Rico Chandrasekharan

Detection of noble gas scintillation light 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.

Noble Gas Scintillation-Based Radiation Portal Monitors and Active Interrogation Systems

Noble gas scintillation detectors (NGSD) combine good scintillation properties such as high light yields and good energy resolution with cost-effective scalability to large detector masses. A unique capability of noble gas scintillators is outstanding discrimination between electron recoils (gamma-like events) and nuclear recoils (n-like events) down to low energy deposits of the order of tens of keVs. This capability allows the construction of fast neutron detectors with good timing capability. This work points out the potential advantages of using NGSDs for Homeland Security applications such as portal monitoring or active interrogation.

High efficiency detection of argon scintillation light of 128 nm using LAAPDs

The possibility of efficient collection and detection of vacuum ultraviolet light as emitted by argon, krypton, and xenon gas is studied. Absolute quantum efficiencies of large area avalanche photodiodes (LAAPDs) are derived at these wavelengths. VUV light of wavelengths down to the 128 nm of Ar emission is shown to be detectable with silicon avalanche photodiodes at quantum efficiencies above 42%. Flexible Mylar foil overcoated with Al+MgF2 is measured to have a specular reflectivity of ~91% at argon emission wavelength. 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