The Wavelength Shifting Optical Module

Large-area low-noise photon sensors with single-photon detection capability play a vital role for many detectors in astroparticle physics, such as neutrino telescopes. In conventional photo-multipliers scintillation light from radioactive decays typically dominates over the thermionic noise, both of which increase with the size of the photosensitive area. Using wavelength-shifting and light-guiding technologies, the Wavelength-shifting Optical Module (WOM) vastly increases the photo-sensitive area while keeping the dark noise rate constant. In a geometry geared towards future extensions of the IceCube neutrino observatory, more than 40% of the light is captured on tubes of 9cm diameter and 90cm length, thus increasing the signal-to-noise ratio by at least an order of magnitude. We show results of the efficiency optimization and prototype evaluation and first steps towards a batch production of modules, as well as present ideas to further increase the SNR by another order of magnitude.