Theoretical analysis of long range turbulent transport in the scrape-off-layer

Simulations of Scrape-Off Layer (SOL) turbulence with free energy content (flux driven) are characterized by profile relaxation and strong outward bursts of density. The ballistic propagation extends well beyond the e-folding length of the SOL. Turbulence stabilisation is achieved by biasing part of the limiter surface. The critical radial extent to achieve this stabilisation is derived. This effect governs the size of the biased ring required to insulate the wall from the long range bursts of matter. The same characteristic scale also governs the critical size of Langmuir probe tips. For probe tips in excess of this size, the flux tube to the probe is found to be decoupled from the background plasma. (author)