<正>In order to achieve the expected beam intensity in the ring, an effective pumping system is used to reduce the pressure in scattering chamber and keep the background vacuum of 10-9 Pa of the ring to be nearly unaffected. The pressure distribution and pumping speed in needed at all stages are calculated. According to the calculation the pressure in the scattering chamber could be decreased to the magnitude of 10-9 Pa by using three stages of collimating and a pumping speed of 1 500 l/s at each stage. Now the general installation of the cluster target has been finished which is shown in Fig.1.