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

TL;DR

This study compares the light yield of PEN and TPB wavelength shifters in liquid argon detectors, finding PEN achieves nearly half the efficiency of TPB, which could simplify future detector construction.

Contribution

It provides the first direct comparison of PEN and TPB in identical liquid argon chambers, quantifying PEN's wavelength shifting efficiency relative to TPB.

Findings

PEN achieves 39.4% of TPB's light yield.

Wavelength shifting efficiency of PEN is approximately 47.2%.

Results support using PEN as a practical alternative in detector design.

Abstract

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$\pm$0.4(stat)$\pm$1.9(syst)% of the yield of the TPB chamber. Using a Monte Carlo simulation this result is used to extract the wavelength shifting efficiency of PEN relative to TPB equal to 47.2$\pm$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.