摘要:

The conversion efficiency of scintillators with several types of electronic excitations is considered. The types and distribution of electronic excitations created in CeF3by the absorption of a high energy photon are reviewed, the effect of the self-trapping processes on the energy transfer efficiency from the excitations in the fluorine subsystem is discussed, limitations imposed on the scintillation yield by the coexistence of two types of excitations are demonstrated. Comparison with the fluorescence excitation of LaxCe1-xF3and LuF3-Ce is made.

ISSN:1042-0150    

DOI:10.1080/10420159908226199

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The ratio of thermoluminescence and scintillation light outputs of Ce : Lu2SiO5(LSO) was measured as a function of gamma-ray dose. Together, they account for only a fraction of the predicted electron—hole pairs. Electron traps saturate rapidly, and their concentration is at least two orders of magnitude less than that of cerium.

ISSN:1042-0150    

DOI:10.1080/10420159908226200

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The effect of several stable trivalentions (Lu, Y and Gd) and pentavalent Nb5+on the radiation resistance and thermoluminescence characteristics of PbWO4is investigated. While rather uniform behaviour is observed for all the trivalent ions, apparently different mechanisms apply in the case of the Nb doping. This fact could be explained by different effect of the dopants on the oxygen sublattice, namely on the concentration of oxygen vacancies. Electron centers based on oxygen vacancy(ies) participate in thermoluminescence processes round 200 K.

ISSN:1042-0150    

DOI:10.1080/10420159908226201

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Various efforts to improve radiation hardness and scintillation properties of lead tungstate with respect to its application in high energy calorimeters by doping with suitable ions like Nb, La, Gd or Lu have been checked for their success mainly by studying optical absorption and thermally stimulated luminescence (TSL) after irradiation at room temperature, in a few cases at liquid nitrogen temperature. Very shallow traps, which contribute to fast scintillation processes, are not stabilized under such conditions. Extending the temperature range for irradiation as well as for experimental studies down to liquid helium temperature, we found new TSL glow peaks and established a correlation to electrons captured by anionic WO4complexes. Their electron spin resonsnance (ESR) data together with other experimental results like temperature dependence of photoconductivity give distinct hints with respect to the energy level scheme of PbWO4.

ISSN:1042-0150    

DOI:10.1080/10420159908226202

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A new cerium-doped crystal has been grown and its fluorescence properties have been investigated through laser and synchrotron spectroscopies. While the crystal exhibits an efficient blue fluorescence when excited in the near UV absorption bands, its fluorescence is strongly quenched when excited in the fundamental absorption regions. This phenomenon is interpreted by a model involving the formation of cerium-bound excitons, their lowest excited state lying closely in energy from the emitting state of Ce3+. The role played by the 4f level of lutetium in the scintillation efficiency of cerium-doped lutetium-based oxide crystals is discussed through the comparison of both systems LaLuO3: Ce and LuAlO3: Ce.

ISSN:1042-0150    

DOI:10.1080/10420159908226203

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Thermally stimulated polarization and depolarization current technique was used to monitor (in a temperture range of 80–473 K) the dielectric relaxations and conduction currents of PbWO4single crystals of different origin and different contamination (mainly) of molybdenum). For both speciments at least one depolarization band was detected at temperatures slightly below and well above room temperature. The band positions and amplitudes were studied as function of the polarization field, temperature and time. Activation parameters of the related processes were determined, and the origin of the relaxations discussed.

ISSN:1042-0150    

DOI:10.1080/10420159908226204

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Optical properties of two pairs of Ce3+-doped scintillating materials, (LiLuF4, LiYF4) and LuF3, LaF3), are presented. 4f14→4f13-5d transitions of Lu3+are shown to occur between 8–10 eV in the transmission spectra of the Lu-based compounds. in this domain, the transfer of electronic excitation from lutetium to crerium is inefficient, the transmission spectra and the corresponding Ce3+excitation spectra being anticorrelated. On the contrary, the excitation of Ce3+is favoured by the presence of lutetium at higher energies, most probably due to the small energy gap between the 4fCe3+ground state and the 4f14Lu3+states forming the top of the valence band.

ISSN:1042-0150    

DOI:10.1080/10420159908226205

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Both calcite and vaterite polyerystalline phases of LuBO3doped with cerium and praseodymium have been prepared and their fluorescence properties investigated in the visible, near UV and VUV regions. The systems exhibit a strong and rapid near UV-blue fluorescence typical of the 5d → 4f parity-allowed transitions of dopants. It is shown that the excitation transfers from excitions and electron-hole pairs to dopants are very efficient. The light yield can be three times more efficient than that of the well-known Bi4Ge3O12scintillator for the best samples.

ISSN:1042-0150    

DOI:10.1080/10420159908226206

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The Thermally Stimulated Luminescence (TSL) properties of undoped and La3+-doped PbWO4and CaWO4crystals have been investigated after room temperature X-ray irradiation. The glow curves of the two tungstates display one principal peak at a very similar temperature (50°C): a common origin of the defects responsible for the trap level can thus be proposed. On the contrary, the emission spectrum of the TSL peak features one single band at 2.1 eV in the case of PbWO4, while a dominant emission at 2.85 eV is detected in CaWO4. In both La3+-doped crystals, less intense TSL signals were found with respect to undoped samples. The nature of the TSL active defects is discussed.

ISSN:1042-0150    

DOI:10.1080/10420159908226207

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Mixed Ce-doped LuxRE3+1-xAlO3: Ce crystals have been grown for RE3+= Y3+and Gd3+ions by the Czochralski method. Quality, reproducibility, dimensions, presence of defects and composition of the crystals were investigated and described. Luminescence and scintillation properties of the crystals are presented and compared with those of YAIO3: Ce. Scintillation light yield and energy resolution of some of the best grown mixed crystals are the same or even higher than that of used YAIO3: Ce (light yield of Lu0.3Y0.7AIO3: Ce is ≈ 15000 ph/MeV and that of YAIO3: Ce is ≈ 13400 ph/MeV).

ISSN:1042-0150    

DOI:10.1080/10420159908226208

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor