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New progresses of lithium coating in EAST J.S. Hu 1 , G.Z. Zuo 1 , Z. Sun 1 , J.G. Li 1 , D. K. Mansfield 2 , L.E. Zakharov 2 1 Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, 230031, China

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New progresses of lithium coating in EAST

J.S. Hu 1, G.Z. Zuo1, Z. Sun1, J.G. Li1 , D. K. Mansfield2, L.E. Zakharov2

1 Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, 230031, China

2 Princeton Plasma Physics Laboratory, MS-27 P.O. Box 451, Princeton, NJ 08543, USA

The 2nd International Symposium on Lithium Applications for Fusion Devices,

April 27 - 29, 2011,Princeton, New Jersey, USA


Outline
Outline

  • Introductions

  • Upgraded lithium coating system for EAST

  • New progresses of lithium coating on EAST

  • Further plan

  • summary


1 introductions
1. Introductions

  • Both EAST and HT-7 are superconducting tokamak.

    • EAST would play a key role for long pulse advanced high performance plasma for ITER within next 5 years.

    • HT-7 would support EAST project both of scientifically and technically.

  • Plasma facing walls would play an important role for a suitable surface for long pulse advanced high performance plasma.

    • Lower impurities

    • Lower particle recycling

    • Lower ratio of H/(H+D)

      • For the improvement of heating efficiency of ICRF

      • To avoid dilution of fusion fuel

  • A better plasma facing wall also is beneficial for the improvement of performance of high parameters plasmas .

    • Low Z-effective and lower impurities radiation

    • Control of Density

    • Long particle and energy confinement Time

    • High plasma temperatures

    • Suppression of ELMS

  • Plasma facing wall also required good heat removal capacity.

  • Lithium seemed best.

  • Low Z=3

  • High O, C getter, low impurity

  • Strong H getter, low ratio of H/(H+D)

  • High fuel retention, but low recycling

  • Flowing liquid lithium first wall

    • keep fresh lithium

    • good heat removal



Pfcs and wall conditioning researches are a main topic for east and ht 7
PFCs and wall conditioning researches are a main topic for EAST and HT-7

  • Plasma facing materials development on EAST

    • Full carbon walls (~60m2) from 2008.

    • Now, we are changing carbon walls to Mo except of divertors.

    • In near 5 years, carbon walls will changed to full W step by step.

    • Later, flowing liquid lithium plasma facing walls would be applied for divertor.

  • Plasma facing materials development on HT-7

    • Carbon limiters from2004 and 407s long plasma had been achieved.

    • Small lithium limiter was successfully tested in 2008-2009.

    • Now, we have changed all carbon limiters to Mo limiters, and will do lithium research in the coming campaign.

  • Researches on wall conditionings in HT-7 and EAST

    • Boronization(C2B10H12) with associated gases of He and D2

    • Siliconization with SiH4 and SiD4

    • Oxidation wall conditioning for C:H codeposts removal.

    • Lithium coating by evaporation, associated by GDC or ICRF discharge, active lithium coating by a dropper, and also liquid lithium limiter.


Liquid lithium limiter in ht 7 in 2008 2009
Liquid lithium limiter in HT-7 EAST and HT-7in 2008&2009

  • SS dish has Mo protection at each side.

  • Lithium plate with plasma facing area ~377cm2 and 3mm in thickness.

  • Set at 230oC during plasma discharge.

  • Free surface and capillary Pore Structure was tested.

  • Hα intensity decreased;

  • The C, O reduced;

  • Loop voltage;

  • Core electron temperature slightly increased;

  • Particle and energy confinement time increased.

Capillary Pore Structure

Toroidal C limiter

SS liners

Belt C limiter at HFS

Movable lithium limiter

Toroidal C limiter


First li coating on east by icrf in 2009
First Li coating on EAST by ICRF in 2009 EAST and HT-7

  • Only 2g lithium evaporated at single position

    • Thin and not uniformed lithium film

    • Short lifetime of the film ~40 shots.

  • Plasma performances were improved

    • SXR radiation and total impurity radiation decreased;

    • Higher and broader electron temperature distribution;

    • Beneficial for high current discharges.

Li emission


2 upgraded lithium coating system on east in 2010
2. Upgraded EAST and HT-7lithium coating system on EAST in 2010

  • Upgraded oven system for pre-coating:

    • Two oven for uniformed coating;

    • Enlarge the oven volume and the filled lithium increased from 2g to 15g;

    • Deeply movable oven to the center of inner vessel for enlarge coating surface.

    • Lithium adding system and heating system were also improved.

      • By evaporation, associated by GDC or ICRF discharge

  • Installed lithium dropper from PPPL for active lithium coating.

  • Lithium oven from Nov.6

    Lithium dropper

    dropper

    Output (mg/s)

    Lithium oven from Sep.1 Nov.6

    Lithium oven

    lithium dropper from PPPL

    Lithium oven


    Lithium coating from oven for east
    Lithium coating from oven for EAST EAST and HT-7

    Red discharge zone during Li coating

    • Evaporated at 500~550oC

    • 1~2Hr./coating;

    • 10~28.2g/coating;

    • ~3.5mg/s,

    • 1~2 coating/day;

    • GDC: 4A

    • ICRF: 20kW, 30MHz

    • He used if required.

    • By a 10~28.4g coating, the effect lifetime of lithium lifetime is about half to one day, and more than 100shots.

    300 ℃

    475 ℃

    ICRF lithium coating


    Active li coating by dropper from pppl
    Active Li coating by dropper from PPPL EAST and HT-7

    120

    • 50mg/s for EAST

    • 3 x106 Li Spheres/s

    • ~2 x D influx EAST

    • 14 x Evaporator Rate

    Li Powder

    100

    80

    Output (mg/s)

    60

    40

    20

    0

    0

    2

    4

    6

    8

    10

    12

    Applied RMS Voltage

    • During plasma discharge, a few mg lithium powder filled directly from the dropper.

    • lithium injected during 550 discharges, and ~30% shots got H-mode.;

    • Total 38.9g lithium powder used.

    Lithium powder

    44 µm dia.

    30 nm Li2CO3

    99.9% Li

    0.1% Li2CO3


    3 main results of lithium coating on east
    3. Main Results of lithium coating on EAST EAST and HT-7

    • Fast plasma recovery after leaks or vessel exposures;

    • Lower particle recycling even if high fuel retention; the retention ratio at over 70%, higher than 17% before the coating;

    • The lifetime of 10-30g li coating is about 100shots;

    • Decrease H/H+D to below 10%(min. ~7%).

    • Reduce impurity radiation, Zeff~2 during plasmas;

    • Suppress MHD activity;

    • Improve plasma confinement

      • Better for plasma density control, socially for long plasmas;

      • Reduce impurities radiation;

      • Suppress MHD and Improve plasma confinement;

      • Reduce threshold energy for L-H transition to easily achieve H-MOD plasmas;

      • Improve coupling efficiency during ICRF heating for high performance plasmas

      • Beneficial for high power and high current plasma operation

        • Achieved 1MA plasma current;

        • Increase plasma duration to >100s.

        • Successfully obtained H-mode plasma;

        • First observed effective ICRF heating;


    The first lithium coating in the 2 nd campaign of east in 2010
    The first lithium coating in the 2 EAST and HT-7nd campaign of EAST in 2010

    • OII and CIII impurity reduce significantly.

    • Zeff decreased very fast to 1.5~2.5.

    • The ratio of H/(H+D) decreased significantly.

    From Dr. Jia Fu

    From Dr. Zhenwei wu


    Plasma performance improved by lithium coating EAST and HT-7

    • Impurity suppressed;

    • Power radiation reduced;

    • Recycling decreased;

    • MHD activity Suppressed.

    • Decrease disruptive plasmas.

    Circular plasmas

    Divertor plasmas with double null


    Lithium coating is better to reduce impurities recycling and h h d
    Lithium coating is better to reduce impurities, recycling and H/(H+D)

    • Even using SiD4 or boronization in D2, both boronization and siliconization on EAST is difficulty to reduce H/(H+D) lower than 25%.

    • Lithium coating is also more effective for impurities suppression.

    • Lithium coating increased the percentage of effective plasmas.

    Definition of effective shot : Ip>200 ,ne>0.5 x1019/cm3,length>4s;

    Before coating wall conditioning, effective plasma is only 7%.


    Plasma performance improved by accumulated lithium coating
    Plasma performance improved by accumulated lithium coating and H/(H+D)

    • Total 67 times and use 982.4g lithium from oven by means of ICRF/GDC or only evaporation

    • 10~28.4g/coating;1-2 time /day(~100 shots)

  • About 38.9g lithium powder was used as active coating from dropper.

  • By lithium coating with one or two time in everyday, H/(H+D) and C, O impurities deceased continually.

  • Plasma performance improved step by step.

  • Long pulse plasmas, high current plasmas, H-mode plasmas, and effective heating plasmas by ICRF were successfully obtained.

  • From RGA data in release gases

    H-mode operation


    The first effective heating of icrh on plasma of east was obtained
    The first effective heating of ICRH on plasma of EAST was obtained

    • After 7 lithium coating with 70g Li, H/(H+D) decreased to ~10%, the first effective heating of ICRH on EAST:No.30294

    • Lithium coating : H/(H+D) ~10%(min ~7%) to lead to improve ICRF heating efficiency (H minority in D).

    • Minority fundamental heating of ICRF: Use H minority in D (Dr.X.Z Zhang)

    H/H+D ~10%

    Stored energy increased ~10kJ

    Te increase d ~200ev


    High current and long plasmas were easily obtained
    High current and long plasmas were easily obtained obtained

    • Via the lithium coating

    • the plasma can be restored quickly and the plasma current can be easily controlled;

    • also the disruption discharges significantly reduces.

    After the 40th and 41st lithium coating, new milestones of EAST--100s and 1MA plasmas were obtained.


    Highest current and longest plasmas of east
    Highest current and longest plasmas of EAST obtained

    1MA, 1.5x1019/cm3

    100s, 100KA, 1x1019/cm3


    H mode plasma of east easily obtained either by li coating by oven or by active li powder injection
    H mode plasma of EAST easily obtained either by Li coating by oven or by active Li powder injection!

    • First H-mode plasma No.32525

    • From No.32525 to 33590, 141 shots H-mode plasma were got:

    • In H-mode plasmas, lithium powder injection: 61 shots, 43.3 %.

    • 32537:

    • ELM-free H-mode with power close to threshold

    • Radiation terminated H-mode

    • Multi L-H-L transitions

    • Increased LHW reflection during H-phase

    • 32924:

    • Reduced radiation by Li evaporation and suppressing Res during ramping up and early shaping into divertor configuration

    From Dr. Baonian Wan


    H mode plasma of east easily obtained either by li coating by oven or by active li powder injection1
    H mode plasma of EAST easily obtained either by Li coating by oven or by active Li powder injection!

    • No. 32537:

    • IT~ 6000A,

    • IP~600kA,

    • ne~2.1,

    • PLHCD~1MW,

    • H/(H+D)~10%,

    • Zeff~2.

    • lithium powder injection from 1.9s to 2.9s;

    • Before this shot

      • ~150g lithium coated by oven;

      • about 20 shots lithium injected.


    Lithium coating beneficial for long H-MODE plasmas by oven or by active Li powder injection!

    New milestone:H-mode Operation 6.4S!

    Ip

    Ip

    ne

    PLHCD

    Beta P

    PICRF

    WDIA

    Da/Ha

    ECE

    Sx-ray

    XUV

    Ip~0.6MA, Bt=1.9T, ΔWDIA>45KJ,PICRF=0.75MW, f=27MHz,PLHCD=1.0MW, f=2.45GHz


    Mhd suppressed and impurities reduced by active li powder injection
    MHD suppressed and impurities reduced by active Li powder injection

    Plasma current(KA)

    CIII emission

    LiII emission

    Ha emission

    MHD signal

    Li injection during long plasma operation


    Fast plasma recovery by lithium coating after leak or vessel exposure
    Fast plasma recovery by lithium coating after leak or vessel exposure

    • In the 2nd campaign in 2010, there are 8 N2 leaks from heat sinks and 4 entry exposures.

    • During the entry exposure, Ar was filled at first, then worker entered vessel with personnel O2 supply.

    • Before 20th lithium coating , the vessel exposed to Ar first and then open window for person entering;

    • After 24.5hr. D2-GDC and He-GDC cleanings, the vacuum reached 1x10-5Pa, however, the first 60 plasmas was disrupted.

    • Only after 45 min He-ICRF and 30g Li coating, repeatable plasma was got.

    • After Li coating, C, O and H/(H+D) decreased fast.


    Distribution of lithium film exposure

    • Lithium film distribution is similar as red discharge zone during lithium coating.

    • Near oven, lithium film could be easily found.

      • The far from oven, the thinner film.

      • Lithium coating is no uniform even if two toroidal symmetricalovens are used and it need more ovens to achieve more uniform lithium coating.

      • The film was easily cleaned by de-ionized water.

    Thick film ~2mm near oven

    After cleaning

    Top divertor near M window


    4 future plan
    4. Future plan exposure

    • Now, we have changed all carbon limiters to Mo limiters in HT-7, and will do lithium research by coating and liquid limiter in the coming campaign.

  • Design flowing liquid lithium limiter for HT-7

    • (1) two long toroidal free surface lithium tray, driven by electromagnetic pump in the outside circuits.

    • (2) long toroidal limiter with trenches structure, driven by thermoelectric MHD force.

    • (3) Or several poloidal lithium limiters.

  • Possibly flowing liquid lithium divertor after 2014 for EAST

    • Successful experiments in HT-7

    • After all PFCs be modified from C to W

    • Flowing liquid lithium divertor


  • The coming campaign of ht 7 in 2011
    The coming campaign of HT-7 in 2011 exposure

    • Lithium re-filling from outer of vessel.

    • CPS structure (SS foam).

    SS foam

    • Lithium coating system from EAST

      • Two ovens evaporation systems

      • One lithium powder injection system

    SS tray


    Flowing liquid lithium limiter for ht 7
    Flowing exposureliquid lithium limiter for HT-7

    Lithium

    j

    Hot

    Cold

    Molybdenum

    j

    Application of thermoelectric MHD effect Cooperation with Prof. David N. Ruzic Lab. In Illinois university

    Test bench for long flowing lithium tray


    EAST Plan in near 5 years exposure

    2011 2012 2013 2014 2015

    Ip(MA) 1.0 1.0 1.0 1.5 1.5

    LHCD(MW, CW)

    2.45GHz 4.0 4.0 4.0 4.0 4.0

    4.6GHz 6.0 6.0 6.0

    ICRF(MW,CW)

    20-75MHz 4.5 4.5 4.5 4.5 4.5

    30-100MHz 1.5 4.5 4.5 4.5 4.5

    NBI(80keV) 8.0 8.0 8.0

    ECRH(140GHz,cw) 2.0 4.0 6.0 6.0

    PFC Mo/C Mo/W/C Mo/W Mo/W W

    Diagnostics 40 45 50 50 50

    Duration(s) 100 200 300 400 400

    t-Hmode(s) 30 60 100 200 400

    With over 20MW CW power and 50 diagnostics, EAST could play a key role for long pulse advanced high performance plasma for ITER within next 5 years.

    Possibly flowing liquid lithium divertor after 2014 for EAST


    Summary exposure

    • With upgraded lithium coating system, we have successfully carried out lithium coating and many interesting results were obtained.

    • Lithium coating is useful for plasma recovery.

    • Lower particle recycling even if high fuel retention after lithium coating;

    • The lifetime of 10-30g lithium coating is more than 100shots;

    • By the coating, record lowest H/(H+D) of EAST(<10%) was got.

    • Lithium coat also significantly reduced impurity radiation, Zeff~2 during plasmas, and suppressed MHD activity;

    • Improve plasma confinement and Increase plasma stored energy;

    • With lithium contribution, a few milestones were got for EAST.

      • Achieved 1MA plasma current;

      • Increase plasma duration to >100s.

      • Successfully obtained H-mode plasma;

      • First observed effective ICRF heating;

    • After ~1kg lithium coating, thick lithium film was found, and it could be easily cleaned by de-ionized water.

    • New program on flowing liquid lithium PFCs is going on.



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