An on-line acoustic fluorocarbon coolant mixture analyzer for the ATLAS silicon tracker

• Published in: 2011 2nd International Conference on Advancements in Nuclear Instrumentation, Measurement Methods and their Applications pp. 1 - 7
• Main Authors: Bates, R., Battistin, M., Berry, S., Bitadze, A., Bonneau, P., Bousson, N., Boyd, G., Botelho-Direito, J., DiGirolamo, B., Doubek, M., Egorov, K., Godlewski, J., Hallewell, G., Katunin, S., Mathieu, M., McMahon, S., Nagai, K., Perez-Rodriguez, E., Rozanov, A., Vacek, V., Vitek, M.
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.06.2011
• Subjects: Acoustics; Instruments; Silicon; Software; Temperature measurement; Temperature sensors; Velocity measurement
• ISBN: 9781457709258; 1457709252
• DOI: 10.1109/ANIMMA.2011.6172830

The ATLAS silicon tracker community foresees an upgrade from the present octafluoropropane (C 3 F 8 ) evaporative cooling fluid - to a composite fluid with a probable 10-20% admixture of hexafluoroethane (C 2 F 6 ). Such a fluid will allow a lower evaporation temperature and will afford the tracker silicon substrates a better safety margin against leakage current-induced thermal runaway caused by cumulative radiation damage as the luminosity profile at the CERN Large Hadron Collider increases. Central to the use of this new fluid is a new custom-developed speed-of-sound instrument for continuous real-time measurement of the C 3 F 8 /C 2 F 6 mixture ratio and flow. An acoustic vapour mixture analyzer/flow meter with new custom electronics allowing ultrasonic frequency transmission through gas mixtures has been developed for this application. Synchronous with the emission of an ultrasound `chirp' from an acoustic transmitter, a fast readout clock (40 MHz) is started. The clock is stopped on receipt of an above threshold sound pulse at the receiver. Sound is alternately transmitted parallel and anti-parallel with the vapour flow for volume flow measurement from transducers that can serve as acoustic transmitters or receivers. In the development version, continuous real-time measurement of C 3 F 8 /C 2 F 6 flow and calculation of the mixture ratio is performed within a graphical user interface developed in PVSS-II, the Supervisory, Control and Data Acquisition standard chosen for LHC and its experiments at CERN. The described instrument has numerous potential applications - including refrigerant leak detection, the analysis of hydrocarbons, vapour mixtures for semiconductor manufacture and anesthetic gas mixtures.