Properties and the influences on plasma performance for the film produced by radio frequency boronization

Citation
J. Li et al., Properties and the influences on plasma performance for the film produced by radio frequency boronization, J VAC SCI A, 18(6), 2000, pp. 2835-2842
Citations number
15
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science","Material Science & Engineering
Journal title
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS
ISSN journal
0734-2101 → ACNP
Volume
18
Issue
6
Year of publication
2000
Pages
2835 - 2842
Database
ISI
SICI code
0734-2101(200011/12)18:6<2835:PATIOP>2.0.ZU;2-Y
Abstract
A new boronization technique focusing on the needs of the future large supe rconducting device has been developed in HT-7 tokamak. The first try on a t okamak gave very promising results. A fine homogeneous and hard a-B/C:H fil m was produced by a pulse ion cyclotron resonance frequency plasma. The fil m shows high adhesion, high thickness and longer lifetime. The ratio of B/C is about 3 up to a depth of 280 nm. X-ray photoelectron spectroscopy analy sis shows that the B-B, B-C, C-C, C-O, and B-O bonds were formed during the boronization. The oxygen content in the film increases from 15% to 25% aft er 250 serious discharges, which demonstrated the strong oxygen gettering b y the film. Good uniformity of the film in both toroidal and poloidal direc tions has been obtained by using long antenna on the high field side. The r ecycling of hydrogen was easily controlled by using helium rf discharge aft er boronization, and very strong wall pumping was observed. Plasma performa nce was significantly improved after boronization. A higher density limit a nd wider operation space were obtained. The strong hard x ray accompanied b y high power lower hybrid current drive was suppressed dramatically. This g ives direct evidence that the thin boron film serves as a protecting layer against the energetic particles, which is very important for future long-pu lse-length discharge. This new technique has been proved to be very effecti ve for conditioning future large magnetic fusion devices. (C) 2000 American Vacuum Society. [S0734-2101(00)01206-9].