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Using Thomson Scattering measurements at multiple poloidal locations to align electron and ion profiles in the DIII-D Pedestal

POSTER

Abstract

Accurate analysis of pedestal physics on the DIII-D tokamak requires spatially aligned measurements of electron and ion temperature and density profiles. Thomson Scattering (TS) and Charge Exchange Recombination Spectroscopy (CER) typically measure at different toroidal and poloidal locations, and alignment using 2D equilibrium reconstructions can introduce millimeter-scale spatial uncertainties in the steep-gradient pedestal region. Such offsets can significantly affect pressure profiles and investigations of pedestal physics. This work uses newly available TS measurements acquired throughout the 2025 campaign taken at the same poloidal location as existing CER chords at the outboard midplane. The midplane TS data provides a spatial reference near the pedestal for aligning tangential TS and CER profiles. This geometry reduces poloidal alignment uncertainties and improves profile accuracy. Alignment is validated by comparing results to prior methods using beam emission from the Main Ion CER system to infer spatial offsets. Additionally, edge temperatures from the aligned TS and CER measurements are compared with 2-point model predictions to assess physical consistency and guide future pedestal transport analysis.

Publication: A. Feyrer, S. R. Haskey, C. Chrystal, C. A. Aidala; Aligning the Thomson scattering and charge exchange recombination diagnostics using neutral beam emission at DIII-D. Rev. Sci. Instrum. 1 April 2024; 95 (4): 043509. https://doi.org/10.1063/5.0189566

Presenters

  • Sophie Hilsabeck

    University of California, Berkeley

Authors

  • Sophie Hilsabeck

    University of California, Berkeley

  • Colin Chrystal

    General Atomics

  • Shaun R Haskey

    Princeton Plasma Physics Laboratory (PPPL)

  • Fenton Glass

    General Atomics