Speaker
Description
See the full abstract here http://ocs.ciemat.es/EPS2019ABS/pdf/P5.1088.pdf
The design of future fusion reactors and their operational scenarios require accurate estimates of the plasma confinement, which is a key parameter for the evaluation of the fusion performance. We are developing a new model that integrates different elements describing the main physics phenomena which determine plasma confinement. We use the ASTRA transport code, which thanks to its modularity allows us to make use of different models to simulate transport in each plasma region. In particular, we are coupling to ASTRA a new pedestal transport model [1], based on empirical observations. For core transport we use the TGLF turbulent transport model, and NCLASS is used for neoclassical transport. We also coupled a simple scrape-offlayer model to ASTRA [2], which provides the boundary conditions at the separatrix, which are a function of the main engineering parameters. By this way no experimental data needs to be imposed at the boundary, and the only inputs of the model are the magnetic field, the plasma current, the heating power, the fueling rate, and the plasma geometry. In the modelling workflow, first a scan in pedestal pressure is performed, by changing the pedestal width. Then the pedestal top pressure is determined using the MISHKA MHD stability code. This modelling framework is tested by simulating ASDEX Upgrade discharges. We show comparisons with experimental fuelling and power scans. The changes of the pedestal structure and the gradients in the plasma core, due to the different combinations of fuelling and heating power, are well captured by the model. We also show that the modelled pedestal height, the energy confinement time and the stored energy, are in agreement with the experimental measurements, and more accurate with respect to the prediction of scaling laws. However, the predictions of the model are sensitive to the plasma core pressure, which has a strong impact on the pedestal stability and on the stored energy, and depends on the reliability of the TGLF transport model. The long term goal is to obtain a robust model which can be used to identify important hidden dependencies affecting global plasma confinement, which are difficult to capture by statistical regressions on global parameters.
References
[1] P.A. Schneider et al., Nuclear Fusion 53.7 (2013), p. 073039.
[2] A. Kallenbach et al., Nuclear Materials and Energy 18 (2019), pp. 166-174.
