Study of Quasi-Snowflake Divertor for CFETR by using SOLPS YE - PowerPoint PPT Presentation

The First IAEA Technical Meeting on Divertor Concepts Study of Quasi-Snowflake Divertor for CFETR by using SOLPS YE Minyou, MAO Shifeng, LUO Zhengping, PENG Xuebing and CFETR Divertor Design Team University of Science and Technology of China Institute of Plasma Physics, CAS Vienna, Austria 01 Oct 2015

Outline Introduction for CFETR Preliminary Design of Snowflake Divertor Simulation Settings and Operational Status Impurity Radiation and Screening Conclusion

Outline Introduction for CFETR Preliminary Design of Snowflake Divertor Simulation Settings and Operational Status Impurity Radiation and Screening Conclusion

Introduction C hina F usion E ngineering T est R eactor ( CFETR ) A good complement for ITER Main missions Fusion Power 200 MW Duty factor 0.3~0.5 Tritium Self-sufficiency Parameter CFETR ITER Plasma Current I p (MA) 8.5/10 15 Major Radius R (m) 5.7 6.2 Minor Radius a (m) 1.6 2.0 Central magnetic field B T 4.5/5.0 5.3 (T) Elongation Ratio κ 2.0 1.70/1.85 Triangle Deformation δ 0.4 0.33/0.48 B.N. Wan, et al., IEEE Trans. Plasma Sci. (2014) Number of TF coils (N) 16 18 Y.T. Song, et al., IEEE Trans. Plasma Sci. (2014)

Introduction Power handling [MW] Injected power P fusion 200 (auxiliary heating: 100 MW) P α 40 P aux 100 ITER G eom etry P radcore (brem+sync.) 40 8 PF1 P SOL= Pα+ P aux– P radcore 100 PF2 6 CS3L P SOL/R [MW/m] 17 Pfus= 200 MW 4 PF3 CS2L Pheat=100+40 2 CS1L MW Z [m ] Comparable with ITER 0 Prad= 40 MW CS1U − 2 PF4 CFETR Divertor Baseline: ITER-like Divertor CS2U − 4 CS3U − 6 P F5 PF6 Exploring effective way to reduce q pk for − 100MW 8 2 4 6 8 10 12 R [m ] future fusion reactor ( P/R ~ 80-100) Snowflake Divertor Engineering limit: q pk < 10 MW/m2

Outline Introduction for CFETR Preliminary Design of Snowflake Divertor Simulation Settings and Operational Status Impurity Radiation and Screening Conclusion

PF Coils of CFETR TURN COILS R(m) Z(m) △ R(m) △ Z(m) S CS3U 1.415 4.995 0.650 1.938 374 CS2U 1.415 2.997 0.650 1.938 374 CS1U 1.415 0.999 0.650 1.938 374 CS1L 1.415 -0.999 0.650 1.938 374 CS2L 1.415 -2.997 0.650 1.938 374 CS3L 1.415 -4.995 0.650 1.938 374 PF1U 3.109 7.642 1.382 1.111 616 PF2U 9.400 6.698 0.909 0.909 324 PF3U 11.554 2.742 0.909 0.909 324 PF3L 11.554 -2.742 0.909 0.909 324 PF2L 9.400 -6.698 0.909 0.909 324 PF1L 3.109 -7.642 1.382 1.111 616 DC1 5.459 -7.792 0.909 0.909 324 Additional PF coils DC1 and DC2 are DC2 7.640 -7.448 0.909 0.909 324 designed to form advanced configuration.

Magnetic Equilibrium Z.P. Luo, et al., IEEE Trans. Plasma Sci. (2014) Coil current Ip= 10MA g121218.02020 8 SF plus PF1U <45 kA/turn 33.3 PF2U -19.4 SF D.D. Ryutov, PoP (2007) 6 CS3U 26.5 4 CS2U PF3U -1 13.5 2 CS1U Z [m] -44.5 0 CS1L -40.5 Primary X-point -2 LSN PF3L CS2L -26.8 44 -4 CS3L 45.3 -6 second X-point PF2L DC2 -9.8 DC1 PF1L Although the distance between two X points 17.2 -8 -5.8 20.5 2 4 6 8 10 R [m] is still far (quasi-snowflake, QSF) due to the limit on the coil currents, increase of flux expansion is significant. Ip [MA] R[m] a[m] βp ιi δu/δl κ Rxpt [m] Zxpt[m] Snowflake 10 5.7 1.59 0.80 1.09 0.45/0.67 2.01 4.6372 -3.1294

Divertor Geometry X.B. Peng, et al., J. Nucl. Mater. (2015,) Divertor is toroidally divided into 60 modules . Each divertor module is about 10 t and has dimensions of radially 2534 mm, toroidally 640 mm and poloidally 1970 mm The targets and the particle reflectors form two deep ‘V’ corners in the inner and the outer divertor private regions There are gaps kept between the dome Parameters inner outer and the two particle reflectors as well as LSN:25° LSN:11° Intersect angle with LCFS going through the cassette at outboard SF: 30° SF: 26° region, for particle pumping and Distance between X-point and LSN:704 LSN:950 controlling by the cryopump supposed targets (along LCFS) (mm) SF: 552 SF: 850 installed on the flange of the lower Dsitance between X-point and LSN:1598 LSN:2650 divertor port VV (along LCFS) (mm) SF: 1477 SF:2935 Distance between cassette and LSN:432 LSN:1366 Spaces are reserved between the cassette VV (along LCFS) (mm) SF: 430 SF: 1163 and the VV or the first-wall for the Gap between dome and 240 487 reflectors (mm) shielding blanket or the diagnostics

Divertor Geometry SOL width in The Δ2 ratio of SF to LSN is ~ 1.5 the OMP for inner target and ~1.2 for outer target, due to the shorter distance between inner target and X-point. When local geometry is taking into consideration, flux expansion Δ1 for SF is smaller than that for LSN due to larger intersect angle for SF . Inner target Outer target

Outline Introduction for CFETR Preliminary Design of Snowflake Divertor Simulation Settings and Operational Status Impurity Radiation and Screening Conclusion

SOLPS Simulation SOLPS （ Scraped-Off Layer Plasma Simulation （ 2D plasma fluid code:B2.5 D2 puffing 3D neutral Monte-Carlo code: EIRENE Input Parameters Value Electron heat flux into SOL 50 MW Ion heat flux into SOL 50 MW  q ~ 5 mm Electron thermal di ff usivities 1.0 m2/s  q ,Eich~ 1.53 Ion thermal diffusivities 1.0 m2/s mm Particle diffusivity 0.3 m2/s Pumping speed (nominal) 20 m3/s 1 Recycling C Target pumping A density scan is performed by using different gas puffing rate Computational Mesh C is used as a substitute for seeding impurity S.F Mao, et al., J. Nucl. Mater. (2015)

OMP Density Separatrix density at OMP increases firstly then decreases when D2 puffing rate is relatively high, while the density at core edge of simulation mesh always increases. The deposition position of D becomes more and more deep.

Operational Status T e,targe t n e,targe t Completely Γ ion detached

Peak heat loads Great Improvement of q pk In consistent with the on outer divertor for SF flux expansion

Outline Introduction for CFETR Preliminary Design of Snowflake Divertor Simulation Settings and Operational Status Impurity Radiation and Screening Conclusion

Impurity Radiation Electron Temperature Impurity Radiation T e (eV) P imp.rad (Wm-3) 5000 2000 1E7 1000 5E6 500 1E6 5E5 200 1E5 100 5E4 50 1E4 20 5E3 10 1E3 5 500 2 100 1 0.1

Impurity Screening Impurity Ratio Impurity Density n carbon n carbon / n tot (m-3) 1E19 0.05 7E18 0.045 5E18 0.04 3E18 0.035 1E18 0.03 7E17 0.025 5E17 0.02 0.015 3E17 0.01 1E17 8E-3 7E16 6E-3 5E16 4E-3 3E16 2E-3 1E16

n C, T e, P along SEP SF vs. IL D2 puffing rate 1x1023 s-1 From XP to target: Higher n imp Lower T e

Impurity Radiation SF vs. IL P imp.rad (Wm-3) QSF IL 1E7 5E6 1E6 5E5 1E5 5E4 1E4 5E3 1E3 500 100 Larger radiation volume Higher radiation power density

Outline Introduction for CFETR Preliminary Design of Snowflake Divertor Simulation Settings and Operational Status Impurity Radiation and Screening Conclusion

Conclusion Preliminary design of magnetic equilibrium and divertor geometry of QSF divertor for CFETR is performed. In the density scan SOLPS modelling, a change of divertor operationa l status is clearly indentified from low-recycling regime to detachment . Both inner and outer q pk can be decreased lower than 10 MW/m2 while the impurity ratio is less than 1.5% . A comparison of out target status between QSF and IL divertor at D2 gas puffing rates of 1x1023 s-1 indicates the heat loads onto outer targ et decreases dramatically due to increased radiation volume and im purity density for QSF divertor.

Thanks for your attentio n !!

SOL Width - 0.78 1.2 0.1 0.02 l = = 0.73 B q P R 1.53 mm T SOL cyl T. Eich, et al., PRL (2015)