Forward modeling of collective Thomson scattering for Wendelstein 7-X plasmas: Electrostatic approximation

Area of Science:

• Plasma physics
• Computational physics
• Fusion energy research

Background:

• Collective Thomson scattering (CTS) is a key diagnostic for measuring plasma properties.
• Accurate numerical modeling is crucial for interpreting CTS data.
• Existing models may have limitations in computational efficiency or scope.

Purpose of the Study:

• To present a novel computational method, eCTS, for collective Thomson scattering (CTS).
• To validate the eCTS model against full electromagnetic simulations.
• To demonstrate the capability of eCTS for inferring bulk ion temperature from experimental data.

Main Methods:

• Development of the eCTS forward model using the electrostatic approximation.
• Benchmarking eCTS against a full electromagnetic model to quantify differences.
• Integration of eCTS into the Bayesian data analysis framework Minerva.
• Analysis of synthetic and real experimental data from Wendelstein 7-X.

Main Results:

• The electrostatic approximation in eCTS provides a computationally efficient method for CTS.
• Differences between electrostatic and electromagnetic models were analyzed and found to be manageable for certain applications.
• The sensitivity of CTS signals to ion temperature and plasma composition was quantified.
• eCTS successfully inferred bulk ion temperature from noisy synthetic data and initial Wendelstein 7-X measurements.

Conclusions:

• The eCTS model is a viable and effective tool for numerical computation of collective Thomson scattering.
• eCTS enables accurate inference of bulk ion temperature, a critical plasma parameter.
• The model's successful application to Wendelstein 7-X data demonstrates its practical utility in fusion research.