2003 Fiscal Year Final Research Report Summary
Measurements of reduction cross sections of metal-oxides by atomic hydrogen
| Project/Area Number |
14580529
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Nuclear fusion studies
|
|---|
| Research Institution | National Institute for Fusion Science |
|---|
Principal Investigator |
SAGARA Akio National Institute for Fusion Science, LHD project, Associate Professor, 大型ヘリカル研究部, 助教授 (20187058)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
SUZUKI Akihiro The University of Tokyo, Faculty of Engineering, Associate Professor, 工学部, 助教授 (80332188)
SUZUKI Hajime Chubu University, College of Engineering, Associate Professor, 工学部, 助教授 (20260044)
KUBOTA Yusuke National Institute for Fusion Science, LHD project, Associate Professor, 大型ヘリカル研究部, 助教授 (50023726)
|
|---|
| Project Period (FY) |
2002 – 2003
|
| Keywords | atomic hydrogen / reduction reaction / plasma-wall interaction / electron cyclotron resonance / dissociated hydrogen / micro-wave / discharge cleaning / chromium oxide |
|---|
| Research Abstract |
The purpose of this research is to measure the reduction cross sections of metal oxides due to irradiation of atomic hydrogen. The results obtained in this study contribute to quantitative prediction and control of behaviors of oxygen impurities due to plasma-wall interactions.
This research has been accomplished with two steps. The first step is to develop a small size atomic-hydrogen source using electron-cyclotron resonance (ECR) plasma. The point in this stage is to newly develop a localized magnetic field for ECR, because the Auger surface analyzer (AES) used in this study is very sensitive to magnetization of the AES material itself. For this purpose, instead of large solenoid coils, a small-size permanent-magnet system has been newly developed, in which many requirements such as UHV and cooling are also optimized.
The second step is to evaluate the flux φ_H of atomic hydrogen by measuring plasma temperature and density. Then, using this atomic hydrogen flux, the time constant τ_d of metal-oxide reduction is measured with AES. From this time constant, the reduction cross section is evaluated as σ_d = 1/(τ_d φ_H).
Experimental results have shown that, in case of Ni, adsorbed oxygen is clearly reduced under the irradiation of atomic hydrogen. The reduction cross section σ_d is evaluated to be about 7x10^<-18> cm^2, which is in good agreement with the values so far estimated in discharge cleaning experiments for plasma-wall conditioning. On the other hand, in case of Cr, no clear reduction of oxygen has been observed. This result is not so different as expected from chemical equilibrium of chromium-oxide against atomic hydrogen. Increase of the flux φ_H is the technical main issue to be developed in future. These results have been mainly presented in plasma research conferences.
|
Research Products
(12 results)
