Residual stresses in tungsten under exposures with ITER ELM-like plasma loads

Abstract

The residual stresses in tungsten targets after repetitive ITER ELM-like plasma pulses have been studied in recent simulation experiments with the quasi-stationary plasma accelerator (QSPA) Kh-50. The experiments were performed for targets preheated at 650 °C, which is above the ductile-to-brittle transition temperature (DBTT), and at room temperature (RT). The number of exposures was up to 400 pulses of duration 0.25 ms, and the magnitude of heat load was below and above the melting threshold.After plasma impacts, the residual stress was analyzed with the x-ray diffraction (XRD) technique using the sin2 ψ method. Symmetrical tensile stresses were measured in a thin subsurface layer. The largest stress (up to 750–850 MPa) was obtained after exposures of RT targets to plasma loads below the melting threshold. Preheating of the target resulted in some decrease of residual stress.