Development of an MCP-based Photon Counting Unit for UV Spectroscopy

Spectroscopic observations in the vacuum and extreme ultraviolet (FUV/EUV) spectral region are of great interest in various scientific fields, such as Solar Physics, the physics of interstellar medium, and planetary exospheres studies. The PLanetary Ultraviolet Spectrometer (PLUS) project aims at developing a novel dual-channel FUV/EUV imaging spectrometer working in 55-200 nm spectral range. Within this context, the MIRA (Microchannel Readout Asic) ASIC has been designed to feature an integrated 2D anode array and photon counting capability. In this framework, the PLUS photon counting unit has been developed where the photon counting detector, i.e., an MCP detector coupled to the MIRA ASIC, has a key role in achieving high count rate capability (100 kcps/pixel), longer detector lifetime and high spatial resolution. The adoption of MIRA ASIC, with an ENC = 20 e−rms, allows operations with lower MCP gain increasing, thus, the MCP lifetime, crucial for long missions in space. In this work, we present the first prototype of the PLUS photon counting unit. Then, we report experimental results of the MIRA Charge Sharing Correction Logic (CSCL) that grants a spatial resolution limited to the MIRA pixel size (35 µm), even in case of charge sharing among pixels.