A Novel wavelength shifter foil for IceCube

The IceCube optical modules are composed of a photomultiplier tube encapsulated in a glass sphere. The encapsulating spectrum below this cut-off does not contribute to the signal production even if the medium in which these photons are generated is transparent down to 250 mm at least. This the collection efficiency ist not yet as high as desirable. We investigated the use of a wavelength shifter layer placed outside the lower hemisphere of the optical modules. The development of a novel wavelength shifter (WLS) has been motivated by the limitations of commercial available materials. In this paper, we report measurements of the improvement in light collection efficiency obtained with a wavelength shifter working in air and in water