Effect of exposure temperature on deuterium retention and surface blistering of tungsten exposed to sequential nitrogen and deuterium plasma

Rolled tungsten (W) was sequentially exposed to nitrogen (N) and deuterium (D) plasma at different surface temperatures to investigate the influence of N pre-irradiation on D retention and surface blistering of W. Surface imaging revealed that significant amounts of blisters are formed after D exposure at 230 and 370 K. However, no blisters were found in the case of 520 K D exposure. In addition, N pre-irradiation increases the areal density of blisters, in particular that of small blisters. This effect becomes more significant for 500 K N exposure compared with 300 K N exposure. D depth profiles show that N pre-irradiation leads to an increase of the D concentration in the near surface. Thermal desorption spectra show that only one main desorption peak appears for the case of 230/520K, while two peaks are found for 370 K D exposure. Though N pre-irradiation does not change the deuterium desorption peak positions, it slightly changes the total D retention. These phenomena indicate a temperature dependence of the effect of N pre-irradiation on the D behavior in W.