Repetitive cleaning of a stainless steel first mirror using radio frequency plasma

Jiao PENG (彭姣); Rong YAN (鄢容); Rui DING (丁锐); Junling CHEN (陈俊凌); Dahuan ZHU (朱大焕); Zengming ZHANG (张增明)

doi:10.1088/2058-6272/aa7629

Plasma Science and Technology > 2017 > 19(10): 105601. > DOI: 10.1088/2058-6272/aa7629

Jiao PENG (彭姣), Rong YAN (鄢容), Rui DING (丁锐), Junling CHEN (陈俊凌), Dahuan ZHU (朱大焕), Zengming ZHANG (张增明). Repetitive cleaning of a stainless steel first mirror using radio frequency plasma[J]. Plasma Science and Technology, 2017, 19(10): 105601. DOI: 10.1088/2058-6272/aa7629

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Repetitive cleaning of a stainless steel first mirror using radio frequency plasma

1 Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, People’s Republic of China 2 University of Science and Technology of China, Hefei 230026, People’s Republic of China 3 The Center of Physical Experiments, University of Science and Technology of China, Hefei 230026, People’s Republic of China

Funds: This work was supported by National Magnetic Confinement Fusion Science Program of China under Contract Nos. 2013GB105003 and 2013GB107004, National Natural Science Foundation of China under Contract Nos. 11475218, 11505231, 11375010 and 11675218.

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Received Date: November 29, 2016

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Abstract

Abstract

First mirrors (FMs) are crucial components of optical diagnostic systems in present-day tokamaks and future fusion reactors. Their lifetimes should be extremely limited due to their proximity to burning plasma, greatly influencing the safe operation of corresponding diagnostics. Repetitive cleaning is expected to provide a solution to the frequent replacement of contaminated FMs, thus prolonging their lifetimes. Three repetitive cleaning cycles using radio frequency plasma were applied to stainless steel (SS) FM samples, to evaluate the change of the mirrors’ optical properties and morphology during each cycle. Amorphous carbon films were deposited on mirror surfaces under identical conditions in three cycles. In three cycles with identical cleaning parameters, the total reflectivity was restored at up to 95%. Nevertheless, with successive cleaning cycles, the FM surfaces gradually appeared to roughen due to damage to the grain boundaries. Correspondingly, the diffuse reflectivity increased from a few percent to 20% and 27% after the second and third cycles. After optimizing the cleaning parameters of the second and third cycles, the roughness showed a significant decrease, and simultaneously the increase of diffuse reflectivity was remarkably improved.
- first mirror,
- stainless steel,
- lifetime,
- repetitive cleaning,
- reflectivity

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References (20)

References

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