doi:10.1088/1748-0221/15/11/P11031engGhosh, S.Haefner, J.Martín-Albo, J.Guenette, R.Li, X.Loya Villalpando, A.A.Burch, C.Adams, C.Álvarez, V.Arazi, L.Arnquist, I.J.Azevedo, C.D.R.Bailey, K.Ballester, F.Benlloch-Rodríguez, J.M.Borges, F.I.G.M.Byrnes, N.Cárcel, S.Carrión, J.V.Cebrián, S.Church, E.Conde, C.A.N.Contreras, T.Díaz, G.Díaz, J.Diesburg, M.Escada, J.Esteve, R.Felkai, R.Fernandes, A.F.M.Fernandes, L.M.P.Ferrario, P.Ferreira, A.L.Freitas, E.D.C.Goldschmidt, A.Gómez-Cadenas, J.J.González-Díaz, D.Gutiérrez, R.M.Hafidi, K.Hauptman, J.Henriques, C.A.O.Hernando Morata, J.A.Herrero, P.Herrero, V.Ifergan, Y.Jones, B.J.P.Kekic, M.Labarga, L.Laing, A.Lebrun, P.López-March, N.Losada, M.Mano, R.D.P.Martínez, A.Martínez-Vara, M.Martínez-Lema, G.McDonald, A.D.Monrabal, F.Monteiro, C.M.B.Mora, F.J.Muñoz Vidal, J.Novella, P.Nygren, D.R.Palmeiro, B.Para, A.Pérez, J.Querol, M.Redwine, A.Renner, J.Repond, J.Riordan, S.Ripoll, L.Rodríguez García, Y.Rodríguez, J.Rogers, L.Romeo, B.Romo-Luque, C.Santos, F.P.dos Santos, J.M.F.Simón, A.Sorel, M.Stiegler, T.Toledo, J.F.Torrent, J.Usón, A.Veloso, J.F.C.A.Webb, R.Weiss-Babai, R.White, J.T.Woodruff, K.Yahlali, N.The, NEXT, collaborationDependence of polytetrafluoroethylene reflectance on thickness at visible and ultraviolet wavelengths in airART-2020-121789Polytetrafluoroethylene (PTFE) is an excellent diffuse reflector widely used in light collection systems for particle physics experiments. However, the reflectance of PTFE is a function of its thickness. In this work, we investigate this dependence in air for light of wavelengths 260 nm and 450 nm using two complementary methods. We find that PTFE reflectance for thicknesses from 5 mm to 10 mm ranges from 92.5% to 94.5% at 450 nm, and from 90.0% to 92.0% at 260 nm. We also see that the reflectance of PTFE of a given thickness can vary by as much as 2.7% within the same piece of material. Finally, we show that placing a specular reflector behind the PTFE can recover the loss of reflectance in the visible without introducing a specular component in the reflectance.2020http://zaguan.unizar.es/record/9740410.1088/1748-0221/15/11/P11031http://zaguan.unizar.es/record/97404oai:zaguan.unizar.es:97404info:eu-repo/grantAgreement/EC/H2020/674896/EU/The Elusives Enterprise: Asymmetries of the Invisible Universe/ELUSIVESThis project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No H2020 674896-ELUSIVESinfo:eu-repo/grantAgreement/EC/H2020/690575/EU/InvisiblesPlus/InvisiblesPlusThis project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No H2020 690575-InvisiblesPlusinfo:eu-repo/grantAgreement/EC/H2020/740055/EU/Molecule for low diffusion TPCs for rare event searches/MELODICThis project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No H2020 740055-MELODICinfo:eu-repo/grantAgreement/ES/MINECO-MCIU/FIS2014-53371-C04info:eu-repo/grantAgreement/ES/MINECO-MCIU/RTI2018-095979info:eu-repo/grantAgreement/ES/MINECO/MDM-2016-0692info:eu-repo/grantAgreement/ES/MINECO/SEV-2014-0398Journal of Instrumentation 15, 11 (2020), [16 pp]All rights reservedhttp://www.europeana.eu/rights/rr-f/info:eu-repo/semantics/openAccess