New Developments in Hybrid Photon Detectors
  New developments in HPD design are presented, triggered by applications in high energy physics and astrophysics. The presented HPD designs are based on three innovations. (i) In order to achieve the highest possible surface coverage in a RICH detector, we introduced a photoelectron focussing method which is efficient to the periphery of the photocathode. (ii) To prevent positive ion feedback in HPDs, we introduced a permanent potential barrier in front of the anode. (iii) To replace a transmittive by a reflective photocathode, we arrived at a conceptually new HPD design with surprisingly good imaging characteristics, high quantum efficiency and low cost. 
Daniel Ferenc