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Title: Development of VUV-Reflective PTFE Coatings

Abstract

GVD Corporation has evaluated its vacuum deposited PTFE coatings as reflecting surfaces to improve the sensitivity of vacuum UV light detection (at 178 nm) in neutrinoless double beta decay experiments at nEXO. By replacing Teflon sheet reflectors with GVD thin films, it is possible to reduce the radiobackground and outgassing issues, which significantly impact measurement signal-to-noise ratios, associated with the PTFE without sacrificing collection efficiency. Three PTFE coating types with different morphologies were tested for their suitability in this application. It was demonstrated that the PTFE coatings surpassed the nEXO target for thorium-232 concentration by 8-fold. Meanwhile, the unoptimized concentration of uranium-238 was already lower than that of Teflon sheets and was within a factor of 4 of meeting the nEXO target. Remaining uranium content was attributed to incorporation of uranium impurities from the filament and can be eliminated by using an alternative filament source. Reflectivity measurements at 193 nm and 220 nm, combined with transmission and refractive index data, showed that the GVD coatings had reflectivity close to that of bulk Teflon. Extrapolation indicates that the reflectivity at 178 nm may already compare favorably with bulk Teflon, and we estimate that the coatings tested would have 75% reflectivity inmore » liquid xenon, compared with 98% of bulk Teflon and 88% for, for VUV-enhanced aluminum (an alternative thin film reflector). This data combined with the broad control over morphology afforded by GVD’s iCVD process will allow for further optimization to reach parity with bulk Teflon in reflectivity.« less

Authors:
 [1]
  1. GVD Corporation
Publication Date:
Research Org.:
GVD Corporation
Sponsoring Org.:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Contributing Org.:
Pacific Northwest National Laboratory
OSTI Identifier:
1491399
Report Number(s):
DOE-GVD-SC0018524
DOE Contract Number:  
SC0018524
Type / Phase:
SBIR (Phase I)
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 36 MATERIALS SCIENCE; neutrino; beta decay; particle physics; nEXO; PTFE, Teflon; ultraviolet; UV; VUV; coating; chemical vapor deposition

Citation Formats

O'Shaughnessy, William Shannan. Development of VUV-Reflective PTFE Coatings. United States: N. p., 2019. Web.
O'Shaughnessy, William Shannan. Development of VUV-Reflective PTFE Coatings. United States.
O'Shaughnessy, William Shannan. Mon . "Development of VUV-Reflective PTFE Coatings". United States.
@article{osti_1491399,
title = {Development of VUV-Reflective PTFE Coatings},
author = {O'Shaughnessy, William Shannan},
abstractNote = {GVD Corporation has evaluated its vacuum deposited PTFE coatings as reflecting surfaces to improve the sensitivity of vacuum UV light detection (at 178 nm) in neutrinoless double beta decay experiments at nEXO. By replacing Teflon sheet reflectors with GVD thin films, it is possible to reduce the radiobackground and outgassing issues, which significantly impact measurement signal-to-noise ratios, associated with the PTFE without sacrificing collection efficiency. Three PTFE coating types with different morphologies were tested for their suitability in this application. It was demonstrated that the PTFE coatings surpassed the nEXO target for thorium-232 concentration by 8-fold. Meanwhile, the unoptimized concentration of uranium-238 was already lower than that of Teflon sheets and was within a factor of 4 of meeting the nEXO target. Remaining uranium content was attributed to incorporation of uranium impurities from the filament and can be eliminated by using an alternative filament source. Reflectivity measurements at 193 nm and 220 nm, combined with transmission and refractive index data, showed that the GVD coatings had reflectivity close to that of bulk Teflon. Extrapolation indicates that the reflectivity at 178 nm may already compare favorably with bulk Teflon, and we estimate that the coatings tested would have 75% reflectivity in liquid xenon, compared with 98% of bulk Teflon and 88% for, for VUV-enhanced aluminum (an alternative thin film reflector). This data combined with the broad control over morphology afforded by GVD’s iCVD process will allow for further optimization to reach parity with bulk Teflon in reflectivity.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2019},
month = {1}
}

Technical Report:
This technical report may be released as soon as January 21, 2023
Other availability
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