Stability and Transport in Compact Quasi-Axisymmetric Stellarators
Authors: M.H. Redi, W.A. Cooper, A. Diallo, G-Y. Fu, C. Nührenberg, A.H. Reiman, R.B. White, M.C. Zarnstorff, and the NCSX Team
Date of PPPL Report: July 2000
Presented at: the 27th European Physical Society's (EPS) Conference on Controlled Fusion and Plasma Physics, June 12-16, 2000, Budapest, Hungary. A "Provisional Collection of Submitted Contributions" can be found at the following web site: http://www.eps2000.kfki.hu (active as of August 16, 2000). Papers are in PDF format.
The potential performance and flexibility of a compact, quasi-axisymmetric (QAS) stellarator design [1], has been addressed by studying the effects of varied pressure and rotational transform profiles on the global, ideal magnetohydrodynamic (MHD) stability and the energetic particle transport [2]. The CAS3D [3] and TERPSICHORE [4] code packages were used in the MHD studies while the ORBITMN/ORBIT3D [5,7,2] code package was used for the transport simulations of the three field period QAS.
To assess robust performance in a medium-size experiment, the VMEC code [6] was used to obtain magnetic flux surfaces for 30 equilibria near the design point [1], while keeping the boundary shape and the average beta fixed at 3.8%. The plasma equilibria obtained were designated P0X/I0Y as follows: P00/I00 was the baseline configuration. P01, P02 and P03 were defined so that P01 was similar to P00, P02 was more peaked than P01, while P03 was broader than P01. P04 was a very broad, parabolic pressure profile and P05 was the pressure profile used in helias reactor studies based on the W7-X design. The iota profiles were chosen as follows: I01 was linear, maintaining iota(0) and iota(a) the same as in I00. I02 and I03 were based on I01 and also kept iota(0) and iota(a) as in the baseline case, but with edge shear increased by a factor of 1.5 and 2. I04 was a linear iota profile with iota(0) as for the other profiles, but iota(a) higher than 0.5, similar to I01. The pressure and iota profiles are shown in Ref. [2].