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EUROfusion Assessment of Alternative Divertor Solutions for DEMO - - PowerPoint PPT Presentation

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EUROfusion Assessment of Alternative Divertor Solutions for DEMO Holger Reimerdes For the WPDTT1 project In close collaboration with WPPMI, WPPFC and WPDTT2 EUROfusion Assessment of Alternative Divertor Solutions for DEMO H. Reimerdes 1 , L.

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SLIDE 1

EUROfusion Assessment of Alternative Divertor Solutions for DEMO

Holger Reimerdes

For

the WPDTT1 project

In close collaboration with

WPPMI, WPPFC and WPDTT2

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SLIDE 2

EUROfusion Assessment of Alternative Divertor Solutions for DEMO

  • H. Reimerdes1, L. Aho-Mantila2, R. Albanese3, R. Ambrosino3, W. Arter4,
  • S. Brezinsek5, H. Bufferand6, G. Calabro7, G. Ciraolo6, D. Coster8,
  • H. Fernandes9, J. Harrison4, I. Kaldre10, K. Lackner8, O. Lielausis10,
  • J. Loureiro9, T. Lunt8, G. Mazzitelli7, S. McIntosh4, F. Militello4, T. Morgan11,
  • N. Pelekasis12, G. Pelka13, V. Pericoli7, V. Philipps5, F. Subba14, F. Tabares15,
  • B. Viola7, R. Wenninger8, R. Zagorski13 and H. Zohm8

1EPFL-SPC, Lausanne, Switzerland, 2VTT, Finland, 3Università di Napoli, Italy, 4CCFE, Culham,

UK, 5Forschungszentrum Jülich, Germany, 6CEA, St. Paul-lez-Durance, France, 7ENEA- Frascati, Italy, 8Max-Planck-Institut für Plasma Physik, Garching, Germany, 9Universidade de Lisboa, IST, Portugal, 10University of Latvia, Latvia, 11DIFFER, Nieweign, The Netherlands,

12University of Thessaly, Volos, Greece, 13IPPLM, Warsaw, Poland, 14Politecnico di Torino, Italy, 15Ciemat, Madrid, Spain

  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 2
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SLIDE 3

Pursue development of alternative divertor solutions as risk mitigation

European roadmap for fusion energy

  • Identified heat exhaust as the main challenge towards the

realisation of magnetic confinement fusion

  • Assess and develop alternative divertor solutions in case

the baseline solution will not extrapolate to DEMO

  • ITER being the ultimate test of the baseline solution
  • Extrapolation of alternatives to DEMO based on today’s

“proof-of-principle” experiments and modelling considered too large

  • Consider a dedicated Divertor Tokamak Test (DTT) facility

to develop alternative(s) to sufficient maturity for deployment in DEMO

  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 3
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SLIDE 4

Outline

EUROfusion assessment of alternative divertor solutions for DEMO § Strategy and baseline § Assessment of alternative divertor configurations § Assessment of liquid metal PFCs

  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 4
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SLIDE 5

Outline

EUROfusion assessment of alternative divertor solutions for DEMO § Strategy and baseline § Assessment of alternative divertor configurations § Assessment of liquid metal PFCs

  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 5
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SLIDE 6

Assessment strategy

  • Focus on solution with high potential to reach sufficient

technological maturity in time for a DEMO to start

  • peration in the 2040s
  • Compare potential “benefits” and “costs” of alternatives

with the baseline DEMO solution

Ø Produce a short-list of the most promising alternatives

  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 6
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SLIDE 7

Compare alternatives with the European baseline divertor solution for DEMO

  • Conventional DEMO scenario with Pelec = 500 MW (R = 8.8 m,

Bt = 5.8 T, IP = 20 MA) [Wenninger, Kemp, private communication]

  • Single null divertor (SND)
  • Tungsten (W) targets
  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 7

Pheat,eff ¡= ¡ 300 ¡MW ¡

2014 DEMO1 (A=3.1)

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SLIDE 8

Compare alternatives with the European baseline divertor solution for DEMO

  • Conventional DEMO scenario with Pelec = 500 MW (R = 8.8 m,

Bt = 5.8 T, IP = 20 MA) [Wenninger, Kemp, private communication]

  • Single null divertor (SND)
  • Tungsten (W) targets
  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 8
  • Target requirements
  • Te,t < 5 eV to avoid W sputtering
  • q⊥,t < 5-10 MW/m2 to avoid target

damage

[You, et al., EFPW (2014)]

Example.: Water cooled ITER-like W monoblock

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SLIDE 9

Compare alternatives with the European baseline divertor solution for DEMO

  • Conventional DEMO scenario with Pelec = 500 MW (R = 8.8 m,

Bt = 5.8 T, IP = 20 MA) [Wenninger, Kemp, private communication]

  • Single null divertor (SND)
  • Tungsten (W) targets
  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 9
  • Target requirements
  • Te,t < 5 eV to avoid W sputtering
  • q⊥,t < 5-10 MW/m2 to avoid target

damage

  • Assumptions
  • Power decay length λq,u~ ρpi ~ 3 mm
  • Min. grazing angle 1.5 Deg ➜

Aw = 2 m2/target

[You, et al., EFPW (2014)]

Example.: Water cooled ITER-like W monoblock

Total radiated fraction Power to outer target (MW) * q⊥,outer,max (MW/m2) Prad/Pheat=90% 20 10 Prad/Pheat=95% 10 5

*Assume a 1:2 in:out asymmetry

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SLIDE 10

Compare alternatives with the European baseline divertor solution for DEMO

  • Conventional DEMO scenario with Pelec = 500 MW (R = 8.8 m,

Bt = 5.8 T, IP = 20 MA) [Wenninger, Kemp, private communication]

  • Single null divertor (SND)
  • Tungsten (W) targets
  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 10
  • Target requirements
  • Te,t < 5 eV to avoid W sputtering
  • q⊥,t < 5-10 MW/m2 to avoid target

damage

  • Assumptions
  • Power decay length λq,u~ ρpi ~ 3 mm
  • Min. grazing angle 1.5 Deg ➜

Aw = 2 m2/target

Ø Radiate 90-95% of the heating power Ø Reduce SOL pressure to reduce power deposition due to recombination processes ➜ (partial) particle detachment

Total radiated fraction Power to outer target (MW) * q⊥,outer,max (MW/m2) Prad/Pheat=90% 20 10 Prad/Pheat=95% 10 5

*Assume a 1:2 in:out asymmetry

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SLIDE 11

Extrapolation of baseline solution to DEMO is uncertain

Main sources of uncertainty are

  • Power decay length λq and wetted area Aw
  • Confinement and its compatibility with high core radiation
  • Stability of detachment under high heat fluxes
  • Ability to sufficiently suppress transients
  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 11
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SLIDE 12

Alternative divertor concepts can help in two ways

  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 12

Increase divertor energy and momentum losses In-situ repair of damaged surface

and/or

Decrease peak heat and particle flux onto the divertor target Increase exhaust capabilities

  • f divertor targets

Liquid metal target armour Distribute power over a greater surface Easier access to detachment/ wider operating regime More robust/stable detachment Alternative magnetic divertor configurations Greater tolerance for transients Thinner armour/convection/ evaporation for higher heat handling capability

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SLIDE 13

Outline

EUROfusion assessment of alternative divertor solutions for DEMO § Strategy and baseline § Assessment of alternative divertor configurations § Assessment of liquid metal PFCs

  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 13
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SLIDE 14

Considered alternative configurations

  • X divertor (XD) [M. Kotschenreuther, et al., Phys. Plasmas 14 (2007) 72502]
  • Increase pol. flux expansion to flare flux surfaces towards target
  • Super-X divertor (SXD) [P.M. Valanju, et al., Phys. Plasmas 16 (2009)

056110]

  • Increase major radius of target (only way to increase Aw at

constant γ without invoking plasma physics)

  • Combine with XD and flare flux surfaces
  • Snowflake divertor (SFD) [D.D. Ryutov, Phys. Plasmas 14 (2007)

064502]

  • Second order null point expands flux near null point
  • In practice always two nearby x-points with SF+ or SF- topology
  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 14
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SLIDE 15

Considered alternative configurations

  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 15

Divertor concept* Key characteristic Geometry Effect on power exhaust X divertor (XD) [Kotschenreuther, et al., Phys. Plasmas 14 (2007) 72502] Increase pol. flux expansion to flare flux surfaces towards target Flaring

  • Stabilise location of detachment front (?)

Longer connection length/ larger SOL volume

  • Cooler targets ease access to detachment
  • Higher volumetric losses ease access to

detachment Lower target tilt

  • Recycling neutrals reflect upstream for

easier detachment (?) Super-X divertor (SXD) [Valanju, et al., Phys. Plasmas 16 (2009) 056110] Increase major radius of target(s) Increase wetted area

  • Lower peak heat flux

Decrease q||

  • Cooler targets ease access to detachment

Introduce gradient in q||

  • Stabilise location of radiation front (?)

Can be combined with an increase of

  • pol. flux expansion

See XD Snowflake divertor (SFD) [Ryutov, Phys. Plasmas 14 (2007) 064502] Second order null point - in practice always two nearby x-points with SF+ or SF- topology Converging flux surfaces towards target

  • Stabilise location of detachment front (?),

albeit close/within confined plasma (distinguish SF+ and SF-) Longer connection length/ larger SOL volume

  • Cooler targets ease access to detachment
  • Higher volumetric losses ease access to

detachment Large low field region and larger shear

  • May affect turbulent transport (?)
  • May broaden/narrow the SOL (?)

*Not necessarily first incarnation

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SLIDE 16

Evaluate feasibility of alternative configurations and compare costs with baseline

  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 16

Constraints

  • Core plasma parameters: R, Bt, IP, κ95, δ95
  • Current density < 12.5 MA/m2
  • Magnetic field < 12.5 T
  • Vertical forces
  • Single PF coil Fz,PF < 450 MN
  • CS stack Fz,CS < 300 MN
  • CS separation Fz,CS,sep < 350 MN
  • Grazing angle of B-field at target γt =1.5 Deg. – tilt target to close

divertor

Costs

  • Total PF coil current (weighted with radius) ➜ Cost of coils
  • TF volume/plasma volume ➜ Higher costs for TF coils
  • Increase of poloidal angle subtended by the divertor ➜ Need for a

higher tritium breeding fraction

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SLIDE 17

The XD configuration

  • Evaluate only as solution for

the outer leg

  • Use (need?) internal coils to
  • btain flux flaring
  • Net-zero current in internal coils

allows for modular design

  • Note
  • Difficulty to increase flaring above

fx,t/fx,min ~1.5 (because of γ)

  • fx,min located in immediate

proximity of the target

Ø Evaluate use of external coils

  • nly
  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 17
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SLIDE 18

The SXD configuration

  • Evaluate only as solution for

the outer leg

  • Use (need?) in vessel coil to

bend leg

  • Note
  • Outer target can be located

behind the neutron shielding

  • No significant increase in

connection length

  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 18

Work in progress

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SLIDE 19

The SXD configuration

  • Evaluate only as solution for

the outer leg

  • Use (need?) in vessel coil to

bend leg

  • Note
  • Outer target can be located

behind the neutron shielding

  • No significant increase in

connection length

Ø Consider 2nd SXD option with poloidal flux expansion

  • Increases connection length
  • Adds in-vessel coils

Ø Evaluate simple SXD using external coils only

  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 19

Work in progress

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SLIDE 20

The SFD configuration

  • Closed divertor relaxed for

lower SPs to increase flexibility of configuration

  • Note
  • Meeting force constraints is

challenging, but feasible

  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 20
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SLIDE 21

XD and SFD are feasible with geometric variations being of order 1

  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 21

SND ¡ XD ¡ SXD ¡ SFD ¡ Limit ¡ Costs ¡

  • Max. ¡Σ ¡|IPF| ¡(MA·√turns) ¡

160 ¡ 194 ¡ 174 ¡ Total ¡IPF,internal ¡(MA·√turns) ¡

  • ­‑ ¡

10 ¡

  • ­‑ ¡
  • Max. ¡force ¡on ¡single ¡coil ¡Fz,PF ¡(MN) ¡

145 ¡ 301 ¡ 439 ¡ < ¡450 ¡

  • Max. ¡CS ¡separaJon ¡force ¡Fz,CS ¡(MN) ¡

130 ¡ 244 ¡ 329 ¡ < ¡350 ¡ Flux ¡swing ¡for ¡current ¡drive ¡(V⋅S) ¡ 330 ¡ 340 ¡ 215 ¡ VTF/Vplasma ¡ 2.9 ¡ 3.6 ¡ 3.8 ¡ Benefits ¡ L||,outer ¡(ρu=3mm) ¡(m) ¡ 114 ¡ 146 ¡ 245 ¡ fx,t/fx,min ¡ 1 ¡ 1.43 ¡ 1 ¡ Rt/Rx ¡ 1.04 ¡ 1.14 ¡ 1.19 ¡ Work in progress

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SLIDE 22

Use models with various degrees of sophistication to predict exhaust performance in DEMO

  • Proposed figures of merit
  • Density for the onset of detachment
  • Impurity concentration for required divertor power loss (e.g. for

q⊥,t,max = 10 MW/m2)

  • Max. divertor power loss before loss of stability/convergence
  • Evaluate He pumping capability
  • Evaluate impurity retention in divertor (seeded and sputtered)

and effect on global confinement

  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 22
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SLIDE 23

Scoping studies identified model capabilities

  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 23

x: ¡works ¡(with ¡limited ¡addiJonal ¡effort), ¡o: ¡works ¡with ¡caveats ¡(e.g. ¡excessive ¡run ¡Jme), ¡-­‑: ¡does ¡not ¡work ¡

COREDIV ¡ TECXY ¡ OSM ¡ EMC3 ¡ EDGE2D ¡ SOLPS ¡ SOLEDGE2D ¡

  • Config. ¡

DEMO ¡SND ¡ x ¡ x ¡ x ¡ x ¡ x ¡ x ¡ x ¡ DEMO ¡XD ¡ x ¡ x ¡ x ¡ x ¡ x ¡ x ¡ x ¡ DEMO ¡SXD ¡ x ¡ x ¡ x ¡ x ¡ x ¡ x ¡ x ¡ DEMO ¡SF+/SF-­‑ ¡

  • /o ¡

x/o ¡

  • /o ¡

x/x ¡

  • ­‑/-­‑ ¡
  • /-­‑ ¡

x/(x) ¡ Physics ¡ Private ¡flux ¡region ¡

  • ­‑ ¡
  • ¡

x ¡ x ¡ x ¡ x ¡ x ¡ Target ¡geometry ¡

  • ­‑ ¡
  • ­‑ ¡

x ¡ x ¡ x ¡ x ¡ x ¡ Dri_s ¡

  • ­‑ ¡
  • ¡
  • ¡
  • ­‑ ¡

? ¡

  • ¡

(o) ¡ KineJc ¡neutrals ¡

  • ­‑ ¡
  • ­‑ ¡
  • ¡
  • ¡
  • ¡
  • ¡
  • ¡

ImpuriJes ¡ x ¡ x ¡

  • ¡
  • ¡

? ¡ x ¡

  • ¡
  • All models calibrate (diffusive) transport coefficients to estimate of

λq,u in the reference SND scenario

  • All models neglect effect of geometry on turbulent transport!
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SLIDE 24

Scoping studies identified model capabilities

  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 24

x: ¡works ¡(with ¡limited ¡addiJonal ¡effort), ¡o: ¡works ¡with ¡caveats ¡(e.g. ¡excessive ¡run ¡Jme), ¡-­‑: ¡does ¡not ¡work ¡

COREDIV ¡ TECXY ¡ OSM ¡ EMC3 ¡ EDGE2D ¡ SOLPS ¡ SOLEDGE2D ¡

  • Config. ¡

DEMO ¡SND ¡ x ¡ x ¡ x ¡ x ¡ x ¡ x ¡ x ¡ DEMO ¡XD ¡ x ¡ x ¡ x ¡ x ¡ x ¡ x ¡ x ¡ DEMO ¡SXD ¡ x ¡ x ¡ x ¡ x ¡ x ¡ x ¡ x ¡ DEMO ¡SF+/SF-­‑ ¡

  • /o ¡

x/o ¡

  • /o ¡

x/x ¡

  • ­‑/-­‑ ¡
  • /-­‑ ¡

x/(x) ¡ Physics ¡ Private ¡flux ¡region ¡

  • ­‑ ¡
  • ¡

x ¡ x ¡ x ¡ x ¡ x ¡ Target ¡geometry ¡

  • ­‑ ¡
  • ­‑ ¡

x ¡ x ¡ x ¡ x ¡ x ¡ Dri_s ¡

  • ­‑ ¡
  • ¡
  • ¡
  • ­‑ ¡

? ¡

  • ¡

(o) ¡ KineJc ¡neutrals ¡

  • ­‑ ¡
  • ­‑ ¡
  • ¡
  • ¡
  • ¡
  • ¡
  • ¡

ImpuriJes ¡ x ¡ x ¡

  • ¡
  • ¡

? ¡ x ¡

  • ¡
  • All models calibrate (diffusive) transport coefficients to estimate of

λq,u in the reference SND scenario

  • All models neglect effect of geometry on turbulent transport!

➜ Expect first results by the end of 2015

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SLIDE 25

Assessment: Alternative configurations

  • Alternative configurations come with increased costs that can

be quantified

  • Potential benefits are less certain, but predictions face similar

uncertainties as predictions for the baseline solution

  • Ongoing effort aims at estimates relative to the baseline solution
  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 25
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SLIDE 26

Outline

EUROfusion assessment of alternative divertor solutions for DEMO § Strategy and baseline § Assessment of alternative divertor configurations § Assessment of liquid metal PFCs

  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 26
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SLIDE 27

Liquid metal based concepts

  • Radiation cooling
  • Eroded/evaporated liquid increases divertor

radiation (stabilising feedback)

  • Evaporation cooling
  • Condensation of evaporated metal spreads heat
  • ver a larger surface area
  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 27
  • Static liquid: Heat removal via conduction
  • Stabilised by a capillary porous system (CPS) [Golubchikov, et al., JNM

(1996)]

  • Moving liquid: Heat removal via advection
  • Liquid metal infused trenches (LIMIT): Stabilise by trenches and drive with

thermo-electric currents [Ruzic, et al., NF (2011)]

Vapour shielding

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SLIDE 28

Liquid metal based concepts

  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 28

LM concept Heat removal Stabilisation Critical issues Static liquid Conduction Capillary porous system (CPS) [Golubchikov, et al., JNM (1996)]

  • Limited heat removal potential

Moving liquid Advection Trenches [Ruzic, et al., NF (2011)] ¡

  • High MHD forces in reactor relevant

magnetic fields oppose movement and limit heat removal capability Radiation cooling Radiation e.g. CPS

  • Li (required for core compatibility) is a

‘poor’ radiator Evaporation cooling Evaporation e.g. CPS

  • High net mass flow (1kg Li/sec for

20MW)

  • Compatibility of high Li pressure with

He pumping capability?

Ø Focus on LM targets based on capillary porous systems (CPS)

  • Solving issues of CPS based solutions is a necessary requirement for

moving liquids

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SLIDE 29

Consider Li and Sn (and their alloy) which face different challenges

  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 29

Lithium Li Tin Sn Z 3 50 Tmelt (°C) 181 233 Tmax,2 (°C)* 482 1255 Tboil (°C) 1340 3053 Power exhaust potential ~10MW/m2* 25MW/m2* Core compatibility Good, but fuel dilution might become a problem Poor, accumulates in the core and strongly radiates Hydrogenic retention Can be high, but depends on temperature Low *[Coenen, et al, PS (2014)]

  • Stationary power exhaust potential of conduction-based systems

determined by surface temperature and thickness of components

  • Surface temperature is determined by
  • Allowable erosion
  • Realisable replenishment rate
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SLIDE 30

Need complete target design to evaluate heat removal capability

  • Heat removal capability may be limited by temperature range of

non-armour components of the target

  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 30

[You, et al., EFPW (2014)]

Example.: Temperature of CuCrZr tube limited by

  • Irradiation hardening at T<200°C
  • Irradiation creep at T>300°C
slide-31
SLIDE 31

Characterisation of material properties

  • Measurements of temperature

enhanced sputtering

  • Sn CPS in Pilot-PSI [Morgan, et

al., JNM (2015)]

  • Measurements of hydrogenic

retention

  • Exposure of Sn to D plasmas in

ISTTOK yields low retention rate (0.068%) [Loureiro, et al., ISLA (2015)]

  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 31

Pilot-PSI Sn CPS ISTTOK Sn sample holder

slide-32
SLIDE 32

Move towards demonstration of LM power handling capability

  • Test cooled (➜ stationary operation) LM limiters in FTU
  • Cooled Li limiter (CLL): first experiments in 2014/15, but not

stationary, CLL currently being improved

  • Li CPS with W mesh
  • Cooled Sn limiter (2016)
  • Sn CPS, plan to test prototypes in Pilot-PSI
  • Increase FTU discharge length from 1.5 to 5s (4.5s achieved)

for stationary exhaust

  • Develop a diverted FTU configuration
  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 32

See G. Mazzitelli, “Experimental results with the Cooled Lithium Limiter (CLL) on FTU”, this meeting.

slide-33
SLIDE 33

Assessment: LM based concepts

  • Need for the development of an integrated solution with the full

LM cycle demonstrating control over the LM and hydrogenic inventory

  • Replenishment
  • LM purging
  • LM migration and recovery
  • Need for the development of a target with a reactor compatible

structural design

  • Materials including coolant
  • Dimensions
  • Possibility for game changers
  • Possible tolerance to transients
  • Possible elimination of tile gaps
  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 33
slide-34
SLIDE 34

Extra slides

  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 34
slide-35
SLIDE 35
  • The plasma temperature at the target has to be smaller

than 5eV to avoid erosion (through physical sputtering)

  • The heat flux onto the divertor target q⊥,t has to be smaller

than 5 MW/m2 to avoid melting (target technology might increase this value by x2-3)

  • Even with a low target temperature the power density due

to the potential energy of the ions would exceed the heat flux limit ➜ Need to reduce pressure at target, i.e. detach the divertor

  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 35

q||,t = !||,t !kTt + Epot

( ) = pt !Tt

1 2 + Epot

Tt

1 2

" # $ % & '

slide-36
SLIDE 36

Other alternative configurations

  • Double null divertor
  • X-point target [B. LaBombard, et al., APS (2013)]/tripod [G.Y. Zheng, et al., FED

(2014)] (between SF- and XD)

  • Also motivated by recent SF- calculations [T. Lunt, et al, EPS (2015)]
  • Negative triangularity tokamak (NTT) [M. Kikuchi, et al., 1st International

E-Conference On Energies 2014]

  • Relies heavily on core physics
  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 36
slide-37
SLIDE 37

Ongoing configuration development

  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 37

XD with external PF coils only SXD with external PF coils only

slide-38
SLIDE 38

Modelling

  • Heat removal (incl. transients)
  • Heat conduction (e.g. RACLETTE, ANSYS)
  • Wetting and replenishment
  • Fluid modelling
  • Edge transport, effect on core performance
  • Transport models (e.g. COREDIV) with appropriate boundary

conditions

  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 38

Dependence of seepage velocity of Li on the capillary radius

[Benos, ¡Pelekasis, ¡GRACM ¡(2015)] ¡

slide-39
SLIDE 39

Li/SN alloys appear to unite positive characteristics of each component

  • Low vapour pressure
  • Preferential evaporation of Li
  • Negligible D retention (indicated by ISTTOK experiments)
  • H. Reimerdes | 1st IAEA TM on Divertor Concepts | Vienna | October 1, 2015 | Page 39