Radiation tolerance study of a digital monolithic pixel sensor for the EUDET-JRA1 project

In the framework of the EUDET-JRA1 project (European Detector R&D towards the International Linear Collider), which consists to design, realize and qualify a high resolution beam digital telescope, based on Monolithic Active Pixel Sensors (MAPS), an intermediate digital chip sensor, MIMOSA22, has already been delivered with good detection performances. Although this intermediate chip has fulfilled all the initial requirements of the project, it was admitted that radiation tolerance behavior of the sensor could be improved, especially if the high precision telescope is used later in a hadron testbeam infrastructure. For this purpose, a new version of the sensor, MIMOSA22-BIS, has been designed, with improvement of several pixel architectures, and using the same AMS 0.35 ¿m opto process of the sensor MIMOSA22. This paper will be focused on tests performed in laboratory, using a ⁵⁵Fe source, and tests performed in CERN-SPS, using a 120 GeV pion beam, in order to characterize detection performances of the chip with MIPs, before and after ionizing irradiation.