Sensitivity of Synthetic Phase Contrast Imaging Measurements to the Parallel Wavenumber Spectrum of Helicon Waves at DIII-D*

Comprehensive full-wave modeling has been performed in preparation for experiments at the DIII-D tokamak with the goal of validating theoretical predictions for helicon waves [1] via measurements from a phase contrast imaging (PCI) diagnostic [2]. The workflow consists of a 2D, highly-resolved, cold plasma, finite element model covering the plasma edge, and 2D calculations of the plasma core with the All ORders Spectral Algorithm (AORSA) full wave code [2], the state-of-the-art model for predicting power absorption and current drive for helicon waves. To predict PCI measurements the helicon path has to be resolved in 3D, which is achieved by stacking calculations of up to 30 toroidal mode numbers. The helicon path is sensitive to the coupled toroidal mode number spectrum of the antenna, which is an area of active study. Our modeling shows that the PCI measurements will provide an indirect measurement of the antenna spectrum.

[1] B. Van Compernolle et al, Nucl. Fusion 61, 116034 (2021)

[2] M. Porkolab et al, Europhysics Conference Abstracts 45A (2021) P.4.1007

[3] C. Lau et al, Plasma Phys. Control. Fusion 61, 045008 (2019)