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.