Experimental Study of the Collimation Problem in a High-Intensity Molecular Beam

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Abstract
The discrepancy between the experimentally observed beam intensities obtained with nozzle sources, and the intensities predicted by the inviscid theory is generally attributed to viscous effects upstream of the ``skimmer.'' Experiments are described which show the scattering of a 1.2-eV nitrogen beam downstream of a ``skimmer'' or collimator. Such scattering can only result from collisions with slow molecules, traveling with the beam, coming from the viscous region upstream. Elimination of this scattering was accomplished by limiting the radial extent of the flow field approaching the ``skimmer,'' and beams were obtained having the theoretically available intensity.
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