Deuterium retention in tungsten coating layers irradiated with deuterium and carbon ions

The effects of carbon ion fraction on deuterium retention in tungsten coating layers were investigated by irradiating the layers with mixed deuterium and carbon ion beams. The mixed ion beams had atomic carbon fractions of up to 3.2% and the sample temperature was either 500 or 700 K. Graphite was formed in the tungsten coating layer at the both temperatures; however, tungsten carbide and ditungsten carbide were not formed at the both temperatures. At 500 K, deuterium was trapped at intrinsic defects and carbon was accumulated in the tungsten coating layer. At 700 K, although trapping deuterium at intrinsic defects was difficult, deuterium was trapped predominantly at carbon accumulated in the tungsten coating layer. Analysis of deuterium desorption spectrum by multipeak fitting suggests that deuterium was retained by C-D bonds in the tungsten coating layer at 700 K.