Measurement of a 2D fast-ion velocity distribution function by tomographic inversion of fast-ion D-alpha spectra
Abstract
We present the first measurement of a local fast-ion 2D velocity distribution function f(v, v). To this end, we heated a plasma in ASDEX Upgrade by neutral beam injection and measured spectra of fast-ion D-alpha (FIDA) light from the plasma center in three views simultaneously. The measured spectra agree very well with synthetic spectra calculated from a TRANSP/NUBEAM simulation. Based on the measured FIDA spectra alone, we infer f(v, v) by tomographic inversion. Salient features of our measurement of f(v, v) agree reasonably well with the simulation: the measured as well as the simulated f(v, v) are lopsided towards negative velocities parallel to the magnetic field, and they have similar shapes. Further, the peaks in the simulation of f(v, v) at full and half injection energies of the neutral beam also appear in the measurement at similar velocity-space locations. We expect that we can measure spectra in up to seven views simultaneously in the next ASDEX Upgrade campaign which would further improve measurements of f(v, v) by tomographic inversion.
Turn this paper into a lesson
ArcXiv compiles a structured reading guide from this paper's metadata: plain-English importance, contributions, prerequisite concepts, which sections to read first, flashcards, and a quiz. Grounded in the abstract, never invented.