Study of detached H-modes in full tungsten ASDEX Upgrade with N seeding by SOLPS-ITER modeling

Transcription

1 Study of dtachd H-mods in full tungstn ASDEX Upgrad with sding by SOLPS-ITER modling I.Yu.Snichnkov 1, E.G.Kavva 1, E.A.Sytova 1, V.A.Rozhansky 1, S.P.Voskoboynikov 1, I.Yu.Vslova 1, A.S.Kukushkin 2,3, D.P.Costr 4, X.Bonnin 5 and th ASDEX-Upgrad Tam. -mail: I.Snichnkov@spbstu.ru 1 Ptr th Grat St.Ptrsburg Polytchnic Univrsity, , Polytchnichskaya ul., 29, Saint Ptrsburg, Russia 2 Kurchatov Institut, Kurchatov sq. 1, Moscow, Russia, 3 RU MEPhI, Kashirskoy sh. 31, Moscow, Russia 4 Max-Planck Institut für Plasmaphysik, EURATOM Association, D Garching, Grmany 5 ITER Organization, CS , Rout d Vinon-sur-Vrdon, St. Paul-lz-Duranc, Franc IAEA FEC 2016 Wdnsday, 19 Octobr 2016

2 Motivation Our currnt undrstanding of divrtor physics indicats that at last partial dtachmnt will b a ncssary condition for opration of futur fusion powr dvics such as ITER, DEMO and byond. Th transition to dtachmnt is activly studid thortically and xprimntally. In rcnt yars a divrtor opration rgim with complt dtachmnt was achivd in ASDEX Upgrad with tungstn walls and nitrogn sding [1-3], and a modling with th SOLPS5.0 transport cod rproducd th main faturs of ths xprimnts [4]. In th prsnt work th modling similar to [4] is prformd by SOLPS-ITER cod [5,6] with a focus on th analysis of th ffct of drifts and currnts on divrtor cooling and on nitrogn distribution. [1] S. Potzl t al ucl. Fusion 54 (2014) [2] F. Rimold t al ucl. Fusion 55 (2015) [3] A. Kallnbach t al ucl. Fusion 55 (2015) [4] F. Rimold t al Journal of uclar Matrials 463 (2015) [5] S. Wisn t al Journal of uclar Matrials 463 (2015) [6] X. Bonnin t al Plasma and Fusion Rsarch 11 (2016)

3 Outlin Dscription of th modling scnario Modling rsults: midplan and targt profils Discussion of nitrogn distribution Currnts and E-fild in th divrtor rgion Conclusions 3

4 Equations Modling stup Computational domain Braginski-lik transport quations analytically rwrittn for plasma spcis according to B2-5.2 concpt [7]; All drifts and currnts ar turnd on; Unknown quantitis ar n, u,t, T, α i 7 D,,,..., Prscribd (not thory-basd) anomalous transport cofficints; Mont-Carlo cod EIREE [8] is coupld rturning sourcs and sinks du to collisions with nutral spcis; [7] V. Rozhansky t al. ucl. Fusion 49 (2009) [8] R. Schnidr t al 2006 Contrib. Plasma Phys

5 D,, i, m 2 /s v, m/s Boundary conditions Modling stup Fuling rat D 2 molculs pr scond; Sding rat from up to atoms/scond; Shath BC at targts; Prscribd n α and T,i dcay lngths at SOL and PFR boundaris; u α / y=0; Zro nt currnt through cor boundary; < u D+ > = 50 km/s, u / y=0 at th cor; Zro nt nitrogn flux at th cor; 5 High rcycling at outr targt Fuling and sding rats in AUG shot #28903 [4] sparatrix CORE 3 First task: D v pinch Prscrib n D and T,i at th cor boundary 2 and fit th anomalous transport cofficints i SOL to match th xprimntal profils at 2.4 s 1 (shown blow): dtachd innr targt, highrcycling outr targt Distanc from sparatrix, m

6 Thn Chang boundary condition Modling stup prscribd n D and T,i prscribd nt D flux ( s -1 ) and hat fluxs (Q =3.2 MW, Q i =1.8 MW) Prform sris of stady stat runs which diffrs from ach othr by sding rat only (kp anomalous transport cofficints unchangd) Focus on th analysis of nitrogn transport and currnts distribution nar targts rathr than on prfct rproducing th xprimnt. 8x x x x10 18 itrogn contnt (total)/10 cor outr divrtor innr divrtor tot 4x x x x x x x x x10 20 Sding rat, ( atoms)/s 6

7 Modling rsults. Outr midplan 7

8 Modling rsults. Outr targt 8

9 Modling rsults. Innr targt 9

10 High rcycling rgim at outr targt itrogn and Dutrium rtain nar th cold dtachd innr targt; Shap of ionization sourc profil rpats th shap of th cold-hot plasma boundary; Strong E-fild (abov 1 kv/m) and high lctric potntial dvlop in th cold plasma rgion 10

11 Elctric fild and currnt j j PS j th j E 1 n ( n T ) T j E E 1 n, high T 1 ( n T ) 0.71 T j E E, 1 n low T 1 ( n T ) 0.71 T, PS currnt dominats in th PFR; thrmolctric on is important in th SOL positiv (towards outr targt) ngativ (towards innr targt) 11

12 Intgratd poloidal fluxs, Intgratd poloidal fluxs, ions/s ions/s Momntum balanc componnts, (/m 3 ) R n itrogn distribution 1 u u 100 top D D D 50 T 2 R 1. 56Z n T i 0 Thrmal forc T R R -50 Friction Elctric forc Prssur gradint 1 u u T -100 D D D i innr outr targt Poloidal coordinat, mtargt 8 n Z Z 1 3/ 2 1/ T i SOL gativ - to th innr divrtor Total (n u pol ) Total (n D u D pol )*10-3 n u (B pol /B) n u ExB top -Dgrad n -3 innr targt Poloidal coordinat, m outr targt innr outr targt Poloidal coordinat, m targt As a rsult, nitrogn rtains at innr targt and laks at outr targt PFR Total (n u pol ) Total (n D u D pol )*10-3 n u (B pol /B) n u ExB -Dgrad n gativ - to th innr divrtor

13 Intrmdiat sding rat puff 1219 puff 1219 puff 1219 puff 1219 puff 1219 puff 1219 puff 1219 puff 1219 Outr divrtor cools with incrasing sding rat, th rgion of cold plasma broadns, whil nitrogn still accumulats nar innr targt; Elctric potntial maximum starts to dvlop nar th ; 13

14 High sding rat (full dtachmnt) Cooling of th confinmnt rgion occurs Elctric potntial pak dvlops at th itrogn starts to accumulat nar th outr targt 14

15 Intgratd poloidal fluxs, ions/s Momntum balanc componnts, (/m 3 ) itrogn distribution (high sding rat) Friction forc still balancs th thrmal forc, and nitrogn vlocity may b stimatd as 1 u u D D D Howvr, in a cold plasma collisional tim bcoms smallr, and D and vlocitis bcom closr to ach othr. ExB drift vortx flux around th qualizs nitrogn dnsity btwn innr and outr divrtor rgions. As a rsult, nitrogn rtains at outr targt too. T i top Thrmal forc Friction Elctric forc Prssur gradint innr targt Poloidal coordinat, m outr targt 1 SOL gativ - to th innr divrtor 0 Total (n u pol ) -1 top innr outr targt targt Poloidal coordinat, m Total (n u )*0.1 D D pol n u (B /B) pol n u ExB -Dgrad n 15

16 T, V I, A Currnt through divrtor targts innr targt outr targt j j PS j th As th plasma nar th outr targt cools, thrmolctric currnt rducs, and changs its sign if outr divrtor plasma bcoms coldr than innr on E18 1E19 1E20 Sding rat, ( atoms)/s positiv (towards outr targt) ngativ (towards innr targt) gativ - towards th innr targt Positiv - tovards th outr targt innr targt outr targt PS currnt dominats in th SOL and in PFR, howvr, dirctions ar opposit, and SOL and PFR parts almost cancl ach othr. Sign of th nt currnt is dfind by thrmolctric currnt. Distanc along th targt, m

17 Conclusions Modling of transition to th dtachmnt in ASDEX Upgrad H-mod with sding is prformd by SOLPS-ITER cod with drifts and currnts turnd on. It is dmonstratd that th B-paralll vlocity of nitrogn is dfind by th balanc of thrmal forc and friction forc. Whn th innr targt is dtachd whil outr is not, th nitrogn is concntratd nar th dtachd innr targt, and as th outr targt dtachs, th nitrogn accumulats nar th outr targt. As th amount of nitrogn incrass and th divrtor rgion cools, a strong lctric fild dvlops to driv th currnt through th zons of low lctric conductivity. Th ExB drift flux bcoms comparabl to diffusiv flux. Thrmolctric currnt rducs with th outr divrtor plasma cooling, and changs its sign as th outr divrtor plasma bcoms coldr than th innr on, similarly bhavs th nt currnt through divrtor plats. 17

18 Supplmntary slid 18

19 Supplmntary slid cor sparatrix innr midplan top outr midplan 19

20 Supplmntary slid cor sparatrix innr midplan top outr midplan 20