Wide-angle ITER-prototype tangential infrared and visible viewing system for DIII-D

• Published in: Review of scientific instruments 2014-11, Vol.85 (11), p.11D855-11D855
• Main Authors: Lasnier, C J, Allen, S L, Ellis, R E, Fenstermacher, M E, McLean, A G, Meyer, W H, Morris, K, Seppala, L G, Crabtree, K, Van Zeeland, M A
• Format: Article
• Language: English
• Subjects: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
• ISSN: 0034-6748; 1089-7623
• DOI: 10.1063/1.4892897

An imaging system with a wide-angle tangential view of the full poloidal cross-section of the tokamak in simultaneous infrared and visible light has been installed on DIII-D. The optical train includes three polished stainless steel mirrors in vacuum, which view the tokamak through an aperture in the first mirror, similar to the design concept proposed for ITER. A dichroic beam splitter outside the vacuum separates visible and infrared (IR) light. Spatial calibration is accomplished by warping a CAD-rendered image to align with landmarks in a data image. The IR camera provides scrape-off layer heat flux profile deposition features in diverted and inner-wall-limited plasmas, such as heat flux reduction in pumped radiative divertor shots. Demonstration of the system to date includes observation of fast-ion losses to the outer wall during neutral beam injection, and shows reduced peak wall heat loading with disruption mitigation by injection of a massive gas puff.