Breakdown of adiabatic invariance of fast ions in spherical tokamaks

The dynamics of fast particles corresponding to keV in NSTX, or alpha a properly rescaled reactor-grade spherical tokamak, is computed numerically through integration the full equations motion. magnetic moment μ these has large oscillations, and even chaotic ones, sizable domain machine. This both practical physical consequences. First, when use guiding-center gyrokinetic calculations for such orbits questionable. Second, capability excite Alfvénic instabilities decreases, since velocity particle fluctuates with respect phase-velocity Alfvén wave, which imposes fluctuating sign energy exchanges this wave. Even are present, conservation toroidal momentum sets strong constraints about volume available particles, their radial diffusion stays bounded.