Performance study of LaBr3:Ce detectors coupled to R2083 PM tube for energy and timing characteristics

Journal of Radioanalytical and Nuclear Chemistry - Performance of 1″?×?1″ LaBr3 (5% Ce) scintillator coupled to Hamamatsu R2083 PM Tube has been investigated for the...     

LaCl3(Ce) and LaBr3(Ce) gamma-ray spectra with various plutonium isotopic and uranium enrichment standards

This report assesses the utility of lanthanum-halide detectors for isotope identification and total mass measurements for uranium and plutonium isotopes. Comparisons to similar measurements with NaI detectors are made.     

Three Bromides of Lanthanum: LaBr2, La2Br5, and LaBr3

Colourless LaBr₃ was obtained via the ammonium-bromide route and in singlecrystalline form by chemical vapour-phase transport with aluminium tribromide. Black single crystals of LaBr₂ and La₂Br₅ have been grown from the melts that are obtained by lithium reduction of lanthanum tribromide in sealed tantalum ampoules at 850°C. The crystal structures of the three bromides of lanthanum were refined: LaBr ₂. 2H₂–MoS₂ type, hexagonal (P6₃/mmc), a = 409.88(4) pm, c = 1390.0(1) pm, R = R_w = 0.092; La ₂ Br ₅. Pr₂I₅ type, monoclinic (P2₁/m), a = 789.09(6) pm, b = 424.89(4) pm, c = 1342.3(1) pm, β = 91.60(1)º, R = 0.067, R_w = 0.055; LaBr₃ . UCl₃ type, hexagonal (P6₃/m), a = 797.13(4) pm, c = 452.16(4) pm, R = 0.036, R_w = 0.032.     

[CuCo(CO)4]n的能谱和能带研究

应用EHMO方法计算了[CuCo(CO)4]n低聚物的能谱和无穷链能带.简单分析和具体计算表明,Cu-Co之间以双电子双中心键结合,Cu-Cu之间则成键较弱.对单体的电子结构研究表明,AuCo(CO)4是不稳定的,因Au尚有余价,能与Lewis碱配位体结合或自身多聚.由四聚体[CuCo(CO)4]4的能谱可以得到[CuCo(CO)4]的近似能带,从而可以在统一基础上解释低聚体的能谱与无穷链的能带,为利用低聚物的理论计算和实验结果预言高聚物的物理及化学性质提供近似依据.     

Quantum yield of Ce3+ and energy transfer between Ce3+ and Tb3+ in borax glasses

Quantum yields of Ce³⁺ in borax glasses were obtained by the comparative method and by lifetime measurements. Energy transfer from Ce³⁺ to Tb³⁺ was detected in borax glasses from the excitation spectrum. The transfer probabilities were calculated from the increase in the Tb³⁺ fluorescence in the presence of Ce³⁺ and the decrease of the Ce³⁺ fluorescence in the presence of Tb³⁺. A linear dependence of the transfer probabilities was found with the squared sum of the concentrations of the donor and acceptor ions. This is consistent with dipolar mechanism and interactions of one Ce³⁺ donor with two Tb³⁺ acceptors, in view of the Fong-Diestler theory.     

植物钙调素与Ce3+离子结合反应的荧光光谱法研究

水合Ce^3＋离子发射强荧光,而用Ce^3＋滴定植物钙调素（CaM）时,Ce^3＋离子荧光被完全淬灭,据此建立了测定Ce^3＋离子与植物钙调素结合位点数及逐级结合常数的方法。实验表明,Ce^3＋离子与植物钙调素的荧光激发光谱及发射光谱形状与光谱强度都有显著差别,前者的荧光强度远大于后者,故CaM存在时可以测定游离Ce^3＋的浓度。Ce^3＋离子荧光淬灭法测定结果说明,在0.5 mol·L^-1KCl溶液中,CaM有4个Ce^3＋离子结合位点。进一步通过Ce^3＋滴定植物钙调素的实验,并结合Excel规划求解法,计算出Ce^3＋与CaM的结合常数,K1=4.17×10^7,K2=1.26×10^7,K3=1.89×10^6,K4=2.04×10^6。     

Elemental survey analysis by neutron activation: simplified estimation of upper limits

A procedure is described for the rapid estimation of concentration upper limits of elements not observed in a sample by routine instrumental reactor neutron activationanalysis. Experimental andtheoreticaljustifications of time-saving steps are given, and necessary precautions in the use of the procedure are discussed. Tables for use with the procedure are included.     

The inelastic neutron scattering spectrum of H3B:NH3 and the reproduction of its solid-state features by periodic DFT

The inelastic neutron scattering (INS) and periodic density functional theory (DFT) vibrational spectra of H3B:NH3 are reported to 1600 cm-1. The H3B:NH3 structural and INS features, specifically the reduced solid-state B:N dative bond length and the altered B:N stretching frequency, are reproduced by the periodic DFT calculations, placing the B:N stretching mode at 800 cm-1, in excellent agreement with experiment relative to previous nonperiodic theoretical treatments of this molecule.     

Comparison of the neutron energy spectrum and neutron fluence rate in the LVR-15 research reactor with fuel with different enrichment

This contribution compares measured neutron energy spectra and neutron fluence rates in the LVR-15 reactor core fully equipped with IRT2M nuclear fuel (enrichment 36% of ²³⁵U in the form of UO₂) and then with a partially replaced core equipped with three IRT4M nuclear fuel assemblies (enrichment 19.7%). The measurements were performed in the LVR-15 reactor at Research Center Rez Ltd. in the Czech Republic, and were related to a planned transition to low-enriched nuclear fuel within the scope of the RERTR programme. An activation method was chosen for the neutron spectrum measurement. Iron, cobalt, nickel, copper, titanium, iridium and niobium foils were irradiated at four positions near the replaced fuel assemblies. Reaction rates for observed reaction channels were determined using gamma spectroscopy. Reaction rates along the height of the reactor core at the same positions were determined using iron, nickel, and cobalt foils. The SAND-II and STAYNL computer programs were used for neutron spectrum adjustment, and input approximation for both programs was calculated using MCNPX (v2.6). The results include a comparison of theoretical and measured data. Differences were found between thermal neutron fluence rates inside IRT2M fuel assemblies and IRT4M fuel. This difference was predicted by preliminary calculations, but it becomes less significant as distance from fuel assemblies increases.     

Clean energy from sugarcane bagasse: quality evaluation by neutron activation analysis

The energy from sugarcane is one of the most important in Brazil’s energy matrix and the efficiency of extraction and processing is fully dependent on the quality of the raw material. The soil present in sugarcane was investigate here as a factor that can affect the production of energy. Chemical elements (Fe, Hf, Sc and Th) determined by instrumental neutron activation analysis were used for tracing soil in sugarcane and its derived bagasse. The lower calorific value (LCV) of bagasse demonstrated a good negative correlation (r = ?0.9727) with the ash content of the bagasse, which in turn was positively correlated to the amount of soil in the sugarcane. Therefore, the presence of soil reduces the production of energy from burning bagasse. The proportion of loss in the LCV was just slightly higher than the soil content, i.e. for an soil content of 10 % a reduction of 12.7 % was observed in the LCV.     

The ferroelectric phase of CdTiO3: A powder neutron diffraction study

The synthesis of bulk samples of polycrystalline CdTiO₃ in both the rhombohedral ilmenite and orthorhombic perovskite forms is described and the structures of these have been refined using powder neutron diffraction data. This involved the preparation of samples enriched in ¹¹⁴Cd. Cooling perovskite-type CdTiO₃ to 4 K induces a ferroelectric phase transition, with the neutron data suggesting the low temperature structure is in Pna2₁. Mode analysis shows the polar mode to be dominant at low temperatures. The ilmenite-structure of CdTiO₃ is compared with that of ZnTiO₃. The refined scattering length of the ¹¹⁴Cd is estimated to be 5.56 fm. Attempts to dope CdTiO₃ with Ca and Sr are described.     

A study of cutting tool wear by neutron activation technique

A study of cutting tool wear with neutron activated cutting tools is described. The effect of cutting speed and cutting feed on the total tool wear is investigated for the tool and workpiece combination under consideration. A relation between relative tool life and cutting speed obtained from experimental data is given     

The determination of tellurium in geological materials using radiochemical neutron activation analysis with a low energy photon detector

A method is described for the trace level determination of Te in geological materials with a detection limit of 5–10 ppb. Destructive thermal neutron activation analysis is used with relatively simple radiochemistry employing efficient precipitation and ion exchange techniques. A germanium Low Energy Photon Detector (LEPD) is used for radioassaying which allows the relatively aboundant X-rays from^123mTe to be measured. This radioactive isotope emits Te Kα and Kβ X-rays at 27–31 keV which are readily resolved by the LEPD and therefore allows interference effects from fission product Te to be minimised giving reliable trace level data of high accuracy. The validity of the method is demonstrated by reporting analytical data for Te in a range of USGS Standard Rocks.     

Vibrational spectrum of BiH3: Six-dimensional variational calculations on high-level ab initio potential energy surfaces

We report a theoretical study of the ground electronic state of BiH₃. The potential energy surface (PES) is obtained from coupled cluster CCSD(T) calculations with a large basis set (289 contracted Gaussian functions). The previously available quartic force field (P4) is extended by adding the dominant quintic and sextic stretching terms to yield improved potential functions in symmetry coordinates (P6) and Morse-type coordinates (M4). Second-order rovibrational perturbation calculations on the P4-PES and full variational calculations on the P6-PES and M4-PES yield almost identical vibrational term values which is rationalized by considering the local mode behavior of BiH₃ and the Morse-type character of the M4-PES. The remaining deviations between the computed and observed vibrational term values must thus be caused by imperfections in the CCSD(T) surface. A refinement of this ab initio surface by a restrained fit to experimental data allows an essentially perfect reproduction of the observed vibrational term values. Variational calculations on this refined surface provide predictions for several overtone and combination bands that have not yet been observed. Dedicated to Hermann Stoll on the occasion of his 60th birthday     

Spectroscopic Studies on Charge Transfer from Ce^3＋ to Yb^3＋ in KMgF3 ： Ce, Yb Nanocrystals

Nanocrystals of KMgF3 single-doped and codoped with Ce^3＋ or/and Yb^3＋ were synthesized separately by the mi-croemulsion method. The X-ray diffraction（XRD） patterns were indexed to show that the KMgF3 crystal system was unchanged. The fluorescent spectra of KMgF3： Ce, Yb polycrystal powders were studied and compared with those of the Ce,Yb doped KMgF3 crystals produced using the high-temperature solid phase method. The diffuse reflection spectra and infrared emission of KMgF3： Ce, Yb were investigated. From the results, the authors could confirm that there were charge transfer processes from Ce^3＋ to Yb^3＋ in both KMgF3： Ce,Yb nanocrystals and polycrystal powders.     

The estimation of barium in biological material by neutron activation analysis

Barium is estimated in biological material by thermal neutron activation analysis and measurement of¹³⁹Ba by γ-counting. The biological material is digested with nitric acid and scavenged with ferric hydroxide. A special fluoride precipitation removes calcium and strontium and the barium is recovered as the chromate. The method allows the analysis of up to 40 samples per day and the sensitivity is 0.1 μg after irradiation for 85 mins at 4·10¹²n·cm⁻²·sec⁻¹.