Benchmarking TPB-coated Light Guides for Liquid Argon TPC Light Detection Systems

Scintillation light from liquid argon is produced at 128 nm and thus must be shifted to visible wavelengths in light detection systems used for Liquid Argon Time Projection Chambers (LArTPCs). To date, designs have employed tetraphenyl butadiene (TPB) coatings on photomultiplier tubes (PMTs) or plates placed in front of the PMTs. Recently, a new approach using TPB-coated light guides was proposed. In this paper, we show that the response of lightguides coated with TPB in a UV Transmitting (UVT) acrylic matrix is very similar to that of a coating using a polystyrene (PS) matrix. We obtain a factor of three higher light yield than has been previously reported from lightguides. This paper provides information on the response of the lightguides so that these can be modeled in simulations for future LArTPCs. This paper also identifies areas of R&D for potential improvements in the lightguide response