A radiation scintillator detector comprising a substrate on which are arranged a scintillator module and a silicon photomultiplier optically coupled one to the other. The detector includes a package comprising an outer casing enclosing said scintillator module and said photomultiplier, said package comprising inside said outer casing an inner casing comprising resin reflecting photons, in particular infrared and/or visible photons, emitted by said scintillator module upon receiving a ionizing radiation, enclosing said scintillator module and said photomultiplier.