Determination of the concentration of SF6 in an accelerator gas mixture by measuring the velocity of sound

A simple and reliable method for determining the concentration of SF6 in an accelerator gas mixture with N2 and CO2 is described. The technique makes use of the low velocity of sound in SF6 (approximately 13 that of air). The sound velocity of the mixture is determined by measuring the spacing of acoustic resonances in a tube filled with the gas. Data from standard gas mixtures containing 0–10% SF6 are presented, showing that the technique is accurate to approximately 0.5% absolute.