ETD

• Belle II
• Monolithic Active Pixel Sensors (MAPS)
• radiation damage
• TJ-Monopix2

This thesis presents the characterization of the TJ-Monopix2 chip after irradiation-induced bulk damage. TJ-Monopix2 is a small collection electrode DMAPS prototype implemented in a modified TowerJazz Semiconductor imaging process.

The tested sensors were irradiated to various fluences, up to 5x10^14 1-MeV-n_eq/cm^2.
The evolution of key parameters, such as threshold, noise and leakage current, was studied as a function of temperature and NIEL equivalent fluence for two of the four types of front-end circuit implemented in the matrix.
We also characterized a cross-talk effect of the clock counter that significantly affected the threshold and noise distributions of the sensors.

The results from a test beam campaign at DESY are also presented, where the detection efficiency of the irradiated sensors was measured at different thresholds and temperatures.

The characterization of the TJ-Monopix2 chip after radiation damage has been crucial in the design of a new chip, OBELIX, the final sensor chosen for the Belle II vertex detector upgrade (VTX), as well as in the design of the VTX detector itself.