Damages on pure tungsten irradiated by compression plasma flows

Abstract

Since the plasma pulse parameters of CPFs (compression plasma flows) are similar to the ones of ELMs (edge localized modes) in TOKAMAK, it can be used to study the ELMs induced transient heat damage on plasma facing materials (PFMs) experimentally. However, it is difficult to directly measure the CPFs energy deposition on the target. We adopted an indirect measuring method and with digital calculation corrections. We observed the damage on pure tungsten samples induced by CPFs with the corrected average energy densities ε from 87 J/cm2 to 158 J/cm2, and the pulse duration about 0.1 ms. The results showed that cracking, melting, ablation damages appeared even at the lowest energy fluence density (87 J/cm2). Two kinds of cracks were observed: primary cracks caused by the brittleness of the W and thermal stress from temperature gradient, and secondary crack caused by thermal stress from resolidification. Many kinds of melting damages including molten flow traces, reticulate pattern, nano sized pinholes at the intersection points of the pattern, micro particles, and columnar crystal grain on the tungsten surface were observed. The ablation damage including droplet ejection and mass loss after irradiation were observed and mass loss increased as the ε increasing.