• Monolithic Active Pixel Sensors (MAPS)
• TJ-Monopix2

This thesis presents the characterization of the TJ-Monopix2 chip, a small collection electrode DMAPS prototype in a modified TowerJazz Semiconductor imaging process.

The threshold distributions for all the different types of front-end circuits implemented in the matrix have been studied, together with their dispersion and noise distributions. We have characterized the Time Over Threshold (TOT) calibration function, which allows to translate the time information to the charge collected in the pixel, using the internal injection circuit. A first absolute calibration has been performed using a iron radioactive source.

We have studied the operation of the matrix at low threshold, that is necessary to maintain good efficiency after irradiation, when radiation damage causes a reduction in the collected charge. During this investigation, a cross-talk issue has been discovered and therefore studied to understand its causes and possible solutions to mitigate this effect.

The characterization of the TJ-Monopix2 chip has been relevant in the design of a new chip, OBELIX, which will be the final prototype chosen for the Belle II vertex detector upgrade (VTX).