The cooling-stacking injection at the HIMAC synchrotron was used to increase the intensity of Ar18+ ion beam. The beam stacking was realized in a horizontal freephase-space, which was created by the HIMAC electron cooler. The stack intensity of (1.5-2.5) / 109 ppp was accumulated at an injection intensity of (0.3-1.0)/109.The lifetime of stack ions is determined by vacuum pressure. The new injected ions were slowly lost at multiple scattering on residual gas atoms at diffusion heating in the vertical direction caused by the acceptance of 30 pi mmmrad and a reduction of cooling force at large betatron amplitudes. The results of numerical simulations and experimental study of cooling-stacking injection on the HIMAC synchrotron are presented
