Development of a new liquid lithium limiter with a re-filling system in HT-7. G. Z. Zuo, J. S. Hu, Z.S, J. G. Li,HT-7 team July 19-20, 2011 Institute of Plasma Physics, Chinese Academy of Sciences, China. HT-7 Data Meeting and Workshop . Hefei, China July 19-20, 2011. Outline. Introduction - PowerPoint PPT Presentation
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ASIP ASIP P P Development of a new liquid lithium Development of a new liquid lithium limiter with a re-filling system in limiter with a re-filling system in HT-7 HT-7 G. Z. Zuo, J. S. Hu, Z.S, J. G. Li,HT-7 team G. Z. Zuo, J. S. Hu, Z.S, J. G. Li,HT-7 team July 19-20, 2011 July 19-20, 2011 Institute of Plasma Physics, Chinese Academy of Sciences, China Institute of Plasma Physics, Chinese Academy of Sciences, China 1 HT-7 Data Meeting and Workshop . Hefei, China July 19-20, 2011 HT-7 Data Meeting and Workshop . Hefei, China July 19-20, 2011
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Development of a new liquid lithium limiter with Development of a new liquid lithium limiter with a re-filling system in HT-7 a re-filling system in HT-7
G. Z. Zuo, J. S. Hu, Z.S, J. G. Li,HT-7 teamG. Z. Zuo, J. S. Hu, Z.S, J. G. Li,HT-7 team
July 19-20, 2011July 19-20, 2011
Institute of Plasma Physics, Chinese Academy of Sciences, ChinaInstitute of Plasma Physics, Chinese Academy of Sciences, China
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HT-7 Data Meeting and Workshop . Hefei, China July 19-20, 2011HT-7 Data Meeting and Workshop . Hefei, China July 19-20, 2011
ASIPPASIPPOutlineOutline
IntroductionIntroduction
Design of the new lithium limiterDesign of the new lithium limiter
Main resultsMain results
Test of re-filling systemTest of re-filling system
Influence on plasma performanceInfluence on plasma performance
Discussion: Discussion: Li emission and plasma disruption
Li erosion and deposition
SummarySummary
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ASIPPASIPPIntroductionIntroduction
Li is Li is developed as an potential alternative PFM for future
fusion devices
Liquid lithium is a self-recovery and renewable PFC material if surface
damages due to erosions
Best way to control recycling and H content, also suppress impurities;
Enhance plasma performance.
Main motivation of liquid lithium limiter (LLL) experiment in
HT-7 is to provide technical support and data accumulation
for future design:
Flowing LLL for HT-7
Flowing liquid lithium divertor (LLD ） after 2014 for EAST
Accumulate data for its application in future fusion reactor. 3
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Graphite PFCs:
Serious H retention and recycling.
Serious erosion and co-deposition with T in future devices.
Reaction between Li and C, reduce H, D trapping.
Li surface should be confined by CPS to avoid splashing due to MHD.
Heater should be reliable.
It required a re-filling system for lithium:
If lithium plates installed before experiment, it would possible lead to
contamination.
No available again, once lithium was used up.4
Lessons from previous Li experimentsLessons from previous Li experiments
ASIPPASIPPDesign of the new lithium limiterDesign of the new lithium limiter
Full metal walls: Change all C tiles to Mo
Using new type SS mesh
Upgrade heater strips with armored structure.
Design a re-filling system outside of HT-7.
Same position, similar area (~400cm2) and same movable system as previous
experiment.
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Re-filling system
Sketch of the new designed LLL system with Re-Sketch of the new designed LLL system with Re-filling systemfilling system
Mo Mo limiterslimiters
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Structure of LLLStructure of LLL
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New SS meshNew SS meshWith 285*145*2.5 With 285*145*2.5 (mm) and pore (mm) and pore radius~100radius~100μμmm
SS tray with SS tray with channels for Li channels for Li reservoir(50cmreservoir(50cm33) )
Pipe and Pipe and heaterheater
SS mesh SS mesh and SS and SS traytray
ASIPPASIPPOutlineOutline
Introduction
Design of the new lithium limiter
Main results
Test of re-filling system
Influence on plasma performance
Li emission and plasma disruption
Li erosion and deposition
Summary
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ASIPPASIPP Liquid Li flow could be driven:
In a pipe with 10mm inner diameter At a low temperature ~250 ℃ Only by gravity force without pushing
by a planed high pressure Ar. Main problems
Hard to control flow velocity and the amount of injected Li.
Hard to control position of lithium injection
So many lithium flow onto the top of SS mesh
Successfully test re-filling system
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After 1st Exp., a lot of liquid lithium was still remained on the top of SS mesh.
ASIPPASIPPInfluence on plasma performance
With LLL,
High retention (with the same Ne, required more gas puffing).
Reduce recycling.
Reduce total impurities radiations.
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ICRF OH
ASIPPASIPPInfluence on plasma performance
Compare some parameters of plasmas before and after using LLL （ r=27cm
）
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After 17th lithium coating, total using ~173g lithium
ASIPPASIPPLi emission and plasma disruption
Plasma performance related with LLL
position( Mo limiters at r=0.27m). While
LLL at r=0.26m, with the same fueling,
low density and Vloop than it at r=0.275m.
However, lots of disruptions if LLL at
r=27cm and 26cm.
– at r=27.5cm, Normal plasmas;
– at r=27cm, ~ 2/3 plasmas disrupted
；
– at r=26cm, ~9/10 plasmas disrupted.11
ASIPPASIPPLi emission and plasma disruption
Possibly due to strong Li emission intensity, there are lots of disruptive
plasmas if LLL as main limiter at r=27cm and 26cm.
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Increased lithium emission intensity
Disruption Stronger Lithium Ejection
ASIPPASIPPPossible reasons for Li emission
Sputtering (sputtering yield 0.5-1)
Evaporation ~1017s-1 (r=260cm,t~0.8s, OH plasma, calculated Max Temp. of
LLL surface in creased to ~360ºC)
Splashing
J×B force (Induced J by plasma, TEMHD, TCMHD, Other MHD instability.)
Possible LLL vibrations during plasma discharge (Lots of Li on top of mesh).
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Large-scale
Droplets
Before disruption, Li emission intensity increased and plasma and LLL interaction
became strong, then plasma disrupted.
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Initial Temp. 220ºC(#112357). POH ~200kW , t~1s; If half power loads on LLL, Q0~6.7MW/m2.
Plasma disruption analysis—Heat flux analysis
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Li SS mesh
T1
J1TE
T2 J2TE
VB
R
TSTEMHDJ
Force (J2TE×B)along radial direction. Force (J1TE×B)was possible to splash lithium.SS tray
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Lithium radial flow observed by fast CCD
Observed by fast CCD, Liquid lithium flew along radial direction seemed corresponding to the direction of force (J2TExB).
The estimated velocity along radial direction ~0.5m/s
0.27s 0.29s 0.32s
High temp. B
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After vent, we have found
1, lots of Li was floated out directly from LLL, possibly due
to too much Li filling.
2, Lots of Li droplets around LLL, possibly strong JXB
force.
3, SS mesh had no any damage and full of Li, indicating
new SS mesh is good for CPS system.
Li erosion and deposition
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After 3rd Exp., thin Li film on mesh, and Li was effectively confined by the CPS.
ASIPPASIPPOutlineOutline
Introduction
Design of the new lithium limiter
Main results
Test of re-filling system
Influence on plasma performance
Li emission and plasma disruption
Li erosion and deposition
Summary
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ASIPPASIPPLiquid lithium was successfully and easily injected into LLL from outside of
HT-7 by re-filling system.
Ø10mm pipe , low Temp.~250 C, driven only by gravity.
Plasma with a lower recycling and a lower radiation was obtained by using
LLL.
The new SS mesh was good for CPS system . SS mesh kept no any damage
in spite of some disruption shots during LLL Exp.
Due to Li emission intensity increase by various reasons, many plasmas was
disrupted while as LLL served as main limiter. In alternative, disruption
enhanced Li erosion, specially Li ejection directly from LLL.
To control Li injection speed and Li splashing during plasma discharge
should be considered.
Summary and Discussion
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Thanks for your attention!
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AcknowledgementThis research is funded by National Magnetic confinement Fusion Science Program under contract 2010GB104002 and the National Nature Science Foundation of China under contract 11075185.
