Light output and collected charge in xenon-doped liquid argon

The light output and the collected charge in xenon-doped liquid argon under 207Bi conversion electron excitation have been studied as a function of an applied electric field with the xenon concentration [Xe] less than 1.9%. With increasing [Xe], the light output was increased and was maximized at [Xe] = 1.9%, having about as twice as much intensity with respect to that in pure argon. The amount of collected charge in xenon-doped liquid argon was nearly equal to that in pure argon up to 2500 ppm of [Xe], above which a slight increase was observed. The increase in light output can be explained by the difference in the conversion efficiency of the POPOP wavelength shifter for 130 nm scintillation photons in liquid argon and for 175 nm scintillation photons in xenon-doped liquid argon.