Influence of tungsten-carbon mixed layer and irradiation defects on deuterium retention behavior in tungsten

摘要

The D_2~+ fluence dependence on deuterium (D) retention was studied to clarify the D retention mechanism in tungsten. The additional D desorption stage was observed around 660 K in the TDS spectrum for a sample implanted with D_2~+ up to the fluence of 10~(23) D~+ m~(-2), which desorption stage was not observed the D_2~+ implanted sample with the fluence less than 10~(22) D~+ m~(-2). TheTEM observation showed that the highly dense voids were formed in tungsten by D_2~+ implantation with the fluence of 10~(23) D~+ m~(-2), considering that the D would be trapped by voids. To understand the D trapping by voids in C~+implanted tungsten, C~+-D_2~+ sequential implantation experiments at various C~+ implantation temperatures were performed. It was found that the amount of D desorbed around 560 K was increased by increasing the C~+ implantation temperature. The formation of the voids was observed with increasing the C~+ implantation temperature by TEM, indicating that the increase of D desorption around 560 K was caused by the formation of voids. However, the desorption temperature of D trapped by voids in C~+ implanted sample was lower than that in D_2~+ implanted one. TEM observation and XPS measurement indicated that this difference was caused by the increase of void size and/or the presence of implanted carbon.