{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,16]],"date-time":"2026-04-16T07:43:35Z","timestamp":1776325415376,"version":"3.50.1"},"reference-count":42,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2022,2,11]],"date-time":"2022-02-11T00:00:00Z","timestamp":1644537600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>The Wavelength-shifting Optical Module (WOM) is a novel photosensor concept for the instrumentation of large detector volumes with single-photon sensitivity. The key objective is to improve the signal-to-noise ratio, which is achieved by decoupling the photosensitive area of a sensor from the cathode area of its photomultiplier tube (PMT). The WOM consists of a transparent tube with two PMTs attached to its ends. The tube is coated with wavelength-shifting paint that absorbs ultraviolet photons with nearly 100% efficiency. Depending on the environment, e.g., air (ice), up to 73% (41%) of the subsequently emitted optical photons can be captured by total internal reflection and propagate towards the PMTs, where they are recorded. The optical properties of the paint, the geometry of the tube, and the coupling of the tube to the PMTs have been optimized for maximal sensitivity based on theoretical derivations and experimental evaluations. Prototypes were built to demonstrate the technique and to develop a reproducible construction process. Important measurable characteristics of the WOM are the wavelength-dependent effective area, the transit time spread of detected photons, and the signal-to-noise ratio. The WOM outperforms bare PMTs, especially with respect to the low signal-to-noise ratio with an increase of a factor up to 8.9 in air (5.2 in ice). Since the gain in sensitivity is mostly in the UV regime, the WOM is an ideal sensor for Cherenkov and scintillation detectors.<\/jats:p>","DOI":"10.3390\/s22041385","type":"journal-article","created":{"date-parts":[[2022,2,13]],"date-time":"2022-02-13T20:34:45Z","timestamp":1644784485000},"page":"1385","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":12,"title":["The Wavelength-Shifting Optical Module"],"prefix":"10.3390","volume":"22","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-7100-5624","authenticated-orcid":false,"given":"Benjamin","family":"Bastian-Querner","sequence":"first","affiliation":[{"name":"Institut f\u00fcr Physik, Humboldt-Universit\u00e4t zu Berlin, 12489 Berlin, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Lucas S.","family":"Binn","sequence":"additional","affiliation":[{"name":"Institute of Physics, University of Mainz, Staudinger Weg 7, 55099 Mainz, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5918-4890","authenticated-orcid":false,"given":"Sebastian","family":"B\u00f6ser","sequence":"additional","affiliation":[{"name":"Institute of Physics, University of Mainz, Staudinger Weg 7, 55099 Mainz, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jannes","family":"Brostean-Kaiser","sequence":"additional","affiliation":[{"name":"Institut f\u00fcr Physik, Humboldt-Universit\u00e4t zu Berlin, 12489 Berlin, Germany"},{"name":"Deutsches Elektronen-Synchrotron (DESY), 15738 Zeuthen, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2643-7126","authenticated-orcid":false,"given":"Dustin","family":"Hebecker","sequence":"additional","affiliation":[{"name":"Institut f\u00fcr Physik, Humboldt-Universit\u00e4t zu Berlin, 12489 Berlin, Germany"},{"name":"Deutsches Elektronen-Synchrotron (DESY), 15738 Zeuthen, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2072-4172","authenticated-orcid":false,"given":"Klaus","family":"Helbing","sequence":"additional","affiliation":[{"name":"Department of Physics, University of Wuppertal, 42119 Wuppertal, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3251-2126","authenticated-orcid":false,"given":"Timo","family":"Karg","sequence":"additional","affiliation":[{"name":"Deutsches Elektronen-Synchrotron (DESY), 15738 Zeuthen, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Lutz","family":"K\u00f6pke","sequence":"additional","affiliation":[{"name":"Institute of Physics, University of Mainz, Staudinger Weg 7, 55099 Mainz, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Marek","family":"Kowalski","sequence":"additional","affiliation":[{"name":"Institut f\u00fcr Physik, Humboldt-Universit\u00e4t zu Berlin, 12489 Berlin, Germany"},{"name":"Deutsches Elektronen-Synchrotron (DESY), 15738 Zeuthen, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Peter","family":"Peiffer","sequence":"additional","affiliation":[{"name":"Institute of Physics, University of Mainz, Staudinger Weg 7, 55099 Mainz, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2492-043X","authenticated-orcid":false,"given":"Anna","family":"Pollmann","sequence":"additional","affiliation":[{"name":"Department of Physics, University of Wuppertal, 42119 Wuppertal, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0780-4274","authenticated-orcid":false,"given":"John","family":"Rack-Helleis","sequence":"additional","affiliation":[{"name":"Institute of Physics, University of Mainz, Staudinger Weg 7, 55099 Mainz, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7057-1007","authenticated-orcid":false,"given":"Martin","family":"Rongen","sequence":"additional","affiliation":[{"name":"Institute of Physics, University of Mainz, Staudinger Weg 7, 55099 Mainz, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9746-6872","authenticated-orcid":false,"given":"Lea","family":"Schlickmann","sequence":"additional","affiliation":[{"name":"Institute of Physics, University of Mainz, Staudinger Weg 7, 55099 Mainz, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3600-587X","authenticated-orcid":false,"given":"Florian","family":"Thomas","sequence":"additional","affiliation":[{"name":"Institute of Physics, University of Mainz, Staudinger Weg 7, 55099 Mainz, 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