Development of HPDs with an 18-mm-diameter GaAsP photocathode for the MAGIC-II

A new type of Hybrid PhotoDetectors (HPDs) with an 18-mm-diameter GaAsP photocathode was developed in order to lower the energy threshold of the MAGIC-II project. The peak value of the Quantum Efficiency (QE) reaches 51% at around 500 nm. Application of the wavelength shifting technique can further enhance the sensitivity in the UV region. Compared to the currently used classical PhotoMultiplier Tubes (PMTs) with bialkali photocathodes, the new HPDs provide practically twice as high photon conversion efficiency. Simulation studies of the new HPDs indicate that they have a sufficiently long lifetime for being used in the MAGIC telescope imaging camera. In this report we present the evaluation results and the performance of these new photodetectors.