas, J. Hawke, A. Kirk, Otto Asunta, T. O'Gorman, S. Allan, Brendan M. Crowley, Matthew Reinke, S. Sangaroon, H. R. Wilson, G. P. Maddison, J. Milnes, M. Valovic, H. F. Meyer, Ivan Lupelli, Ray M. Sharples, T. C. Hender, Marco Cecconello, Yang Liu, L. Piron, D. Harting, S. J. Diem, Jonathan Graves, H. J. C. Oliver, Greg Colyer, J. C. Hillesheim, Nick Walkden, J. Simpson, J. Adamek, S. E. Sharapov, G. Fishpool, A. Patel, Sandra C. Chapman, M. Turnyanskiy, Anders Nielsen, S. Elmore, N. C. Hawkes, D. S. Darrow, B. Lomanowski, L. Garzotti, Edmund Highcock, D. Dunai, R. G. L. Vann, Luke Easy, Young-chul Ghim, Fulvio Militello, Y. Ren, A. N. Saveliev, David Taylor, W. Boeglin, J. R. Robinson, L. Pangione, Yasushi Ono, I. T. Chapman, Michael Barnes, W. A. Cooper, B. Lloyd, Felix I. Parra, J. Holgate, Michael F. J. Fox, A. Meakins, Ahmed Diallo, Ben F. McMillan, G. Cunningham, Hiroshi Tanabe, G.J. McArdle, J. Mailloux
Rok vydání: 2015
Předmět:
Zdroj: Nuclear Fusion, 55, 104008
Nuclear Fusion
ISSN: 0029-5515
0741-3335
0010-4655
0093-3813
Popis: The Mega Ampère Spherical Tokamak (MAST) programme is strongly focused on addressing key physics issues in preparation for operation of ITER as well as providing solutions for DEMO design choices. In this regard, MAST has provided key results in understanding and optimizing H-mode confinement, operating with smaller edge localized modes (ELMs), predicting and handling plasma exhaust and tailoring auxiliary current drive. In all cases, the high-resolution diagnostic capability on MAST is complemented by sophisticated numerical modelling to facilitate a deeper understanding. Mitigation of ELMs with resonant magnetic perturbations (RMPs) with toroidal mode number n RMP = 2, 3, 4, 6 has been demonstrated: at high and low collisionality; for the first ELM following the transition to high confinement operation; during the current ramp-up; and with rotating n RMP = 3 RMPs. n RMP = 4, 6 fields cause less rotation braking whilst the power to access H-mode is less with n RMP = 4 than n RMP = 3, 6. Refuelling with gas or pellets gives plasmas with mitigated ELMs and reduced peak heat flux at the same time as achieving good confinement. A synergy exists between pellet fuelling and RMPs, since mitigated ELMs remove fewer particles. Inter-ELM instabilities observed with Doppler backscattering are consistent with gyrokinetic simulations of micro-tearing modes in the pedestal. Meanwhile, ELM precursors have been strikingly observed with beam emission spectroscopy (BES) measurements. A scan in beta at the L–H transition shows that pedestal height scales strongly with core pressure. Gyro-Bohm normalized turbulent ion heat flux (as estimated from the BES data) is observed to decrease with increasing tilt of the turbulent eddies. Fast ion redistribution by energetic particle modes depends on density, and access to a quiescent domain with ‘classical’ fast ion transport is found above a critical density. Highly efficient electron Bernstein wave current drive (1 A W−1) has been achieved in solenoid-free start-up. A new proton detector has characterized escaping fusion products. Langmuir probes and a high-speed camera suggest filaments play a role in particle transport in the private flux region whilst coherence imaging has measured scrape-off layer (SOL) flows. BOUT++ simulations show that fluxes due to filaments are strongly dependent on resistivity and magnetic geometry of the SOL, with higher radial fluxes at higher resistivity. Finally, MAST Upgrade is due to begin operation in 2016 to support ITER preparation and importantly to operate with a Super-X divertor to test extended leg concepts for particle and power exhaust.
Databáze: OpenAIRE
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