Effects of hydrogen molecular desorption on the heat load on plasma facing materials

Abstract

Measurements of the heat load on C (isotropic graphite) and W targets were performed in linear steady plasma facility MAP-II (materials and plasma), which produces a low-energy hydrogen plasma 10-20 eV with an electron density of (1.0-5.0) × 10 17 m −3 . From the measurements of the heat removed by the target coolant, heat flow to the target and Balmer intensities near the targets we found that the heat load was larger on the C target than W because of higher molecular hydrogen desorption. The population densities of vibrational levels in the d 3 u state of molecular hydrogen shifted to higher levels near the C target in the spectroscopy of the Fulcher band. From these results, it was found that molecular hydrogen desorption plays an important role in the heat load on plasma facing materials and it depends on the materials, which have different characteristics of hydrogen molecular desorption and energy states of desorbed hydrogen.