A digital autoradiography system based on the Medipix2 chip: images of 3H and 14C microscales

In the framework of the MAMA project, funded by INFN, we have assembled a digital imaging system for beta and gamma autoradiography based on the Medipix2 single photon counting read-out chip bump-bonded to a 300 μm thick silicon pixel detector. This system has 256×256 square pixels of 55 μm pitch for a total sensitive area of 14×14 mm2. Each pixel contains two discriminators and a 13-bit counter. The detection threshold is about 6 keV and a noise is about 10−3 cps/mm2. Real time images have been obtained of 3H and 14C autoradiographic scales. The minimum detectable activity is 0.32 Bq in 14 h for 3H and 0.012 Bq in 10 h for 14C.