Development of an innovative hybrid single-photon imaging detector based on a Timepix4 CMOS ASIC embedded as pixelated anode

An innovative single-photon detector is presented, based on a vacuum tube containing a photocathode, a microchannel plate, and a Timepix4 CMOS application-specific integrated circuit (ASIC) as its readout anode. This detector has been developed to detect up to 1 billion photons per second over a 7 cm2 active area, while achieving exceptional position resolution of 5 − 10 µm and timing resolution below 50 ps. The Timepix4 ASIC, which features approximately 230 thousand pixels equipped with both analog and digital front-end electronics, operates on a data-driven architecture, and it allows data transmission with bandwidth reaching up to 160 Gb/s.The configuration and readout of the Timepix4 are controlled by FPGA-based external electronics, either the SPIDR4 DAQ system or the custom DAQ system developed by INFN Ferrara. The DAQ system, the DAQ software and the analysis software developed are presented.
A characterization of a Timepix4 v2 assembly bonded to a 100 µm thick planar n-on-p Si detector has been performed. The presented characterization includes charge calibration and charge resolution estimation, as well as estimation of the timing performance. A picosecond laser setup has been used to illuminate the sensor and generate electron-hole pairs in the silicon bulk, controlling the amount of charge, and the time and position of the generated signal. The timing resolution per single pixel hit was measured at 107 ps, taking into account the silicon’s contribution as well. When considering pixel clusters, the timing resolution improves to below 50 ps.
The ceramic carrier quality tests will be presented too, consisting of mechanical and electrical measurements, as well as a diagnostic of the basic operation of the Timepix4 ASIC mounted on the ceramic.
Furthermore, the characterization procedure of the first prototypes of the phototubes will be discussed. It includes dark count rate and gain measurements, as well as timing resolution estimation.
Currently, a single prototype has been tested; the characterization and comparison of the other prototypes is ongoing.
Regarding the prototype tested, the expected dark count rate and gain trends have been obtained. The dark count rate results to be in the range between ∼ 1 Hz/cm2 and ∼ 30 Hz/cm2 , depending on the MCP bias. The gain ranges from O(10^3) to O(10^5), depending on the MCP bias. 
A non-uniform dark count structure has been observed across the matrix, and further studies are ongoing to better understand its source.
The timing resolution has been estimated with a method analogous to the one used to estimate the one of the assembly bonded to a Si detector. The single pixel timing resolution obtained is (107 ± 6) ps, while the cluster timing resolution reaches (88 ± 5) ps.
Eventually, a testbeam organized to characterize the developed phototubes with a Cherenkov setup is described.