  A study of the self-organization of vacancy clusters in irradiated materials
is presented. Using a continuum stochastic model we take into account dynamics
of point defects and their sinks with elastic interactions of vacancies.
Dynamics of vacancy clusters formation is studied analytically and numerically
under conditions related to irradiation in both reactors and accelerators. We
have shown a difference in patterning dynamics and studied the external noise
influence related to fluctuation in a defect production rate. Applying our
approach to pure nickel irradiated under different conditions we have shown
that vacancy clusters having a linear size 6 nm can arrange in statistical
periodic structure with nano-meter range. We have found that linear size of
vacancy clusters at accelerator conditions decreases down to 20%, whereas a
period of vacancy clusters reduces to 6.5%.
