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Reflectivity of Tyvek

In a previous study conducted by the University of California, Irvine, the directional reflectance of Tyvek material was measured. Their results indicate that the Tyvek reflects approximately 90% of incident visible light into the subtending hemisphere and this reflectance is virtually independent of the angle of incidence. However, these results are accurate for Tyvek exposed to air and do not necessarily apply to the conditions that Tyvek will be exposed to in KamLAND, in which the Tyvek is under water. Indeed, to the naked eye, it appears that the reflectance of Tyvek decreases when it is submerged in water.

A preliminary experiment was conducted at Duke University to measure the difference between air and water in reflectance of Tyvek. To do this, a Helium-Neon laser (wavelength of 632.8 nm) was shone on both dry Tyvek and Tyvek submerged in water. Small corrections involving plexiglass-air and plexglass-water interfaces still need to be made and a more in-depth study of the angular dependence of reflected light must be done. Nevertheless, an initial, and rather crude, measurement of normal light indicates that (20 +/- 10)% less light is reflected when the Tyvek is under water as opposed to in air. This would translate to a directional reflectance of (72 +/- 9)% for underwater Tyvek. As mentioned above, a more thourough and more precise investigation will follow.

Last updated: September 13, 1999