Charge collection properties of X-ray irradiated monolithic active pixel sensors

CMOS monolithic active pixel sensors (MAPS) constitute a novel technique for position sensitive charged particle detectors. Their development is driven by the requirements of vertex detectors for future high-energy and nuclear physics experiments as well as by those of biomedical applications, namely highly granular dosimetry. The radiation hardness of MAPS-detectors is subject to intensive studies. Their resistance against up to ∼1012 neq/cm2 was demonstrated [M. Deveaux, G. Claus, G. Deptuch,W. Dulinski, Y. Gornushkin, M. Winter, Nucl. Instr. and Meth. A 512 (2003) 71-76]. On the other hand, only poor data are available so far about their resistance against ionising doses. This paper summarises the results of radiation hardness studies on two different MAPS-detectors up to a dose of 1 MRad.