Simulation of Angle and Energy Resolved Fluxes of Escaping Neutral Particles from Fusion Plasmas with an Isotropic Ion Distribution

Multidirectional diagnostics employing high-resolution atomic energy spectrometers [1, 2] are being used to study the ion component heating mechanisms and fast ion confinement in helical plasmas. Since the natural atomic flux source is not localized in contrast to the pellet charge exchange [3,4] or diagnostic neutral beam methods [5], the correct interpretation of such measurements in a complex toroidally asymmetric geometry requires careful numerical modeling of the neutral flux formation and knowledge of the charge exchange target distributions, relevant cross-sections, and the magnetic surface structure. The measured neutral flux calculation scheme for LHD geometry was given in [6], and the influence of the geometry effect on the interpretation of measured data was shown. The current method was applied for the simulation of the experimental signal of the angular-resolved multi-sightline neutral particle analyzer (ARMS-NPA) [1] along it's 20 sightlines in the LHD geometry configuration. In order to check the influence of the geometry effect on the interpretation of experimental results, calculations were conducted for the isotropic Maxwellian plasma-ion-energy probability density function. The behavior of the calculated and experimental ion spectra from neutral beam injector (NBI) is discussed.