Demonstrating the γ-transparencyγ-transparency of a CMOS pixel detector for a future neutron dosimeter

The RaMsEs group (Radioprotection et Mesures Environnementales) is working on a new compact device for operational neutron dosimetry. The electronic part of the detector is made of an integrated active pixel sensor, originally designed for tracking in particle physics. This device has useful features, including a high detection efficiency for charged particles, a good radiation resistance, a high readout speed and a low power consumption. Moreover, because of the thinness of the active layer, these CMOS sensors have low sensitivity to γ-raysγ-rays, which is an attractive feature for neutron issues. In order to determine the γγ response of the sensor, measurements have been carried out with a γγ source of 60Co (1.17 MeV and 1.33 MeV). Other experiments have been performed with a fast neutron source of AmBe. We demonstrate the good discrimination between recoil protons from fast neutrons and from γ-backgroundγ-background. Our results show that with an appropriate threshold, most γ-raysγ-rays that generate photoelectrons can be removed from detection.