Investigation of Skimmer Interaction Influences on the Production of Aerodynamically Intensified Molecular BEAMS

摘要

An intensive investigation of the dependence of the intensity on various dynamic and geometric quantities was conducted for nozzle beams skimmed from large, quasi-inviscid free jets of nitrogen and argon. Additional measurements of the total skimmer flux, the beam profiles and speed distribution were made and compared to the observed beam intensity for a sample case. It was possible to collect enough information under conditions free from background and condensation effects to recognize the main contributions to the beam attenuation. The results illustrate the validity of the original Kantrowitz-Grey idealization as a limiting form. Restrictions are apparently imposed by effects of condensation and polymerization, the presence of shock waves, typical rare-fraction phenomena, and ill-designed skimmer-end wall geometries. The interpretation of the observed scattering attenuation leads to a semitheoretical description of the beam flux and consequently to the prediction of a system-specific optimum beam intensity and an optimum skimmer diameter depending only on the performance of the nozzle exhaust and skimmer exhaust system. (Author)