Direct Measurement of High-Pressure Gas Density With an Ion-Chamber Densitometer

The dependence of ion-chamber current on the density of the filling gas has been investigated, experimentally and analytically, to explore the use of an ion chamber as a high-pressure gas densitometer. A flat-plate ion chamber with a self-contained beta-particle source (Sr⁹⁰-Y⁹⁰) was used in experiments with methane, nitrogen, and carbon dioxide and for pressures up to 2000 psia and densities up to 9 lbm/ft³. Over an appreciable density range, the linearity of the current-density response was good with a static sensitivity of about 10⁻¹⁰ amp/(lbm/ft³) and a reproducibility of ±0.5 percent. Variables which could be used to increase the static sensitivity and the linear range were identified.