Synthetic Data Comparisons against Experimental W7X and HSX CECE Data

Transport driven by the nonlinear, turbulent interaction of ion and electron scale fluctuations plays a critical role in determining the performance of stellarators. Understanding and mitigating the effects of turbulent transport is crucial for the efficient operation of these devices. With accurate physics modelling, a path for turbulence optimization on a stellarator design can be paved. Validation studies, which involve the rigorous comparison of numerical simulations with experimental data, provide a pathway to enhance theoretical and numerical models of plasma microturbulence.

For a direct comparison between numerical and experimental data, simulated output needs to be modified appropriately through a synthetic diagnostic, which takes into account the spatial and temporal resolutions of an experimental diagnostic. A synthetic diagnostic has been created and was applied to an analytical example for verification [1]. Good agreement was found, giving confidence to the accuracy of the model.

The synthetic diagnostic was also applied to nonlinear flux-tube GENE simulations microturbulence at experimentally relevant parameters for both the W7X and HSX stellarators. Tolerances for the free parameters of the diagnostic were explored, and acceptable agreement was found with CECE data. This comparison is a building block for a complete validation study of the GENE code. The initial set up of a validation is also presented.

[1] Bravenec, R. V., & Wootton, A. J. (1995). Effects of limited spatial resolution on Fluctuation Measurements (invited). Review of Scientific Instruments, 66(1), 802–805. https://doi.org/10.1063/1.1146226

This work was carried out within the framework of the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No. 101052200—EUROfusion) and by the U.S. Department of Energy under Contract No. DE-SC0020990. Views and opinions expressed are, however, those of the author(s) only and do not necessarily reflect those of the European Union or the European Commission. Neither the European Union nor the European Commission can be held responsible for them.