Direct comparison of PEN and TPB wavelength shifters in a liquid argon detector

A large number of particle detectors employ liquid argon as their target material owing to its high scintillation yield and its ability to drift ionization charge over large distances. Scintillation light from argon is peaked at 128 nm and a wavelength shifter is required for its efficient detection. In this work, we directly compare the light yield achieved in two identical liquid argon chambers, one of which is equipped with polyethylene naphthalate (PEN) and the other with tetraphenyl butadiene (TPB) wavelength shifter. Both chambers are lined with enhanced specular reflectors and instrumented with SiPMs with a coverage fraction of approximately 1%, which represents a geometry comparable to the future large scale detectors. We measured the light yield of the PEN chamber to be 39.4 +/- 0.4(stat) +/- 1.9(syst)% of the yield of the TPB chamber. Using a Monte Carlo simulation this result is used to extract the wavelength shifting efficiency of PEN relative to TPB equal to 47.2 +/- 5.7%. This result paves the way for the use of easily available PEN foils as a wavelength shifter, which can substantially simplify the construction of future liquid argon detectors.

Automated summary

The study compared the light yield achieved in two liquid argon chambers equipped with PEN and TPB wavelength shifters, with the PEN chamber's yield being 39.4% of the TPB chamber's. Utilizing Monte Carlo simulation, the efficiency of PEN relative to TPB for wavelength shifting was determined to be 47.2%. This suggests that using readily available PEN foils as a wavelength shifter can streamline the construction of future liquid argon detectors.