Author: Bitadze, A.
Paper Title Page
WEPMN038 A Combined On-line Acoustic Flowmeter and Fluorocarbon Coolant Mixture Analyzer for the ATLAS Silicon Tracker 969
  • A. Bitadze, R.L. Bates
    University of Glasgow, Glasgow, United Kingdom
  • M. Battistin, S. Berry, P. Bonneau, J. Botelho-Direito, B. Di Girolamo, J. Godlewski, E. Perez-Rodriguez, L. Zwalinski
    CERN, Geneva, Switzerland
  • N. Bousson, G.D. Hallewell, M. Mathieu, A. Rozanov
    CNRS/CPT, Marseille, France
  • R. Boyd
    University of Oklahoma, Norman, Oklahoma, USA
  • M. Doubek, V. Vacek, M. Vitek
    Czech Technical University in Prague, Faculty of Mechanical Engineering, Prague, Czech Republic
  • K. Egorov
    Indiana University, Bloomington, Indiana, USA
  • S. Katunin
    PNPI, Gatchina, Leningrad District, Russia
  • S. McMahon
    STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
  • K. Nagai
    University of Tsukuba, Graduate School of Pure and Applied Sciences,, Tsukuba, Ibaraki, Japan
  An upgrade to the ATLAS silicon tracker cooling control system requires a change from C3F8 (molecular weight 188) coolant to a blend with 10-30% C2F6 (mw 138) to reduce the evaporation temperature and better protect the silicon from cumulative radiation damage at LHC. Central to this upgrade an acoustic instrument for measurement of C3F8/C2F6 mixture and flow has been developed. Sound velocity in a binary gas mixture at known temperature and pressure depends on the component concentrations. 50 kHz sound bursts are simultaneously sent via ultrasonic transceivers parallel and anti-parallel to the gas flow. A 20 MHz transit clock is started synchronous with burst transmission and stopped by over-threshold received sound pulses. Transit times in both directions, together with temperature and pressure, enter a FIFO memory 100 times/second. Gas mixture is continuously analyzed using PVSS-II, by comparison of average sound velocity in both directions with stored velocity-mixture look-up tables. Flow is calculated from the difference in sound velocity in the two directions. In future versions these calculations may be made in a micro-controller. The instrument has demonstrated a resolution of <0.3% for C3F8/C2F6 mixtures with ~20%C2F6, with simultaneous flow resolution of ~0.1% of F.S. Higher precision is possible: a sensitivity of ~0.005% to leaks of C3F8 into the ATLAS pixel detector nitrogen envelope (mw difference 156) has been seen. The instrument has many applications, including analysis of hydrocarbons, mixtures for semi-conductor manufacture and anesthesia.