Indexed by:Journal Article

First Author:Wu, Xingwei

Correspondence Author:Wu, XW (reprint author), Dalian Univ Technol, Sch Phys & Opt Engn, Key Lab Mat Modificat Laser Ion & Electron Beams, Chinese Minist Educ, Dalian 116024, Peoples R China.

Co-author:Ding, Hongbin,Wang, Yong,Wang, Zhiwei,Feng, Chunlei,Li, Cong

Date of Publication:2015-09-01

Journal:12th Russia/CIS/Baltic/Japan Symposium on Ferroelectricity (RCBJSF) and 9th International Conference on Functional Materials and Nanotechnologies (FM&NT)

Included Journals:Scopus、CPCI-S、EI、SCIE

Document Type:J

Volume:90

Issue:9

ISSN:0031-8949

Key Words:inverse photon efficiency; optical emission spectroscopy; cavity ring-down spectroscopy

Summary:The hydrocarbon impurities formation is inevitable due to wall erosion in a long pulse high performance scenario with carbon-based plasma facing materials in fusion devices. The standard procedure to determine the chemical erosion yield in situ is by means of inverse photon efficiency D/XB. In this work, the conversion factor between CH4 flux and photon flux of CH A -> X transition (effective inverse photon efficiency PE-1) was measured directly using a cascaded arc plasma simulator with argon/methane. This study shows that the measured PE-1 is different from the calculated D/XB. We compared the photon flux measured by optical emission spectroscopy (OES) and calculated by electron impact excitation of CH(X) which was diagnosed by cavity ring-down spectroscopy (CRDS). It seems that charge exchange and dissociative recombination processes are the main channels of CH(A) production and removal which lead to the inconsistency of PE-1 and D/XB at lower temperature. Meanwhile, the fraction of excited CH(A) produced by dissociative recombination processes was investigated, and we found it increased with T-e in the range from 4% to 13% at T-e < 1 eV. Our work suggests that the CH spectroscopy should be reinterpreted and the conversion factor should have a new definition instead of D/XB since the electron impact excitation is not the only channel of CH(A) production. These results have an effect on evaluating the yield of chemical erosion in divertor of fusion device.