Experimental Characterization of the ORION ASIC: The Read-Out Circuit for X-gamma-Ray Detection of the THESEUS Mission Spectrometer

This work is focused on the design summary and experimental characterization of the ORION ASIC, a multi-die integrated circuit for X and gamma ray detection designed for the THESEUS mission related imaging and XGIS instrument. An overview of the complete electronic read-out acquisition channel including its design peculiarities is thus given. ORION front-end system is made up by a very low noise analog front-end pre-amplifier circuit on a dedicated die and a full custom, versatile, mixed signal back-end chip on a second die. The back-end includes the rest of the analog chain, 3 dedicated hysteresis-less ADCs and a suitable logic for event type extraction and time-stamp assignment. In the experimental results the correct extraction of different event types (X, gamma) has been verified to be processed correctly by the system, as well as time-stamp assignment. Also the analog chain and A/D conversion target required linearity in the dynamic range of interest have been met. Configuration of the ASIC can be performed by loading a serial register, while output data is delivered in parallel form for fast read-out in the single channel version. An additional custom SPI I/O is available in the imminent multi-channel version.