Simulation of hydrocarbon reflection from carbon and tungsten surfaces and its impact on codeposition patterns on plasma facing components

Determination of the sticking coefficient of energetic hydrocarbon molecules by molecular dynamics

“…The quantity shown is the gross sticking coefficient, because the net sticking coefficient cannot be reconstructed from the literature data. The results from this work match the data from Ohya et al [6] quite well up to an energy of 50 eV, despite the fact that a different interaction potential was used. Above that energy, all gross sticking coefficients in that work are one.…”

“…It is therefore advisable to constrain the use of BCA results to projectiles energies above 50 eV. Figure 5 shows a comparison between the results from the MD Simulations from this work and the studies by Alman et al [5] and Ohya et al [6]. The quantity shown is the gross sticking coefficient, because the net sticking coefficient cannot be reconstructed from the literature data.…”

“…To take into account the influence of the sample surface, the simulations are done on an amorphous hydrocarbon sample that is similar to the kind of material that grows from the impacting projectiles. Similar studies were performed by Alman et al [5] and Ohya et al [6]. Alman et al [5] used an amorphised graphite sample, focussing on low projectile energies (25 meV -50 eV) with sequential bombardment, using the Brenner hydrocarbon potential [7].…”

“…Alman et al [5] used an amorphised graphite sample, focussing on low projectile energies (25 meV -50 eV) with sequential bombardment, using the Brenner hydrocarbon potential [7]. The simulations by Ohya et al [6] operated on a sample of hydrogenated and amorphised graphite using the Juslin potential [8] and projectile energies up to 100 eV. The database built by these publications was extended with respect to angle of incidence as well as to higher projectile energies.…”

Modelling of carbon deposition from CD4injection in the far scrape-off layer of TEXTOR

“…Cross-field diffusion has been neglected here. Outside the QMB aperture on the cylinder top surface, MD-based reflection coefficients [5] are used: R CH4 = R CH3 = 1, R CH2 = 0.9, R CH = 0.6, R C = 0.3. Within the area of the QMB aperture a reflection coefficient of R = 0 is applied to assess the flux of species entering the QMB housing-this information is used as input for the 3D-GAPS code to analyse the detailed transport within the QMB housing, see section 3.2.…”