The Band-Gap Approach for Turbulence and Instabilities Mitigation in Fusion Plasma

This work explores a novel approach to mitigating turbulence in fusion plasmas through spatially modulated plasma profiles. The fundamental idea of turbulent waves suppression proposed in this work is based on the Floquet-Bloch theory, explaining the formation of the zone structure of the electron energy in the crystal lattice or band-gap dispersion properties of photonic crystals. By imposing a harmonic modulation on plasma parameters, we introduce conditions that alter the propagation characteristics of turbulent and MHD waves, a primary source of transport and instabilities in fusion devices. This modulation approach resembles band-gap formation in solid-state and photonic crystals, where spatial periodicity suppresses wave propagation within specific frequency bands. This work does not provide any mathematical novelty. The mathematical framework shown here (based on the Mathieu equation) essentially resembles the well known Floquet-Bloch theory. It reveals how a controlled spatial variation of turbulent wave phase velocity can effectively attenuate turbulence and instabilities. Several methods for implementing this modulation in plasma, including RF waves, static magnetic field perturbations, and modulated density profiles, are proposed as potential paths for achieving stable confinement. This concept could provide a versatile and potentially more controllable alternative to existing turbulence suppression techniques, with the goal of improving stability and confinement across a variety of magnetized fusion configurations.