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

1. International Symposium on Plasma Surface Interactions 2008.5.26 Toledo, SPAIN 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 Contents 1. Overview of JT-60SA and Requirements of Divertor 2. Assessment of Divertor Plasma Performance 3. Design and R&D of divertor components 4. Summary and Future Work

2. Euratom JT-60SA ITER JT-60SA is a combined project of Japan-EU satellite tokamak program under the BA and Japanese domestic program 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 research towards DEMO Sustaining DEMO relevant high-bN = 3.5-5.5 & non-inductive current driven plasma (R/a>2.6) with highly shaped configuration x2 6m R/a~2.6 SlimCS(DEMO concept) compact design (R/a=2.6) of tokamak reactor. 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.

3. Euratom JT-60SA Performance of lower divertor • Vertical target • V corner • Connecting and pumping through private region had been confirmed by divertor simulation. Lower divertor Ref. N. Asakura, et al. , in 34th EPS, H. Kawashima, et al., in ISFNT-8 Basic requirements of divertor in JT-60SA 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 ITER-like Plasma 6m Exchanged divertor cassette Performance assessment of upper divertor for DEMO-like plasma (high k, high d and low A) will be reported in this presentation. Cryopanel Lower divertor for ITER-like plasma

4. Two type of upper divertor were compared Euratom JT-60SA V corner Outer target Private dome Inner target Upper divertor should be compact to allow high k, high d and low A plasma under the limitation of divertor cassette and VV geometries. W-shaped with shallow V corner • Allowing high k and low A plasma • 2-cm SOL can be led to target • Insufficient heat load reduction? Vertical target with deep V corner • Effective for heat load reduction? • 1.5-cm SOL can be led to target • Allowable k and A slightly degrade Interference with a divertor cassette and VV Outer target Private dome Inner target 0.5 m

5. Divertor plasma performances in USN configuration were evaluated by using SOLDOR/NEUT2D code Euratom JT-60SA SOLDOR: 2D fluid for plasma NEUT2D: 2D Monte-Calro for neutrals Non-corona model: for carbon radiation profile Spump Cimp = 1% Ref. :H. Kawashima, et al., Plasma Fusion Res. 1 (2006) 031. K. Shimizu, et al., J. Nucl. Mater. 313-316 (2003) 1277. Gpuff Qout=37MW Thermal diffusivities ci,e=1m2/s Particle diffusion coefficient D=0.3m2/s Recycling coefficient of D at first wall =1 Residence parameter netres=4x1015s/m3 Gion=2x1021s-1

6. 5 5 4 4 W-shaped with shallow V corner 3 3 ne Euratom 20 2 2 Density (1020/m3) Temperature (eV) W-shaped 15 1 1 Ti JT-60SA Te Vertical target 100 100 0 0 Heat flux (MW/m2) 10 80 80 5 60 60 ne Vertical target with deep V corner 0 40 40 Distance from the separatrix (m) 20 20 Density (1020/m3) Temperature (eV) Ti 0 0 Te Distance from the separatrix (m) on the outer divertor target Vertical target with deep V corner reduces peak heat load W/O gas puff, Spump =50m3/s Vertical target with deep V corner obtain higher density and lower temperature near the separatrix. With gas puff (puff = 5 x1021/s) W-shaped11 MW/m2 Vertical target 5 MW/m2 (detached)

7. Particle balance and its controllability were compared Gpump Gpump GnetOD GnetOD GrecOD 0.7 GrecOD 0.7 -2.2 -1.3 Euratom 2.0 66.1 2.9 GnetID GnetID 65.0 GrecID GrecID JT-60SA 65.6 65.4 nD0 nD0 W-shaped with shallow V corner Vertical target with deep V corner (1022 D/s) Gion=0.2x1022 D/s Gpuff=0.5x1022 D/s Spump=50m3/s • 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.

8. Thermal expansion CFC monoblock lamination of fiber Euratom 30mm JT-60SA 30mm 2000 °C IRTV image at 15MW/m2 Coolant header Backplate 1500 °C CuCrZr cooling tube OFCu compliant layer after heat load test Brazed CFC mono-block weak erosion due to sublimation Outer target plate 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.

9. Euratom Inner and Outer Baffles Outer Target JT-60SA Private Dome Palette Inner Target Exhaust Hole Divertor Cassette Cryopanel Cooling Water Pipes Divertor and its maintenance Divertor targets, private dome and baffles are mounted on a divertor cassette for maintenance by remote handling. Lifting Cassette, carrying to Palette Carryingout fromVV Divertor can be maintained after carrying out through horizontal port. Weight and size of divertor cassette is limited. Bottom divertor with divertor cassette Ref. T. Hayashi, et al: Transactions of the American Nuclear Society 96, 783 (2007)

10. Euratom JT-60SA Summary 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

12. Detailed simulation model of divertor Euratom Dome p,in V-shaped corner JT-60SA p,out L-shaped corner pump Chevron albedo Cryo-pump Density and temperature distribution in outer divertor with gas puff “V-shaped corner” with gas puff allowable level 15 “V-shaped corner” without gas puff Te “L-shaped corner” with gas puff ne 10 Heat flux at outer target (MW/m2) “L-shaped corner” without gas puff Exhaust Backflow 5 V-shaped corner V-shaped corner 0 0.0 0.1 0.2 0.3 2.5 2.5 R (m) R (m) 3.0 3.0 Distance from strike point (m) “V-shaped corner” enhance detachment and reduce heat flux 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” 34th EPS H. Kawashima, et al “Design study of JT-60SA divertor for high heat and particle controllability” in ISFNT-8

13. Detachment can be controlled by changing the plasma configuration in vertical target with V-shaped corner Euratom JT-60SA 11cm higher X-point standard X-point 813 828 888 837 45 9 1 35 (x1021D/s) 10 10 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.

14. Remote handling for divertor cassette maintenance Vehicle-type system (adopted in ITER) Top view of vessel rail support Arm drive unit can handle up to 900 kg weight, and it is inserted throughhorizontal port (width of ~60 cm). Euratom rail Divertor cassettes are 36 (toroidally 10): weight of one cassette is ~500kg for CFC target, ~800kg for Tungsten target JT-60SA 225º swing arm rail support straight motion arm manipulator Palette Removal of divertor Cassette Rail Manipulator Removing Screw Cutting pipe Lifting Cassette, carrying to Palette Divertor cassette Carrying out of VV Handing to Palette Ref. T. Hayashi, et al: Transactions of the American Nuclear Society 96, 783 (2007)

15. JT-60SA Euratom Heat load test of bolted armor 600C (saturated) Water-cooled bolted armor for inboard FW Cu alloy heatsink 70mm Carbon tile Metal tile 125mm 110mm Surface Temperature at 1 MW/m2 x 100s Base space for sensors and etc. VV Vehicle type RH system with dual arm manipulator and support vehicle Support vehicle Support vehicle with rack for tiles and tools Vehicle Tile rack changer Rail support Vehicle Tile rack Light weight manipulator Rail Tile chuck mechanism Light weight manipulator Camera & Lamp Rail support Rail support More than 10000 armor tiles will be replaced within 1 year for transition from carbon wall to metal (tungsten) wall in future. Bolted armor for first wall and its maintenance A bolted armor on a water-cooled heatsink for a first wall can remove ~1MW/m2 of heat flux.