Neutron radiation hardness of monolithic active pixel sensors for charged particle tracking

Monolithic Active Pixel Sensors (MAPS) for charged particle tracking consist of a novel detection technique, where the detecting element is inseparable from the readout electronics, both of them being integrated on the same substrate. As radiation hardness is mandatory for most applications, the resistance of a MAPS-detector design against irradiation is currently subject to intensive studies. Parameters such as charge-to-voltage conversion gain, pixel leakage current, noise and charge collection efficiency are investigated as a function of integrated dose. First- and second-generation prototypes, MIMOSA1 and MIMOSA2, were irradiated with up to 1013 neq/cm2 for this purpose. Preliminary results are presented. The charge-to-voltage conversion gain and noise were found to be almost stable and the leakage current was observed to raise moderately. On the other hand, the pixel charge collected came out to be substantially affected by the highest fluences considered.