Overview Impact of 3D fields (RMP) on edge turbulence and turbulent transport

Trilateral Euregio Cluster Overview Impact of 3D fields (RMP) on edge turbulence and turbulent transport TEC Yuhong Xu Laboratory for Plasma Physics, Ecole Royale Militaire - Koninklijke Militaire School, Euratom-Belgian State Association, Avenue de la Renaissance 30, B-1000 Brussels, Belgium* On assignment at Plasmaphysik (IEK-4) Forschungszentrum Juelich, Germany * Partner in the Trilateral Euregio Cluster (TEC) Thanks to: all contributors and the TEXTOR team! Association EURATOM-Belgian State Ecole Royale Militaire / Koninklijke Militaire School 1 LPP ERM - KMS

Outline Introduction (how/why RMP affects edge turbulence?) Experimental setup Experimental results (TEXTOR + other machines) Impact of RMP on edge equilibrium profiles (T e, n e,, E r ) Impact of RMP on edge fluctuation amplitude and transport Impact of RMP on edge turbulence spectrum [S(f), S(k)] Impact of RMP on blob transport in the SOL Impact of RMP on GAM zonal flows Summary

Introduction How/Why does the RMP affect edge turbulence? RMP coils Magnetic perturbation of B r (B r /B ~ 10-3 ) island (chains) at resonant surfaces overlap (stochastic) B r induces radial electron current new charge balance of j r B r induces radial field-line diffusion/transport by D M =(B r /B) L c (D D M C s ) B r modifies the k // dynamics, // =(b 0 +b r ) affect turbulence eddies B r opens field lines at plasma boundary increase sheath dissipation 3

Distinction of ergodic zone (EZ) and laminar zone (LZ) EZ: (i) L c > L k (e-folding length of adjacent field lines); (ii) c >1 LZ: L c < L k, stochasticity has no meaning / parallel transport dominates Laminar zone Ergodic zone fast probe r Poincaré plot provided by M. W. Jakubowski Laminar plot [different colors number of poloidal turns]

Experimental setup (RMP) TEXT 7/, 7/3 Tore Supra 18/6 DIII-D 8-15/3 JET -3/1- MAST 0/3+5/3 AUG m/1-4 TEXTOR 3/1,6/, 1/4 DIII-D (R. Moyer, PoP1, 056119) Carbon tile DED coil (@ HFS) TEXTOR-DED (O. Schmitz, NF48, 04009 ) Resonant surface at q ~3 5

Diagnostics for edge turbulence study at TEXTOR Top-View of TEXTOR Langmuir probes ERM, Belgium GPI (gas puff imaging) ERM, Belgium Reflectometry Reflectometry FZJ, Germany Li-BES (Beam emission spectroscopy) KFKI, Hungary GPI Probe head Mo. pins (d = 1- mm) BES Boron-nitride body (isolator) 6

Impact of RMP on edge equilibrium profiles (I) Laminar zone Ergodic zone SOL I DED1 I DED5 f (V) 1 3 Before DED DED ramp DED plateau r (cm) Radial dependence of floating potential Typical RMP discharge waveform at TEXTOR (6/ DED) Y. Xu, EPS(008), O4-6 8

Similar impact of RMP on V f profile in other machines TEXT V f profile affected by RMP in MAST (SOL / X-point) V f profile affected by RMP in TEXT (Limiter) P. Tamain, PPCF 5, (010) A. Wootton, JNM 176-177 (1987) 9

Impact of RMP on edge equilibrium profiles (II) Ergodic zone Laminar zone SOL w/o RMP with RMP T e (ev) n e (x10 19 m -3 ) P e (r) = n e T e E r (V/cm) r (cm) r (cm) 10

What is neoclassical E r? Understanding the change of E r by RMP

Understanding the change of E r by RMP no RMP, J //e doesn t across magnetic surface RMP With RMP Y. Xu, M. Schoor, et al., NF 47, 1696 (007)

Comparison with theoretical modelling on E r profiles Inside the plasma edge, theoretical modelling of E r agrees well with experimental results both w/o RMP. Y. Xu, M. Schoor, et al., NF 47, 1696 (007) 13

Impact of RMP on edge fluctuation amplitude and transport 1/4 DED, TEXTOR 6/ DED, TEXTOR n~ ~ e f ~ E n~ e ~ f ~ E r = <n ~ e E~ >/B 6/ DED, TEXTOR r 3/1 DED, TEXTOR r 1/4 DED, stationary probe in Ergodic Zone Y. Xu et al., NF 47, 1696 (007) Y. Xu et al., PRL 97, 165003 (006) Radial profiles of fluctuations without (open points) and with (solid points) RMP. 15

Impact of RMP on edge fluctuation amplitude and transport ~ n e ED phase J. Payan, NF 35, 1357 (1995) P. Tamain, PPCF 5, 075017(010) Very similar to TEXTOR results! 16

Impact of RMP on edge turbulence spectrum [S(f)] S(f) of ~ f (3/1 DED TEXTOR) S(f) of ~ n e (6/ DED TEXTOR) S(f) of n~ e SOL w/o RMP with RMP P. Devynck, NF 4, 697 (00) ~ S(f) of f (1/4 DED TEXTOR) S(f) of ~ n e (6/ DED TEXTOR) ~ S(f) of f Ergodic Zone Y. Xu et al., NF47 (007), PRL97,(006) J. Robinson, PPCF54, 105007 (01)

Impact of RMP on edge turbulence spectrum [S(k)] w/o RMP with RMP [ 6/ DED, EZ at TEXTOR] [ 6/ DED, EZ at TEXTOR] S (k ) S (k r ) *,i k (cm -1 ) *,e outwards k r (cm -1 ) inwards Y. Xu et al., NF 47, 1696 (007) Suppression of large-structure turbulence (small k and k r ) Reduction of correlation length (broadening of k spectra) J. Payan, NF 35, 1357 (1995) k (cm -1 )

RMP effects on correlation length Ergodic zone Laminar zone w/o RMP with RMP l cr (cm) Ergodic zone E r shear reduced with RMP E r l c (cm) r (cm) r (cm) LZ and EZ show distinctive features! 0

RMP effects on turbulence propagation *,i with RMP *,i w/o RMP *,e *,e w/o RMP with RMP SOL V ph k, f f k k, f S( k S( k,, f ) f ) Profile of poloidal V ph (km/s) Limiter *,i Ergodic Zone *,e r (cm) Contour plots of S(k, f ) 1

RMP effects on turbulence propagation TEXTOR Y. Xu et al., PRL 97, 165003 (006) P. Tamain, PPCF 5, 075017(010) At TEXTOR, influence of RMP on the poloidal rotation is consistent with E r xb drift. In MAST tokamak, a similar reversal of poloidal rotation is observed.

Intermittent blob transport in the SOL 4~5cm # 101798 Probe trace limiter PDF of I s in SOL SOL edge I sat PDF of I s in edge I sat V r =E B T 1 km/s Radial profile of I s limiter ~ ~ r = n V r Y. Xu et al., PPCF(005), NF(009)

Impact of RMP on blob transport in the SOL w/o RMP with RMP I sat ~ V r ~ ~ ~ r = n V r ~ < r > * Independent of edge profile / RMP-phase variations global effects 5 Y. Xu et al., NF49, 035005 (009), consistent with modelling D. Reiser PoP 14, (007)

Impact of RMP on blob transport in the SOL Interpretation: Blob dynamics: M i B n~ t n 0 t ~ // ~ J // ( ~ p) ~ ~ ~ ~ Te V / ( ) ( ) ( ~ E, rn // J // e // n0v //, i n0 n) e generation n dissipation // J // nec s / L c O. Garcia, PoP (006) (i) Nonzero k // damp turbulence eddy development => suppress large eddy (blob) structures. (ii) Shorter L c with RMP enhances the sheath dissipation => radial velocity decreases. 6

Impact of RMP on GAM zonal flows Ohmic phase (I DED =0) I DED = 3 ka I DED = 7.5 ka 6/ DED RMP reduces the LRC (V f ), which is dominated by GAM oscillations. Y. Xu et al., IAEA (010), EXC/9-3

Impact of RMP on GAM zonal flows Ohmic phase (I DED =0) I DED = 3 ka I DED = 7.5 ka 6/ DED Y. Xu et al., PPCF53, 095015 (011) 9

Impact of RMP on GAM zonal flows GAM frequency 10 khz TEXTOR Y. Xu et al., NF51, 06300 (011) J. Robinson, PPCF54, 105007 (01) 30

Impact of RMPon LRC and zonal flows (RFX-mod) Whereas LRCs are observed in tokamaks & stellarators, no clear signature of the LRC was seen hitherto in the edge of RFX-mod. The absence of LRC (ZF) in the RFP may due to magnetic stochasticity of island 31 chains. P. Scarin et al., IAEA (010), Daejeon

Possible mechanism parallel dynamics (D. Reiser, et al.,) M i n0 ~ ~ // J // p ( ~ ) B t ~ V//, i M ( ~ in0 // p) t n~ 1 ~ ~ ~ 1 ( ) ( ) ( ~ // J // // n0v //, i n0 p) t e e ~ ~ ~ n e J n e 0 // p e 0 // 0 // ~ V t C R n s n~ ~ RMPV 0 0, RMP (1) () (3) (4) m* A0 r m n 0 i 0 = B R (sin r cos r 0 0 0 1 // // r 1 qr A * 0 r0 0 1 1 R r B 0 ) * A A ( r r 0 0 * A0 ( r)cos( m* n* ), B r m* A0 / r 0 ) 3 i RMP C R s 0 (1 1 q ) i q RMP C R s 0 0 w/o RMP, RMP =0 R C s 0 (1 1 q ) With RMP, RMP 0 damping effects on GAM! I DED However, the complete effects by RMP on turbulence coupling are much more complex!

Impact of RMP on the radial profile of Renolds stress I p =00kA, q(a)=6.3, <n e0 >=1.0x10 19 cm -3 I p =50kA, q(a)=5.9, <n e0 >=1.5x10 19 cm -3 33

More sophisticated model M i n0 ~ ~ // J // p ( ~ ) B t ~ V//, i M ( ~ in0 // p) t n~ 1 ~ ~ ~ 1 ( ) ( ) ( ~ // J // // n0v //, i n0 p) t e e ~ ~ ~ n e J n e 0 // p e 0 // 0 // by M. Leconte and P. Diamond Phys. Plasmas 18, 08309 (011) Phys. Plasmas 19, 055903 (01) RMP induce a linear coupling of zonal potential and zonal density reduction of zonal flow energy by a predator-prey process. Increase of L-H transition power threshold 34

What is the cost-benefit ratio of RMP? (P. Diamond, Alfven Lecture 011, Strasbourg) 35

Summary With RMP, edge equilibrium profiles (n e,t e, V f, E r ) are modified. With RMP, edge fluctuation amplitudes and transport are affected. With RMP, both S(f) and S(k) are modified. With RMP, turbulence correlation lengths are changed. With RMP, turbulence poloidal propagation changes sign, consistent with E r XB flow change. With RMP, blob transport is reduced in the SOL. With RMP, GAM zonal flows are suppressed. All above results suggest that a stochastic magnetic boundary by RMP may have profound influence on edge turbulence and turbulent transport, and hence, for plasma-wall interaction / plasma confinement.