Reconstruction of electron trajectories in high-resolution Si devices for advanced Compton imaging

Abstract

Compton imaging has been demonstrated to provide excellent detection and localization capabilities in the search and characterization of radiation sources. However, the currently achievable sensitivity is limited by the Compton cone, which is backprojected. By measuring the initial trajectory of the Compton electron, the cone may be reduced to a cone segment with a corresponding increase in sensitivity. We have demonstrated the ability to measure electron trajectories (tracks) in thick ( 650 μ m ), fully depleted silicon scientific CCDs, with a spatial resolution of 10 μ m in 2D. These measured tracks have been used to benchmark simulations of electron physics and detector response. We have developed an electron track algorithm to measure the initial electron direction in 3D from the CCD image, and utilized the modeled electron tracks to evaluate the angular resolution as a function of energy and initial direction for electrons up to ∼ 500 keV . For electrons above 150 keV and 30° out-of-plane, we have achieved an in-plane angular uncertainty of σ α ≲ 40 ∘ , and an out-of-plane uncertainty of σ β ≲ 30 ∘ in each hemisphere.