asipp development of a new liquid lithium limiter with a re-filling system in ht-7 g. z. zuo, j. s....

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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


Introduction

Design of the new lithium limiter

Main results

Test of re-filling system

Influence on plasma performance

Li emission and plasma disruption


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.


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After 3rd Exp., thin Li film on mesh, and Li was effectively confined by the CPS.


Introduction

Design of the new lithium limiter

Main results

Test of re-filling system

Influence on plasma performance

Li emission and plasma disruption


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.

asipp development of a new liquid lithium limiter with a re-filling system in ht-7 g. z. zuo, j. s....

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