Proof of principle of G-APD based hybrid photodetectors

We performed a proof of principle experiment which demonstrates the suitability of pixelized Geiger mode avalanche photodiodes (G-APD) for the detection of photoelectrons at energies in the 10 keV range. A pumped UHV set-up with CsI photocathode, illuminated by a UV flash lamp, is used to generate photoelectrons of defined energy. The results indicate that G-APDs can be considered as anodes in hybrid photodetectors with the potential of improved performance when compared to conventional photomultiplier tubes. The concept of a G-APD based HPD has advantages but also clear drawbacks. We discuss the particular case of the X-HPD where a G-APD based anode could lead to improved detection efficiency and timing as well as to a more cost-effective production process.