engleski

MALTA: an asynchronous readout CMOS monolithic pixel detector for the ATLAS High-Luminosity upgrade

The ATLAS collaboration is currently investigating CMOS monolithic pixel sensors for the outermost layer of the upgrade of its Inner Tracker (ITk). For this application, two large scale prototypes featuring small collection electrode have been produced in a radiation-hard process modification of a standard 0.18 μm CMOS imaging technology: the MALTA, with a novel asynchronous readout, and the TJ MONOPIX, based on the well established "column-drain" architecture. The MALTA chip is the first full scale prototype suitable for the development of a monolithic module for the ITk. It features a fast and low power front-end, an architecture designed to cope with an hit-rate up to 2 MHz/mm2 without clock distribution over the matrix, hence reducing total power consumption, and LVDS drivers. Laboratory tests confirmed the performance of the asynchronous architecture expected from simulations. Extensive test beam measurement have proved an average detection efficiency of 96% before irradiation at a threshold of ∼ 250e− with dispersion of ∼ 30e− and ENC lower than 10e−. A non fully functional masking scheme, forces operation at relatively high thresholds, causing inefficiency. A severe degradation of efficiency has been measured after neutron irradiation at a fluence 1e15 1 MeV neq/cm2. Consistent results have been produced with the TJ MONOPIX. A correlation with inefficiency plots and pixel layout has triggered TCAD simulations, ending up to two possible solutions, implemented in a new prototype, the miniMALTA.

particle tracking detectors ; radiation-hard detectors ; electronic detector readout concepts ; front-end electronics for detector readout

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