[Problems to be Solved] A phoswich radiation detector, which can easily discriminate between detection signals on gamma rays and thermal neutrons, and which can selectively acquire signals on thermal neutrons, is provided.
[Means to Solve the Problems] In a phoswich radiation detector having two scintillators and discriminating between thermal neutrons and gamma rays, the detector comprises a scintillator for detecting thermal neutrons, such as LiCaAlF6:Eu, which has a light yield of more than 1500 photons/neutron, and a scintillator for detecting gamma rays, which has a permeable end on a shorter wavelength than the light emission wavelength of the thermal neutron scintillator. The scintillator for detecting gamma rays is characterized by being either an organic solid scintillator, such as a plastic scintillator, which does not contain a total amount of 10 mol % or more of elements selected from 6Li, 10B and Gd, or an inorganic single crystal scintillator, such as lithium glass (containing 6Li and Ce) or BGO, which has an effective atomic number Zeff of 30 or larger and which does not contain a total amount of 10 mol % or more of elements selected from 6Li, 10B and Gd.