Münster 2017 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 6: Instrumentation I

HK 6.7: Talk

Monday, March 27, 2017, 18:15–18:30, F 072

Radiation Damage Caused by Neutron Capture in Boron Doped Silicon Pixel Sensors — •Benjamin Linnik, Tobias Bus, Michael Deveaux, Dennis Doering, and Ali Yazgili for the CBM-MVD collaboration — Goethe-Universität Frankfurt

CMOS Monolithic Active Pixel Sensors (MAPS) are considered as an emerging technology in the field of charged particle tracking. They will be used in the vertex detectors of experiments like STAR, CBM and ALICE and are considered for the ILC and the tracker of ATLAS. In those applications, the sensors are exposed to sizeable radiation doses.
While the tolerance of MAPS to ionizing radiation and fast hadrons is well known, the damage caused by thermal neutrons was so far not studied in detail. Those neutrons initiate nuclear fission of ¹⁰B dopants found in the P-doped silicon forming the active medium of MAPS. This effect can be expected to increase radiation damage beyond the predictions of the NIEL (Non Ionizing Energy Loss) model for pure silicon.
We estimate this effect by calculating the additional NIEL created by the fission fragments. Moreover, we show first measured data for CMOS sensors, which were irradiated with cold (1.8 meV) neutrons. The empirical results contradict the prediction of the updated NIEL model both, qualitatively and quantitatively: The sensors irradiated with slow neutrons show an unexpected and strong acceptor removal, which is not observed in sensors irradiated with 1 MeV neutrons.

*This work has been supported by BMBF (05P15RFFC1), GSI and HIC for FAIR.