Carbon transport and escape fraction in a high density plasma beam

Abstract

Hydrocarbon injection experiments on molybdenum targets facing high-density plasmas in Pilot-PSI were simulated with the 3D Monte Carlo impurity transport and PSI code ERO. Impurity transport and calculation of redeposition profiles were decoupled by calculating carbon redistribution matrices with ERO. Redeposition was found to be strongly dependent on the electron density. The calculated average number of recycling events of hydrocarbon molecules on the surface went up from from 1.5 for n e = 5 • 10 19 m −3 to 19.2 for n e = 4 • 10 20 m −3 ; at the latter density, only 2.4% of the hydrocarbon molecules escapes the simulated plasma beam without returning to the target at least once. Agreement with experimental deposition profiles in argon was fair. The results in hydrogen point towards a strong gradient in chemical erosion yield along the target.

Spontaneous synthesis of carbon nanowalls, nanotubes and nanotips using high flux density plasmas

“…One could think of varying the heat flux, sample and cooling geometry in order to control the amount of carbon being sputtered from the sample. Carbon migration through the plasma and redeposition under described plasma loading conditions are being extensively studied with the 3D Monte Carlo impurity transport and plasma-surface interactions code ERO [83,84]. Ultimately, one could think of using such code as a predictive model for deposition experiments.…”

Erosion/re-deposition modeling in an ITER divertor-like high-density, low-temperature plasma beam

“…This allows us to greatly simplify the analysis: it enables separation of the modeling of impurity transport in the plasma and the calculation of actual redeposition profiles on the target. ERO has been used in this way previously to reproduce the deposition profile during methane injection [16], but this required careful matching of the erosion yield along the target to reproduce the experimentally observed deposition pattern.…”

“…• Tichmann et al have published energy-dependencies [20] and angular dependencies [21] of the sticking probabilities for CH x (0 ≤ x ≤ 4) on a-C:H films with properties identical to those experimentally obtained from real films. The temperature was held at 300 K. These rates were used in previous ERO simulations [16] and will be used here as a reference.…”

“…Erosion from a bin continues until the layer is depleted; the initial layer thickness is equal to the experimentally measured layer thickness outside the beam center. The redeposition is calculated using ERO simulation; this process is described in [16]. After iteration over many (small) time steps, the net erosion profile is obtained.…”

Plasma–Surface Interactions Under High Heat and Particle Fluxes

“…As a consequence, every eroded particle will experience a cycle of erosion/re-deposition events before it can eventually escape the plasma beam. Modeling shows that every CH molecule eroded from the surface, for a density of 4×10 20 m −3 , will visit the surface in average 19 times before actually escaping the plasma beam [26]. As a result, this strong material recycling reduces the net surface erosion and it has been experimentally determined that up to 90 % of the eroded material is re-deposited back on the surface [4].…”