Nonlinear MHD simulation of DC helicity injection in spherical tokamaks
Author: Adam B Bayliss
Requested Type: Poster Only
Submitted: 2006-12-18 15:29:56
Co-authors: C.R. Sovinec, N.W. Eidietis
Contact Info:
University of Wisconsin - Madison
1500 Engineering Dr
Madison, WI 53706
United States
Abstract Text:
Natural elongation and small aspect ratio contribute to the enhanced confinement of the spherical tokamak (ST) over the conventional tokamak configuration. However, due to its small central column, the effectiveness of Ohmic drive in an ST is limited hence a noninductive means of forming plasma is beneficial. DC helicity injection has been successfully employed to produce a tokamak-like plasma with either a poloidal-gap voltage known as coaxial helicity injection [HIT-II, NSTX] or a biased cathode gun configuration [CDX, PEGASUS]. Both configurations are studied in a 3D nonlinear MHD computation using the NIMROD code [Sovinec et. al. JCP 195, 355 (2004)]. Our studies of the gun-driven discharge aim to simulate the formation, merger, and relaxation of the current filaments to the tokamak-like plasma. In coaxial helicity injection the numerical studies will follow the "bubble-burst" formation and subsequent relaxation through nonlinear MHD processes. Over the lifetime of the helically-driven experimental shot, the extent to which the merged plasma exhibits amplication of poloidal flux reported in PEGASUS, HIT-II, and NSTX will be explored along with the application of Ohmic drive to the startup plasma.
Characterization: E10
Comments:
Please place with other PSI-center posters in this session
