1 HT-7/EAST ASIPP Oxidation wall conditionings on H T-7 and EAST superconducting tokam aks J.S Hu, J.G Li, Y.P Zhao EAST Team [email protected]Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui 230031, China PSI-19, May 24-28, 2010, San Diego, California, USA
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1 HT-7/EAST ASIPP Oxidation wall conditionings on HT-7 and EAST superconducting tokamaks J.S Hu, J.G Li, Y.P Zhao EAST Team [email protected] Institute of.
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HT-7/EAST ASIPP
Oxidation wall conditionings on HT-7 and EAST superconducting tokamaks
1. Thermo-O: with Bt; Access to all areas, specially to shadow ereas; low removal rate, but could be improved with high wall Temp.(e.g.350oC) and higher oxygen pressure(e.g.>1000Pa)
2. O-GDC: without Bt; On Line-of-insight surface, effecitive area larger than O-ICR, specially to far positions, such as pump ducts; limited O2 pressure; Continously High removal rate even on Low Twalls, high O retention
3. O-ICR: with Bt; On Line-of-insight surface; limited O2 pressure; Continously high removal rate even on Low Twalls, low O retention
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3. Oxidations between HT-7 and EAST3.1 O-ICRF in EAST
full metal walls at 400K Full carbon walls at room Temp.
Similar behaviors during oxidation, and similar influence of power, pressure, pumping speed and wall conditions.
HT-7/EAST ASIPP
J. Nucl. Mater., 390–391 (2009) 929
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•ICR power and Pressure: particle energy and plasma density•Plasma volume:plasma power density•PFCs materials and Plasma fuels : source of C, H, and D•Configration and Plasma facing surfaces:cleaning area•Pumping speed: particles exhaust•RF antenna: coulpling power•Wall temperatures: oxidation efficiency
3.2 1:1 He/O-ICRF betweenHT-7 and EAST
HT-7/EAST ASIPP
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3.3 Removal rates in 20kW 0.014Pa He/O-ICR
HT-7 EAST(metal walls) EAST carbon walls
plasma volume 2.6 16 16
plasma facing surfaces
12 60 60
plasma-facing material
20% carbon +SS Full SS Full carbon
plasma fuel D2 H2 D2
configuration Limiter divertor divertor
Antenna Single antenna at high field side both for ICWC and heating
Two dedicated at low field side specially for ICWC
Two dedicated at low field side specially for ICWC
Wall temperature 400-420K ~400K ~300K
Removal rates for C 1.9×1021atoms/h 1.3×1022atoms/h 1.5×1022atoms/h
Removal rates for H 2×1021atoms/h 2.5×1022atoms/h 4.1×1022atoms/h
•Plasma could be recovered, but tens disruptive shots(32-97) are required. •After oxidation, impurities increased and Ha decreased. •Impurities, such as C, O, decreased shots by shots. •In 2007 experiments, 1g Boronization after He/O-ICR made plasma recovery easily, Zeff~2.5 was got in the recovered plasmas.
Less O retention and boronization helps the plasma recovery.
HT-7/EAST ASIPP
Fusion Eng.&Des., Vol.83(2008)689
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5. Prediction for ITER
HT-7/EAST ASIPP
Device Series Parameters Removal rates for C (atoms/h)
Removal rates for H (atoms/h)
Estimated C removal rate for ITER with 3MW ICR (atoms/h)
To remove 700g T in ITER, it would require 0.5~7hrs of wall conditioning with 3MW O-ICR discharges.
Assuming with a same oxygen pressure, mian factors, such as power density, cleaning surface and actively pumping, are linearity effect on the deposits removal.
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HT-7/EAST ASIPP
•Series oxidation experiments were carried out on HT-7 and EAST.
•O-GDC appeared to be the most efficient on HT-7. However, O-ICR was almost as good and could be applied with the magnetic field in ITER.
•O-ICR on both EAST and HT-7 revealed that power density, working pressure, plasma facing area and materials, pumping speed and wall temperatures were main factors influencing on the deposits removal.
•High power, low oxygen pressure and He in O-ICR are beneficial for reducing oxygen retention.
•Plasma discharges could be recovered by effective cleanings and boronization.
•To remove 700g T in ITER, it would require 0.5~7hrs by 3MW O-ICR cleanings.
•Oxidation treatment is one of the most promising methods for amorphous tritiated carbon layers removal for ITER.