UWAVS first mirror plasma cleaning technology using 30–60 MHz RF discharges
other
The PBS 55 GA Upper Wide Angle Viewing System (UWAVS) provides real-time, simultaneous visible and IR images of the ITER diverter region via optical systems located in the upper port plugs of the ITER vacuum vessel. Optical performance is expected to deteriorate due to mirror contamination from plasma operations and imaging and temperature measurements are expected to reach unacceptable error levels. In the UWAVS design, a first mirror (FM) cleaning system will be implemented to maintain / restore optical performance General Atomics (GA)leads the design of the UWAVS for ITER and has teamed with the Netherlands Organization for Applied Scientific Research (TNO)and Lawrence Livermore National Laboratories (LLNL)for the effort. This work was performed under the guidance of Princeton Plasma Physics Laboratory (PPPL). In ITER, first mirrors for UWAVS are expected to experience contamination with Be, and W. Small levels of contamination (in the order of 10 nm) can significantly degrade optical performance of the mirror. The preferred cleaning technique is radio-frequency (RF) plasma cleaning, which utilizes ion fluxes in gas discharge plasmas. A laboratory RF plasma setup in representative UWAVS geometry was created. In the present report, feasibility of the cleaning technology is discussed.
TNO Identifier
961359
ISSN
09203796
Publisher
TNO
Source title
29Th Symposium on Fusion Technology, SOFT 2016, 5-9 September 2016, Prague, Czech Republic
Collation
1 p.
Place of publication
Delft, The Netherlands
Files
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