Development of a custom on-line ultrasonic vapour analyzer and flow meter for the ATLAS inner detector, with application to Cherenkov and gaseous charged particle detectors

Precision sound velocity measurements can simultaneously determine binary gas composition and flow. We have developed an analyzer with custom microcontroller-based electronics, currently used in the ATLAS Detector Control System, with numerous potential applications. Three instruments monitor C sub(3) F sub(8) and CO sub(2) coolant leak rates into the nitrogen envelopes of the ATLAS silicon microstrip and Pixel detectors. Two further instruments will aid operation of the new thermosiphon coolant recirculator: one of these will monitor air leaks into the low pressure condenser while the other will measure return vapour flow along with C sub(3) F sub(8)/C sub(2) F sub(6) blend composition, should blend operation be necessary to protect the ATLAS silicon tracker under increasing LHC luminosity. We describe these instruments and their electronics.