An investigation into lithium evaporation and redeposition with multi-mesh capillary pore systems (CPS) has been performed on a one-cathode linear plasma device. A diagnostic system has been used to monitor the lithium evaporation process in the vicinity of the specimen surface, with the adjustable plasma parameters of electron temperature ranging from 0.4–0.9 eV and electron density from 0.8–3.2 × 1019 m−3. The experimental results show that the lithium evaporation rate follows the reduction scaling ratio of 1.94:1.69:1.00 as the number of mesh layers is increased from two to four, which is closely related to the time-dependent fraction weighted average surface binding energy (i.e. evaporation heat) elevation because a fraction of lithium atoms is adhered to the mesh surface. From the viewpoint of nanoscale physics, a new formula is derived for the first time to qualitatively explain the physical mechanism of evaporation heat, or of time-dependent fraction weighted dual average surface binding energy with minor elevation in this special concomitant configuration CPS, which consists of liquid lithium and multi-meshes. The reason for this phenomenon is that the mesh surface binding force acts on a fraction of the adhered lithium atoms, leading to a minor elevation in the evaporation heat. The lithium vapor plays a modest shielding role from the incident heat flux dumping by stopping power plus lithium impurity radiation enhancement, as in the impurity radiation divertor, otherwise the thermal equilibrium of the system could not be attained. In addition, an experimental comparison with a nonactive target and a semi-empirical temperature-dependent model calculation have been applied to further verify the shielding effect. It has been observed that the redeposition rate increases with the applied discharge current.
Liquid lithium divertor characteristics and plasma–material interactions in NSTX high-performance plasmas