The C4F10 Cherenkov detector for DIRAC-II

A new threshold Cherenkov detector using C4F10 gas radiator was built and put into operation in the DIRAC-II experiment at CERN. Running on the C4F10 at room temperature and atmospheric pressure, the detector discriminates between pions and kaons in the momentum range of 4–8GeV/c. A compact radiator–gas recirculation system including a gas–liquid separation unit, hollow-fibre membranes and molecular sieves ensures gas purity for a long term of operation without a significant loss of the gas. The system is robust and stable and the pressure in the two detector vessels is regulated in the range of ±0.5mbar. We report on the design and the technical aspects of the detector and its response in the DIRAC 2007 run.