1. Correlation between Electron Transport and Shear Alfven Activity in NSTX College W&M Colorado Sch Mines Columbia U Comp-X General Atomics INEL Johns Hopkins U LANL LLNL Lodestar MIT Nova Photonics New York U Old Dominion U ORNL PPPL PSI Princeton U Purdue U SNL Think Tank, Inc. UC Davis UC Irvine UCLA UCSD U Colorado U Maryland U Rochester U Washington U Wisconsin Culham Sci Ctr U St. Andrews York U Chubu U Fukui U Hiroshima U Hyogo U Kyoto U Kyushu U Kyushu Tokai U NIFS Niigata U U Tokyo JAEA Hebrew U Ioffe Inst RRC Kurchatov Inst TRINITI KBSI KAIST POSTECH ASIPP ENEA, Frascati CEA, Cadarache IPP, Jülich IPP, Garching ASCR, Czech Rep U Quebec NSTX Supported by D. Stutman 1, N. Gorelenkov 2, L. Delgado 1, M. Finkenthal 1, E. Fredrickson 2, S. Kaye 2, E. Mazzucato 2, K. Tritz 1 For the NSTX Research Team [1] Johns Hopkins University [2] PPPL, Princeton University Presenter N. Gorelenkov 50 th APS/DPP Meeting

2. NSTX 50 th APS/DPP – GAEs and electron transport (Stutman)‏November 17, 2008 2 T e flattens in some NSTX H-modes as P b increased  i 6 MW  NC 2 4 0.20.40.60.8 10 1 10 2 10 3  e PB (m 2 /s)‏ r/a 6 MW 4 2 0.20.40.60.8 T e  keV)‏ r/a 0.5 1.0 01 20 ms variability 6 MW 1 MA 0.45 T 0.45 s Not caused by low-f MHD or fast ion (FI) radial redistribution  e PB ≥10 m 2 /s inside r/a ≤0.4, while  i ~  NC Perturbative experiments support PB transport picture

3. NSTX 50 th APS/DPP – GAEs and electron transport (Stutman)‏November 17, 2008 3 GS2 growth rates (s -1 )‏ ksks 10 3 10 4 10 5 10 -1 10 0 10 1 10 2 r/a=0.4  ExB 0.2 fluctuation level when turbulence significant 10 -2 10 -4 10 -6 High-k power (a.u.)‏ k   e ~0.25  tan ~0.25 f (MHz)‏ 021-2 GAE/CAE band n~ 4-5 n~ 6-8 n~ 1-3 0.4 0.50.6 2.0 1.0 Mirnov frequency (Mhz)‏ t (s)‏ 0.5 1.5  T e is too low for kinetic instabilities  Weak high-k fluctuations Persistent 0.5–1.1 MHz GAE/CAEs (Global and Compressional Alfvén Eigenmodes)‏ (Gorelenkov et al. NF 2003)

4. NSTX 50 th APS/DPP – GAEs and electron transport (Stutman)‏November 17, 2008 4 NBI power scan leads to fast ion density change in the core preheat 0.4 s 6 MW time of transport comparison 4 MW 2 MW few t beam s.d 1 MA 0.45 T q ‘frozen’ by preheating, P b then stepped almost constant q, n e,  ExB Strong variation in fast ion (FI) density  expected GAE drive 6 2 4 q MSE 2 4 6  ExB (x10 6 s -1 )‏ n e (x3 10 13 cm -3 )‏ 1 2 0.2 0.5 1 TRANSP FI density (x10 -2 J/cm 3 )‏ 0.40.60.8 r/a

5. NSTX 50 th APS/DPP – GAEs and electron transport (Stutman)‏November 17, 2008 5 T e flattening,  e increase correlate with GAE intensity 0.40.50.40.50.40.5 pre-heat 1.0 0.8 0.6 0.4 0.2 f (MHz)‏  B wall ≤1 G r/a 0.20.60.8 0.3 0.6 0.9 0.4 r/a 0.20.60.80.4 20 40 60 6 MW 4 2 t (s)‏ T e  keV)‏  e  m 2 /s)‏ 0.0 GAE band 2 MW4 MW6 MW Plasma with strong GAEs have flat T e, high central  e Plasmas with faint/no GAEs have peaked T e, low  e

6. NSTX 50 th APS/DPP – GAEs and electron transport (Stutman)‏November 17, 2008 6 10 -2 10 -4 10 -6 Line averaged fluctuation amplitude 0.8 0.4 -2012 f (MHz)‏ Mirnov frequency (MHz)‏ 0.495 0.505 10 -4 10 -5 t (s)‏ n~2,3 n~5-6 n~7 1.2 Interferometry shows significant GAE amplitudes High-k diagnostic in interferometric mode at r/a=0.25 Peak  n e likely higher,  B r /B ~ m  n e /n e e Broadband, overlapping GAE character at high P b 6 MW

7. NSTX 50 th APS/DPP – GAEs and electron transport (Stutman)‏November 17, 2008 7 Characteristic frequencies of thermal species: f GAE = ~400–600kHz, but may go higher. transit (passing) frequency f te = v || /2  qR = 2MHz at T e = 1keV bounce (trapped) frequency f be = v || (r/2R) 1/2 /2  qR = 560kHz at q 0 = 1.25, R = 1m, a = 0.6m, r/a = 0.23 electron Coulomb scattering frequency ce = 0.7  10 11 sec -1, ( ee+ ie )/  ce = 6  10 -7 thermal ion cyclotron frequency f ci = 3MHz. 14 GAEs with n = 1 – 8; m is such that f = 400–600kHz are used in guiding center simulations for e-transport. Electrons can resonantly interact with GAEs in NSTX Theory for ORBIT:  B=rot (  *R 0 *B 0 )‏ GAE frequency equals to trapped electron f be GAE frequency equals to trapped electron f be : resonances are w gae – w be =0.

8. NSTX 50 th APS/DPP – GAEs and electron transport (Stutman)‏November 17, 2008 8 Use ORBIT, guiding center code Apply to H-mode NSTX plasma Test e-particle simulations produce thermal electron transport ORBIT predicts:  e >10m 2 /s at  >10 -4 (  B r /B=m  n e /n e e=~10 -2 )‏ At such perturbation level x r /R >  m / k || r = ~  /  = ~4*10 -4 at r/a=0.25. This is on the same order as high-k diagnostic measured GAE amplitudes. ORBIT code predicts significant e-transport due to GAEs

9. NSTX 50 th APS/DPP – GAEs and electron transport (Stutman)‏November 17, 2008 9 Summary T e flattening in NSTX H-modes is observed. Flattening correlates with intensity of shear Global Alfvén Eigenmode (GAE) activity. GAEs apparent as broadband 0.5–1.1 MHz magnetic and density fluctuations. First assessment with ORBIT code, test particle simulations indicates GAEs may resonantly couple with the bulk (~1 keV), primarily trapped electrons.  e = 10m 2 /s for electron heat transport from ORBIT simulations requires  n e /n e ~ 10 -4, on the same order as was measured by high-k diagnostic.

10. NSTX 50 th APS/DPP – GAEs and electron transport (Stutman)‏November 17, 2008 10 GAEs GAEs and T e flattening correlate also in L-modes high  e DTM eITB RSAEs A cause for T e flattening also inside tokamak eITBs? T e (keV)‏