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Investigation of ECRF Heating and Wall Conditioning in HT-7 Tokamak: Insights and Procedures

This report outlines the investigation into the applications of Electron Cyclotron Range of Frequencies (ECRF) for plasma heating, non-inductive current drive, and wall conditioning on the HT-7 Tokamak. Key methodologies include optimizing wall conditioning through ECRF and IC-DC processes, analyzing plasma density profiles, and employing diagnostics. Results demonstrate localized plasma conditions favorable for boronization and suggest further optimization parameters for enhanced plasma performance and efficiency in future experiments, highlighting the technique's viability for sustained operation.

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Investigation of ECRF Heating and Wall Conditioning in HT-7 Tokamak: Insights and Procedures

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  1. First EC-DC on HT-7 X. GAO, Y. W. YU, Y. YANG May 1, 2007

  2. Outline • Investigation • Parameters • Procedure • Diagnostics • Prospect

  3. Investigation • ECRF (Electron Cyclotron Range of Frequencies) may be used for heating, non-inductive current drive, start-up and burn-though, plasma control, and wall conditioning. • The reference process for wall conditioning involves … and EC-DC or IC-DC (see below) with toroidal field using D2 and He. －ITER Technical Basis (PDD2-7)

  4. Investigation B∅=B0R0/R ω=neB∅/me Radial plasma density profile, ne ~ zero at R < Rresonance; nearly constant density ~ 1016m-3 at R > Rresonance. ion flux or “plasma loss” is distributed over a very large area of the wall at R > Rresonance. --Alcator C-Mod Mini-Proposal

  5. Investigation • C-Mod: • localize B film growth to • a) produce thicker B films on the outer divertor shelf for a given duration of ECDC • b) avoid B film growth in the antennae. • in-situ tile conditioning and surface heating --Alcator C-Mod Mini-Proposal (2007)

  6. Investigation • TRIAM-1M • the wall conditioned by only ECR-DC is good in both OH and LHCD plasmas. • ECR-DC has no problems with thermal insulation and is suitable for operation in a steady magnetic field. --Wall conditioning using 2.45 GHz ECR-DC on superconducting tokamak TRIAM-1M

  7. Parameters • Parameters (HT-7 Apr. 30, 2007): • Working Gas Species: Helium • Toroidal Field: ~0.09 T(~200A) • Vertical Field: No • Pressure: 1.3E-2 Pa • RF Power: 10 KW, 8 KW • Diagnostics • QMS（王厚银） • OMA（符佳、王光祺）

  8. Procedure（一） • 内真空室用＃1机组分子泵，其他全部关闭 • 设定充气压强1.3E-3 Pa，冲入氦气 • 投入LHW10 KW • 等离子体点亮并持续10分钟

  9. Procedure（二） • 保持其他参数不变，降低LHW功率至8 KW • 等离子体点亮 • 持续9分钟后因LHW电源故障停止

  10. Diagnostics-Video • 等离子体被点亮 • 等离子体位于低场侧 HFS LFS Side view Top view

  11. Diagnostics -QMS 10 KW 8 KW 清洗效果不明显

  12. Diagnostics -QMS 真空室内气体成分前后比较

  13. Diagnostics-OMA

  14. Diagnostics-OMA 在硼化过程中出现了明显的H峰，而ECRH中的H峰不明显

  15. Preliminary results • 实现了LHW D.C. • 用于清洗的参数有待优化 • 观察到有利于硼化控制的局域化的等离子体

  16. Prospect • 清洗 • 改变纵场强度 • 调整气压 • 加入垂直场 • 硼化 • 尝试用于硼化

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