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Two-fluid simulations of merging-compression start-up in the Mega-Amp Spherical Tokamak

Author: Adam J. Stanier
Requested Type: Consider for Invited
Submitted: 2012-12-06 11:23:21

Co-authors: P.K.Browning, M.Gordovskyy, K.McClements, M.Gryaznevich, V.S.Lukin

Contact Info:
University of Manchester
JBCA, Alan Turing Building, Ox
Manchester, Lancashire   1234
UK

Abstract Text:
One attractive option for the design of a future Spherical Tokamak (ST) Power Plant involves removal of the central solenoid. Towards this goal, a series of start-up experiments have been performed on the Mega Amp Spherical Tokamak (MAST, Culham UK) to obtain a high beta ST plasma without using the current drive of the central solenoid. One plausible start-up method is the merging-compression technique, in which two plasma tori with parallel currents are produced around poloidal field coils. These tori are attracted to each other and merge at the mid-plane of the vessel through magnetic reconnection to form ST configurations with plasma currents of around 0.5 MA. This reconnection process leads to extremely rapid plasma heating, with temperatures rising from a few eV to more than 1 keV on millisecond timescales.

We will show the results of two-dimensional fluid simulations of the merging process, with parameters approximating those of the MAST device. These simulations were performed using the HiFi framework (eg. Lukin and Linton 2011) in both cartesian and cylindrical geometry. We will discuss two-fluid effects as well as the effects of the tight aspect ratio toroidal geometry on the merging process. We will compare our results with experimental data from MAST, and discuss the applicability of our results to other ST merging experiments (eg. TS-3/4 and UTST, University of
Tokyo).

This work was funded by STFC, the US DoE Experimental Plasma Research program, the RCUK Energy Programme under grant EP/I501045 and by the European Communities under the Contract of Association between EURATOM and CCFE. The views and opinions expressed herein do not necessarily reflect those of the European Commission.

[1] Lukin VS and Linton MG, Nonlinear Processes in Geophysics 18, 871 (2011)

Characterization: 1.2,4.0

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