1995 Fiscal Year Final Research Report Summary
Development and Ability Enhancement of Super-High Energy Sinchillator Materials
| Project/Area Number |
06452317
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Inorganic materials/Physical properties
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| Research Institution | The University of Electro-Communications |
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Principal Investigator |
NAKATA Ryouhei Univ.Electro-Commun.Electronic Engineering, Professor, 電気通信学部, 教授 (10017353)
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| Co-Investigator(Kenkyū-buntansha) |
TANAKA Katsumi Univ.Electro-Commun.Electronic Engineering, Assoc.Prof., 電気通信学部, 助教授 (30155121)
KAWANO Katsuyasu Univ.Electro-Commun.Electronic Engineering, Assoc.Prof., 電気通信学部, 助教授 (90017418)
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| Project Period (FY) |
1994 – 1995
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| Keywords | Super-High Energy / Scintillator / Crystal Growth / Lattice Defects |
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| Research Abstract |
Luminescence spectra by X-ray excitation have been investigated on the Eu^<2+> ion doped into the fluorite-type Ca_<1-x>Sr_xF_2 and Sr_<1-x>Ba_xF_2 mixed crystal systems. With changing the mixture ratio x (0<x<1), two mainly kinds of spectra were followed ; the UV band from electron trap by V_k center in host fluorite crystals and the blue band due to the transition from 4f^7 to 4f^65d of the doped Eu^<2+> ion. In longer wavelength region, two weak bands were found, regarding as the luminescence originated from the Eu^<3+> ion. The peak wavelength, integrated intensity and lifetime of observed luminescence were investigated as the functions of the mixture ratio as well as the Eu concentration. A luminescence mechanism was proposed on the energy transfer among concerned processes such as lattice distortions due to creation of mixed crystals, a hole migration from Eu^<2+> to Eu^<3+> through V_k center and the degeneracy of excited states of Eu^<2+> in BaF_2. The quantitative treatment of energy transfers among the above cited centers will be carried out by resolving the rate equations of populations of each center. The analyzes of luminescence decay to X-ray pulse excitaion take important roles to approach to true comprehension. To simplify the problem, the excited state ^1SIGMA_u of V_k center is assumed as a holesupply/elecron-demand level to the excited e_g down-most level, meanwhile electrons-supply to ^1SIGMA_u and e_g band are regarded as constant. As a matter of fact, we may make best fit the experimental curves of response for X-ray pulse (gamma=20 nS) excitation using suitable parmeters under the given condition. It is concluded that p32/p31, the energy transfer rate from the ^1SIGMA_u level of V_k center to the e_g band lower-most level of Eu^<2+> ion, is estimated as 3.2% at maximum for Ca_<0.8>Sr_<0.2>F_2 : Eu (0.5mol%).
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