Neoclassical transport in the CHS device and its outlook for improvement

Abstract

The 1/ν neoclassical transport is computed for the standard, the drift-orbitoptimized and the quasi-axisymmetric versions of CHS. For the computations, a new method is used which is based on the integration along magnetic field lines. The calculations show the advantage of the quasi-axisymmetric CHS configuration over the standard configuration resulting in a reduced 1/ν transport. It is shown that also for the drift-orbit-optimized configuration the 1/ν transport is reduced; however, by a smaller amount than for the quasiaxisymmetric configuration.

Effective ripple in the CHS-qa configuration

“…The corresponding results for 3/2 eff are shown in figure 4, curve 1 for the case without perturbation. These results are not worse than the corresponding results obtained earlier in [8] for the preceding CHS-qa version 2w39. However, the aspect ratio for 2b32 (3.2) is smaller than the one for 2w39 (3.9).…”

“…The latter harmonics are of essentially smaller amplitudes in comparison with the quasi-symmetric ones. In section 4.3, distributions of B on magnetic surfaces are considered (see figures [6][7][8]. Note that in magnetic coordinates the ripple from the discrete character of modular coils is not considered; however, this ripple is taken into account for real-space calculations in the next subsection.…”

“…Here, the v an quantity is studied for a number of magnetic surfaces of the 2b32 configuration. The analogous study for CHS has already been carried out in [8]. Also for v an computations, a method based on integration along magnetic field lines [11,24] is used.…”

Configuration characteristics of the Chinese First Quasi-axisymmetric Stellarator

“…mirror ripples in figure 5(c) do not significantly give rise to the increase of neoclassical transport. This code is also used to evaluate neoclassical transport properties in LHD, CHSqa, W7-x et al [43][44][45] and optimization of stellarotors [15]. Generally, in comparison with quasi-isodynamic and quasihelical configurations, the neoclassical transport in QAs is lower when other device parameters are similar.…”

Quasi-Symmetry in Stellarator Research. 5. Status of Physics Design of Quasi-Axisymmetric Stellarators. 5.2. Physics and Engineering Design of CHS-qa.

“…5.1.3). Figure 5 shows the effective ripples of 2w39 configuration as a function of minor radius [14]. It also shows the values for two configurations (standard and inward shifted) of CHS as a reference.…”