In this paper transient phenomena related to the electron heat transport when
electron cyclotron resonance heating (ECRH) power is switched on or off are
investigated by predictive and interpretative transport analysis. In the latter
two numerical approaches—one based on the transport code ASTRA and
the other by COBRA code—are compared. The transport simulations were
done in the ASTRA code based on a critical ∇Te/Te model. The results for
the evolution of the electron temperature in steady state and transient phases are
compared with the experiment. The changes of the heat diffusivity with
the ECRH power are compared with the results of the transport calculations
from the interpretative analysis. The critical ∇Te/Te model reproduces well
both the heat diffusivity and the electron temperature evolution in the region
outside the ECRH deposition, and the results show good agreement with the
experimental data there. The model cannot recover the electron temperature
changes inside the ECRH deposition region with accuracy due to the simple
assumption made in transport below the threshold. |