Application of New Ultrasonic Instrumentation to Real-time Monitoring and Analysis of Binary Gases Mixtures

Custom ultrasonic instruments have been developed for continuous monitoring and real-time measurement of composition and flow in binary gas mixtures. These characteristics are derived from measurements of sound transit time along two opposite directions -parallel or tilted to the gas flow direction. The flow rate is then calculated from the transit time difference while the average is used to compute sound velocity by comparison with a sound velocity/composition database. Five devices are integrated in the Detector Control System of the ATLAS experiment at the CERN Large Hadron Collider. Three instruments monitor C3F8 and CO2 coolant leaks into the nitrogen-purged envelopes of the inner silicon tracker; respectively with precisions better than +/- 2 x 10(-5) and +/- 10(-4). Two further instruments are used to monitor the new thermosiphon C3F8 evaporative coolant recirculator. One of these measures C3F8 vapour return flow to the condenser while the other tracks air ingress into the condenser. The precision of these instruments highlights their potential in other applications requiring continuous binary gas composition monitoring.