CdTe hybrid pixel detector for imaging with thermal neutrons

We present tests of a thermal neutron imaging system based on a high-resolution hybrid pixel device Medipix2. The system consists of the Medipix2 readout chip bump bonded to a 1 mm thick CdTe detector (featuring 256×256 square pixels with 55 μm pitch). The CdTe detector is used as direct counter of thermal neutrons. Neutrons interact with cadmium nuclei by means of the 113Cd(n,γ)114Cd reaction producing 558 keV gamma rays and internal conversion electrons. The spatial resolution of the imager measured by projection of an opaque edge made of cadmium was 450 μm. This value appears in good agreement with Monte–Carlo simulations we made. Neutron radiograms of two test samples are given.