“…Therefore, because the carbon fluence could be too low to saturate grain surfaces and pore surfaces with carbon and enable carbon atoms to penetrate into tungsten grains, WC and W 2 C were not formed in the tungsten coating layer. Note that because W 2 C is formed in the tungsten coating layer exposed to JT-60U divertor plasmas [16], WC or W 2 C are expected to be formed by mixed ion beam irradiation for longer times or higher sample temperatures.…”