Neutron detector comprising an optical fission chamber with a reflective optical cavity and a detection head coupled to the chamber comprising an optical lens and a fibre-optic coupler

A neutron detector comprising:

• at least one seal-tight ionization chamber in which optical transduction occurs, which chamber is called an OFC, acronym of optical fission chamber, each chamber extending along a longitudinal axis (X) and comprising:
• a seal-tight hollow body bounding internally an optical cavity and comprising at least one inner wall coated at least partially with at least one layer of fissile material, the optical cavity being filled with a gas and which is capable of being ionized by an ion resulting from a reaction between a neutron and the fissile material,
• a window, arranged at one of the longitudinal ends of the hollow body and configured to seal the optical cavity,
• an optical lens, fastened by bonding to or integrally formed with the window, the optical lens being configured to focus photons received by the window,
• a mirror, arranged at the other of the longitudinal ends of the hollow body, which end is opposite the longitudinal end where the window is arranged, the mirror being configured to reflect photons towards the window,
• a detection head comprising a fibre-optic coupler comprising a plurality of optical fibres by way of inputs, said optical fibres being arranged in the focal plane of the lens, and one optical fibre by way of output, in which optical fibre the optical signals received by the inputs are summed.