Design and R&D of Plasma Facing Components and Assessment of Divertor Performance

S. Sakurai, H. Kawashima, S. Higashijima, K. Shimizu, K. Masaki, N. Asakura, T. Hayashi, Y. K. Shibama and A. Sakasai

Contents1. Overview of JT-60SA and Requirements of Divertor2. Assessment of Divertor Plasma Performance3. Design and R&D of divertor components4. Summary and Future Work

International Symposium on Plasma Surface Interactions2008.5.26

Toledo, SPAIN

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JT-60SA is a combined project of Japan-EU satellite tokamak program under the BA and Japanese domestic program

SlimCS (DEMO concept)compact design (R/a=2.6) of tokamak reactor.

ITER

6m

JT-60SA Euratom

Ref. M. Kikuchi, et al in Fusion Energy 2006 (Proc. 21st Int. Conf. Chengdu, 2006) (Vienna: IAEA) CD-ROM, FT/2-5 and http://www-naweb.iaea.org/napc/physics/FEC/FEC2006/html/index.htm.

ITER support research for accomplishment of the mission

Sustaining ITER relevant plasmas (R/a=3.1) with high density, good confinement and high power heating

ITER supplement researchtowards DEMO

Sustaining DEMO relevant high-N = 3.5-5.5 & non-inductive current driven plasma (R/a>2.6) with highly shaped configuration

x2

R/a~2.6

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Basic requirements of divertor in JT-60SAJT-60SA Euratom

070315_iter_s-5_d10cm_new2

6m

Lower divertor for ITER-like plasma

Upper divertor for DEMO-like plasma Heat reduction and particle control in ITER-like and DEMO-like plasma configuration Power handling with cooled divertor target and maintenance by divertor cassette and remote handling system Flexibility in plasma facing materials for PMI research by armor tiles bolted on heatsink

Cryopanel

divertor cassette

ITER-like Plasma

ExchangedPerformance of lower divertor Vertical target V corner Connecting and pumping through private regionhad been confirmed by divertor simulation.

Ref. N. Asakura, et al. , in 34th EPS, H. Kawashima, et al., in ISFNT-8

Lower divertor

Performance assessment of upper divertor for DEMO-like plasma (high , high and low A) will be reported in this presentation.

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Two type of upper divertor were compared

W-shaped with shallow V corner Allowing high and low A plasma 2-cm SOL can be led to target Insufficient heat load reduction?

JT-60SA Euratom

Innertarget

Outertarget

V corner

Private dome

Interference with a divertor cassette and VV

Private dome

Innertarget

Outertarget

0.5 m

Upper divertor should be compact to allow high , high and low A plasma under the limitation of divertor cassette and VV geometries.

Vertical target with deep V corner Effective for heat load reduction? 1.5-cm SOL can be led to target Allowable and A slightly degrade

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Qout=37MW

ion=2x1021s-1

puff

Spump

Divertor plasma performances in USN configuration were evaluated by using SOLDOR/NEUT2D code

JT-60SA Euratom

SOLDOR: 2D fluid for plasmaNEUT2D: 2D Monte-Calro for neutralsNon-corona model: for carbon radiation profile

Cimp = 1%

Ref. :H. Kawashima, et al., Plasma Fusion Res. 1 (2006) 031. K. Shimizu, et al., J. Nucl. Mater. 313-316 (2003) 1277.

Thermal diffusivities i,e=1m2/s

Particle diffusion coefficient D=0.3m2/s

Recycling coefficient of D at first wall =1

Residence parameter neres=4x1015s/m3

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Vertical target with deep V corner reduces peak heat load

Vertical target 5 MW/m2 (detached)

JT-60SA Euratom

W-shaped 11 MW/m2

With gas puff (puff = 5 x1021/s)

W/O gas puff, Spump =50m3/s

0

5 106

1 107

1.5 107

2 107

0 0.1 0.2 0.3Distance from the separatrix (m)

20

15

10

5

0

Hea

t fl

ux

(MW

/m2 )

W-shaped

Vertical target

Vertical target with deep V corner obtain higher density and lower temperature near the separatrix.

W-shaped with shallow V corner

0

1 1020

2 1020

3 1020

4 1020

5 1020

0

20

40

60

80

100

0 0.1 0.2 0.3

0

1 1020

2 1020

3 1020

4 1020

5 1020

0

20

40

60

80

100

0 0.1 0.2 0.3Distance from the separatrix (m)

5

4

3

2

1

0

100

80

60

40

20

0

5

4

3

2

1

0

ne

ne

Te

Te

Ti

Ti

Den

sity

(10

20/m

3 )D

ensi

ty (

1020

/m3 )

Tem

per

atu

re (

eV)

on the outer divertor target

Vertical target with deep V corner

100

80

60

40

20

0

Tem

per

atu

re (

eV)

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Particle balance and its controllability were comparedJT-60SA Euratom

Detachment occurs at 6~7x1023 D/s of recycling flux from outer target. Inner divertor is pumped and outer divertor is fueled through private region. Vertical target can obtain detachment at a half fueling for W-shaped divertor. Particle balance changes sensitively with pumping speed in W-shaped divertor.

recID

netID

netOD

recOD

0.7

65.6

2.0

pump

-1.366.1

nD0

recID

netID

netOD

recOD0.7

65.4

2.9

pump

-2.2

65.0

nD0

ion=0.2x1022 D/s

puff=0.5x1022 D/s

Spump=50m3/s

W-shaped with shallow V corner Vertical target with deep V corner (1022 D/s)

Spump

(m3/s)

W-shaped (1022D/s) Vertical (1022D/s)

recID net

ID recOD net

OD OD recID net

ID recOD net

OD OD

30 60.5 3.0 70.3 -2.3 detach

40 62.5 2.8 66.6 -2.2 attach

50 65.4 2.9 65.0 -2.2 attach 65.6 2.0 66.1 -1.3 detach

100 70.0 1.6 67.7 -1.0 detach

200 72.1 1.5 56.0 -0.9 attach

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Mono-block CFC target can remove heat flux of 15MW/m2

Short mockup of water-cooled mono-block CFC target survives 1450 cycle heat load at 15 MW/m2 and 600 cycle at 20 MW/m2.

30mm

Backplate

Coolant header

Thermal expansion

30mm

Outer target plate

CFCmonoblock

CuCrZr cooling tubeOFCu compliant layer

CFC mono-block

Brazed

JT-60SA Euratom

lamination of fiber

1500 °C

2000 °CIRTV image at 15MW/m2

weak erosion due to sublimation

after heat load test

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Divertor and its maintenance

Private Dome

Inner Target

Outer Target

Inner and Outer Baffles

Divertor Cassette

Cryopanel

Exhaust Hole

Cooling Water Pipes

Bottom divertor with divertor cassette

Divertor targets, private dome and baffles are mounted on a divertor cassette for maintenance by remote handling.

Palette

Lifting Cassette,carrying to Palette Carrying out from VV

Ref. T. Hayashi, et al: Transactions of the American Nuclear Society 96, 783 (2007)

JT-60SA Euratom

Divertor can be maintained after carrying out through horizontal port.

Weight and size of divertor cassette is limited.

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JT-60SA Euratom

Performance of W-shaped divertor and vertical target divertor were compared as a upper divertor for DEMO-like configuration by using 2D plasma fluid (SOLDOR) and neutral Monte-Carlo (NEUT2D) code.

Vertical target with deep V corner can obtain partial detachment and reduce peak heat flux in outer divertor with a half net fueling for W-shaped divertor.

W-shaped divertor with shallow V corner can change particle balance at the outer divertor with small change in pumping speed.

Mono-block type CFC divertor target is promising for heat removal up to 15MW/m2.

A remote handing system and divertor cassettes will be introduced to maintain in-vessel components under high dose rate environment.

Future Work

Confirmation and optimization of the effect of V corner depth

Improvement of simulation (SONIC code = SOLDOR+NEUT2D+IMPMC)

=> K. Shimizu et al., P3-72 in this conference.

Detailed design optimization, Qualification of mass production of target

Summary

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12

“V-shaped corner” enhance detachment and reduce heat flux

JT-60SA Euratom

Distance from strike point (m)

Heat flux at outer target (MW/m2)

0.0 0.1 0.2 0.30

5

10

15

“V-shaped corner”with gas puff

allowable level“V-shaped corner”without gas puff“L-shaped corner”with gas puff“L-shaped corner”without gas puff

albedoChevron

Cryo-pump

p,out

p,in

pump

Dome

V-shaped corner

L-shaped corner

Detailed simulation model of divertor

R (m)2.5 3.0

Te

V-shaped corner

neExhaustBackflow

R (m)2.5 3.0

V-shaped corner

Density and temperature distribution in outer divertor with gas puff

ne along the separatrix increases especially in “V-shaped corner” due to particle backflow and recycling enhancement by “V-shaped corner”. Partially detachment reduces Te along the separatrix in the “V-shaped corner”.

Outer divertor plasma is detached with medium gas puffing and peak heat flux is reduced with “V-shaped corner”

Ref. N. Asakura, et al “Physics issues and simulation of the JT-60SA divertor for large heat and particle handling” 34 th EPS H. Kawashima, et al “Design study of JT-60SA divertor for high heat and particle controllability” in ISFNT-8

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JT-60SA Euratom

10

813

888

9 1

11cm higher X-point

828

837

4535

10

standard X-point

(x1021D/s)

Detachment can be controlled by changing the plasma configuration in vertical target with V-shaped corner

Control of detachment in JT-60SA is important issue similar to ITER:

Standard X-point configuration4.5x1022 D/s is exhausted from inner divertor, while large part is supplied to outer divertor leg.efficiently produce detachment at Outer strike-point in the V-corner. "Circulation" of neutrals in ITER divertor was simulated (Kukushkin, PPCF 2002) Higher X-point configurationflow pattern changes, and both-side pumping is expected. Plasma becomes attached at Outer strike-point, while inner divertor detachment slightly extends to the upstream.

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Remote handling for divertor cassette maintenance

ManipulatorRail

Divertor cassette

Palette

Cutting pipe

Removing Screw

Lifting Cassette,carrying to Palette Handing to Palette Carrying out of VV

Removal of divertor Cassettemanipulator

rail support

rail support

rail

swing armstraight motion arm

225º

Top view of vessel

Divertor cassettes are 36 (toroidally 10): weight of one cassette is ~500kg for CFC target, ~800kg for Tungsten target

Arm drive unit can handle up to 900 kg weight, and it is inserted through horizontal port (width of ~60 cm).

Vehicle-type system (adopted in ITER)

JT-60SA Euratom

Ref. T. Hayashi, et al: Transactions of the American Nuclear Society 96, 783 (2007)

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Bolted armor for first wall and its maintenance

600C (saturated)

Surface Temperatureat 1 MW/m2 x 100s

110mm125mm

Heat load test of bolted armor

JT-60SA Euratom

Rail support

Light weight manipulator

VehicleRail support

Rail support

Rail

Support vehicle with rack for tiles and tools

Support vehicle

Vehicle

Light weight manipulator Camera & Lamp

Tile chuck mechanism

Tile rack changer

Tile rack

More than 10000 armor tiles will be replaced within 1 year for transition from carbon wall to metal (tungsten) wall in future.

Vehicle type RH system with dual arm manipulator and support vehicle

Water-cooled bolted armor for inboard FWCarbon tile

Metal tileCu alloy heatsink

VV

Base

space for sensors and etc.

70mm

A bolted armor on a water-cooled heatsink for a first wall can remove ~1MW/m2 of heat flux.