Vacuum calculations for hydrogen pellet targets at WASA and PANDA

Abstract: We have performed calculations in order to evaluate the vacuum conditions for the twohadron physics experiments WASA and PANDA. WASA is an ongoing experiment whereasPANDA is an experiment under construction. There is an interest in improving the vacuumconditions for these experiments in order to reduce background interactions. The experimentswere modelled as longitudinal conductance limited vacuum systems in the molecular flowregime and the calculations were performed with VAKLOOP. The approach was to fit amodel of WASA to measurement data and then extend this model to PANDA in order tomake predictions. The model of WASA was successful in the sense that it reproduced themeasurement data within the measurement uncertainty. The model of PANDA showed somediscrepancies in comparison with calculations from the Target Technical Design Report ofPANDA, but an overall similar pressure profile is obtained. Finally, we have considered a wayof improving the conditions at PANDA by including extra pumping capacity in the system,concluding that lowering the pressure at the interaction point for PANDA is challenging. Anoutlook for further modelling is to make a more detailed comparison between our model andthe one from the Target Technical Design Report.