Aligning the Thompson Scattering and Charge Exchange Recombination Diagnostics Using Neutral Beam Emission at DIII-D

This work addresses discrepancies in the alignment of the H-mode pedestal profiles of the electron and ion properties as measured by the Thompson Scattering and the Charge Exchange Recombination Spectroscopy (CER) diagnostics on DIII-D plasmas. While alignment of these profiles is key for accurate studies of pedestal physics, misalignments can occur due to differences in the poloidal and toroidal locations of the measurements and departures from axisymmetric magnetic fields. Emission from neutral beam particles due to impact excitations is measured by the Main Ion CER (MICER) diagnostic and is used to infer electron density at the same locations as CER measurements. This measurement is compared with the electron density measured by Thompson Scattering which then enables alignment of ion and electron profiles. FIDASIM simulations are used to infer electron densities and assess various effects on the beam emission such as neutral velocities and the finite excited state lifetime. This analysis is performed on historic DIII-D shots as well as shots from the 2022 experimental campaign.



This work was supported in part by the U.S. DOE under the Science Undergraduate Laboratory Internships (SULI) Program at General Atomics, and under DE-FC02-04ER54698 and DE-AC02-09CH11466