Continuous or pixelated scintillators?, not longer a discussion

Gamma ray detectors merging continuous and pixelated crystal arrays are described. We show a pilot study about the detector performance of an innovative scintillation design that simultaneously uses both a continuous and a crystal array. This novel idea is the base of a high-resolution and high-sensitivity gamma ray detector. Alternatively monolithic or crystal arrays can be mounted on the front or in between this and the photosensor to improve spatial or photon depth of interaction resolution, without sensitivity detriment. We have successfully tested a total scintillation thickness of ~20 mm. A new photosensor and readout electronics were developed for this purpose. We built a large array of 12X12 SiPMs (SensL) and also 16X16 MPPCs (Hamamatsu). Two readout electronics have been used, one based on 3 scalable ASICs for the array of 144 SiPMs and one based on a diode circuit that provides signals for each row and column (16+16). A center of gravity algorithm is used in this pilot experiment. We have already tested several configurations (1.5X1.5 mm² and 2X2 mm²) with crystal arrays in the front, followed by a monolithic painted black scintillator of 12 mm thickness (50X50 mm² base). An energy resolution as good as 13% was found for single pixels.