1. Motivation power exhaust in JT-60SA tokamak. 2. Tool COREDIV code. 3. Operational scenarios of JT-60SA. 4. Results. 5.

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2 1. Motivation power exhaust in JT-60SA tokamak 2. Tool COREDIV code 3. Operational scenarios of JT-60SA 4. Results 5. Conclusions K. Gałązka Efficient power exhaust in JT-60SA by COREDIV Page 2

3 The Institute of Plasma Physics and Laser Microfusion Plasma Focus PF1000 Space applications Diagnostics (Soft X-Ray, neutrons) DTT1/DTT2 SN, DN, Snowflake, Liquid Li/Sn divertor Division of Theoretical Analysis W7X Field line tracing Grid computation MST1 WEST JET JT-60SA Power exhaust High f rad scenarios Multiple seeding Detachment D-T campaign Laser-driven plasma jet generation and PWI (Zagórski, Ivanova-Stanik, Stępniewski, Pełka, Gałązka, Chmielewski, Poradziński, Potrykus) ITER DEMO EAST K. Gałązka Efficient power exhaust in JT-60SA by COREDIV Page 3

4 JT-60SA tokamak is situated in Naka, Japan. It will be initially equipped with carbon divertor, and after some years of operation upgraded to tungsten. Superconducting coils, long pulse operation is forseen. Note: first plasma in Operational scenarios are pepared, the feasibility studies of power exhaust by various impurities has been done. Construction schedule ( K. Gałązka Efficient power exhaust in JT-60SA by COREDIV Page 4

5 Analysis of scenario #2 was done with help of COREDIV code. Parameter name Unit scn#2 I p MA 5.5 B T T 2.25 R T / a m 2.96 / 1.18 κ 1.87 H 98(y,2) 1.3 P aux MW 41 <n e > VOL / n e (0) m / 7.7 Main parameters of scn#2 No effect of limiting the power delivered to the divertor target for C divertor by impurity seeding. Maximum f rad =63% with Ne. N Impurity seeding: N, Ne, Ar, Kr. Only limiting P aux or increase of <n e > VOL leads to a solution. R. Zagórski et al., Nucl. Fusion 56 (2016) (7pp) K. Gałązka Efficient power exhaust in JT-60SA by COREDIV Page 5

6 <Z eff > = 3 For W divertor it is possible to limit P TOT PLATE down to 10 MW/m 2 and below by using Ne, Ar or Kr seeding. Why? Strong W radiation in the core limits P 2SOL n e sep /<n e > = 40% D = 0.5 m 2 /s <Z eff > = 3 K. Gałązka et al., Plasma Phys. Control. Fusion 59 (2017) K. Gałązka Efficient power exhaust in JT-60SA by COREDIV Page 6

7 P RAD CORE ~20 MW P RAD SOL ~11 MW CORE SOL DIV P aux 41 MW P 2SOL ~21 MW (>H-L transition) P 2PLATE ~10 MW High-Z impurity (seeded) Low/medium-Z impurity (seeded/intrinsic C) Intrinsic C production K. Gałązka Efficient power exhaust in JT-60SA by COREDIV Page 7

8 1D central plasma (CORE) + 2D scrape-off layer (SOL) and divertor Self-consistient, integrated modeling (coupling on the separatrix) Anomalous + neoclassical transport (diffusion-based transport in the core, multifluid description in the SOL) Production and transport of impurities (gas puff, recycling, sputtering at the target) Atomic processes (ionization/recombination/charge exchange) Transport barier implemented COREDIV aims at studying the role of impurities for plasma cooling and power exhaust. Simplifications: Slab geometry with no private region Neutrals described by a simple analytical model Given equilibrium (no current/field evolution) No plasma rotation Gain: One calculation in 4-12 h time/processor R. Stankiewicz, R. Zagórski J. Nucl. Mater. (2005) R. Zagórski et al., Nucl. Fusion 53 (2013) K. Gałązka Efficient power exhaust in JT-60SA by COREDIV Page 8

9 symmetry plane Divertor divertor plate Input parameters: I p, B T, <n e >, <n e sep >, H98, P aux, q 95, κ, ε, D = D,e =D,i, χ e = χ i = 2 D τ from IPB98(y,2) confinement time scaling Recycling proces for main plasma/impurities: R = (Ψ div - Ψ in )/ Ψ div SOL Ψ div Target Sputtering coefficient (also by seeding gases) accounts for the intrinsic impurity y(m) production at the target plate Gas puff source is situated in the divertor region (see arrow) n a x =0 V x a= Ψ in a Wall: T, n, v y =0, SCRAPE-OFF LAYER v x a x =0 a Q a= ana Ti ei a V x x =0 x-point gas puff e Q = n V x T e e e e a V =h c LCMS 0 0 Separatrix x(m) a a V V =0, inp, Q inp x x =0 x K. Gałązka Efficient power exhaust in JT-60SA by COREDIV Page 9 x sa

10 L-H transition power coincides with the divertor power limit R Xe =0.925 gas puff Maximum radiation f rad 50% SOL C radiation, CORE Xe radiation P PLATE TOT 20.8 MW much too high T PLATE e 36 ev far from detachment Additional seeding with Ar fixed Xe rate ( ) K. Gałązka Efficient power exhaust in JT-60SA by COREDIV Page 10

11 P RAD SOL = 7.6 MW P RAD CORE = 11.7 MW P RAD SOL = 7.0 MW P RAD CORE = 13 MW P RAD SOL = 5.7 MW P RAD CORE = 12.8 MW For each case the maximum radiation f rad 50% Not possible to limit P TOT PLATE below 20 MW with the selected mixture. A trial with W seeding (artificial)? K. Gałązka Efficient power exhaust in JT-60SA by COREDIV Page 11

12 Puffing position at X = 5.3 m Strong plasma flux towards the taget plate in the area of puffing. Possible reason for failiure of seeding. Moving the gas puff to the midplane. K. Gałązka Efficient power exhaust in JT-60SA by COREDIV Page 12

13 Puffing position at X = 2.9 m Almost 2x lower plasma velocity in the new area of gas puff. Core plasma more accessible. Smaller velocities at the target plate. K. Gałązka Efficient power exhaust in JT-60SA by COREDIV Page 13

14 R Xe =0.25 now before Maximum radiation f rad 80% SOL carbon radiation, CORE Xe radiation P TOT PLATE 6.8 MW OK T e PLATE 4.7 ev OK Close to L-H transition. A scan with Ar at ( ) Non-recycling, high-z impurity is potentially a good candidate for the power exhaust. K. Gałązka Efficient power exhaust in JT-60SA by COREDIV Page 14

15 R Xe =0.25 now before P RAD SOL = 7.5 MW P RAD CORE = 18.3 MW f rad = 62 % P RAD SOL = 7.0 MW P RAD CORE = 21.7 MW f rad = 69 % Using a combination of 2 impurities gives a possibility to manage the power exhaust (core/sol ratio). K. Gałązka Efficient power exhaust in JT-60SA by COREDIV Page 15

16 <Z eff > = 3.3 <Z eff > = 2.9 Similar densities achieved Slightly higher T e and n e peaking for the midplane seeding R Xe =0.25 midplane divertor K. Gałązka Efficient power exhaust in JT-60SA by COREDIV Page 16

17 in midplane In divertor Non-recycling impurities behave differently, depending on where the gas puff is. Opened a new way to follow. K. Gałązka Efficient power exhaust in JT-60SA by COREDIV Page 17

18 Low recycling case a much higher seeding is applicable. High recycling case regardless the seeding, the source is due to recycling. K. Gałązka Efficient power exhaust in JT-60SA by COREDIV Page 18

19 The mechanism of seeding is dominated by the recycling in the case of recycling impurity and is independent of the source position Non-recycling, high-z impurity (like W) is a possible solution for the power exhaust problem in JT-60SA Use high-z (W/Mo/Sn pellets?) impurity puffing at midplane + low-z impurity in the divertor (Ar/Ne gas puff) midplane divertor K. Gałązka Efficient power exhaust in JT-60SA by COREDIV Page 19

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