First results from MAST

Sykes, A and Akers, RJ and Appel, LC and Arends, ER and Carolan, PC and Conway, NJ and Counsell, GF and Cunningham, G and Dnestrovskij, A and Dnestrovskij, YN and Field, AR and Fielding, SJ and Gryaznevich, MP and Korsholm, S and Laird, E. A. and Martin, R and Nightingale, MPS and Roach, CM and Tournianski, MR and Walsh, MJ and Warrick, CD and Wilson, HR and You, S (2001) First results from MAST. Nuclear Fusion, 41 (10). pp. 1423-1433. ISSN 0029-5515

Abstract

MAST is one of the new generation of large, purpose-built spherical tokamaks (STs) now becoming operational, designed to investigate the properties of the ST in large, collisionless plasmas. The first six months of MAST operations have been remarkably successful. Operationally, both merging-compression and the more usual solenoid induction schemes have been demonstrated, the former providing over 400 kA of plasma current with no demand on solenoid flux. Good vacuum conditions and operational conditions, particularly after boronization in trimethylated boron, have provided plasma current of over 1 MA with central plasma temperatures (ohmic) of order I keV. The Hugill and Greenwald limits can be exceeded and H mode achieved at modest additional NBI power. Moreover, particle and energy confinement show an immediate increase at the L-H transition, unlike the case of START, where this became apparent only at the highest plasma currents. Halo currents are small, with low toroidal peaking factors, in accordance with theoretical predictions, and there is evidence of a resilience to the major disruption.