Characterization of the Hamamatsu S8664 avalanche photodiode for X-ray and VUV-light detection

We present the first operation of the VUV-sensitive avalanche photodiode (APD) from Hamamatsu to xenon scintillation light and to direct X-rays of 22.1 keV and 5.9 keV. A large non-linear response was observed for the direct X-ray detection. At 415 V APD bias voltage it was of about 30% for 22.1 keV and about 45% for 5.9 keV. The quantum efficiency for 172 nm photons has been measured to be 69±15%.