Measuring the density of a molecular cluster injector via visible emission from an electron beam

Lundberg, D. P.; Kaita, R.; Majeski, R.; Stotler, D. P.
October 2010
Review of Scientific Instruments;Oct2010, Vol. 81 Issue 10, p10D707
Academic Journal
A method to measure the density distribution of a dense hydrogen gas jet is presented. A Mach 5.5 nozzle is cooled to 80 K to form a flow capable of molecular cluster formation. A 250 V, 10 mA electron beam collides with the jet and produces Hα emission that is viewed by a fast camera. The high density of the jet, several 1016 cm-3, results in substantial electron depletion, which attenuates the Hα emission. The attenuated emission measurement, combined with a simplified electron-molecule collision model, allows us to determine the molecular density profile via a simple iterative calculation.


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