Vacuum predictions and measurements for an internal Pellet Target at a storage ring

Measurements with low ZZ targets at internal experiments typically imply a gas load which deteriorates the vacuum of a storage ring. Future experiments need reliable estimates for the expected vacuum conditions in order to design 4π4π detectors closely surrounding the interaction area.We present a method for the calculation of the resulting vacuum of such a complex system using a Pellet Target. In order to test the method, a vacuum system with diagnostic tools has been set-up and a Pellet Target was operated under realistic conditions. The results for the absolute vacuum agree within factors of two with the expected pressures.