a Gas System for a Large Multi-Cells Detector

In complex detectors for high energy and nuclear physics experiments a high number of multi-cell gas detectors (in the range of thousands) are often used. In such cases a parallel, reliable, automatic, continuous monitoring gas system has to be built and operated in order to control and check the operational parameters (gas mixture composition, pressure, flux, gas losses...) that affect the detector performances and safety requirements. FINUDA is an experiment employing a large gas multi-cell detector and the gas system built and operated to flow its straw tubes is described. Straw tubes are used in FINUDA for charged particle tracking. The total number of tubes is 2424 (similar to 2.5 m long, 1.5 cm diameter) with a gas volume of about 0.51 each. They are mounted on three super layers (each one composed by two staggered layers) one axial and two stereo. The straws are made of thin aluminized mylar and each one is flown individually. The gas system has been designed to offer modularity, parallel layout, immunity from individual straws leakage, safety and remote control. An automatic gas bottle inversion system has also been implemented and will be described.