The Hall A Wire-chamber Gas System Ops Manual

  
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Two detector systems in the Hall-A spectrometers make use of potentially flammable gasses: the Vertical Drift Chambers (VDC) and the Focal Plane Polarimeter (FPP) straw tubes. This document is intended to address the practical need for a users manual for this gas supply system as well as the formal requirement for a written operating procedure. Th
The Hall A Wire-chamber Gas System Ops Manual - schematic

e reader specifically interested in safety systems and compliance with safety regulations is referred to the sections Overview, Interlocks, Checklist, Interlock System, Calculation of Hazard Class, Refrigerator Safety, and Call List. As of this writing both detector systems (FPP and VDC) are using a mixture of Argon and Ethane in roughly equal proportions, plus about 1% ethanol. The Argon and Ethane are supplied from high-pressure gas bottles. They are combined in the desired proportion by a mixing system and this mixture is passed through a bath of ethyl alcohol which is maintained at a fixed temperature. See Figure 2. 3-1 for a schematic diagram of the gas supply / mixing system. The gas mixture is delivered to gas distribution racks in the Hadron Spectrometer and the Electron Spectrometer. The transmission lines and the distribution plumbing have been designed as if the FPPs and VDCs were actually independent systems using different gas mixtures. This design was chosen in order to ease the expected transition to such a system in the future. Also supplied is a source of purge gas, currently pure argon. The distribution racks provide, for each detector, selection of either operating gas or purge gas, flow control and metering, overpressure relief to protect the detector components, exhaust flow measurement, and backflow prevention. The bulk gas supply consists of two bottles each of Argon and Ethane. Except for fittings...



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