TITLE: Scaling of the far SOL turbulence as a function of (1), the average density keeping other plasma parameters constant. (3), the plasma current keeping other plasma parameters approximately constant. (2), the toroidal magnetic field keeping other plasma parameters approximately constant. Authors: G. Y. Antar B. LaBombard, J. Terry, S. Zweben and M. Greenwald

GOALS and MOTIVATION Obtain the scaling of the convective part of radial transport on the main plasma parameters. This scaling should allow us to determine more accurately the behavior of avaloids (or blobs) in ITER-like devices and thus to answer the question: How long ITER-like devices can run in L-mode? Understand the role of convective transport in setting the density limit. Confirm (or not) the existence of a critical normalized density n/n G below (above) which avaloids role increase (decrease). Verify that the velocity is ExB-driven by changing the toroidal magnetic field. Insights on the instability generating avaloids as the different scalings are obtained.

B toroidal [Tesla]5.4 Tesla for discharges [1-7] 3 Tesla for [8-9] Tesla [10-16] -7 discharges with the toroidal magnetic field changing from shot to shot and the plasma current, position and density are constant. Normalized density (n/nG) [1-9] -Slowly ramping the density up in 5 discharges to cover the full scan.[1-5] -2 discharges repeat the scan for small and large n/nG at a different plasma current.[6-7] -2 discharges repeat the scan for small and large n/nG at a different magnetic field.[8-9] 0.6 Plasma current [MA] MA [17-21] -5 discharges with 4 plateaux in each discharge incrementing of 250 kA each lasting 200 ms. 0.8 IpIp time Normalized density scan (I)Plasma current scan (II)Toroidal field scan (III) Discharge scenarios

Diagnostics Langmuir probes: –The mid-plane probe sits at a fixed position retracted 2 cm away from the LCFS. –The target probes (at least some) set to record the ion saturation current. –The high-field probe also set to measure the ion saturation current. Normal density and temperature profile measurements. Edge imaging using short shutter time-scales. Edge photo-diodes.