Void ensemble response to periodical variations of irradiation conditions

On the basis of the rate theory approach to void swelling the authors consider analytically the response of the radiation-induced defects to harmonic oscillations of irradiation parameters. The small deviations δx of the squared radius from its value in the stationary regime are shown to obey, in a linear approximation, the equation of a forced oscillator with damping. The term corresponding to an external force accounts for periodical variations of the damage rate or the irradiation temperature or both. The damping decrement σ considerable exceeds the intrinsic frequency of the system Ω, which means that in real irradiation conditions no resonance phenomena can exist. Thus, the deviations δx could be significant only for frequencies ωeff = Ω 2/2σ. The average void growth rate, however, remains practically unaffected by irradiation parameters pulsing almost in the whole temperature range of swelling except in the zone adjacent to the high temperature limit of swelling. Numerical data for meson physics facility irradiation with a typical frequency of 100 Hz and duty factor of 10-2 are presented