Publication Date:
2016-07-28
Description:
A design to extend the unique divertor Thomson scattering system on DIII-D to allow measurements of electron temperature and density in high triangularity plasmas is presented. Access to this region is selectable on a shot-by-shot basis by redirecting the laser beam of the existing divertor Thomson system inboard — beneath the lower floor using a moveable, high-damage threshold, in-vacuum mirror — and then redirecting again vertically. The currently measured divertor region remains available with this mirror retracted. Scattered light is collected from viewchords near the divertor floor using in-vacuum, high temperature optical elements and relayed through the port window, before being coupled into optical fiber bundles. At higher elevations from the floor, measurements are made by dynamically re-focusing the existing divertor system collection optics. Nd:YAG laser timing, analysis of the scattered light spectrum via polychromators, data acquisition, and calibration are all handled by existing systems or methods of the current multi-pulse Thomson scattering system. Existing filtered polychromators with 7 spectral channels are employed to provide maximum measurement breadth ( T e in the range of 0.5 eV–2 keV, n e in the range of 5 × 10 18 –1 × 10 21 m 3 ) for both low T e in detachment and high T e measurement up beyond the separatrix.
Print ISSN:
0034-6748
Electronic ISSN:
1089-7623
Topics:
Electrical Engineering, Measurement and Control Technology
,
Physics
