CeF₃ scintillation crystals shows a large contribution of a fast component and it would become the material of choice for high energy and nuclear physics and also for medical applications (PET).

During the last decade, CeF₃ crystals were regarded as one type of the most promising scintillators for the next generation experiments in high energy physics because of their high density, fast response and high radiation resis-tance. These scintillators are relatively new; in fact, their good characteristics were discovered for small (few cm3) samples in 1989. During the following years, the properties of CeF₃ crystals were intensively investigated, in particular, by the Crystal Clear Collaboration (see Ref. and references therein). The main characteristics are: (i) density equal to 6:16g/cm3; (ii) light yield 45% of that of NaI(Tl); (iii) refractive index equal to 1.62 at 400 nm; (iv) emission peaks at 286, 300 and 340 nm: Moreover, several decay components have been recognized: the most important ones have decay time equal to 5 and 30 ns; respectively. The material is non-hygro-scopic; the melting point is at 1443℃; the light yield has only a small dependence on temperature (0.05%/℃); the thermal-neutron cross-section is equal to 0.65 barn; near 2 orders of magnitude lower than that of CsI.