A Combine On-Line Acoustic Flowmeter and Fluorocarbon Coolant Mixture Analyzer for The ATLAS Silicon Tracker

TL;DR

This paper presents a new acoustic instrument and SCADA software for real-time measurement of C3F8/C2F6 coolant mixtures and flow in the ATLAS silicon tracker, enhancing cooling control and radiation protection.

Contribution

It introduces a novel acoustic measurement device and software system for precise, real-time analysis of coolant mixtures and flow in high-energy physics detectors.

Findings

Achieved a mixture resolution of 3.10-3 for ~20% C2F6

Flow resolution of 2% of full scale up to 30 g/s

Detected leaks of C3F8 with sensitivity < 5.10-4

Abstract

An upgrade to the ATLAS silicon tracker cooling control system may require a change from C3F8 (octafluoro-propane) to a blend containing 10-30% of C2F6 (hexafluoro-ethane) to reduce the evaporation temperature and better protect the silicon from cumulative radiation damage with increasing LHC luminosity. Central to this upgrade is a new acoustic instrument for the real-time measurement of the C3F8/C2F6 mixture ratio and flow. The instrument and its Supervisory, Control and Data Acquisition (SCADA) software are described in this paper. The instrument has demonstrated a resolution of 3.10-3 for C3F8/C2F6 mixtures with ~20%C2F6, and 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 < 5.10-4 to leaks of C3F8 into the ATLAS pixel detector nitrogen envelope (mw difference 160) has been seen. The instrument has many potential applications, including the analysis of mixtures of hydrocarbons, vapours for semi-conductor manufacture and anaesthesia.