New generation of coded aperture collimators for imaging ionizing radiations

Remote visualization of X-rays and gamma rays is essential for nuclear safety and high-energy astrophysics, enabling the safe decommissioning of nuclear facilities and the detection of transient cosmological events. Indirect imaging techniques primarily rely on Compton imaging for a wide field of view and coded aperture-mask imaging for high angular resolution. My thesis advances coded aperture imaging by introducing new coded masks with 3D geometry, which expand the field of view beyond 90° while maintaining fine angular resolution within a few degrees for photon energies below 59.5 keV. We developed two prototypes: a hemispherical Tantalum mask with an Archimedean spiral pattern, achieving a 153° field of view and 2° angular resolution, and a Tungsten mask with an improved coded pattern and enhanced operational characteristics, expanding the field of view to 160°. We capture ionizing radiation using advanced Cadmium Telluride sensors: Timepix3, featuring ultra-high pixel resolution, and Caliste-HD, which provides cutting-edge spectroscopic capabilities. We also developed the “3D Projector Code” toolkit, allowing real-time system response simulation under the zero-energy approximation, facilitating rapid prototyping of 3D masks. Simulation evaluations, validated by experimental results, confirm the wide-field imaging capabilities of the new imaging systems. Future work will focus on enhancing mask designs and optimizing image reconstruction.