The influence of wall conditionings on hydrogen evolution and removal on EAST
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ASIPP
EAST
The influence of wall conditionings on hydrogen evolution and removal on EAST
Y.W.Yu, J.S.Hu, X.Gao, J.H.Li, Y.Chen and Y.P.Zhao
Institute of Plasma Physics, Chinese Academy of Sciences
CUP- PWI/PFC and Fusion Technologies
27-29 October, 2008, Huangshan Anhui, China
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EASTOutline
Introduction Wall conditioning on EAST Hydrogen evolution and removal Summary
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EASTIntroduction
EAST 2006-2007
316L stainless steel
Mo limiter
GDC anodeICRF ant
ennaGDC anode
ICRF antenna
Graphite wall
2008 Full graphite R=1.85 m, a=0.48 m
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EASTWall conditioning on EAST
Baking GDC: He/D2, 2 A
ICRF: 30 MHz, He/D2, 5-30 kW Boronization
ICRF + C2B10H12
Base pressure Ultimate pressure Partial pressure (from RGA)
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EASTOutline
Introduction Wall conditioning on EAST Hydrogen evolution and removal
Baking GDC ICRF cleaning Boronization
Summary
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EASTHydrogen evolution
Hydrogen & wall recycling Specific source of H
Wall deflation H2 puffing Boronization
C2B10H12
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EASTBaking
Improve wall release Base pressure of H2
Similar trend in curve
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EASTGDC
Use one of four electrodes, 2 A Helium 0.5-0.8 Pa Obvious removal of H2
4 hours GDC in He
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EASTICRF cleaning
Typical parameters: ICRF Power: 5-30 kW, 0.5s ON/ 2s OFF Gas species: He/D2
Neutral pressure: (0.5-1)x10-2 Pa
ICRF plasma
HFS LFS
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EASTICRF cleaning
Influence of parameters ICRF power Gas species Neutral pressure
Totally ~ 2 hours ICRF in D2 + He
Notable removal of H2 by ICRF cleaning
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EASTBoronization
Great increment of H2
Major H injection (C2B10H12)
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EASTBoronization
Enhanced wall recycling Ha emission at breakdown Higher H2 removal by ICRF
Followed ICRF cleaning was
effective to remove hydrogen
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EASTRemoval & Base pressure
Pressure in cleaning & base pressure GDC: Similar trend ICRF: Approximate same
GDC only used at the beginning
Base pressure reflects wall condition
Pressure in cleaning can also reflect!
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EASTSummary
Baking, GDC and ICRF cleaning were effective ways to remove hydrogen on EAST
Boronization (C2B10H12) was a major injection of hydrogen, followed ICRF cleaning was effective to remove hydrogen
Partial pressure of H2 in discharge cleaning had the similar trend with that of base pressure, it could also reflect wall condition besides base pressure
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EASTAcknowledgement
Thank you for your attention!