Reflectivity Spectra for Commonly Used Reflectors

Abstract

Abstract-Monte Carlo simulations play an important role in developing and evaluating the performance of radiation detection systems. To accurately model a reflector in an optical Monte Carlo simulation, the reflector's spectral response has to be known. We have measured the reflection coefficient for many commonly used reflectors for wavelengths from 250 nm to 800 nm. The reflectors were also screened for fluorescence and angular distribution changes with wavelength. The reflectors examined in this work include several polytetrafluoroethylene (PTFE) reflectors, Spectralon, GORE diffuse reflector, titanium dioxide paint, magnesium oxide, nitrocellulose filter paper, Tyvek paper, Lumirror, Melinex, ESR films, and aluminum foil. All PTFE films exhibited decreasing reflectivity with longer wavelengths due to transmission. To achieve reflectivity in the 380 to 500 nm range, the PTFE films have to be at least 0.5 mm thick-nitrocellulose is a good alternative if a thin diffuse reflector is needed. Several of the reflectors have sharp declines in reflectivity below a cut-off wavelength, including (420 nm), ESR film (395 nm), nitrocellulose (330 nm), Lumirror (325 nm), and Melinex (325 nm). PTFE-like reflectors were the only examined reflectors that had reflectivity above 0.90 for wavelengths below 300 nm. Lumirror, Melinex, and ESR film exhibited fluorescence. Lumirror and Melinex are excited by wavelengths between 320 and 420 nm and have their emission peaks located at 440 nm, while ESR film is excited by wavelengths below 400 nm and the emission peak is located at 430 nm. Lumirror and Melinex also exhibited changing angular distributions with wavelength.

Results from the first use of low radioactivity argon in a dark matter search

“…After some experimentation [22,23], Lumirror 188 E6SR was chosen. Lumirror is a highly reflective voidbased reflector between two protective layers [24,25]. These protective layers allow the reflector to be submerged in scintillator without significant loss of reflectivity [22].…”

“…It is built from carbon steel and internally protected from corrosion by a layer of Permatex resin. In order to improve the light collection efficiency, the interior surface of the WCV and the exterior of the LSV sphere are covered with a layer of Tyvek [24,41].…”

Study of scintillation counter consisting of a pure CsI crystal and APD

“…In the further studies we used OKEN-6262A. It was already demonstrated that the Gore-Tex teflon has the largest reflectivity among the well-known soft reflectors even in the ultraviolet (UV) range [8]. We measured signals from the counters with the teflon of different thicknesses.…”

Solar gamma-ray spectrometer GRIS onboard the International Space Station

“…This prototype has an excellent resolution (FWHM 5.9% @ 662 keV) for a big CsI(Tl) crystal based detectors. This is a result of ESR film reflector usage (Janecek, 2012).…”