A combined ultrasonic flow meter and binary vapour mixture analyzer for the ATLAS silicon tracker

Bates, R.; Battistin, M.; Rozanov, A.; Bozza, G.; Da Riva, E.; Berry, S.; Botelho-Direito, J.; Bousson, N.; Doubek, M.; Mathieu, M.; Vacek, V.; Degeorge, C.; McMahon, S.; Bonneau, P.; Berthoud, J.; Nagai, K.; Giugni, D.; Katunin, S.; Godlewski, J.; Boyd, G.; Zwalinski, L.; Lombard, D.; Perez-Rodriguez, E.; Bitadze, A.; Vitek, M.; Rossi, C.; DiGirolamo, B.; Hallewell, G.

doi:10.1088/1748-0221/8/02/P02006

Article
Report number	arXiv:1210.4835
Title	A combined ultrasonic flow meter and binary vapour mixture analyzer for the ATLAS silicon tracker
Author(s)	Bates, R. (Glasgow U.) ; Battistin, M. (CERN) ; Berry, S. (CERN) ; Berthoud, J. (CERN) ; Bitadze, A. (Glasgow U.) ; Bonneau, P. (CERN) ; Botelho-Direito, J. (CERN) ; Bousson, N. (Marseille, CPPM) ; Boyd, G. (Oklahoma U.) ; Bozza, G. (CERN) ; Da Riva, E. (CERN) ; Degeorge, C. (Indiana U.) ; DiGirolamo, B. (CERN) ; Doubek, M. (IEAP CTU, Prague) ; Giugni, D. (INFN, Milan ; Milan U.) ; Godlewski, J. (CERN) ; Hallewell, G. (Marseille, CPPM) ; Katunin, S. (St. Petersburg, INP) ; Lombard, D. (CERN) ; Mathieu, M. (Marseille, CPPM) ; McMahon, S. (Rutherford) ; Nagai, K. (Tsukuba U., GSPAS) ; Perez-Rodriguez, E. (CERN) ; Rossi, C. (Genoa U.) ; Rozanov, A. (Marseille, CPPM) ; Vacek, V. (DESY) ; Vitek, M. (DESY) ; Zwalinski, L. (CERN)
Publication	2013
Imprint	18 Oct 2012
Number of pages	30
Note	Comments: 30 pages, 24 figures, 3 tables KEYWORDS: Sonar; Saturated fluorocarbons; Flowmetry; Sound velocity, Gas mixture analysis 30 pages, 24 figures, 3 tables KEYWORDS: Sonar; Saturated fluorocarbons; Flowmetry; Sound velocity, Gas mixture analysis
In:	JINST 8 (2013) P02006
DOI	10.1088/1748-0221/8/02/P02006
Subject category	Detectors and Experimental Techniques
Accelerator/Facility, Experiment	CERN LHC ; ATLAS
Abstract	An upgrade to the ATLAS silicon tracker cooling control system may require a change from C3F8 (octafluoro-propane) evaporative coolant to a blend containing 10-25% of C2F6 (hexafluoro-ethane). Such a change will reduce the evaporation temperature to assure thermal stability following radiation damage accumulated at full LHC luminosity. Central to this upgrade is a new ultrasonic instrument in which sound transit times are continuously measured in opposite directions in flowing gas at known temperature and pressure to deduce the C3F8/C2F6 flow rate and mixture composition. The instrument and its Supervisory, Control and Data Acquisition (SCADA) software are described in this paper. Several geometries for the instrument are in use or under evaluation. An instrument with a pinched axial geometry intended for analysis and measurement of moderate flow rates has demonstrated a mixture resolution of 3.10-3 for C3F8/C2F6 molar mixtures with 20%C2F6, and a flow resolution of 2% of full scale for mass flows up to 30gs-1. In mixtures of widely-differing molecular weight (mw), higher mixture precision is possible: a sensitivity of <5.10-5 to leaks of C3F8 into part of the ATLAS tracker nitrogen envelope (mw difference 160) has been seen. An instrument with an angled sound path geometry has been developed for use at high fluorocarbon mass flow rates of around 1.2 kgs-1 - corresponding to full flow in a new 60kW thermosiphon recirculator under construction for the ATLAS silicon tracker. Extensive computational fluid dynamics studies were performed to determine the preferred geometry (ultrasonic transducer spacing and placement, together with the sound crossing angle with respect to the vapour flow direction). A prototype with 45deg crossing angle has demonstrated a flow resolution of 1.9% of full scale for linear flow velocities up to 15 ms-1. The instrument has many potential applications.
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