Comparison of the UV Reflectivity from
Tyvek
Carlos Hojvat
Fermilab
February 22, 1996
Abstract
Measurements of UV reflectivity were performed for 3 different types of Tyvek[reg.] commonly used for detector applications.
Introduction
Tyvek[reg.] has been used succesfully as a reflector for scintillator counters. It has been proposed as a liner for the interior of the water tank detectors in order to increase the light collected by the PMT's.
Samples of Tyvek[reg.] types 1025B (there some uncertainty about if this type was B or D), 1055B and 1073B were tested for diffuse reflectivity. Type 1025B has been used for SSD prototyping, by Fermilab E831 and E871 experiments. Type 1055B is the european common house wrap utilized by Michigan State University. Type 1073B has been used extensively by the Fermilab KTeV group.
Measurements were performed with a HP8451A Diode Array Spectrometer from the Particle Detector Group at Fermilab. Illumination was provided by a Mercury lamp with a 313 nm filter, the light being incident at approximately 45 degrees to the surface of the sample. This wave length is a standard for comparing the response of samples to the UV range, specially with scintillators. The diode detector array is located at 90 degrees with respect to the surface of the sample, several inches away. The illuminated area has a diameter of the order of 0.25".
Results
Each quoted measurement is an average of 5 measurements performed by the spectrometer, no standard deviation is available for the instrument's internal averaging. In addition, measurements were repeated at a minimum of 6 different spots on both sides of the samples. From these later measurements a mean value and a standard deviation are calculated. The number of measurements is indicated for each sample.
The diffused reflected response from the samples matches well the narrow spectrum transmitted by the 313 nm filter, essentially a single peak at that wave length. This peak was integrated between 300 and 600 nm. The results are shown in the following table and figure.
Reproducibility of the measurements has been measured before to be of the order of 0.9%. A sample of SCSN 81 scintillator was measured at the begining and end of the series of measurements for a further check on stability.
Material Measurements Integral 300 R.m.s. R.m.s. %
to 600 nm
SCSN 81 2 2946 104 3.5
1025 7 9303 599 6.4
1055B 6 10517 713 6.8
1073B 6 7060 538 7.6
Conclusions
The measurements do not indicate significant difference on the diffused reflectivity of Tyvek[reg.] types 1025 and 1055B. On the other hand type 1073B shows significant less reflectivity.
Acknowledgments
The assistance of Anna Pla-Dalmau of the Research Division Particle Detector group is gratefully acknowledge.