Influence of thin alien layers on hydrogen reflection and trapping by PFM

Investigations of the influence of carbon and hydrocarbon layers on the trapping and reflection of hydrogen isotopes by tungsten were carried out with BCA based computer code SCATTER. It is shown that for small layer thickness the trapping efficiency depends on the hydrocarbon film composition. At layer thickness of a few nanometers energy dependence of the trapping efficiency has a non-monotonous character with a minimum at primary energies about 100–1000 eV and continuous increment with energy at higher energies. The possible reason of this effect is briefly discussed. Comparison between the trapping efficiencies of different hydrogen isotopes in a C–W target is also presented.