CAMIS: A Cylindrical Active Mask Imaging System

Detecting and locating radiological and nuclear materials at distances of 10 meters or more in urban and cluttered environments continues to pose challenges in nuclear security and proliferation detection. Previous approaches have focused on large-area radiation imaging using planar configurations of detectors and passive masks. However, these approaches suffer from limitations such as limited field-of-view (FOV) and reduced detection efficiency due to absorption in the mask. To address these limitations, we have developed the Cylindrical Active Mask Imaging System (CAMIS). This system comprises 128 NaI(Tl) (10cm)<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> detectors. These detectors are arranged in a cylindrical configuration, enabling gamma-ray imaging with a full 360-degree azimuthal FOV. The active mask elements within the system are arranged in a pseudo-random configuration, providing unique encoding for all incident directions within the FOV. CAMIS offers an effective detection area of approximately 1 square meter across the entire 360° FOV in the horizontal plane, achieving a mean angular resolution of 10:9° in the azimuthal direction and 12:9° in the polar direction measured by taking the FWHM of a cross-section at the maximum reconstructed intensity.