Theoretical and experimental molecular beam angular distribution studies for gas injection in ultra-high vacuum

A dedicated set-up was designed and constructed for the purpose of accurately measuring flux distributions out of gas injectors of various shapes into ultra-high vacuum (UHV). Angular flux profiles of nitrogen exiting through various axially symmetric injectors over a range of flow rates are measured. The intent of these experiments is to validate a self-consistent simulation model based on the cosine law of molecular scattering on the walls. The experimental results give a clear confirmation of the proposed model within the limits of the molecular flow regime. Beyond this limit, the experimental profiles become flow rate dependent and gradually deviate from the model predictions.