Ionization Balance in the Rotating Radiation Belt Accompanying Complete Divertor Detachment in LHD

Abstract

A spectroscopic measurement is performed for a plasma in a rotating radiation belt, which accompanies the complete divertor detachment recently realized in the Large Helical Device (LHD) [J. Miyazawa et al., Nucl. Fusion 46, 532 (2006)]. The population distribution over the exited levels is experimentally determined from the Balmer series line intensities and is compared with the result of the collisional-radiative model calculation to determine the electron temperature T e and density n e . No reasonable pair of T e and n e is found when either the ionizing plasma or the recombining plasma is assumed. A good fitting is obtained under an assumption of the ionization balance plasma with T e = 1.8 eV and n e = 2 × 10 20 m −3 . These parameters are confirmed through analysis of a high-wavelength-resolution measurement for the Balmer series lines which clearly exhibit the Stark broadening effect.

Observation of Marfes in the Wendelstein 7-X stellarator with inboard limiters

“…A much better studied radiation belt is the so-called Serpent in the heliotron LHD [15] which forms the plasma operational limit in the so-called Serpens mode. The Serpent is also a high-density plasma structure with densities in the range from 2 to 5 * 10 20 m −3 [16,17] but has a more complex geometry than the axisymmetric Marfe in a tokamak. We focus here on measurements in W7-X and a first analysis of the radiation belts in order to understand the physical nature of the phenomenon and the relation to Marfes in tokamaks and Serpents in LHD.…”

“…A much better studied radiation belt is the so-called Serpent in the heliotron LHD [15] which forms the plasma operational limit in the so-called Serpens mode. The Serpent is also a high-density plasma structure with densities in the range from 2 to 5 × 10 20 m −3 [16,17] but has a more complex geometry than the axisymmetric Marfe in a tokamak.…”

Time-resolved measurement of radical populations in extreme-ultraviolet-light-induced hydrogen plasma

“…The population densities of H radicals n(p) at p = 3, 4, and 5 between 30 and 40 ns were obtained from the absolute intensities of H α , H β , and H γ emissions. The population density of H * at each level (from p = 2 to p = 20) was calculated with the CR model 23,24) for various plasma electron densities and electron temperatures as shown in Fig. 4.…”