Environmental effects on TPB wavelength-shifting coatings

The scintillation detection systems of liquid argon time projection chambers (LArTPCs) require wavelength shifters to detect the 128 nm scintillation light produced in liquid argon. Tetraphenyl butadiene (TPB) is a fluorescent material that can shift this light to a wavelength of 425 nm, lending its...

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Bibliographic Details
Main Authors: Chiu, C. S., Ignarra, Christina, Bugel, Leonard G., Chen, H., Conrad, Janet, Jones, Benjamin James Poyner, Katori, Teppei, Moult, Ian James
Other Authors: Massachusetts Institute of Technology. Department of Physics
Format: Article
Language:en_US
Published: Institute of Physics Publishing 2014
Online Access:http://hdl.handle.net/1721.1/88416
https://orcid.org/0000-0002-9429-9482
https://orcid.org/0000-0002-4819-4081
https://orcid.org/0000-0002-6393-0438
https://orcid.org/0000-0003-3837-3921
https://orcid.org/0000-0001-6243-1453
Description
Summary:The scintillation detection systems of liquid argon time projection chambers (LArTPCs) require wavelength shifters to detect the 128 nm scintillation light produced in liquid argon. Tetraphenyl butadiene (TPB) is a fluorescent material that can shift this light to a wavelength of 425 nm, lending itself well to use in these detectors. We can coat the glass of photomultiplier tubes (PMTs) with TPB or place TPB-coated plates in front of the PMTs. In this paper, we investigate the degradation of a solution-based, embedded TPB coating in a laboratory or factory environment to assess the viability of long-term TPB film storage prior to its initial installation in an LArTPC. We present evidence for severe degradation of this type of coating due to common fluorescent lights and ambient sunlight in laboratories, with potential losses at the 40% level in the first day and eventual losses at the 80% level after a month of exposure. We determine the degradation is due to wavelengths in the UV spectrum, and we demonstrate mitigating methods for retrofitting lab and factory environments.