This paper presents the Monte-Carlo simulation of charged particles motion in aluminum film of several tens micrometers thickness, which is a sensor part of a strip-detector. It was considered that secondary electrons are generated by copper ions Cu++ with energy 5 - 25 keV. An elastic collisions with target atoms, atomic levels ionization and electron capture have been taken into account for the ions, and for the secondary electrons – elastic collisions with target atoms, atomic levels ionization, plasmons and phonons generation. The derived dependence of the charge accumulated by sensor on ion beam energy is matching experimental data.