Introduction of HL-2M divertor design G.Y. Zheng 1 , X.R. Duan 1 , - PowerPoint PPT Presentation

The 1 st IAEA Technical Meeting on Divertor Concepts Introduction of HL-2M divertor design G.Y. Zheng 1 , X.R. Duan 1 , X.Q. Xu 2 , D.D. Ryutov 2 , L.J. Cai 1 , X. Liu 1 , J.X. Li 1 , T.Y. Xia 3 , Y.Y Lian 1 , L. Xue 1 , Y.D. Pan 1 and B. Li 1 1 Southwestern Institute of Physics, Chengdu, China 2 Lawrence Livermore National Laboratory, Livermore, USA 3 Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, China Vienna, 29 September – 2 October 2015 HL HL-2A 2A

Content 1. Configuration design of HL-2M 2. Properties of divertor configurations 3. Divertor target geometry and simulation 4. Engineering design and X-point control 5. Plan and summary HL HL-2A 2A

HL-2A • R: 1.65 m • a: 0.40 m • B t : 1.2~2.7 T • Configuration: Limiter, LSN divertor • I p : 150 ~ 480 kA 1.0 ~ 6.0 x 10 19 m -3 • n e : • T e : 1.5 ~ 5.0 keV • T i : 0.5 ~ 2.8 keV Heating: Diagnostics: over 30, e.g. CXRS, MSE, ECEI… ECRH/ECCD: 5 MW Fuelling system (H 2 /D 2 ): Gas puffing (LFS, HFS, (6 X 68 GHz/0.5MW/1s, 2 X 140 GHz/1W/1s) divertor), Pellet injection (LFS, HFS), SMBI /CJI (LFS, HFS) NBI (tangential) : 3 MW LFS: f =1~80 Hz, pulse duration > 0.5 ms LHCD: 2 MW (4/3.7 GHz/500 kW/2 s) gas pressure < 3 MPa HL HL-2A 2A

HL-2M (new tokamak, under construction) Mission: high performance, high beta, and high bootstrap current plasma; advanced divertor (snowflake, tripod), PWI. Main parameters Plasma current I p = 2.5 (3) MA Major radius R = 1.78 m Minor radius a = 0.65 m Aspect ratio R/a = 2.8 Elongation Κ = 1.8 -2 Triangularity δ > 0.5 Toroidal field B T = 2.2 (3) T Flux swing ΔΦ= 14Vs Heating power 25 MW HL-2M tokamak HL-2A HL 2A

High performance plasma and advanced divertor  Heat flux at target can be roughly compared, (total heating power is 25MW, λ q less than 2mm with Ip = 3MA). HL-2M  Mitigation of heat flux at target to support HL-2M high performance operation.  Test the engineering and physics issues relevant to to fusion reactor, such as ITER and CFETR. HL HL-2A 2A

CS and PF coil parameters of HL-2M CS and PF coil CS and PF coil parameters of HL parameters of HL-2M 2M Ncoil Ncoil Max(k Max(k R(mm) R(mm) Z(mm) Z(mm) W(mm) W(mm) H(mm) H(mm) A) A) (Nr Nr × Nz Nz) 28(2 × 14) PF1 912 185 50.4 352.4 14.5 28(2 × 14) PF2 912 586 50.4 352.4 14.5 28(2 × 14) PF3 912 987 50.4 352.4 14.5 28(2 × 14) PF4 912 1388 50.4 352.4 14.5 28(5 × 6) PF5 1092 1753 183 220 38 27(7 × 4) PF6 1501 1790 257 146 39.41 28(5 × 6) PF7 2500 1200 183 220 39 28(5 × 6) PF8 2760 480 183 220 35.29 96(2 × 48) CS 748 0 116.75 3442.3 110 All of PF Coil current can be reversed for HL-2M HL-2M HL-2A HL 2A

Standard divertor to advanced divertor Snowflake Tripod HL-2M  PF4/L and PF6/L as divertor coils to generate two separate X-points;  PF5/L adjusts position of the two X-points to satisfy design requirements, such as snowflake Standard divertor divertor configuration. HL HL-2A 2A

Equilibrium benchmark by EFIT and CORSICA EFIT CORSICA I p (MA) R (m) a (m) Κ δ up δ down l i β p EFIT 1.2 1.71 0.56 1.698 0.265 0.735 1.17 0.645 CORSICA 1.2 1.71 0.55 1.694 0.255 0.745 1.17 0.64 HL-2A HL 2A

Snowflake configurations of HL-2M I p (MA) R (m) a (m) Κ δ up δ down l i β p 2.0 1.78 0.62 1.73 0.3 0.74 1.20 0.60 SF divertor- Standard divertor Exact SF divertor SF divertor-plus minus HL-2A HL 2A

Snowflake divertor to Tripod dievrtor Tripod Tripod SF-minus Exact-SF  When the plasma current reduces, the second X-point is fixed and first X point is forced to moved up by take advantage of poloidal field of CS coil:  When plasma current is 0.9MA, the distance between the X-points will be more than 50cm. HL HL-2A 2A

Weak B p region of HL-2M SF divertor Standard SF-minus Exact-SF SF-plus Standard divertor Fast convective heat transport around weak B p can increase power sharing among the divertor legs and broaden the heat flux profile at target. D.D. Ryutov, et al., Contrib. Plasma Phys., 52, 539, 2012; PPCF, 54, 124050, 2012. HL HL-2A 2A

Weak B p region of HL-2M SF/Tripod divertor  When the distance between the two X-points becomes large, configuration loses features of snowflake divertor, becoming just two separate X-points;  Tripod configuration has a long divertor leg and three outgoing branches of the separatrix. HL HL-2A 2A

Magnetic shear and curvature analysis of SF  Same main parameters, R, a, I p , k 95 , q 95.  Same pressure and current profiles. (Local magnetic shear ) The integrated magnetic shear Radius of curvature on outer mid-plane The local shear HL HL-2A 2A

Snowflake-minus improves P-B mode instability The linear growth rate  The snowflake-minus has the closest X-point to the outer mid-plane is able to affect the property of ballooning modes.  The second X-point improves the bad curvature in favor of the suppression of P-B modes. HL HL-2A 2A

Configuration evolution during VDE κ 95 β p δ 95 Parameters I p (MA) R 0 (m) a (m) l i B t (T) Value 1.00 1.71 0.55 1.65 0.60 1.06 0.25 2.20 SF The hot vertical displacement phase The TQ and the CQ phase SD HL-2A HL 2A

Divertor engineering design consideration  The configurations (standard, snowflake and tripod) of HL-2M can be explored by optimizing the target geometry;  High cooling ability to support the high heat flux operation;  Flexible support structure, and well protection for cooling pipe system; 30cm  Easy installation, maintenance and update. HL HL-2A 2A

Target plate geometry of HL-2M Divertor target geometry is expected to be compatible with the configurations of HL-2M. I p =2MA I p =2MA Snowflake minus Standard divertor Exact snowflake HL HL-2A 2A

B p / B t value around target of HL-2M divertor Standard divertor Snowflake minus  γ min ≈ B p /B t sin α ., if γ min too small, the shadows and hot spots may appear on the plate;  γ min is assumed to be 1/50 of a radian (roughly 1 degree). Exact snowflake HL HL-2A 2A

Mesh of SD and SF 140 Standard divertor 120 Snowflake divertor 100 Surface expansion I p =2MA 80 I p =2MA Surface expansion 60 40 20 0 0.00 0.01 0.02 0.03 0.04 Distance from separatrix at outer middle plane (m) 2.5 Standard divertor Snowflake divertor 2.0 Ratio of connection length Connection length 1.5 Snowflake minus Standard divertor 1.0  If If λ q =2mm of HL-2M, the plasma-wetted area: 0.5 more than 1.5m 2 of SF and about 0.3m 2 of SD; 0.0 0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035 0.040  P=12MW, 8MW/m 2 of SF, 40MW/m 2 of SD. Distance from separatrix at outer middle plane (m) HL-2A HL 2A

Simulation boundary conditions of SD and SF  Cross field transport factor: D = 0.2m 2 /s, χ e = χ i = 0.5m 2 /s;  Power flows into SOL/Divertor regions: P = 12MW, P i =P e =6MW;  The density is fixed about 4cm inside the separatrix, and the upstream density n e,sep = 2.5*10 19 /m 3 ;  The pumping gas speed S=50m 3 /s;  Carbon as impurity is included;  When I p =2.0MA, the plasma density limit is about 1.5*10 20 /m 3 . HL HL-2A 2A

Heat flux distribution of SD and SF 6 6x10 6 5x10 Standard divertor Snowflake divertor 6 4x10 Heat flux W/m 2 6 3x10 6 2x10 The heat flux distribution at outer 6 1x10 target of snowflake minus The heat flux distribution at outer 0 target of standard divertor 0.0 0.1 0.2 0.3 0.4 0.5 0.6 Distance from separatrix at outer target (m) Heat flux profiles at outer target  2MW/m 2 of SF, and about 5.8/m 2 of SD. HL-2A HL 2A

Electron density at outer target of SD and SF Standard divertor 21 1.4x10 Standard divertor Snowflake divertor 21 1.2x10 21 1.0x10 Density (/m 3 ) 20 8.0x10 20 6.0x10 20 4.0x10 20 2.0x10 Snowflake minus 0.0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 Distance from separetirx at outer targte (m) Electron density at outer target HL-2A HL 2A

Carbon ion density distribution of SD C1+ C2+ C3+ C5+ C6+ C4+ HL HL-2A 2A

Carbon ion density distribution of SF C1+ C2+ C3+ C5+ C6+ C4+ HL HL-2A 2A

Zeff distribution of SD and SF Standard divertor Outer mid-plane 3.0 Standard divertor Snowflake divertor 2.5 Near X point Near X point 2.0 Zeff 1.5 Snowflake minus 1.0 0 20 40 60 80 100 From inner target along poloidal direction to ourter target Inner target Outer target HL-2A HL 2A

Peak heat flux at outer target of SF and SD 6 8x10 7 1.2x10 Standards divertor 6 Snowflake divertor 7x10 Standard divertor 7 Snowflake divertor 1.0x10 6 6x10 2 ) P=12MW 6 2 ) Heat flux (W/m 5x10 6 8.0x10 Heat flux (W/m 6 4x10 6 6.0x10 6 3x10 6 6 4.0x10 2x10 6 1x10 6 2.0x10 19 19 19 19 19 8 10 12 14 16 18 2.1x10 2.4x10 2.7x10 3.0x10 3.3x10 Power flows into SOL/Divertor region (MW) 3 ) Electron density at outer mid-plane ( m Peak heat flux at target with different Peak heat flux at target with different power flows into SOL/Divertor region Electron density at outer mid-plane  The peak heat flux of SF is about 35% of SD (P=8-18MW);  n e,sep = 2.0*10 19 /m 3 ， 2.3MW/m 2 of SF, 10.8MW/m 2 of SF. HL-2A HL 2A

SF and Tripod divertor configurations, Ip = 0.5MA Ip = 0.5MA Ip = 0.5MA Ip = 0.5MA Tripod 2 Snowflake minus Tripod 1 HL HL-2A 2A