The removal of co-deposited hydrocarbon films from plasma facing components using high-power pulsed flashlamp irradiation

The use of carbon-based materials for first wall components in tokamaks results in the formation of hydrocarbon deposits on divertor components that could lead to a high level of tritium retention in future fusion devices. Experiments at UMIST have demonstrated that photonic cleaning using high power Xenon flashlamp sources is an efficient method for removing such films and represents a good candidate technology for international thermonuclear experimental reactor (ITER) operations. Studies have shown that effective film removal occurs at a fluence threshold of between 1.9 and 2.5 J/cm2. The by-products of the cleaning process, both particulates and gases, have been characterised using particle sizing spectrometry and quadrupole mass spectrometry respectively. It is found that hydrogen, methane, acetylene, ethylene, ethane and carbon dioxide are the principal gaseous products produced during the cleaning process, which also produces a significant fraction of particulates in the size range 2–20 μm.