The influence of wall conditionings on hydrogen evolution and removal on EAST

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

EASTOutline

Introduction Wall conditioning on EAST Hydrogen evolution and removal Summary

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

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)

EASTOutline

Introduction Wall conditioning on EAST Hydrogen evolution and removal

Baking GDC ICRF cleaning Boronization

Summary

EASTHydrogen evolution

Hydrogen & wall recycling Specific source of H

Wall deflation H2 puffing Boronization

C2B10H12

EASTBaking

Improve wall release Base pressure of H2

Similar trend in curve

EASTGDC

Use one of four electrodes, 2 A Helium 0.5-0.8 Pa Obvious removal of H2

4 hours GDC in He

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

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

EASTBoronization

Great increment of H2

Major H injection (C2B10H12)

EASTBoronization

Enhanced wall recycling Ha emission at breakdown Higher H2 removal by ICRF

Followed ICRF cleaning was

effective to remove hydrogen

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!

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

EASTAcknowledgement

Thank you for your attention!