WLS System for the Pressurized Helium Calorimeter ``PHeSCAMI''

The possible presence of low-energy anti-deuterons in cosmic rays is a golden channel to test the antimatter asymmetry in the Universe or to identify annihilating Dark Matter particles in the galactic halo. The PHeSCAMI (Pressurized Helium Scintillating Calorimeter for AntiMatter Identification) project aims to study a new signature for the identification of anti-deuteron and anti-protons in cosmic rays. In particular, when a Z=-1 heavy antiparticle is stopping in Helium, it can produce an exotic atom having lifetime of microseconds. Helium gas is a fast scintillator, thus a relatively simple calorimetric measurement of the stopping particle kinetic energy is possible. A two-stage Wavelength Shifter (WLS) system is necessary to convert the VUV (80 nm) scintillation light into visible. The perfor mances of the FB118 WLS, manufactured by “Glass to Power”, are investigated. A promising usage of FB118 as a high-efficiency Cherenkov radiator is also inferred.