Towards a direction-sensitive optical module for neutrino telescopes based on a hybrid photon detector

The optical modules of all currently operating neutrino telescopes contain one standard PMT with a large hemispherical photo-cathode. The maximum spatial resolution of this detection principle is thus limited to the photo-cathode area and no information is obtained on the direction of the incoming photons. We propose a new direction-sensitive design featuring a fisheye lens and a hybrid photon detector. The lens system maps incoming photons from one direction on a well-defined point on the photo-cathode of the hybrid photon detector. The photo-electrons are accelerated in a cross-focussed optics and detected using a pixelated anode, which allows for very high spatial resolution. As a candidate chip for the photo-electron detection we propose the Timepix detector of the Medipix family. We have successfully shown its capability to detect photo-electrons in the experiment and evaluated the time resolution by simulation and measurement.