Stabilization of interchange modes in mirror plasmas by a nonlinear rf-plasma wave coupling process

Area of Science:

• Plasma Physics
• Fusion Energy Research
• Nonlinear Dynamics

Background:

• Mirror-confined plasmas are susceptible to interchange instabilities.
• Radiofrequency (rf) waves are used for plasma heating and confinement.
• Understanding wave-particle interactions is crucial for plasma stability.

Purpose of the Study:

• To investigate the consequences of nonlinear coupling between pump rf waves and interchange modes in mirror plasmas.
• To identify conditions for achieving interchange-stable operation.
• To elucidate the role of resonance in nonlinear wave coupling.

Main Methods:

• Experimental studies of plasma behavior.
• Theoretical analysis of nonlinear coupling.
• Full radiofrequency (rf) wave simulations.
• Parameter space exploration including rf power and gamma (omega(0)/Omega(i)).

Main Results:

• A stable operation window for interchange modes was demonstrated.
• The existence of this window depends on applied rf power and the ratio gamma.
• Nonlinear wave coupling is responsible for the stable window near resonance (gamma ≈ 1).

Conclusions:

• Nonlinear coupling between rf waves and plasma modes can stabilize mirror plasmas.
• Specific rf power and frequency conditions (gamma ≈ 1) are key to achieving stability.
• Theoretical and simulation results confirm the existence and mechanism of the stable operation window.