A threshold Cherenkov detector for K+/π+K+/π+ separation using silica aerogel

A new threshold Cherenkov detector has been built for the detection of charged pions in the focal plane of a magnetic spectrograph. Silica aerogel with refractive index of n=1.05n=1.05 is applied as a radiator. The detector exhibits a very high detection efficiency for pions with momenta ⩾900MeV/c. Using two Cherenkov detectors in series a very high pion suppression factor of 105105 was achieved.