Fuel removal from tile gaps with oxygen discharges: reactivity of neutrals

Thomas Schwarz-Selinger, Udo von Toussaint, Christian Hopf, Wolfgang Jacob
2009 Physica Scripta  
Carbon removal in so-called remote areas, where no energetic species can reach the surface, is investigated with low-temperature glow discharges in pure oxygen. Plasma-deposited amorphous hydrogenated carbon thin films are used as a model system for redeposited films. Erosion measurements are performed on flat substrates as well as on two different 3D test structures. One design consists of 19 mm deep gaps with widths ranging from 0.5 to 4 mm to simulate ITER tile gaps. A second design consists
more » ... ond design consists of a flat box-like structure where particles can enter only through a narrow slit. Measurements are performed for substrate temperatures ranging from 290 to 580 K. Erosion rates follow an Arrhenius-type dependence on substrate temperature with an effective activation energy of 0.25 eV. While at room temperature the surface loss probability of the dominant eroding species is 50 % it becomes smaller at elevated temperatures. At elevated temperatures the films are not only removed faster but simultaneously erosion penetrates deeper into the gaps.
doi:10.1088/0031-8949/2009/t138/014009 fatcat:ofipe7hf6fcltkei4dzinpweae