No abstract

Hydrogen is the main constitute of plasmas in HANBIT magnetic mirror device, therefore, measurement of the emission from excited levels of hydrogen atoms is an important diagnostic tool. From the emissivity of Hα radiation one can derive quantities such as the neutral hydrogen density and the source rate, i.e., the rate at which the plasma protons are replenished by ionization of neutral atoms diffusing into the plasma. The reconstruction of emissivity profiles from Hα radiation measurement is a highly undetermined and ill-posed inversion problem, due to the restricted viewing access, number of chords and the increased noise level. An unbiased and consistent probability theory based approach within the framework of Bayesian inference is provided by the maximum entropy method which is independent of model assumptions, but allows any prior knowledge available to be incorporated. The formalism is applied to the reconstruction of Hα emissivity profiles in HANBIT magnetic mirror device.