1. Density Fluctuations as an Intrinsic Mechanism to Keep Self-consistent Shape of Pressure Profile
EX/11-2Rb
Density fluctuations significantly rises in OH during density decay after gas puff switched off
Turbulence level at 2/3a behaves in similar way with the particle flux through this radius: it is minimal at zero flux and rises both in density ramp up or down.
Heat fluxes are not affected by strong turbulence rise.
Density fluctuation level decreases in ECRH despite of L mode confinement degradation
It is determined by requirement to keep certain density and pressure profiles and not related to ionization flux, energy confinement or heating power
Density decay processes in OH after gas switch off (left) and ECRH (middle and left ) are similar
Density rise during ECRH postponed “density pump out” (middle), while heating in decay stage (right) caused immediate pump out
The electron pressure peaking factor [P(r)/P(a/2)] at the decay stage approached the same marginal value 2.8 and caused dramatic decrease of particle confinement
Density fluctuation level is minimal in optimal pressure profile with peaking factor 2.3;
It rises when electron pressure profile deviated from the optimal in both cases: broadening by gas puff , or peaking by gas switch off or central ECRH.
In both cases the induced particle fluxes directed to reestablish the optimal pressure profile