Detection of VUV light at high quantum efficiency with large area avalanche photodiodes (LAAPDs)

Large Area Avalanche Photodiodes (LAAPDs) were used for a series of systematic measurements of the scintillation light in Ar, Kr, and Xe gas. Absolute quantum efficiencies are derived. Values for Xe and Kr are consistent with those given by the manufacturer. For the first time we show that argon scintillation (128 nm) can be detected at a quantum efficiency above 40 % . Low-pressure argon gas is shown to emit significant amounts of non-UV radiation. The average energy expenditure for the creation of non-UV photons in argon gas at this pressure is measured to be below 378 eV. Further, the principle of light collection by means of flexible Al + MgF 2 reflectors has been shown to work for argon scintillation light.