QE/PDE of VUV Photodetectors for BaF 2 Readout

Because of its ultrafast scintillation of less than 0.6 ns decay time barium fluoride (BaF 2 ) crystals have attracted a broad interest in the communities pursuing ultrafast detectors for future HEP experiments, GHz hard X-ray imaging for future XFEL facilities and medical imaging. A crucial issue of this application is photodetector response down to the VUV range. In this paper, we report quantum efficiency and photon detection efficiency measured for several photodetectors down to 200 nm and their corresponding figures of merit for detecting the ultrafast component and the ability of suppressing the slow component.