A high resolution Mirnov array for the Mega Ampere Spherical Tokamak.

Area of Science:

• Plasma Physics
• Fusion Energy
• Electromagnetism

Background:

• Increased neutral-beam heating and alpha particle production in fusion plasmas drive energetic particle modes.
• These modes exhibit electromagnetic signatures detectable by Mirnov coils, posing diagnostic challenges.
• Higher injection energies lead to increased oscillation frequencies and wave numbers, complicating detection.

Purpose of the Study:

• To address challenges in designing high-frequency magnetic diagnostics for fusion plasmas.
• To present new techniques for modeling stray capacitance and optimizing coil positioning.
• To serve as a roadmap for developing advanced magnetic diagnostics.

Main Methods:

• Developed new techniques for modeling stray capacitance in Mirnov coils.
• Implemented optimized coil positioning strategies for wide wave number band detection.
• Conducted a case study on the outboard Mirnov array for high-frequency acquisition at the Mega Ampere Spherical Tokamak.

Main Results:

• Demonstrated improved frequency response by accounting for stray capacitance and transmission line effects.
• Showcased effective coil positioning for confident identification of oscillations across a broad wave number spectrum.
• Validated the techniques in a high-frequency acquisition scenario.

Conclusions:

• Optimized Mirnov coil design is crucial for accurately diagnosing high-frequency energetic particle driven modes in fusion plasmas.
• Advanced modeling of coil capacitance and strategic positioning enhance diagnostic capabilities.
• The presented roadmap facilitates the development of next-generation magnetic diagnostics for fusion research.