[Problems to be Solved] A radiation detector, which is improved in the detection efficiency of a photodetector for light emitted by a scintillator, which has excellent long-term operational stability, and which is excellent in time resolution and count rate characteristics, is provided with the use of the scintillator with a short fluorescence lifetime.
[Means to Solve the Problems] A radiation detector is constructed by installing an optical wavelength conversion layer, which is composed of, for example, an organic fluorescent substance using polyvinyl toluene as a base material, between a scintillator composed of a fluoride single crystal, such as a Ce-containing LiCaAlF 6 crystal, and a photodetector having a light entrance window material composed of a transparent glass material such as borosilicate glass. In the radiation detector, the peak wavelength of light emitted by the scintillator is 360 nm or less, and the peak wavelength of light after conversion by the optical conversion layer is 400 nm or more. Preferably, the refractive indexes of the scintillator and the optical wavelength conversion layer are both 1.35 to 1.65.