5 research outputs found
Photodegradation Mechanisms of Tetraphenyl Butadiene Coatings for Liquid Argon Detectors
We report on studies of degradation mechanisms of tetraphenyl butadiene (TPB)
coatings of the type used in neutrino and dark matter liquid argon experiments.
Using gas chromatography coupled to mass spectrometry we have detected the
ultraviolet-blocking impurity benzophenone (BP). We monitored the drop in
performance and increase of benzophenone concentration in TPB plates with
exposure to ultraviolet (UV) light, and demonstrate the correlation between
these two variables. Based on the presence and initially exponential increase
in the concentration of benzophenone observed, we propose that TPB degradation
is a free radical-mediated photooxidation reaction, which is subsequently
confirmed by displaying delayed degradation using a free radical inhibitor.
Finally we show that the performance of wavelength-shifting coatings of the
type envisioned for the LBNE experiment can be improved by 10-20%, with
significantly delayed UV degradation, by using a 20% admixture of
4-tert-Butylcatechol.Comment: 12 pages, 9 figures. Submitted to JINS