In the paper, the distributions of structure damage created in alpha-phase of gallium oxide by keV fluorine, phosphorus and xenon ion irradiation, have been obtained at room temperature. A noticeable effect of the average individual collision cascade density on the stable damage production efficiency at the surface was established. In contrast to many other semiconductors, an intermediate damage peak appeared in the alpha-Ga2O3 between the surface and bulk maxima. This intermediate peak visible in the RBS/C spectra at low damage levels was discovered for the first time. Characteristic peculiarities of the discovered maximum were investigated.