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Abstract: Thirty millimeter diameter single crystal of Nd3+ doped LuF3 was grown using LiF as solvent. The single phase crystallization was confirmed by the powder X-ray diffraction, and high structural perfection was demonstrated by X-ray rocking curve (XRC) measurements. FWHM of XRC for 220 reflection was 32arcsec. No remarkable absorption due to unfavorable impurities was observed from optical absorption measurements in the VUV spectral region. The crystal showed the VUV luminescence peaking around 178nm that is consistent with the 4f25d–4f3 transition of Nd3+ ion. The luminescence intensity of Nd:LuF3 under X-ray irradiation was significantly higher than that of reported VUV scintillators such as Nd:LaF3 or Nd:LiLuF4. [Copyright &y& Elsevier]

Novel dicyanido-bridged dicationic RuIIISSRuIII complexes [{ Ru(P(OCH3)3)2}2(µ-S2)(µ-X)2{µ-m-C6H4(CH2CN)2}]- (CF3SO3)2 (4, X Cl, Br) were synthesized by the abstraction of the two terminal halide ions of [{RuX(P(OCH3)3)2}2- (µ-S2)(µ-X)2] (1, X = Cl, Br) followed by treatment with m-xylylenedicyanide. 4 reacted with 2,3-dimethylbutadiene to give the C4S2 ring-bridged complex [{ Ru(P(OCH3)3)2}2{µ-SCH2C(CH3)=C(CH3)CH2S}(µ-X)2{µ-m-C6H4(CH2-CN)2}](CF3SO3)2 (6, X Cl, Br). In addition, 4 reacted with 1-alkenes in CH3OH to give alkenyl disulfide complexes [{Ru(P(OCH3)3)2}2{µ-SS(CH2CCHR)}(µ-CI)2{µ-m-C6H4(CH2CN)2}](CF3SO3) (7: R CH2CH3, 9: R = CH2- CH2CH3) and alkenyl methyl disulfide complexes [{Ru(P(OCH3)3)2}2{µ-S(CH3)S(CH2C=HR)}(µ-Cl)2{µ-m-C6H4(CH2- CN)2}](CF3SO3)2 (8: R = CH2CH3, 10: JR = CH2CH2CH3) via the activation of an allylic C-H bond followed by the elimination of W or condensation with CH3OH. Additionally, the reaction of 4 with 3-penten-1-ol gave [{Ru- (P(OCH3)3)2}2{µ-SS(CH2C=CHCH2OH) }(µ-Cl)2{µ-m-C6H4(CH2CN)2}](CF3SO3) (11) via the elimination of H+ and [{Ru(P(OCH3)3)2}2(µ-SCH2CH=CHCH2S)(µ-Cl)2{µ-m-C6H4(CH2CN)2}](CF3SO3)2 (12) via the intramolecular elimination of a H2O molecule. 12 was exclusively obtained from the reaction of 4 with 4-bromo-1-butene. [ABSTRACT FROM AUTHOR]

Nd 0.1, 0.5, 1, and 3 mol% doped YLiF 4 crystalline scintillators were prepared by Tokuyama Corp. and their optical and scintillation properties from vacuum ultraviolet (VUV) to near infrared (NIR) wavelengths were investigated. 4f–5d absorption bands appeared in VUV and several absorption bands due to 4f–4f transition were observed in visible-NIR wavelengths. Nd 3+ 5d–4f emission was observed around 180 nm under 160 nm excitation and intense line due to 4 F 3/2 → 4 I 11/2 at 1064 nm appeared under 500 nm excitation. In X-ray induced radioluminescence, both VUV and NIR emissions were observed. Scintillation decay times of VUV emission was 40–80 ns while that of 4f–4f ones at visible wavelength were around 12–15 μs. When 252 Cf neutron was irradiated, VUV scintillation light yield resulted around 90 ph/n. [ABSTRACT FROM AUTHOR]

Abstract: Sixty millimeter diameter single crystal of Nd3+ doped LiLuF4 was successfully grown by the Czochralski technique. No remarkable absorption due to unfavorable impurities was observed from optical absorption measurements in the vacuum ultra-violet spectral region. The high crystallinity and homogeneous luminescence characteristics were found from X-ray rocking curve and cathode-ray luminescence respectively. X-ray excited luminescence spectrum was measured and the significant 4f25d–4f3 luminescence at 182nm was observed in the grown crystal. The pulse height spectrum was taken upon γ-ray irradiation. As a result, the grown crystals demonstrated sufficient response to the γ-ray showing the light yield of 420±30photons/MeV. The decay curve under α-ray irradiation was also investigated and described by two component decay kinetics which consists of the decay constants of 34 and 450ns. [Copyright &y& Elsevier]

Abstract: Two-inch diameter Nd3+ doped LaF3 single crystals were successfully grown by the Czochralski technique. No remarkable absorption due to unfavorable impurities or color centers was observed from optical absorption measurements in the vacuum ultra-violet spectral region. The high crystallinity and homogeneous Nd3+ distribution were found from X-ray rocking curve and chemical composition analysis, respectively. X-ray excited luminescence spectrum was measured and the significant 4f25d–4f3 luminescence at 173nm was observed in the grown crystal. The pulse height spectrum and scintillation decay curves were taken upon γ-ray irradiation. As a result, the grown crystals demonstrated sufficient response to the γ-ray, the light yield of 140±30photons/MeV, and fast scintillation decay of 7.6ns. [Copyright &y& Elsevier]

In order to develop novel scintillating materials, we grew 0.5 mol%, 1 mol%, and 3 mol% Nd-doped LuLiF4 scintillators by the micro-pulling down method, because LuLiF4 has a very wide band gap and Nd3+ shows fast and intense 5d-4f emission as a luminescence center. The transmittance and emission peaks were examined in these three samples by using our original spectrometer made by Bunkou-Keiki Company. At wavelengths longer than 180 nm, approximately 60-80% transmittance with three absorption peaks around 140, 160 and 175 nm and emission peak at approximately 180 nm were observed for all the crystals. Light yields and decay time constants of the samples irradiated by 241Am αray were measured using photomultiplier tubes R8778 (Hamamatsu). The light yield of the 1 mol% doped LuLiF4 was 700 photons/ 5.5MeV α that is much greater than that of Nd:LaF3 scintillator (100 photons/5.5MeV α). As for decay time profiles, the main component of Nd:LuLiF4 was 12 ns in the case of α-ray irradiation. 137Cs 662 keV γ-ray photoabsorption peak was detected in 1 mol% doped LuLiF4 only, and the light yield was 300 ph/MeV. [ABSTRACT FROM AUTHOR]

We discuss the origin of the fast luminescence component induced by fast electrons generated in gamma-ray interactions in Ce doped LiCaAlF 6 scintillators. Although the slow luminescence component induced by Ce 3+ emissions depends on the Ce concentration in the LiCaAlF 6 scintillator, the fast component is independent. The fast component is suggested to be generated in the host matrix of the LiCaAlF 6 crystal. From quantitative considerations based on Frank–Tamm equation, which shows the light yield of the Cherenkov radiation, the Cherenkov radiation was determined as the origin of the fast component. We, additionally, found that the slow rise time of main Ce 3+ emissions in the Ce:LiCaAlF 6 scintillator plays an important role to perform the pulse shape discrimination. [ABSTRACT FROM AUTHOR]

Abstract: Vacuum Ultra violet (VUV) scintillators, have a short decay time around several ns, and therefore can be used in high counting rate applications. New Nd-doped BaY2F8 VUV scintillator crystals were successfully grown by a micro-pulling down (μ-PD) method and their optical properties and radiation response were investigated. All the BaY2F8 samples with 0.5, 1, 3, 7 and 10 mol% Nd concentration had 5d-4f luminescence peaks at 185, 237 and 270 nm. Although this scintillator has low light output around 70 photons/5.5-MeV alpha, which was determined from our pulse height measurement, we found that the decay time of this crystal reached 13 ns which is a typical value for the VUV scintillators. [Copyright &y& Elsevier]

Abstract: Cerium-doped LiCaAlF6 (Ce:LiCAF) crystals have been studied as scintillators in application to thermal neutron detection. Three crystals: high-doping Ce:LiCAF, low-doping Ce:LiCAF with 50% enrichment of 6Li (both 10mm×10mm×2mm, rectangular) and high-doping Ce:LiCAF with 95% enrichment of 6Li (Ø50.8mm×2mm, discus) coupled to Photonis XP5300B PMT, were tested. The response of these crystals to neutrons emitted from a paraffin moderated 238PuBe source has been investigated. Thermal neutron peaks have been found at a Gamma Equivalent Energy (GEE) of ∼2.5MeV for high-doping Ce:LiCAF (50% 6Li), ∼2MeV for low-doping Ce:LiCAF (50% 6Li) and ∼1.9MeV for high-doping Ce:LiCAF (95% 6Li). The light output of Ce:LiCAF was also measured (175–250phe/MeV from sample to sample). Lithium-6 glass GS20 from Saint Gobain was used as a reference scintillator (Ø50mm×2mm, circle). Relative neutron efficiency, normalized to that of GS20 lithium glass, as well as gamma-neutron intrinsic efficiency for all tested samples was calculated. Intrinsic efficiency on thermal neutron detection for small Ce:LiCAF samples was estimated at about 32–35% of that of GS20 and for large Ce:LiCAF sample as about 82% of that of GS20. [Copyright &y& Elsevier]

Abstract: To design new scintillating materials, it is very important to understand detailed information about the events, which occurred during the excitation and emission processes under the ionizing radiation excitation. We developed a streak camera system equipped with picosecond pulsed X-ray source to observe time- and wavelength-resolved scintillation events. In this report, we test the performance of this new system using several types of scintillators including bulk oxide/halide crystals, transparent ceramics, plastics and powders. For all samples, the results were consistent with those reported previously. The results demonstrated that the developed system is suitable for evaluation of the scintillation properties. [Copyright &y& Elsevier]

Abstract: Er- and Tm-doped LiCaAlF6 (LiCAF) single crystals were grown by the micro-pulling-down (μ-PD) method. The crystals were transparent, 2.0mm in diameter and 30–40mm in length. Neither visible inclusions nor cracks were observed. Photoluminescence spectra of Er- and Tm-doped LiCAF were measured. Broad band emission due to the Tm3+ and Er3+ 5d–4f transitions dominated the spectrum at 163.5 and 165 nm respectively. These emissions had shortest wavelength among the fluoride crystal hosts ever reported at room temperature experiments. The vacuum ultraviolet (VUV) luminescent crystals are attractive as scintillators for radiation detectors, which employ photosensitive gases (such as TMAE or TEA) or photocathodes (such as CsI) sensitive mostly to VUV photons. [Copyright &y& Elsevier]

Abstract: Ce 1%, 2%, and 3%-doped LiCaAlF6 (LiCAF) single crystals were grown by the micro-pulling-down method. The crystals were transparent, 2.0mm in diameter and 30–60mm in length. Neither visible inclusions nor cracks were observed. Optical properties, including absorption coefficient, and photoluminescence emission spectra were measured. The strong absorption line was observed at 260nm, and absorption coefficients of this line were proportional to Ce3+ concentration. Emission due to Ce3+ 5d–4f transition peaking around 285nm and 310nm were observed by 260nm excitation. Simulating a neutron irradiation, 241Am 5.5MeV α-ray was used to excite the samples. After a correction of a quantum efficiency of photomultiplier tube and compared with Li–glass scintillator GS20, light yield of 6600ph/n, and 41ns decay were achieved 3% doped. [Copyright &y& Elsevier]

Ce2% : 6LiCaAlF6 (6LiCAF) single crystal (nominal composition) with 2 mm in diameter and 50 mm in length was grown by the micro-pulling-down method. Emission from the perturbed Ce3+ centers was observed in an α-ray excited radioluminescence. The neutron response was compared with Li-glass (GS20, Saint-Gobain) using 252Cf. The scintillation decay time of Ce2% 6LiCAF is 38 nsec, which is twice as short as that of GS20. Using Hamamatsu photomultiplier H7416 the photoelectron yield about a half of that of GS20 has been measured for the Ce : 6LiCAF single crystal. Considering the light yield of GS20 (6000 phot/neutron) and the spectral correction due to the different emission peak position in both materials, the light yield of Ce : 6LiCAF single crystal is estimated about 4200 phot/neutron. [ABSTRACT FROM AUTHOR]