Case study of a flowfield using a pentode

A pentode vacuum-tube, used as a fast-response pressure-gauge, was found to be well suited for measuring gas pulses into a vacuum chamber through a sonic orifice. Static and dynamic calibration curves with fitted equations are presented for nitrogen and carbon dioxide. Placement of a skimmer between the pentode and nozzle provided the means by which a certain portion of the plume could be observed, but the skimmer also produced the possibility of shock interference. The gauge was used to characterize the flowfield, and the axial and radial results compared well with Ashkenas and Sherman results. A theoretical model of the pressure within the skimmer as a function of time was also developed and compared to the pentode results.