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Recently, we have demonstrated a method to record the longitudinal phase-space distribution of a pulsed cryogenic buffer gas cooled beam of barium fluoride molecules with high resolution. In this paper, we use this method to determine the influence of various source parameters. Besides the expected dependence on temperature and pressure, the forward velocity of the molecules is strongly correlated with the time they exit the cell, revealing the dynamics of the gas inside the cell. Three observations are particularly noteworthy: (1) The velocity of the barium fluoride molecules increases rapidly as a function of time, reaches a maximum 50–200 µ s after the ablation pulse and then decreases exponentially. We attribute this to the buffer gas being heated up by the plume of hot atoms released from the target by the ablation pulse and subsequently being cooled down via conduction to the cell walls. (2) The time constant associated with the exponentially decreasing temperature increases when the source is used for a longer period of time, which we attribute to the formation of a layer of isolating dust on the walls of the cell. By thoroughly cleaning the cell, the time constant is reset to its initial value. (3) The velocity of the molecules at the trailing end of the molecular pulse depends on the length of the cell. For short cells, the velocity is significantly higher than expected from the sudden freeze model. We attribute this to the target remaining warm over the duration of the molecular pulse giving rise to a temperature gradient within the cell. Our observations will help to optimize the source parameters for producing the most intense molecular beam at the target velocity. [ABSTRACT FROM AUTHOR]

Because of its fast scintillation component with subnanosecond decay time, BaF2 crystals are considered as a candidate for ultrafast crystal calorimeters for future high energy physics experiments at the energy and intensity frontiers. Undoped BaF2, however, has a slow scintillation component with 600 ns decay time, which causes pile-up. In the part I of this paper, we report investigations on La doping in BaF2 crystals to suppress the slow component. While typical fast/slow (F/S) ratio observed in undoped BaF2 is 1/5, La-doped BaF2 crystals were found to improve this ratio to about 1/1. The overall F/S ratio, however, is considered not sufficient for pile-up suppression. [ABSTRACT FROM AUTHOR]

Future high-energy physics experiments at the energy and intensity frontiers will face a challenge of severe radiation environment from both ionization dose and charged and neutral hadrons. The high-luminosity large hadron collider, for example, will present an environment, where up to 130 Mrad ionization dose, 3 \times 10^14 charged hadrons/cm2 and 5 \times 10^15 neutrons/cm2 are expected. In this paper, we report our investigation on charged hadron-induced radiation damage in BaF2, LYSO/LFS, and PWO crystals up to 3 \times 10^15 protons/cm2 by using 800-MeV protons at the Los Alamos Neutron Science Center. Comparison is made between radiation damages induced by protons and ionization dose alone. [ABSTRACT FROM AUTHOR]

At the China spallation neutron source-white neutron sources (CSNS-WNS), the BaF2 (barium fluoride) detector array in planning is designed for neutron capture cross section measurements with high accuracy and efficiency. Once proton beam collides with the spallation target, the neutrons will fly from the target to specimen surrounded by BaF2 array and produce cascaded $\gamma $ rays eventually. The time of flight (TOF) corresponds to the neutron energy. To identify $\gamma $ signals from the high $\alpha $ -particle background, pulse shape discrimination (PSD) technique is usually used according to the ratio of fast to slow component in the signal. Waveform digitization is a valid supporting technology for PSD. In order to precisely obtain the wave and time information carried by detector signal, and to maximally cover the signal dynamic range, a universal digitizer with 1 GSps sampling rate and 12-b resolution has been designed based on a 3U PXIe platform in this paper. Besides waveform digitization, this customized digitizer also measures TOF precisely based on the digitized waveform data and technique of time-to-digital converting on field-programming gate array. Test results show that this digitizer can achieve good static and dynamic performance. The specification of effective number of bits is better than 9.43 b within 198 MHz. Digitizer proposed in this paper can meet the requirements for BaF2 spectrum at CSNS-WNS. [ABSTRACT FROM AUTHOR]

Gigahertz hard X-ray imaging for the proposed matter-radiation interaction in extreme project presents an unprecedented challenge to front imager in both speed and radiation hardness. Novel fast scintillators are to be developed to face these challenges. This paper presents an investigation on the optical and scintillation properties for a set of fast inorganic scintillators. Transmittance, emission, light output, and decay time were measured. Based on this investigation, we plan to take two approaches to develop inorganic scintillators with subnanoseconds of decay time for the gigahertz hard X-ray imaging. One is yttrium-doped barium fluoride single crystals, and another is based on gallium-doped ZnO nanoparticles. [ABSTRACT FROM AUTHOR]

Barium fluoride (BaF2) crystal has a fast scintillation light peaked at 195 and 220 nm with a sub-ns decay time. This ultrafast scintillation promises a wide application in an area where extreme fast timing is important, such as future high-energy physics experiments, gigahertz hard X-ray imaging, and time-of-flight positron emission tomography. BaF2 crystal, however, has also a slow scintillation component peaked at 310 nm with a decay time of about 600 ns, which causes pileup. Suppression of the slow scintillation component by selective doping, such as Ce, La, Tm, and Y, was discussed 20 years ago. In this paper, we report suppression of the slow component in BaF2 crystals by yttrium doping. Single crystals with 1 at% Y doping were grown by vacuum Bridgman technique at the Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, China. Their radioluminescence, optical transmittance, light output, fast/slow ratio, decay kinetics, and light response uniformity were measured. The results show that 1 at% Y doping suppresses the slow scintillation component in BaF2 crystals by a factor of 6, while the fast component remains unaffected. [ABSTRACT FROM AUTHOR]

Applications, such as high energy physics experiments at intensity frontier, time-of-flight positron emission tomography, ultrahigh repetition radiation imaging, and positron annihilation lifetime spectroscopy, etc., have raised increasing demands on the time response of scintillators. Development of ultrafast scintillators becomes one of focuses in recent studies. Barium fluoride (BaF2) crystal is a unique ultrafast scintillator with a sub-nanosecond fast scintillation component, its slow scintillation component with a decay time of about 0.6 μs, however, will cause serious pileups at high counting rates. As an effective approach to suppress the slow component in BaF2 crystals, doping has attracted continuous attention over the past three decades. This paper reviews the history of suppression of slow component in BaF2 crystals by doping, and then proposes basic principles on selecting doping elements. Suppression characteristic and mechanisms of slow component in BaF2 crystals doped with rare-earth metals (La, Y, Lu, Sc), alkali earth metals (Mg, Sr), transition metal (Cd), and alkali metal (K) are highlighted, and application research is introduced. The challenge and opportunity of slow component suppression by doping are also prospected. [ABSTRACT FROM AUTHOR]

• The OPP structure can operate in the violet light band. • The OPP structure realizes an angle selection within 30° range. • The OPP structure provides a new method to realize angle selection through ENZ principle. • The OPP structure can enhance angle selection sensitivity by incorporating dynamic anti-reflection structures. In this paper, an optical privacy protection (OPP) structure is designed for violet light, leveraging the unique epsilon-near-zero (ENZ) properties of YaBa 2 Cu 3 O 7 material along with an anti-reflection structure. To tackle the challenges posed by temperature regulation constraints, the zinc fluoride barium lanthanum aluminum magnesium hexafluoride glass is incorporated as the background medium. The findings indicate that this proposed configuration demonstrates a remarkable transmissivity exceeding 91 % in the TM wave for angles ranging from −30°∼ 30°. It is worth noting that the transmittance significantly drops close to zero beyond –33.7° or 33.7° angles. Moreover, an impressive transmittance of over 98 % is achieved within the TE wave range of −30°∼ 30°, while experiencing a sharp decline towards nearly zero beyond –33.9° or 33.9° angles. The designed OPP effectively operates across the frequency range of 680 ∼ 790 terahertz, encompassing the violet optical spectrum. It consistently exhibits a rectangular coefficient exceeding 0.84 in the TE wave and surpasses 0.87 in the TM wave, demonstrating its exceptional performance characteristics within these respective modes. [ABSTRACT FROM AUTHOR]

The barium zirconate titanate coated with dopamine is an excellent dielectric material. Herein, we prepared a type of BaLaZrTiO3 (BLZT) powder by hydrothermal method and coated BLZT with dopamine (DA). Then, casting method was applied to synthesize a composite film by adding BLZT/DA‐BLZT powders to polyvinylidene fluoride (PVDF) respectively. Results show that DA‐BLZT@PVDF films perform better than BLZT@PVDF films in term of energy storage property and dielectric property. The dielectric constant and energy storage density of DA‐BLZT@PVDF films were all higher than that of BLZT@PVDF films and the dielectric loss was lower than BLZT@PVDF films. X‐Ray Diffraction (XRD) demonstrated the typical perovskite structure was existing in BLZT powder. TEM and SEM also showed that the surface of BLZT powder was successfully coated with DA and uniformly dispersed in PVDF. This research provided an avenue to significantly improve the electrical properties of composite films. [ABSTRACT FROM AUTHOR]

This paper describes the study of the surface morphology of BaF2 epitaxial films grown by means of molecular beam epitaxy in various growth regimes on a CaF/Si(100) surface, which is performed by means of atomic force microscopy. The CaF layers were obtained on a Si(100) substrate in a low-temperature growth regime ( T = 500 °C). The technological regimes of growth of BaF continuous films with a smooth surface on CaF/Si(100), suitable as buffer layers for the subsequent growth of PbSnTe layers or other semiconductors, such as AB, and solid solutions based on them. [ABSTRACT FROM AUTHOR]

Single-phase samples of the Ba1−xCexF2+x solid solution (x = 0.3–0.4) were synthesized by directional crystallization in the form of single crystals and by co-precipitation from aqueous nitrate solutions using potassium fluoride as a fluorinating agent in the form of nanopowders. The cathodoluminescence of the pressed powder samples was studied in comparison with the BaF2: Ce single crystals in 250–460 nm (2.7–5 eV) spectral range upon excitation by an electron accelerator. The cathodoluminescence spectra of the samples revealed a wide band in the range of 3.0–4.0 eV, which consists of two typical components of Ce3+ with decay time 23 ns in the case of single crystals and three decay times 27 ns, 140–170 ns, and ~600 ns in the case of pressed powders. The decay time of the short-wavelength component (27 ns) in the case of pressed powders is close to the lifetime of the excited state of the Ce3+ ion. The developed X-ray phosphors can be applied for embedding in diamonds for diamond–nanoparticle composite preparation. [ABSTRACT FROM AUTHOR]

Organic–inorganic composite scintillators, demonstrating advantages of easy large-area preparation and a high detection efficiency, have shown enormous potential application prospects in radiation detection and imaging. In this study, bulk polystyrene (PS) composite scintillators were successfully prepared by embedding inorganic BaF2 particles with a loading amount of up to 80 wt% during the polymerization process of the plastic scintillator. The inorganic BaF2 particles were uniformly dispersed in the organic matrix. With the increase of the loading amounts of BaF2 particles, the X-ray-excited luminescence intensity of the PS-BaF2 composite scintillators was about eight times higher than that of the commercial pure plastic scintillator. The scintillation counts under the gamma ray (59.5 KeV) irradiation also showed that the detection efficiency was obviously enhanced by BaF2 particle loading. More importantly, their scintillation pulse retains the decay kinetics of the organic matrix without loading the slow-decay component of BaF2. This work provides a promising solution for the application of the PS-BaF2 composite scintillator in high-efficiency radiation detection and large-area imaging. [ABSTRACT FROM AUTHOR]

BaF2 crystal is well known for its short fluorescent decay time for its fast component. In measuring the time profile of γ-ray flux density, it is important to suppress the contribution from the slow component in the BaF2 crystal. A multiple reflection and multiple-path (MRMP) short-wavelength pass filter is manufactured to achieve this goal, which can filter the slow component by wavelength selection. To accurately investigate the time profile of the fast component in the BaF2 crystal, <3 ps pulse length γ-ray source is used. The experimental results show that this filter reduces the slow scintillation light emitted from the BaF2 crystal by 99.7% with a detection efficiency of ≈ 0.11 electrons/γ for the fast component. The rise time, full-width at half-maximum (FWHM), and duration time for the fast component in a BaF2 detector are 0.31, 1.12, and 2.92 ns, respectively. The fast fluorescent component of the BaF2 crystal is short enough for subnanosecond pulse radiation detection. [ABSTRACT FROM AUTHOR]

This paper examines how the transformation of BaF from a single-crystalline to polycrystalline state as a result of uniaxial hot-forming influences its properties. With increasing strain, the microstructure of the material changes from a nonuniform polycrystalline one, with a block size of about 1 mm, to a classic ceramic structure made up of grains in which dislocations form walls, resulting in a subgrain structure. The best mechanical characteristics are offered by the ceramic produced at a strain on the order of 700%. The intensity of the fast X-ray luminescence component (band at 220 nm) is independent of strain, whereas that of the slow component (band at 310 nm) decreases with increasing strain. [ABSTRACT FROM AUTHOR]

New coordination polymers with 2D network structures with fluorine directly coordinated to the metal ion were prepared both via mechanochemical synthesis and fluorolytic sol–gel synthesis. Depending on the synthesis route, the samples show different particle sizes, according to SEM imaging. The crystal structures of barium acetate fluoride, strontium acetate fluoride, and lead acetate fluoride (BaF(CH3COO), SrF(CH3COO) and PbF(CH3COO)) were solved from X-ray powder diffraction data. The structure solution is backed by the results from 19 F MAS NMR, FT IR data, and thermal analysis. The calculated chemical shifts of the 19 F MAS NMR spectra coincide well with the measured ones. It turns out that the grinding conditions have a remarkable influence on the mechanochemical synthesis and its products. Our systematic study also indicates a strong influence of the atomic radii of Ca, Sr, Ba, and Pb on the success of the syntheses. [ABSTRACT FROM AUTHOR]

Ternary oxides containing Sn2+ are rare and difficult to prepare using solid state reaction due to disproportionation of Sn2+ at high temperature. In this paper, nanoparticles of barium titanate doped with different amounts of Sn2+ consisting of single phase perovskite structure were successfully synthesized for the first time by using a microwave-assisted solvothermal reaction. The particle sizes were about 20–40 nm in diameter and increased with increasing the amount of doped tin. Solidified ceramic bodies were obtained using a spark plasma sintering method under argon atmosphere avoiding the disproportionation and oxidation of Sn2+ in the air. The grain size and dielectric constant of the sintered body decreased with increasing the amount of doped tin. [ABSTRACT FROM AUTHOR]

Coated-conductor applications of YBCO require YBCO layers with high Jc and a thickness of several micrometers. The barium fluoride process offers a convenient way of depositing crack-free fluorinated precursor layers up to 5 microns thick. However, converting thick precursor layers into c-axis-oriented YBCO flints is challenging due to extensive nucleation of random grains. In this paper we address this problem with both a theoretical and experimental analysis of YBCO nucleation. We utilized optical polarization contrast to observe YBCO nuclei imbedded in the precursor matrix. We observed that the nuclei density strongly depends on processing parameters, with the oxygen partial pressure being one of the strongest factors. During ex-situ processing the nuclei merge and form grains and the nuclei density is, therefore, directly related to the grain size of YBCO film. It is desirable to have a small grain structure, since large grains do not connect well and the Jc of such a film is low. However, attempts to increase the nuclei density also generates more randomly oriented grains. Therefore the optimization of ex-situ processing is essentially finding a balance between c-axis grain density and random grain content. [ABSTRACT FROM AUTHOR]

Based on the literature data, the most used chemical element for the removal of the contaminant fluoride ions from different water systems was the Al followed by the Zr, Mg, Fe, C, and several others elements that form stable Me–F complexes. The application of mixed composite adsorbents is a modern tendency, but in this study, the dry aluminum sulfate was tested for direct chemical elimination of the fluoride ions from real industrial zinc sulfate electrolytes. The behavior of the used fluorine ion-selective electrode (FISE) was tested in the presence of sodium fluoride and aluminum sulfate. For suppression of the negative role of the aluminum ions on the FISE potential citrate total ionic strength adjustment buffer (TISAB) was used for appropriate ex situ analytical measurements of the fluoride ions in the real zinc electrolytes from the different hydrometallurgical purification stages. The elimination of the free fluorine ions was tested at room temperature (18–27 °C) and by heating up to 40 °C. The obtained results show that at room temperature, the efficiency of the reaction between F− and Al3+ ions was not very satisfied. Maximum 13% from the initial fluoride concentration was reduced at real conditions. By heating the process was intensified up to 75–95%, but in excess of non-reacted aluminum ions that additionally contaminated the electrolyte for zinc electrowining. The experimentally proven advantages and disadvantages revealed that the elimination reaction needs further optimizations before any applications at plant conditions. Factors as temperature was beneficial, whereas pH was hard for operation since the dry aluminum sulfate acidified the plant electrolytes and the zinc sulfate matrix precipitated easy by titration from acid to neutral conditions. [ABSTRACT FROM AUTHOR]

Barium lanthanum fluoride powders have been prepared by reacting barium nitrate and lanthanum nitrate in molten sodium nitrate at 350 and 450°C, using a sodium fluoride as a fluorinating agent. A fivefold excess of sodium fluoride has been shown to prevent pyrohydrolysis. We have identified a phase of variable composition with the fluorite structure, Ba1–xLaxF2+x (0.3 < x < 0.5), which has high ionic conductivity (2.3 × 10–4 S/cm at 500 K) and an activation enthalpy for ionic transport of 0.50 ± 0.01 eV. [ABSTRACT FROM AUTHOR]

The “in programming barium fluoride (BaF2) detector array” is one of the experiment facilities at China Spallation Neutron Source-White Neutron Sources, which is designed for the measurement of neutron capture cross section with high accuracy. It consists of 92 crystal elements with completely $4\pi $ solid-angle coverage, which needs 92 analog channels and 92 digitization channels for data acquisition. Accordingly, the readout electronics is comprised with four distributed readout PXIe crates, containing 46 field digitization modules (FDMs). Each FDM supports two valid channels for signal digitizing. In this paper, evaluation software is designed for evaluating the performance of BaF2 readout electronics. It focuses on evaluating the performance of data transmission, waveform digitizing, and working status monitoring. Test results show that the evaluation software can correctly acquire and assemble data from the BaF2 readout system and evaluate the analog digital converter (ADC) performance under ADC test mode. FDMs in the readout system can also be monitored and controlled by this software in real time. [ABSTRACT FROM AUTHOR]

In this paper, we investigated the hardware implementation of two feedforward neural networks (NNs) using a field-programmable gate array (FPGA), then used the networks for alpha–gamma discrimination in barium fluoride (BaF2). The BaF2 detector output was sampled using a 1-GSPS ADC, and then we extracted six information of the pulses in FPGA as the input features to the NNs. The performance of this method turned out very good, the false alarm rate of the networks was less than 0.3%. Besides, dead time of the networks was less than 820 ns. Low logic occupancy is also discussed. [ABSTRACT FROM AUTHOR]

The short-wavelength sub-nanosecond luminescence in BaF 2 material, discovered in the early 80s, gave a new direction to research into fast scintillators and phosphors. In contrast to 'typical' luminescence occurring within the forbidden band gap, the new type of emission was due to transitions between the upper core and valence bands. Thus it was named core-valence luminescence (CVL); the terms cross-luminescence and Auger-free luminescence have also been used. Given its unusual nature, this new luminescence process has attracted considerable interest in the field of condensed matter physics. During the sequent decades (till the end of the previous century) CVL has been experimentally observed in several dozen compounds and the conditions for detecting CVL have been established. Interest in this kind of luminescence increased in recent years due to the emergence of new methods of crystal synthesis, the development of high-speed solid-state photodetectors, and the construction of unique modern set-ups using synchrotron radiation. This paper analyzes the numerous studies of CVL, obtained mainly over the past decade. Experimental and theoretical data on this topic are considered in detail. Special attention is given to new results on scintillation characteristics of BaF 2 in the form of single crystals, ceramics, nanoparticles, and composites. The features of CVL in binary and ternary compounds are discussed. Some Cs- and Ba-based ternary halides show relatively high light yields and represent promising fast scintillators. The prospects of using materials with CVL as fast scintillators for time-of-flight positron emission tomography and other applications are deliberated. • Overview of recent theoretical and experimental findings on Core Valence luminescence. • Most attractive CVL crystals for ultrafast scintillator applications analyzed. • Prospects for future studies and underexplored CVL materials listed. [ABSTRACT FROM AUTHOR]

The NL-eEDM collaboration is building an experimental setup to search for the permanent electric dipole moment of the electron in a slow beam of cold barium fluoride molecules [NL-eEDM Collaboration, Eur. Phys. J. D 72, 197 (2018)]. Knowledge of the molecular properties of BaF is thus needed to plan the measurements and, in particular, to determine the optimal laser-cooling scheme. Accurate and reliable theoretical predictions of these properties require the incorporation of both high-order correlation and relativistic effects in the calculations. In this work, theoretical investigations of the ground and lowest excited states of BaF and its lighter homologs, CaF and SrF, are carried out in the framework of the relativistic Fock-space coupled cluster and multireference configuration interaction methods. Using the calculated molecular properties, we determine the Franck-Condon factors (FCFs) for the A 2 Π 1 / 2 → X 2 Σ 1 / 2 + transition, which was successfully used for cooling CaF and SrF and is now considered for BaF. For all three species, the FCFs are found to be highly diagonal. Calculations are also performed for the B 2 Σ 1 / 2 + → X 2 Σ 1 / 2 + transition recently exploited for laser-cooling of CaF; it is shown that this transition is not suitable for laser-cooling of BaF, due to the nondiagonal nature of the FCFs in this system. Special attention is given to the properties of the A′2Δ state, which in the case of BaF causes a leak channel, in contrast to CaF and SrF species where this state is energetically above the excited states used in laser-cooling. We also present the dipole moments of the ground and excited states of the three molecules and the transition dipole moments (TDMs) between the different states. Finally, using the calculated FCFs and TDMs, we determine that the A 2 Π 1 / 2 → X 2 Σ 1 / 2 + transition is suitable for transverse cooling in BaF. [ABSTRACT FROM AUTHOR]

This paper reports on semilocal and hybrid density functional analysis of charge-transition levels of native defects in BaF2 structure. The transition level is defined as the Fermi level where two defect charge states have the same formation energy. The errors arising from the small supercell size effects have been relieved through extrapolating the formation energies to the limit of infinite supercell size. The level placement in the corrected band gap is achieved using a correction factor obtained from the difference between the valence band maxima in semilocal and hybrid calculations. The band gap size from hybrid calculation is validated using the full-potential, linearized augmented planewave method with the modified Becke-Johnson exchange potential. Our results are sufficiently accurate and, thus, significant for direct comparison with experiments. [ABSTRACT FROM AUTHOR]

Phase formation in the BaF 2 -CeF 3 system has been studied in the aqueous nitrate media by co-precipitation technique with the use of HF and NH 4 F as fluorinating agents. Formation and properties of fluorite-type Ba 1-x Ce x F 2+x (х = 0.32–0.58) and tysonite-type Ce 1-y Ba y F 3-y (y = 0–0.20) solid solutions are described in the present paper. [ABSTRACT FROM AUTHOR]

This paper reports on semilocal and hybrid density functional analysis of charge-transition levels of native defects in BaF2 structure. The transition level is defined as the Fermi level where two defect charge states have the same formation energy. The errors arising from the small supercell size effects have been relieved through extrapolating the formation energies to the limit of infinite supercell size. The level placement in the corrected band gap is achieved using a correction factor obtained from the difference between the valence band maxima in semilocal and hybrid calculations. The band gap size from hybrid calculation is validated using the full-potential, linearized augmented planewave method with the modified Becke-Johnson exchange potential. Our results are sufficiently accurate and, thus, significant for direct comparison with experiments. [ABSTRACT FROM AUTHOR]

Single crystals of Ca1– хBaхF2 (x = 0.001–0.05 and 0.85–0.99) solid solutions have been grown by the Bridgman method, and their thermal conductivity has been measured in the range 50–300 K by an absolute steady-state axial heat flow technique. The thermal conductivity of all samples has been shown to decrease with increasing temperature. At 300 K, the lowest thermal conductivity of the samples with x ≤ 0.05 exceeds 6 W/(m K), and that of the samples with x ≥ 0.85 is a factor of 2 lower. [ABSTRACT FROM AUTHOR]

Radiation defects in barium fluoride single crystals doped with cadmium have been investigated by luminescence and absorption spectroscopy, as well as by electron spin resonance spectroscopy. Three types of Cd [ABSTRACT FROM AUTHOR]

Abstract: This paper has proposed a new progress of optical interconnections, taking into account the following items such as its ultimate device bandwidth, its available transmission bit rates based on soliton transmission technique, its ultimate transmission link bandwidth, and the product of the link bandwidth and its transmission length. Two items of special emphasis in the basic design of optical interconnection are polymethyl metha acrylate (PMMA) and barium fluoride (BaF2) waveguides, and the optical source cast as vertical cavity surface emitting laser diode (VCSELD), made of either AlGaAs at operating wavelength of 1.3μm or aluminum gallium indium phosphors (AlGaInP) at operating wavelength of 1.55μm; special emphasis is focused on both the above two items under different operating conditions including both thermal and electrical effects. The optical interconnect is built up on the bases of two VCSELD and one optical link where thermal effects of both diodes and links are included. The good performance of the optical interconnect is deeply and parametrically investigated under wide ranges of the affecting parameters. The high speed performance is processed through three different effects, namely the device 3-dB bandwidth, and the link dispersion characteristics. [Copyright &y& Elsevier]

Featured Application: laser surface-processing. Monocrystalline barium fluoride (BaF2) slab targets were irradiated by focused 46.9-nm laser radiation at various fluence levels above the ablation threshold. Well-developed ablation patterns with sharp edges were studied by AFM (atomic force microscopy). Their inner surfaces were uniformly covered by periodic structures. The spatial period of the ripples depends on the laser fluence. When the sample is rotated by 45°, the orientation of the grating-like structure changes accordingly. Thus, the grating vector of the periodic structure seems to be coupled to the crystallographic planes of the single crystal. This means that the XUV-laser induced ripples reported here differ from LIPSS (laser-induced periodic surface structures) associated with interference phenomena occurring on illuminated surfaces. Therefore, other mechanisms are discussed to explain the formation of the periodic nanostructures reported in this article. [ABSTRACT FROM AUTHOR]

The anodic dissolution of the Mn5Si3 electrode in 0.5 M H2SO4 + (0.0025–0.05) M NaF solutions is studied by the methods of polarization, capacitance, and impedance measurements. The kinetic order of the reaction of dissolution of silicide with respect to NaF as a function of the potential and the differential capacitance as a function of the potential and the concentration of NaF are calculated. It is shown that the effect of sodium fluoride, which activates the anodic dissolution of Mn5Si3 in a sulfuric acid solution, is associated with a weakening of the passivating effect of oxygen-containing silicon compounds and manganese oxides; with an increase in the concentration of NaF, the role of manganese in the kinetics of anodic processes on silicide increases and the role of silicon decreases. The mechanisms and kinetic laws of the anodic processes taking place on the Mn5Si3 electrode are discussed. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the effect of GeO2 glass former on the physical and electrical properties of BaFe0.5Nb0.5O3 (BFN) perovskite ceramics. The BFN powder was prepared by a conventional mixed-oxide method and the GeO2 contents, ranging from 1 to 5wt.%, were subsequently added to the calcined BFN powder. The mixtures were pressed and sintered to form dense ceramics. We showed that, with the addition of GeO2, the maximum density was achieved at lower sintering temperature, approximately 200–225°C lower than those required by the pure BFN ceramic. However, the densities of these GeO2 doped BFN ceramics were slightly lower than those of pure BFN due to the occurrence of pores. We also found that the addition of GeO2 reduces the dielectric loss at room temperature from 4.29 to 0.39–0.79 but the dielectric constant at room temperature decreased with the increased GeO2 concentrations. With small amount of added GeO2, ferroelectric property of BFN ceramics was also obtained, as confirmed by their hysteresis loops. [Copyright &y& Elsevier]

Abstract: The multiplicity of emission following neutron capture at isolated resonances carries valuable information on the resonance spin. Several methods utilizing this information have been developed. The latest method was recently introduced for analyzing the data from time-of-flight measurements with detection systems. The present paper describes a generalization of this method. The goal is the separation of the yields belonging to the two neutron capturing state spins of isolated (or even unresolved) s-wave neutron resonances on targets with non-zero spin. The formalism for performing this separation is described and then tested on artificially generated data. This new method was applied to the data obtained for the reaction using the DANCE detector system at the LANSCE facility at Los Alamos National Laboratory. The analyzing power of the upgraded method is supported by combined dicebox and geant4 simulations of the fluctuation properties of the distributions. [Copyright &y& Elsevier]

Abstract: Barium Fluoride (BaF2), mainly used in optical applications, has similar properties to those of CaF2 but better stability under environmental conditions. In this paper, we report measurements of loss tangent and the real part of the relative permittivity ε r of single crystal BaF2 in the temperature range from 14 to 290K at frequencies of 8, 10.4, 12.1, 17.6, 21.1 and 24.4GHz. Microwave properties of BaF2 were determined by measurements of the resonance frequency and the unloaded Q-factor of TE011 and quasi TE0mn modes cylindrical cavities containing the sample under test. Two techniques namely Hakki–Coleman Dielectric Resonator and dielectric post resonators have been used for characterizing the dielectric material. Losses due to the uncalibrated cables and adaptors inside the cryocooler are accounted in the calculation of unloaded Q-factor using the Transmission Mode Q-Factor data processing technique. The permittivity of BaF2 exhibited a 5% increase from 6.9 (14K) to 7.35 (290K). The loss tangent increased from 1×10−5 to 1.1×10−4 over the measured temperature range, 14–290K at a frequency of 10.4GHz. The measured microwave properties show that BaF2 can be used in many microwave devices. [Copyright &y& Elsevier]

This paper presents results obtained on barium ferrite thick films prepared by electron beam evaporation. First of all, we have looked at the influence of substrate temperature on the films properties. Then, we have fixed the substrate temperature to 700 °C and the effects of films thickness on the different properties has been investigated. Indeed for a substrate temperature of 700 °C we have observed that the layers are crystallized in the BaM phase with in-plane preferential orientation. However, a secondary non magnetic phase (BaFe2O4), which can modify the magnetic properties, appears on some layers. [Copyright &y& Elsevier]

An innovative method for utilizing synthetic calcium fluoride (CaF2), recovered from fluoride-containing semiconductor wastewater, and waste sulfuric acid (H2SO4) to produce hydrofluoric acid (HF) was investigated. The research was set to study the low-temperature production of HF via reaction of synthetic CaF2 and waste H2SO4. The impact of four factors, including H2SO4 concentration, total volume (H2SO4 + H2O)/CaF2 ratio, drying temperature of synthetic CaF2, and reaction carried out under different temperature, on HF productivity was investigated in this study. HF yield increased with increasing H2SO4 concentration and total volume/CaF2 ratio under room temperature. Generally, reactions carried out under low-temperature (< 100 °C) had a positive impact on HF yield. The higher temperature led to an increase in absorbed-HF but a decrease in total-HF. The reaction of commercial CaF2 and 70% H2SO4 had a higher absorbed-HF yield of 61.7% than synthetic CaF2 and 70% waste H2SO4, which had a yield of 36%. This was due to the higher purity of the commercial CaF2 and fewer interference ions in H2SO4. HF productivity was lowered by CaSO4, which hindered the reaction of reactants and also the generation of fluorosulfuric acid. [ABSTRACT FROM AUTHOR]

Barium fluoride (BaF2) crystals are attracting much attention as efficient inorganic scintillator promising for high‐energy physics, industrial inspection, and other fields because of the fast component of the decay time (0.6 ns) and high radiation resistance. However, two major drawbacks limit its practical application: (i) a slow decay time of ~600 ns is derived from self‐trapping excitons; (ii) the absolute light yield from the fast luminescence component is not competitive. The introducing of rare earth ions and preparation of BaF2 polycrystalline ceramics is considered to be effective measures to solve these bottlenecks. Pr3+ is extremely suitable as the activated ion of scintillation materials, which possess emission peaks located in visible band and the faster 5d–4f transition. In this work, highly sinterable Pr3+:BaF2 precursor powder was synthesized via the coprecipitation method by adjusting the reactant concentration and temperature. The morphology and microstructure of as‐synthesized powders were characterized using scanning electron microscopy (SEM) and transmittance electron microscopy analysis. The 5 at.% Pr3+:BaF2 transparent ceramic with a transmittance of 50.7% at the wavelength of 500 nm was fabricated by hot pressing the as‐prepared powders at 900°C for 4 h under the axial pressure of 50 MPa. The SEM images of ceramic cross‐section show that the residual pore is the main light scattering source. The absorption and emission spectrum of ceramic samples were discussed. [ABSTRACT FROM AUTHOR]

We introduce FeCo‐BaF and FeCo‐SiN nanogranular films exhibiting giant Faraday effect. These films have a nanocomposite structure, in which nanometer‐sized FeCo ferromagnetic granules are dispersed in BaF2 or Si3N4 matrix. FeCo‐BaF film has a good figure of merit of Faraday effect from the crystalized BaF2 matrix. FeCo‐SiN film has a large refraction index from the nature of Si3N4 matrix. These properties contribute to the practical application of nanogranular films to optical devices. [ABSTRACT FROM AUTHOR]

Barium fluoride windows are commonly used in infrared microspectroscopy because of their good transmission and their nonhygroscopic characteristics. The latter feature is particularly useful for biological specimens. The difference in infrared focus from visible focus occurs particularly at low frequencies, due to differing indices of refraction at various wavelengths, causes experimental problems. The work described in this paper addresses this issue. One example of this is illustrated with recent studies of bone sections by microspectroscopy at small mask sizes that require working around this problem when estimating the contents of phosphate and carbonate which absorb at low frequencies. When using a single 2 mm thick BaF2 dispersive substrate it is necessary to adjust infrared focusing of the transmitted radiation onto the detector by maximizing the single beam response of the microspectrometer specifically for the band or bands being studied. At optimum infrared focus the projected image of the mask degrades in the visible view. Thus it was necessary to alternate between the visible focus for the image capture and the optimum infrared focus for scanning the spectrum. The problems and limitations imposed from dispersive substrates were summarized by Carr where the focus shift response by wavelength was calculated for several common substrate materials. The relative transmission resulting from extreme focus shifts which ranged from 20 to 140 μm was determined specifically for a 2 mm thick BaF2 disk at various wavelengths. Of the various nondispersive infrared transmitting materials that exist, the experimentation presently reported involves diamond windows of different dimensions. Whereas the benefit of using a diamond or another substrate with minimal dispersion is obvious, the limitations of size, cost and interference fringes warrant consideration. Single beam spectra as well as spectra of specimens obtained with these alternatives illustrate their utility in solving the problem of dispersive windows in infrared microspectroscopy. [Copyright &y& Elsevier]

This paper calculated the electronic structure of color centers in BaF2 crystal (including F-, F+-, FA[Sr]-, V-centers) by using the embedded-cluster discrete variational method. A comparison between calculated results and optical experimental results confirms that the 640 and 580nm absorption peak is attributed to F-center and FA-center, respectively, and there exists the reserve transformation of FA-center ↔ F-center. The 1.0 eV luminescence peak in thermoluminescence spectrum is attributed to V-center. Meanwhile, a movement of the Fermi energy level of BaF2 is due to presence of color centers. [Copyright &y& Elsevier]