1. Density Peaking in JET (NBI fueling dominant) and DIII-D (transport dominant) Originates from Different Sources at Low υ*
For the first time electron particle transport coefficients D and V have been measured in H-mode with high resolution diagnostics.
The NBI particle source is found larger than expected and contributing 50-60% to the peaking in plasmas with Te/Ti~1 and at υ*= in JET
On DIII-D dissimilarly to JET, the inward pinch contributes 70-90% to the density peaking, the fraction increasing with decreasing υ*
On C-Mod, I-mode particle transport characteristics are similar to those of L-mode, no dependence on υ*
The difference between JET and DIII-D H-mode discharges with respect to density peaking within these υ* scans is the different turbulence regime – on DIII-D the Trapped Electron modes (TEM) play a stronger role due to the lower υ*, higher magnetic shear and larger R/Lte than in JET.
These υ* scan form an excellent set of data to validate transport models and codes – TGLF and GENE seem both relatively well to be able to predict density peaking in various plasma conditions.
The lesson learned is that in order to be able to predict the density peaking well, one needs to know the plasma regime well, and this is certainly true when extrapolating to future devices.
Tuomas Tala | CORE DENSITY PEAKING EXPERIMENTS … - DRIVEN BY FUELING OR TRANSPORT? IAEA FEC 2018| EX4-4 | |