Anomalous Transport Modeling of HSX Plasmas
Author: Walter A Guttenfelder
Requested Type: Consider for Invited
Submitted: 2006-12-20 13:51:15
Co-authors: D.T. Anderson, F.S.B. Anderson, J.M. Canik, K.M. Likin, J.N. Talmadge
Contact Info:
HSX Plasma Laboratory, UW-Madison
1415 Engineering Dr.
Madison, WI 53706
USA
Abstract Text:
The improvement of core transport in the quasi-helically symmetric (QHS) configuration of HSX as compared to a configuration with the symmetry intentionally broken (Mirror) has recently been demonstrated. This is largely due to the improvement of neoclassical transport via quasi-symmetry. However, under present operating conditions, it is unclear if there are significant differences in the anomalously large edge transport. Langmuir probe measurements have demonstrated the similarity of the edge turbulence characteristics (fluctuation levels and correlation lengths) in both symmetric and non-symmetric configurations with the same heating power. Furthermore, measured density-potential cross phases and inferred growth rate spectra (using bispectral analysis) are found to be similar to trapped electron mode (TEM) linear stability predictions. To test whether current models can reproduce the anomalously large transport in HSX, the theory-based Weiland ITG/TEM anomalous transport model [1] is applied to the ECRH plasmas in HSX. Although this axisymmetric model cannot treat 3D geometry effects, recent 3D gyrokinetic linear stability calculations [2] have demonstrated the impact of the local geometry on ITG/CTEM linear growth rates in stellarators. As an approximation to the results of [2], the largest value of local bad curvature in the low field/ballooning region of HSX is used in the evaluation of [1], with no free fit parameters. This approximation provides a reasonable prediction of linear growth rates compared to those from the 3D gyrokinetic calculation. The model input particle and ECRH power source rates are determined from 3D DEGAS and ray tracing calculations, respectively. The predicted density and temperature profiles are in reasonable quantitative agreement with a number of experimental profiles in the quasi-helically symmetric configuration. The model also predicts profile changes similar to experiment in the non-symmetric Mirror configuration. This work is supported by DOE grant number DE-FG02-93ER54222.
[1] H. Nordman et al., Nucl. Fusion 30, 983 (1990)
[2] G. Rewoldt et al., Phys. Plasmas 12, 102512 (2005)
Characterization: E1
Comments:
Please group our two abstracts together:
[1] John Canik
[2] Walter Guttenfelder
