The collimation of intense atomic beams by parallel tube-arrays

We report on a series of experiments to characterize the collimation of atomic vapor beams. Hot $^{6}$Li atoms were emitted from an atomic beam source and collimated by various tube-array sections. Flux intensity profiles were obtained with several arrays for tubes having a range of shape factors, $\gamma $ = d/L. Measurements were made in the molecular and hydrodynamic flow regimes (i.e. for different Knudsen parameters).