Radiation Hardness Studies of Monolithic Active Pixel Sensors ...

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Abstract
CMOS Monolithic Active Pixel Sensors (MAPS) demonstrated excellent performances in tracking
detectors for charged particles. They provide an outstanding spatial resolution (few µm) and
detection efficiency (> 99,9%) in combination with very low material budget (0,05% X0 per
sensor) and good radiation tolerance (> 1 MRad, > 3 · 1013 neq
cm2 ). MAPS are the technology of
choice for micro vertex detectors for the heavy ion experiments STAR and CBM and a potential
candidate for a micro vertex detector at the ILC. Due to the luminosities needed to address the
physic questions, radiation tolerance is in the focus of the sensor optimization. To approach the
requirements of these experiments regarding radiation tolerance, the radiation tolerance of the
sensors is being evaluated and improved within a joined R&D project carried out by the IPHC
Strasbourg and IKF Frankfurt. The master thesis is part of this project.
The master thesis focuses on the radiation damage in the sensors which could be reduced by
thermal annealing. This was suggested by previous studies which were however restricted to
ionizing radiation damage only. The results were reproduced and complemented by a first
systematic study of the annealing effects of neutron irradiated MAPS. The feasibility of annealing
ionizing radiation damage in the presence of non-ionizing radiation damage will be
demonstrated.
The results of the studies will be presented and the option to recover a strongly irradiated, MAPS
based vertex detector by means of thermal treatment will be discussed.