NIMROD Simulations of Low-q Disruptions in the Compact Toroidal Hybrid Device (CTH)
POSTER
Abstract
Nonlinear MHD simulations of low-q disruptions in the CTH are presented. CTH is a current carrying stellarator that is used to study the effects of 3D shaping. The application of 3D shaping stabilizes low-q disruptions in CTH [M. D. Pandya et al., POP 22, 2015]. The amount of 3D shaping is controlled by adjusting the external rotational transform, and it is characterized by the ratio of the external rotational transform to the total transform: $f ={ \iota_{vac}}/{\iota}$. Disruptions are routinely observed during operation with weak shaping ($f<0.05$). The frequency of disruptions decreases with increasing amounts of 3D shaping, and the disruptions are completely suppressed for $f> 0.1$. Nonlinear simulations are performed using the NIMROD code [C.R. Sovinec et al., JCP 195, 2004] to better understand how the shaping suppresses the disruptions. Comparisons of runs with weak ($f=0.04$) and strong ($f=0.10$) shaping are shown.
*This material is based upon work supported by Auburn University and the U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences under Award Numbers DE-FG02-03ER54692 and DE-FG02-00ER54610.