Investigation of a four layer DOI detector combined with laser processed boundaries

Depth of interaction detector is essential to achieve high spatial resolution and high sensitivity. Our group has developed an isotropic 3D detector, X'tal cube. For the crystal block, a laser processing was applied to a monolithic crystal to generate laser-processed boundaries (LPBs) inside the crystal block. The LPB is expected to give appropriate photon scattering effect as well as reduction of assembling steps compared with gluing small pieces of crystals. In this paper, we introduced the LPB to our former 4-layer DOI detector based on the reflector control, which projects 3D positions of interaction crystal to a 2D position histogram of the Anger-type calculation. The key point of proposed detector are that we set photo detectors at only one side and applied LPBs to crystals. To investigate features of four layer DOI detector combined with LPBs, we compared three conditions for the gaps between crystals in the 2 × 2 array: the air, the room temperature vulcanizing (RTV) rubber and the LPB. In the LPB case, actual crystal size was 4 mm × 4 mm × 5 mm, and the 2 × 2 segmentations were made by the laser processing. For these three patterns, we carried out both experiments and simulations. Almost all crystal responses were separated in the proposed detector with the LPB, although separation was not clearer than results with the other conditions because responses corresponded to the 2 × 2 crystal array had a tendency to get together. On the other hand, clusters can be discriminated clearer at detector edge.