MALTA2 is a depleted monolithic active pixel sensor (DMAPS) designed for tracking at high rates and typically low detection threshold of ∼150e−. A precise knowledge of the threshold is crucial to understanding the charge collection in the pixel and specifying the environment for sensor application. A simple procedure is developed to calibrate the threshold to unit electrons making use of a dedicated charge injection circuit and an Fe-55 source with dominant charge deposition of 1600e−. The injection voltage is determined which corresponds to the injection under Fe-55 exposure and is the basis for charge calibration. The charge injection circuit incorporates a capacitance with design value of Cinj= 230 aF. Experimentally, the average capacitance value for non-irradiated samples is found to be Cinj,exp= 257 aF. The 12 % divergence motivates the need for the presented precise calibration procedure, which is proposed to be performed for each MALTA2 sensor.
@article{arxiv.2501.13562,
title = {Charge calibration of MALTA2, a radiation hard depleted monolithic active pixel sensor},
author = {Lucian Fasselt and Ignacio Asensi Tortajada and Prafulla Behera and Dumitru Vlad Berlea and Daniela Bortoletto and Craig Buttar and Valerio Dao and Ganapati Dash and Leyre Flores Sanz de Acedo and Martin Gazi and Laura Gonella and Vicente González and Sebastian Haberl and Tomohiro Inada and Pranati Jana and Long Li and Heinz Pernegger and Petra Riedler and Walter Snoeys and Carlos Solans Sánchez and Milou van Rijnbach and Marcos Vázquez Núñez and Anusree Vijay and Julian Weick and Steven Worm},
journal= {arXiv preprint arXiv:2501.13562},
year = {2025}
}