25th IAEA Fusion Energy Conference - IAEA CN-221

Study of ITB Formation, Electron Heat and Density Flux Structure in New ECRH/ECCD Experiments at T-10 Tokamak

14 Oct 2014, 08:30

4h

Green 8-9 (Hotel Park Inn Pribaltiyskaya)

Poster Poster 1

Speaker

Dr Sergey Neudatchin (IFT, NRC Kurchatov Institute)

Description

In the present report, we focus at the analysis of four transport processes in T-10. First, we analyze inward electron heat pulse propagation (HPP) created by switch-on of additional off-axis ECRH on a sawteeth-free background sustained by off-axis ECRH. The presence of slow and diffusive inward HPP with “dynamic” hi-e value close to power balance value shows that the so-called “heat pinch” is either absent or very small. Second, analysis of sawtooth density oscillations in the regimes with central ECRH and in the experiments with ECCD current drive to damp the sawteeth oscillations (PECRH <0.7 MW), shows that the electron pinch velocity value is close to the neoclassical one in the plasma centre. Under PECRH > ~ 1.5 MW, ne profiles become hollow (or fully flat within the errorbars) at r/a<0.5 and we observe sawteeth density oscillations with inverted phase (rise at r=+/- 4cm and decay at r=+/-12cm). The decay of ne in the centre between the crashes is explained by the presence of the outward electron convective velocity with V p ≈ 0.3 m/s at r/a= 0.35. Third, a set of experiments with programmed plasma motion allows us to analyze fine detail of Te profile with ECE measurements. No signs of clear ITB at the q=1 surface have been observed so far (PECRH up to 0.9 MW). In several shots, the existence of a narrow ITB with a 0.5 cm width and a doubled Te gradient can be suggested within the erorbars. Finally, a new type of ITB created by sawteeth oscillations almost damped by off-axis ECCD has been found. A sawteeth crash causes the rise of Te outside rs and heat pulse does not propagate outside during 15 ms. The value of χe becomes 2.5 times lower compared with the L-mode scaling. The experiments with various values of current generation and reflectometer measurements are under the way.

Presentation materials

summary

Slide_EX-P1-43_.pdf