Demonstration of a two-dimensional divertor Thomson scattering system on DIII-D

Paul J Schroeder; Fenton Glass; Thomas O'Gorman; Thomas N Carlstrom; Adam G McLean; Matthias Watkins; Doug A Taussig; Rejean L Boivin

doi:10.1063/5.0173911

Demonstration of a two-dimensional divertor Thomson scattering system on DIII-D

Rev Sci Instrum. 2023 Dec 1;94(12):123504. doi: 10.1063/5.0173911.

Authors

Paul J Schroeder¹, Fenton Glass¹, Thomas O'Gorman², Thomas N Carlstrom¹, Adam G McLean³, Matthias Watkins¹, Doug A Taussig¹, Rejean L Boivin¹

Affiliations

¹ General Atomics, P.O. Box 85608, San Diego, California 92186-5608, USA.
² DT Fusion Consulting, Kilcarroon, Clogheen, Cahir, Tipperary E21 DE93, Ireland.
³ Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94550, USA.

PMID: 38085054
DOI: 10.1063/5.0173911

Abstract

Recent upgrades providing two-dimensional divertor Thomson scattering (DTS-2D) measurements of Te and ne during a DIII-D plasma shot and a thorough description of system components and their functionality are presented. This system expands the capabilities of the existing single divertor Floor measurement location by introducing seven additional laser beam path options in the poloidal plane, spanning major radii from 1.062 to 1.335 m. The system redirects ∼1 J, 50 Hz Nd:YAG laser pulses to the new beam paths within 20 ms, stepping through each path on the divertor Floor every 200 ms during a plasma shot. The laser is redirected using an ex-vessel, fast-steering mirror to one of eight in-vessel beam paths oriented underneath the vessel tiles. Up to eleven measurement positions per beam path, from -1.35 to -1.13 m below the machine midplane, are available by dynamically refocusing the ex-vessel collection fiber array using a high-speed linear stage. Current measurement positions above the divertor Shelf are retained via a hole in the fixed, in-vessel mirror, allowing laser pass through.