Advnaced Plasma Diagnostics in the MUSE Stellarator Using Advanced Microwave Interferometry Techniques*

The MUSE stellarator is distinguished from other plasma devices by its unique design employing quasi-axisymmetric geometry facilitated by permanent magnets and planar circular coils. This configuration simplifies the traditionally complex design of stellarators while maintaining steady-state operation.

Initial characterization of the plasma parameters was conducted utilizing a double Langmuir probe, which established the baseline of plasma conditions. Following, these preliminary measurements, a microwave interferometer was implemented as a non-invasive diagnostic tool to assess plasma density. This technique offers several advantages over invasive diagnostics, such as the ability to measure plasma parameters without perturbing the plasma state, and it is independently calibratable.  These measurements were cross-validated with data obtained from the double Langmuir probe, confirming the accuracy of the interferometer.

The measurements of the Langmuir probe and interferometer are used to identify RF heated plasmas that can be used to measure flow-damping, for testing the quasi-axisymmetry optimization.  The flow damping measurements will use a Mach probe to measure the decay in rotation induced by externally imposed electric fields.