1. Changes in Edge Turbulence with  * and Toroidal Rotation Input in NSTX M. Gilmore, S. Kubota, W.A. Peebles, and X.V. Nguyen Electrical Engineering Dept., University of California, Los Angeles D. Stutman Johns Hopkins University Presented at the 44th Annual APS Division of Plasma Physics Meeting Orlando, FL Nov 11-15, 2002 and the NSTX Team

2. Experiment Overview Parameter scans were performed in NB plasmas with L-mode edges - B toroidal scans (3 - 6 kG on axis)   * - NBI line changed (source A, C)  toroidal rotation input - n e, I p, NBI power were also scanned Neon was puffed at the edge, and penetration tracked via USXR Turbulent correlation lengths were monitored in the edge of the confinement region by a two channel 20-30 GHz O-mode homodyne reflectometer located on the outboard midplane (n CR  5  10 12 - 1.1  10 13 cm -3 ). [See S. Kubota, GP1.119]. Cutoff layers where these measurements were made were a few cm inside the LCFS: 0.90  r/a  0.98 (R  141 - 149 cm) T e  20 - 100 eV, L n  5 - 12 cm

3. Cutoff Layers were Stationary During Correlation Measurements Although the line average density continued to ramp up throughout the shot, the edge density changed little during I p flattop shot 108213 measurements

4. Temporal Characteristcs of Fluctuations Changed Little Broadband Power Spectra Small (if any) Doppler shifts observed with changes in NB line, I p, B t Autocorrelation times (1/e)  AC ~ 10  s, and showed no parametric changes Gaussian pdf’s with low intermittency in the confined plasma region (High intermittency and skewed pdf’s observed in SOL) Power Spectrapdf shot 108211, 108213 shot 108211, 245-255 ms

5. Radial Correlation Lengths Scaled with  s at Fixed B tor /I p (Constant q cyl,edge )  r normalized to  s vs.  B  q cyl,edge  aB  /R 0 B  ; nL constant  r vs. |B| at cutoff  r  6-7   s (  s  1/  B  )  r  4-5   s,tor (  s,tor  1/B tor )  r  3-4   s,pol (  s,pol  1/B pol ) B tor = 3.75 kG6 kG Neon penetration rate decreased with B tor (D. Stutman) q 95 varied  6  7.5

6. Normalized Correlation Lengths Decreased with B tor at Fixed I p (1 MA)  r normalized to  s vs. B Scaling by  s,toroidal,  s,poloidal showed the same trend Neon penetration rate decreased with B tor (D. Stutman) q 95 varied  5  9  r versus B B tor = 3.75 kG6 kG Resolution limited ?

7. No Clear Trend in  r with I p at Fixed B tor  r normalized to  s vs. I p  r vs. I p B t = 4.5 kG, nL constant Scaling by  s,toroidal,  s,poloidal showed the same trend q 95 varied  7.5  5.5 Neon penetration rate decreased with I p - possible threshold effect (D. Stutman) Threshold in  r at ~ 1 MA ?

8. Summary The scaling of radial correlation lengths,  r, with discharge parameters a few cm inside the LCFS (0.90 < r/a < 0.98) has been investigated in NB heated plasmas with L-mode edges. Diagnostics now coming on line, such as CHERS upgrade [GP1.130], MSE [GP1.132], and edge rotation [GP1.131], will allow more detailed interpretation. In particular, it is planned to perform detailed comparisons with gyrokinetic simulations (e.g. GYRO, etc.) as well as data from other devices (e.g. DIII-D). -  r decreased with increasing B t and correlated with Ne impurity penetration rates -  r scaled with  s during the constant B t /I p (q cyl ) scan. - However, more complicated dependencies were observed in other scans, indicating that parameters such as q and rotation profiles also have important effects