Vacuum Predictions and Measurements for an Internal Pellet Target

Measurements with low Z targets at internal experiments typically imply a gas load which deteriorates the ring vacuum. Future experiments need reliable estimates for the expected vacuum conditions in order to design 4-pi 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.