The state of the art of core–valence luminescence (CVL) in a number of halides (BaF2, CsCl, LiBaF3, etc.) is analysed. The following items are discussed: common properties of CVL, a suppression of ...slow emission component in BaF2, an effect of secondary excitation density on intensity and decay profile of the emission, a neutron–gamma discrimination, spectrum simulations, impurity-associated CVL, an origin of slow- and long-wavelength CVL components, a lattice relaxation, vibrations of lattice environment and phonon broadening of the emission bands.
Experimental results on impurity-associated CVL of Rb1−xCsxBr(x<0.2) are presented and discussed. It is shown that the impurity-associated luminescence gives us a convenient way for the improvement of light output and variation of the emission wavelength of the scintillators.
The fast component of the barium fluoride (BaF2) crystal luminescence with the emission peak at 220 nm allows those crystals to be employed in fast calorimeters operating in harsh radiation ...environment. However, the slow component with the emission peak at 330 nm and about 85% of the total emission light could create big problems when working at a high radiation rate. In this work we report results of tests of multilayer filters that can suppress luminescence in the range from 250 nm to 400 nm, which covers most of the BaF2 slow component luminescence. The filters are made by spraying layers of rare earth oxides on a quartz glass substrate. Filters typically comprise 200-220 layers. A few filters were prepared by spraying thin layers on quartz glass. The filters have a peak transmittance of about 70-80% in the range of 200-250 nm. Measurements of the light output of the BaF2 crystal with and without a filter between the crystal readout end and the PMT demonstrate substancial suppression of the slow component. To our knowledge, this kind of filters are produced and tested for the first time.
The state of the art of fast scintillator development is considered. Decay curves of some scintillators measured at pulsed (
0.5
ns
) X-ray excitation are presented. Literature results are analyzed ...and summarized. It is shown that radiative core-valence transitions are best suited for subnanosecond and nanosecond scintillations, while rare earth ions show efficient scintillation with decay constants of tens of nanoseconds in oxygen-based crystals. Emissions from both Ce
3+ ions and core-valence transitions in a crystal are particularly useful for neutron/gamma discrimination. Promising emission mechanisms are proposed to be used in fast scintillators.
Luminescence of a CaWO4 scintillator was studied in the temperature range 77–500K using intense laser excitation in the 450–600nm spectral region. Characteristics of the observed blue emission are ...similar to those of the intrinsic luminescence of calcium tungstate. The emission is concluded to be caused by cascade excitation of CaWO4 that results in a two-photon excited (TPE) luminescence. The features of TPE luminescence of CaWO4 are analysed in comparison to those obtained with UV and X-ray excitation.
X-ray excited luminescence of some molybdates Mikhrin, S.B; Mishin, A.N; Potapov, A.S ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2002, Letnik:
486, Številka:
1
Journal Article
Recenzirano
The main scintillation characteristics: spectra, decay times, yields of CaMoO
4, SrMoO
4, NaLa(MoO
4)
2 single crystals are measured under X-ray excitation. CaMoO
4 exhibits a good energy efficiency ...(
η=0.2 of CsI:Tl), but slow (
τ≈16
μs) main decay component, and SrMoO
4 correspondingly shows
η=0.06,
τ≈1.0
μs. NaLa(MoO
4)
2 has the largest fast component
τ≈4.2
ns, but a very small yield. All studied crystals offer high resistance against X-ray irradiation.
A small-size short-pulsed X-ray source is described whose main components are a three-electrode X-ray tube operating at 30 kV and 0.5 A and a fast GaAs modulator connected coaxially to the tube grid. ...The ultimate parameters of the source are subnanosecond pulse duration and 100-kHz repetition pulse rate. The detection system allows the measurements to be carried out in the 200-800 nm spectral range over the time intervals from 0.5 ns to 50 /spl mu/s with resolution not worse than 0.1 ns. The decay time curves of an organic scintillator and CdI/sub 2/, Gd/sub 2/O/sub 2/S:Pr, and Cs/sub 2/NaCeCl/sub 6/ crystals are presented.
Storage effect in LiRESiO4:Ce3+, Sm3+, RE=Y,Lu phosphor Sidorenko, Andrei V.; Bos, Adrie J.J.; Dorenbos, Pieter ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/2005, Letnik:
537, Številka:
1-2
Journal Article
Recenzirano
Good storage properties after irradiation have been observed in doubly rare-earth-doped LiRESiO4:Ce3+,Sm3+, RE=Y,Lu powders. We present strong arguments that in the studied materials Ce3+ ions play a ...role of hole trapping and Sm3+ ions of electron trapping centres. Additionally, oxygen vacancies are also involved in electron trapping, however they can be removed by appropriate thermal treatment. During thermal stimulation of irradiated LiRESiO4:Ce3+,Sm3+, RE=Y,Lu an electron from Sm2+ is released into the conduction band formed by SiO4 and further migrates to Ce4+ centers. This causes the TL peak at 340K in LiLuSiO4:Ce3+,Sm3+ and at 400K in LiYSiO4:Ce3+,Sm3+ upon heating rate of 1Ks. Very fast and efficient photo-stimulated luminescence (PSL) have been observed upon stimulation with an IR laser (λ=830nm). The presented materials can be utilized in Image Plates for X-ray or neutron position sensitive detection.
Modern scientific investigations of scintillation characteristics in new materials make high demands to experimental set-ups. For any in-depth study of new materials complex experimental devices are ...needed. In this work, we present our experimental complex for studying the main scintillation properties of luminescent materials. As an object of investigation for a demonstration of this set-up possibilities the Pr-doped phosphors have been chosen.
The developed device allows us to hold the following measurements: emission spectra, kinetics, relative light output under steady state and pulsed X-ray excitations, thermo-stimulated luminescence and afterglow. Some new results in the Pr-doped phosphors’ luminescent characteristic investigations which have been obtained via this facilities are presented in this paper.
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