Energy and temperature dependences of ion-induced electron emission from polycrystalline graphite

The dependences of the yield γ of ion-induced kinetic electron emission from polycrystalline graphite on ion energy E were measured under high-fluence Ar+ and N2+ ion irradiation in energy range 6–30 keV from room temperature to 400 °C. It has been observed that the step-like pattern of temperature dependence γ(T) at the dynamic radiation damage annealing temperature Ta is gradually transformed with decreasing ion energy until γ virtually ceases to depend on temperature. The experimentally obtained energy dependence of the ratio γ(T > Ta)/γ(T < Ta) has been analyzed using the theory of ion-induced kinetic electron emission. Some threshold values of the level of radiation damage νd measured in dpa under steady state of high-fluence Ar+ and N2+ irradiation have been found. When ν becomes less than a threshold value νd, the graphite lattice is virtually not disordered. It has been found that νd for Ar+ ions is greater than νd for N2+ ions.