Outgassing coefficient development for improved leaktightness sensitivity in vacuum drift testing

Abstract

The parameters of vacuum outgassing are developed into variable gang coefficients adaptable to all materials, shapes, and conditions. Programmable equations and cascading charts for design and test use are presented. Outgassing data is introduced for rigid foams, honeycomb, and braided cable evacuation and is synthesized into area/volume effect factors applicable to any material. Coefficients for predicting bulk outgassing are shown to provide a rapid and optimized method for improving the leaktightness sensitivity of drift testing so much so as to be used in lieu of leak checking by mass spectrometer. Detectable inleakage rates for the vacuum pressure−rise (drift) method of determining leaktightness are defined for test articles of small volume to large space simulation chambers and underground nuclear effects testbeds. Offered as a test aid adjunct are nomograms developed for direct determination of true pressures from comparative readings of thermocouple and radiation type ionization gauges which are air calibrated but subjected to unknown concentrations of water vapor or helium.