2024 – Electron cyclotron mode conversion in plasma with relativistic electrons

Electron cyclotron mode conversion in plasma with relativistic electrons

2024 Research Campaign, Frontier Science

Purpose of Experiment

Generation and absorption of electron cyclotron (EC) radiation is a fundamental physics phenomena underlying many observations in space, ionospheric, and fusion plasmas. A particular case is the resonant interaction of relativistic electrons (RE) with the EC waves and while the lower frequency whistler-type waves generated by relativistic electrons have been observed in tokamaks, the higher-frequency EC waves (which are typically also “internal” modes) are not detectable outside the plasma without an intricate mode-conversion process. These waves do not interact directly with relativistic electrons due to their high phase velocity nor can they be injected into plasma above the cutoff density. However, a unique opportunity exists to convert the “free space” O-mode into an internal plasma slow-X mode (a.k.a Z-mode). The phase velocity of the slow-X mode can approach the speed of light, providing the possibility for direct RE-wave interaction. When injected at optimal angles (calculated for a specific equilibrium) O-mode is expected to be converted into slow-X mode at the O-mode cutoff surface.

Experimental Approach

This experiment will explore both O and X-modes launched at and away from the optimal angle to attempt to access this mode conversion scenario and will then explore the effect of these slow-X mode waves on the relativistic electron population.

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