OPTIMIZATION OF LIQUID METAL ADVANCED TARGETS … · optimization of liquid metal advanced targets...

Francisco L Tabarés On behalf of the TJ-II Team

Laboratorio Nacional de Fusion. Ciemat. Av Complutense 40 28040 Madrid. Spain

OPTIMIZATION OF LIQUID METAL ADVANCED TARGETS

(OLMAT)

OUTLOOK

DTT Meeting Frascati, JUne 2017

- Status of LM selection for DEMO

- The OLMAT project

- Connection with DTT Project

Previous Research • EFDA PEX project • EUROFusion PFC, DTT1&2 WP’s - Possible liquid metals: LI, Sn, LiSn - CPS structure ( Heat conduction+vapor shielding)


LiSn (USA APEX Choice)


Li/Sn<30% Excellent properties as LM: -H retention ~ 0.01% -Low Pvap -No Sn sputtering/evaporation -etc… -BUT: Alloy Long term composition stability? Thermal conductivity?

- Need to address effect of Li deposition on hot alloy. - Check for eutectic formation

Use as LM pioneered by TJ-II Team in Isttok and TJ-II experiments (Tabarés, Loureiro et al. PSI Rome)


Ts Ti

Tc

d1 d2

q

CPS Structure

Cooling

λ1 λ2

Power Exhaust Issues

Ts (°(Tw=150 ) 1% FLUX

d1(mm) (CPS)

d2(mm) (struc)

P (MW/m2)

Tin optim. 1277 1 3 28.75

Li optim. 480 1 3 8.25

But: Thermal conductivity CPS+Li?: optimize structure Maximum T Li?: Redeposition efficiency + T retention

Coenen et al Phys. Scripta 2014

Comparative analysis


Which LM maximizes conductive heat exhaust?

+ - H retention - Material Compatibility - Cooling issues - Close Loop/refilling - Wetting - CPS design parameters - ….. Many answers already available from previous work

Ex. Li +water cooling? Maximum Liquid Li in vessel

Need of impurity seeding? Stability of LiSn alloys…

Integration issues:

Γ max from code calculations:

+ sputtering


Standard CPS structure

kCPS=a.kLi+ (1-a).kW

Keep “a” at a minimum: Fabrication of W sheets with tailored pores and surface texturing by laser already in progress by Spanish collaborators.

+Convective transport?

CPS design


The OLMAT Project

Phase 1) Comparative studies (short pulse, no ELMs) Phase 2) Addition of ELM-like loads (Laser pulses) Phase 3) Long NBI pulse+ ELMs Phase 1) - LM ( Li, Sn , LiSn) - CPS structure

Project developed in three (parallel) phases

+ Target issues: CPS design + cooling+ LM refilling

Alternate use of TJ-II as a test bed and a magnetized fusion device for LM alternative target research

European Facilities Hot Plasma+ LM: - FTU: CLL, no NBI, narrow ports - ISTTOK: no NBI, small tokamak - TJ-II: NBI+ LM experience+ easy

access

EF Test Facilities: - GLADIS: No Li operation - JUDITH: e- beam. Raster. - PSI-2/ JULE: No Li operation - MAGNUM: Weakly devoted to LM

experiments to date. Small spot.


Performance of Liquid Metal-based targets during slow transients up to Power Fluxes of 20 MWm-2. LMs: Li, Sn and LiSn. Comparative study DEL-1

Impact of the CPS design on its ability to withstand high power fluxes. DEL-2

Combined effect of ELMs and high, steady, power fluxes on the LM target. DEL-3 In situ determination of the surface refilling time for each CPS structure DEL-4 Effect of H content on theses parameters at levels below the sat. solubility limit. DEL-5 Stability of LiSn alloys in the presence of strong redeposition. DEL-6 Redeposition efficiency of ejected material.* DEL-7 Radiation of the local plasma at high concentrations of LM constituents.* DEL-8 Effect of nuclear damage of the CPS mesh (stainless steel) on reactivity and mechanical properties degradation under LM-filled exposure to the plasma.* DEL-9 * E t l ti t di t l th h d li

Expected (minimum) deliverables :


RESOURCES. TJ-II

NBI-2 NBI-1

Heliac Stellarator 4 periods R=1.5 m <a>= 15-25 cm BT=1 T ECH : 2x300kW,53.2 GHz NBI:2x700 kW, >30 KeV Vol Plasma ~ 1m3

Low Z scenarios : - 2 Liq Lithium Limiters - First Wall Boronization - Vacuum Lithiation

LLL in TJ-II


- Two LLL installed in TJ-II ( heated, movable, diagnosed) - Spare manipulator system,1 m drive, motorized - To be recycled (adapted) for OLMAT LM target positioning


RESOURCES. NBI

Working gas Hydrogen Accel voltage 35 keV Accel current 60 A Decel voltage 1.5 keV Decel current 10 A Arc voltage 150 V Arc current 1200 A Pulse duration 150 ms Duty cycle ≤ 1 % Gas throughput 20-40Torr.l.s-1

NBI present Characteristics

Possible operation w/o neutralizers: +35%

X (mm)

47,6oC

0,0oC

Jan-June July-Dec Jan-June July-Dec Jan-June July-Dec Jan-June July-Dec Jan-June July-Dec Jan-June July-Dec

Phase ILM Target design & construction (1,2,3)LM Target support and Actuator: design & constructionDuct chamber modifications: design & constructionTJ-II Vessel modifications: design & implementationFinal LM target installationLM Target Operation (1,2,3) LM Target LM Target LM TargetTJ-II Plasma Operation TJ-II TJ-II

Phase IILaser purchase & preparationsFinal Laser installationLM Target Operation: Laser experiments (4) LM Target

Phase IIIIon Source DesignBeamline & Duct modifications designBeamline components designPower supply, Control & Cooling: Design Ion Source procurementBeamline & Duct procurementBeamline components procurementPower supply, Control & Cooling procurementLM Target: new designs & construction(4,5)Power supply, Control & Cooling modif. implementationInstallation & commissioning Ion Source & Beamline & DuctLM Target Operation: Long Pulse NBI + Laser (5,6) LM Target LM TargetTJ-II Plasma Operation TJ-II TJ-II

Year 6Year 1 Year 3

New NBI (Long Pulse)+laser

Old NBI (short pulse)+laser

Old NBI (Short Pulse)

Year 2 Year 4 Year 5

Deliverables Del1&2 Del 3,4&5 Del 6&7 Del 8&9

Time table


Connection with DTT project


OLMAT Phases 1-3 Optimized target

fabrication

Figures of merit: - Experienced Team in LM research - Divertor space - Hot FW

DTT


Towards an Integrated Scenario with LMs


- All topics addressed in CIEMAT ( Lab + TJ-II): WPPFC, DTT1 &DTT2 + Spanish Funding - Not all included in OLMAT

F. Tabares, Nucl.Fus.2017


Phase 2. ELM impact

Effects of ELMs simulated so far with: - Electron beams (Judith, RF) - Laser Pulses ( many devices) Ej. Nd YAG, 1 ms, 10-25 Hz, 1-21 kW in Magnum PSI - QSPA’s ( RF, Ukranie) -Plasma V/I modulation (PILOT PSI, Magnum)

OLMAT: fiber lasers. -Requirements: Pulse length up to 1 ms, peak energy: 1MJ/m2, rep rate: up to 1000 Hz. -Several models available in the market -Pulse mode. Look for LM emission in the NB plasma. Evaluation of refilling time by changing the repetition frequency. Can provide power loads of > 10 MW/m2 if focused in CW mode Ample experience in IPPLM Warsaw (LIBS) Convenient coupling through optical fiber to the VV. Aimed at accumulating thousands of ELMs ( thermal stress tests) and potential dry-out (including depletion of one of the components in an alloy). Pure pulsed laser irradiation (w/o NBI plasma ) is also foreseen.


Phase 3. Long NBI pulse operation

New source of PINI type. Aiming at more relevant time scales (up to 5 s) Limited use of available NBI components Strong demand on man power Activities will be initiated in Phase 1 already ~ 1 year of installation and commissioning required Will allow for validating extrapolations from previous phases


Budget

Total= 2623,5 k€

Detailed budget plan


Project Year Description Human resources (Person years) Human resources (kEuros) Hardware etc (kEuros)

OLMAT TJ-II 2017 Preparation phase 1 2,5 156,25 10

OLMAT TJ-II 2017 Preparation Phase 3 3,6 225 0

OLMAT TJ-II 2018 6 month Phase 1 operation 6 375 10

OLMAT TJ-II 2018 laser purchase & preparations Phase 2 0,5 31,25 200

OLMAT TJ-II 2018 Preparation Phase 3 3,9 ( +IPPLM) 243,75 200

OLMAT TJ-II 2019 6 month Phase 1 operation 6 375 10

OLMAT TJ-II 2019 Preparation Phase 3 3,5 218,75 300

OLMAT TJ-II 2020 6 month Phase 1+2 operation, new targets 7,5 (+IPPLM) 468,75 15

OLMAT TJ-II 2020 Preparation Phase 3 3 187,5 200

OLMAT TJ-II 2020 Commissioning Phase 3 4 (+ IPPLM) 250 150

OLMAT TJ-II 2021 Commissioning Phase3 4 250 150

OLMAT TJ-II 2021 6 month Phase 1+2 operation, new targets 7,5 468,75 15

OLMAT TJ-II 2022 6 month Phase 1+2+3 operation, new targets 7,5 468,75 15

OLMAT TJ-II 2023 6 month Phase 1+2+3 operation, new targets 7,5 468,75 15

0

TOTALS 67 4187,5 1290

Further extension of operations beyond 2023 would be desirable

Risk analysis

On TJ-II Operation: Risk Level Action Impact - Contamination Small (Ph I&II) Insert Large VV delay? of NBI source Medium (Phase III) Withdraw NBI - Window coverage Medium Shutters foreseen no - Flaking of deposits Medium Cleaning between no

campaigns


On Project Risk Level Action Impact - Failure of targets Medium Redesign assumed in

the structure of the project

- Shortage in budget low Additional Funding moderate - Delay in building the medium Use external shops budget increase or

targets delay in goals

Extension to Demonstration Phase:


AUG Large Manipulator

S W O Impact of OLMAT

on normal operation of TJ-II and NBI sources

Realization of close loop systems

Corrosion issues Hot LM handling

T Explore alternative

DEMO plasma-wall solutions

Strong contribution to maturity of LM concepts

Impact on cooling strategies

Large use of present facilities

Combined LM studies in TJ-II

HS reactor relevant

Lack of actual Divertor plasma scenarios. Need of modelling

Limited puse duration

Disruption power loads achievable only in a small area

Leverage in modelling and validation strategies

Close loop development

New EF facility for Demo-relevant PWI issues



LM and NBI Experience In TJ-II: Design, fabrication and instalation of Li ovens for evaporative wall coating Design fabrication and operation of small CPS probes: Li and LiSn tested Biasing, heating and TDS of samples (limiters) exposed to the plasma

At the Lab. H retention and desorption studies of Li and LiSn vs temperature an external pressure Measurement of Secondary Electron Emission of LM´s (Sn, Li and LiSn) in GD plasma Effect of mesh type on evaporation and H trapping/release Studies of LiH formation/decomposition Effect of Li oxidation on Sputtering and SEE yields. Preparation of LM samples for insertion in TJ-II Etc..


NBI experience Two NB lines (34 kV, 700 kW, 150 ms) are operated routinely. The NBI construction cost was funded by EURATOM under contract EUR FU (97) CCFP 74/8.5 Team Activities (related to LM Target tasks). Design of: The NBI cooling system The thermal protections of the vacuum chamber, as well as the Beam Target Calorimeters, for which power deposition and finite element codes were used in the design phase. Beam Characterization: -Water calorimetry. -Thermocouple measurements -Fast Ion Gauges (FIG). -Infrared thermography. Beam simulations: Some of the used codes: DENSB, ANSYS: beam transmission, wall temperature OPTIMUS: gas efficiency, pumping, reionization losses FAFNER: beam-plasma interaction FAFTRAYN: ion trajectories in the stray magnetic field of TJ-II

EF PPPT (WPBB, WPMAT, WPENS) + BA (IFMIF EVEDA) + Technofusion (national prog): Development of a Liquid Metal closed loop Ion Irradiation facilities Material characterization techniques

T retention issues


LiD formation

Equilbrium presure and saturated solubility of H,D and T on lithium at temperatures between 400 ad 650 ºC. Values of P and cH at 550 ºC are highlighted by circles. Also shown as P eq (ex), the experimental values obtained for a H2/Li system at Ciemat

Choosing the right CPS structure

• Basic considerations: Capillary pressure/Refilling time/Heat tansmission


P=2σ cosθ/r t = 4l2 η/ r.σ

TJ-II experimental hall


NBI#2 (Counter)

NBI#1 (Co)

RESOURCES. LM Laboratory

EF WP PFC and DTT



Resources not available Laser System: ELM simulation+ CW heating if required


NBI vs Plasma exposure

-Effect of particle energy: 35 keV vs <10eV + ELMs (kV): no significant impact (Power deposition range<<film thickness + strong H mobility in liquid metals -Effect of pulse duration: <0.2s vs SS.

Extrapolation needed. Verify with long pulse (5s) Achievement of SS temperature through vapor shielding? Sample preheating

- Only comparative studies for short NBI pulses OK for ELMs (<ms laser pulse)

-Particle fluxes: 4.1021 m-2s-1 vs 1024 m-2s-1. Pplasma: 40 Pa vs 30-100Pa -Retention: Similar P plasma: Comparative studies of gas vs plasma exposure. Issues of hydride formation can be addressed. -Spatial extend: ok . Large interaction area redeposition cycle available -Redeposition. Due to local plasma formation and inelastic collisions near the surface. Diagnostics available. Possibility to extrapolate through modeling. Also, studies in attached dep. probes. Feed back to TECXY code (Zagorski et al)

Issues. Differences:

Raclette modeling

Feed back from AHG • Extrapolation from NBI-driven to Divertor Plasmas. Impact on redepostion and

vapour shielding studies. Modelling activities. - Present codes ( in development): COREDIV and TECYX ( Zagorski). Strong need

of input data for model validation. 1.75 ppys allocated for collaboration with IPPLM - Vapour shielding models: FOREV-2D (Pestchany) and VP models by Skovorodin

et al ( Phys. Plasmas 2016):

-Emin stored in material surface required. - Ablation plasma: ne>1023 m-3! -No dependence on method of heating. - Same value for W found - OLMAT:4 MJ/m2 (phase I and II) Model validation?


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OPTIMIZATION OF LIQUID METAL ADVANCED TARGETS … · optimization of liquid metal advanced targets...

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