Temperature-dependent fluorescence emission spectra of acrylic (PMMA) and tetraphenyl butadiene (TPB) excited with UV light

Acrylic (poly(methyl methacrylate) or PMMA) is commonly used as a material for vessels to hold scintillating liquids in rare-event searches. Certain types of PMMA can fluoresce with a low efficiency at room temperature. We have investigated the fluorescence spectra under 280 nm ultraviolet (UV) excitation of the PMMA used in the DEAP-3600 dark matter search at various low temperatures. Fluorescence of this PMMA is observed, with an increasing intensity as the sample is cooled from a temperature of 300 K down to 4 K . The common wavelength-shifter tetraphenyl butadiene (TPB) is also measured for use as a reference.