Spatial channeling of energy and momentum of energetic ions by destabilized Alfvén eigenmodes

Transcription

1 Spatial channling of nrgy and momntum of nrgtic ions by dstabilizd Alfvén ignmods Ya.I. Kolsnichnko 1,V.V. Lutsnko 1, R.B. Whit, Yu.V. Yakovnko 1 1 Institut for Nuclar Rsarch, Kyiv, Ukrain Princton Plasma Physics Laboratory, Princton, USA 1

2 Outlin Introduction Spatial channling of nrgy & momntum (ignmod channling) Effcts of channling

3 Introduction Rol of nrgtic-ion-drivn instabilitis Consquncs of instabilitis can b diffrnt Wak influnc on confinmnt of plasma and nrgtic ions instability can b usd for plasma diagnostics Anomalous loss of nrgtic ions wll known ffct Dtrioration of th plasma nrgy confinmnt studid not sufficintly Spatial channling (ignmod channling) of nrgy and momntum of nrgtic ions topic of this prsntation 3

4 Plasma nrgy Introduction Dcras of plasma nrgy in W7-AS during Alfvén instabilitis W7-AS discharg #3473 W7-AS discharg # Tim (s) 0.31 A. Wllr t al, Phys. Plasmas 8 (001) 931 Ya.Kolsnichnko, Yu. Yakovnko, V. Lutsnko, R. Whit, A. Wllr, Nucl. Fusion 50 (010)

5 Introduction Anomalous lctron hat conductivity Physics: Wav nlargs th particl radial xcursions du to finit lctric ~ conductivity of th plasma and finit E, whras th Coulomb collisions provid a random walk. Dpnding on lctron collision frquncy and wav amplitud, various rgims ar possibl. ~ E ~ ick ib ˆ r ck r V E /( VTk B) fluid k k V B k B W7-AS: During th crash, plasma is in th anomalous collisional rgim, k V T v [T(0)=90 V, n ~10 0 m -3, k ~10-3 cm -1 ]. Masurd Calculatd dw dt p col Wp P ( t) E1 E E. abs 13ms 3ms, Ya.Kolsnichnko, Yu.Yakovnko, A. Wllr, t al. Phys. Rv. Ltt. 94 (005)

6 Introduction Dtrioration of fficincy of plasma hating in NSTX during Alfvén instabilitis D. Stutman t al., Phys. Rv. Ltt. 10, (009): Th incras of th injctd powr by a factor of 3 did not incras th cntral tmpratur. At 6 MW, TRANSP calculatd c is strongly nlargd in th cor rgion, xcding Bohm valu, and rducd at th priphry. N. Gorlnkov t al., Nucl. Fusion 50 (010) 08401: Multipl GAE mods lad to stochastic lctron motion, which rsults in strong nhancmnt of lctron hat conductivity. 6

7 7 Plasma hating and hat flux causd by th wavs COL b m n b C F P n P n t F D, 1 s b s n m J D col w Q Q rq r r t T n 1 3 B n m B T F r M k V d M k q 3, 3 D F r M k V d Q B m n w D, 3 Q>> div q for > *. Hating by wavs xcds cooling! Thrfor, anomalous transport can hardly xplain Stutman s xprimnt. Ya.Kolsnichnko, Yu. Yakovnko, V. Lutsnko, R. Whit, A. Wllr, Nucl. Fusion 50 (010) Introduction

8 Eignmod channling of nrgy and momntum: basic ida During Enrgtic-Ion-drivn Instabilitis th nrgtic ions mit th wavs which ar absorbd by th plasma. Enrgtic Ion nrgy & momntum Wavs Bulk plasma Typically, th rgion of mission (Rgion 1) dos not coincid with th rgion of absorption (Rgion ). Rgion 1 Emission of th wavs Rgion Absorption of th wavs This implis that th nrgy and momntum of nrgtic ions is channld from Rgion 1 to Rgion. 8

9 Channling by GAE mods Alfvn continuum branchs Enrgtic ions Rgion of th wav damping r a r r Mod location GAE mod rcivs th nrgy and momntum of th bam ions insid th rgion r < r a, but givs th nrgy and momntum to lctrons at r ~ r. r a r a Plasma dg 9

10 Effcts of channling Enrgy channling lads to plasma hating by th nrgtic ions byond th rgion of localization of th nrgtic ions Momntum channling lads to plasma rotation and frquncy chirping 10

11 Enrgy channling Th nrgy channling causd by GAEs lads to th cooling of th plasma cor and th incras of T at th priphry whn (i) r a < r (ii) g a W ~ P inj (iii) Fast ions in wid nrgy rang ar rsonant: E rs = ( E 1, E ), with E 1 <<E ~E 0, E 0 is th birth nrgy. 11

12 Momntum channling and plasma rotation Sktch of th plasma rotation during nrgtic-ion-inducd instabilitis for ra r This rotation lads to transint frquncy chirping du to changing Dopplr shift. Whn r a <r, th frquncy chirping down taks plac aftr th bginning of th instability. 1

13 A modl for th NSTX xprimnts Assum: No GAEs or wak GAEs at MW; strong GAEs at 6 MW Elctron transport at 6 MW is as wak as at MW Plasma is hatd by NBI through Coulomb collision at MW, but mainly through th wavs at 6 MW n ( i c c ) T( r) T( a) a dr r b dr r Q r r 0 Q w Q d rq P d rq (1 ) P 3 w total 3 b total inj inj 1r xp a, a w( r r ) xp a b w Q Hr, r, and a w ar adjustabl paramtrs., 13

14 Calculatd tmpratur and masurd tmpratur in th NSTX xprimnts c Tmpratur calculatd in our modl with r /a=0.6 and a w =10; =0 for MW; =0.8 for 4 MW; =0.98 for 6 MW; c i + c n ; c =c ( MW) and c i =c NEO, n (r) of Stutman, EPS conf-007. D. Stutman t al., PRL (009): Masurd tmpratur and thrmal conductivity cofficints. At 6 MW, c is strongly nlargd in th cor rgion and rducd at th priphry. Ya. Kolsnichnko, Yu. Yakovnko, V. Lutsnko, Phys. Rv. Ltt. 104 (010)

15 Frquncy chirping in Wndlstin 7-AS Shot #3473 For Alfvn wavs 7.5%, Estimat from our thory: W n T ~ B / B ~ B B 10 3 W n T Ti.710 ui mu i ~ 10 and ~ 3kHz V r i tim ui m V 5 g a W tak g/=10 - (Kolsnichnko t al., NF-006) and that th chirping tim =th pr-crash duration= 0.7 ms. W n T i i VTi t r Ya.Kolsnichnko, Yu. Yakovnko, V. Lutsnko, R. Whit, A. Wllr, Nucl. Fusion 50 (010)

16 Summary Dstabilizd ignmods can channl th nrgy and momntum of nrgtic ions to th rgion whr th dstabilizd wavs ar dampd. Th nrgy channling sms th main mchanism rsponsibl for th dtrioration of th fficincy of plasma hating during multipl GAE mods in NSTX xprimnts with high NBI powr. Th momntum channling lads to plasma rotation and transint frquncy chirping. It can xplain strong frquncy chirping in th W7-AS shot #3473. Th plasma hating by th wavs with * xcds th plasma cooling through th thrmal conduction and convction causd by th wavs. 16