Scintillation yield in high pressure xenon and xenon doped with methane

Scintillation light and ionization yields in pure xenon and xenon doped with various concentration of methane (0.2-2%) have been measured as a function of the reduced electric field (E/N) from 0 to 4/spl times/10/sup -18/ Vcm/sup 2/ at a pressure of 2.6 MPa. The measurements of photons and electrons have been made in gaseous xenon excited by /sup 241/Am alpha particles. High purity xenon was used to fill a high-pressure xenon chamber equipped with MgF/sub 2/ window coupled to a photomultiplier tube (PMT). The scintillation light in xenon-methane mixture is observed to decrease as the concentration of methane increases.