Investigation of lower hybrid wave polarization in WEST

Theoretical studies identified the potential for $k_\perp$ rotation to impact lower hybrid (LH) wave propagation and absorption, and recent experimental analysis showed consistency between experimental LH current drive observations and modeling including $k_\perp$ rotation for Alcator C-Mod. Investigations on C-Mod indicate that rotation of $k_\perp$ may be due to scattering of the LH waves from density fluctuations. Conventional ray-tracing of LH waves assumes $k_\perp$ to be normal to the flux surface at the starting point of the ray. The DSELF diagnostic on WEST measures the LH wave electric field components ($E_R$, $E_Z$, $E_\phi$) near the antenna via dynamic Stark effect spectroscopy, which then constrains the angle of $k_\perp$ rotation used at the launch point of rays in the model ($\sim \arctan(E_Z/E_R)$). This rotation of $k_\perp$ impacts the up/down-shifts of $k_{||}$ as well as the ray trajectory itself, leading to broader or more peaked absorption depending on the direction of rotation. Ray-tracing/Fokker-Planck simulations including $k_\perp$ rotation for WEST are presented in this work and compared with experimental data.