Sputtering by Non-recycling Ions Mixed Materials

The conditions where net erosion turns into net deposition for carbon irradiation may further be complicated by effects of surface temperature, influencing the self-sputtering yield by radiation-enhanced sublimation (RES) as well as the diffusion and surface segregation of implanted impurities. An example is introduced in Fig. 9.4b, where the erosion of W due to C+ bombardment 

Sputtering by Simultaneous Impact of Multi-species Ions 

The erosion properties of layers formed during bombardment with nonrecycling ions are modified due to simultaneous bombardment with different ions such as DT fuel ions from the fusion plasma. Experimentally, these conditions were simulated, by the bombardment of W with 3.0 keV CH3 at 300 K and 1000 K. The resulting particle energies are 2.4 keV for C and 200 eV for H. The erosion was evaluated from the experimental weight change of the sample [34]. 

To interpret the results the code package TRIDYN + DIFFUSEDC + YCHEM was developed [33]. In TRIDYN H ions were added as additional incident species with fraction h = 75% in the beam. In addition to the inclusion of chemical sputtering by YCHEM (see Sect. 9.3) a concentration dependent diffusion of carbon was added using a diffusion coefficient D(C) as determined from separate experiments [33]. The chemical sputter yield Ychem was taken from literature data and was 10%. In Fig. 9.5 the results of the calculation are compared to experimental data for irradiation of W with CHg at 1000 K [34] and with pure C at 1030 K. The simulations reproduce the experimental values well within the error bars. One can clearly see, that the 

For the simulation at 300 K the diffusion of C can be neglected such that the DIFFUSEDC step could be omitted in the simulation and only TRIDYN+YCHEM were used. A chemical sputter yield of 4% was assumed. A similarly good agreement with the data is obtained as at 1000 K [32], 

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