Voronov O. Physical and technological principles of creation of radiation-sensitive materials based on activated crystals of KDP group

The thesis is devoted to development of physical and technological principles for creation of promising radiation-sensitive materials on the base of activated crystals of KDP group, elaboration of the technology for the growth of crystals doped with isomorphic and non-isomorphic activators, aimed at the obtaining of scintillation materials which possess high intrinsic selectivity with respect to neutrons and discrimination of gamma-radiation. There are revealed regularities in the influence of thallium ions, molecules of organic phosphors and organometallic rare-earth complexes, as well as ammonium salicylate and thallium salicylate complexes, on the processes of the growth (the growth kinetics) of KDP and ADP crystals. Luminescence of thallium-doped KDP group crystals excited by UV photons or X-rays is caused by the radiative electron transitions 3Р1 →1S0 in Tl+ ions with characteristic emission and absorption spectra at 275 nm (4.5 eV) and 220 nm (5.76 eV), respectively. The nature of luminescence in KDP crystals doped with Се3+ (max= 350 nm) is caused by the radiative electron interconfiguration transitions 5d → 4f in cerium ions. Found are regularities in manifestation of scintillation properties in thallium- or cerium-doped KDP crystals under the action of ?-, ?-, ?-radiation and fast neutrons (0.1 -10) MeV. In the latter case scintillations are caused by secondary ionizing radiation (recoil protons and recoil oxygen nuclei). They are bound up with the recombination mechanism of the emergence of scintillations with participation of radiation L- and D-defects of the hydrogen sublattice, which transfer electronic excitations from the crystal volume to the Tl+ or Ce3+ luminescence center. The efficiency of fast neutron detection is on a par with the one of organic scintillators and amount to 12-16%. Crystals KDP: (Tl, Ce) have internal discrimination of n/γ signals up to 102. Key words: KDP crystals, fast neutrons detection, recoil protons, monocrystal scintillators, registration efficiency, neutron/gamma discrimination.