Application of a Synthetic Diagnostic and Comparison to HSX 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.

In order for a direct comparison, simulated data 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 [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 of

TEM microturbulence at experimentally relevant parameters for the HSX stellarator. 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 with HSX. Future work also includes a full validation study for the W7X stellarator.

[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