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Description
The Multi-channel Integrated Zone-sampling Analogue-memory based Readout (MIZAR) ASIC was designed in a 65 nm CMOS technology as part of NASA’s POEMMA Balloon with RADIO (PBR) mission. The chip is implemented to acquire the optical Cherenkov signals generated by Extensive Air Showers (EASs) induced by Ultra-High Energy Cosmic Rays (UHECRs) or τ showers produced by the interaction of Cosmic Neutrinos (CNs) with the crust of the Earth. The 64-channel ASIC is connected to a Silicon Photomultiplier (SiPM) matrix, where a channel is composed of 256 cells, sampling the waveform at the nominal rate of 200 MS/s. Within each cell, an analogue memory is evaluated in parallel using a Wilkinson Analog-to-Digital Converter (ADC) and stored in a digital memory. MIZAR also provides a 64-bit hitmap as a dual threshold first-level trigger. An external control FPGA is used for evaluating the hitmap and the output data. The ASIC can be configured to work with an ADC resolution ranging from 8 to 12 bits, and each channel may be segmented into units of 32, 64, or 256 cells each. The first batch of ASICs was produced and delivered in March 2025. In this work, we present some results of an extensive testing campaign. Dark count measurements were performed with the setup at room temperature; the data analysis suggests that the entire acquisition chain is sensitive down to the single photoelectron level.