Precise stellarator quasi-symmetry can be achieved with electromagnetic coils

Area of Science:

• Plasma physics
• Fusion energy research
• Applied electromagnetism

Background:

• Quasi-symmetric magnetic fields offer excellent charged particle and plasma confinement.
• Achieving high-precision quasi-symmetry in practice has been a significant challenge.
• Previous methods for generating quasi-symmetric fields had limitations in precision and complexity.

Purpose of the Study:

• To investigate the practical generation of recently discovered, highly precise quasi-symmetric toroidal magnetic fields.
• To assess the engineering feasibility and complexity of coils required for these fields.
• To evaluate the particle confinement properties of these new magnetic field configurations.

Main Methods:

• Utilized electromagnetic coil designs with low curvature and significant separation.
• Performed simulations to analyze the precision of generated quasi-symmetric fields.
• Simulated the confinement of high-energy charged particles using guiding center trajectories.

Main Results:

• Demonstrated that moderately complex electromagnetic coils can accurately produce highly quasi-symmetric fields.
• Found that coil length is critical for approximating quasi-symmetry, with departures comparable to Earth's magnetic field for optimized configurations.
• Magnetic surfaces extend significantly beyond the plasma core, enhancing confinement.
• Simulations showed superior confinement of energetic particles compared to previous coil designs, with minimal loss in reactor-scaled scenarios.

Conclusions:

• The newly discovered quasi-symmetric magnetic fields are practically achievable with moderate coil engineering.
• These fields represent a significant advancement for applications requiring long-term confinement of energetic particles, such as nuclear fusion.
• The extended magnetic surfaces and enhanced confinement properties make these configurations highly promising for future fusion reactors.