- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
X-ray scintillator Gd2O2S:Tb3+ materials obtained by a rapid and cost-effective microwave-assisted solid-state synthesis
摘要： In this work, the microwave-assisted solid-state (MASS) synthesis is reported as a rapid, cost-effective and environmental-friendly way to prepare Gd2O2S:Tb3+ X-ray scintillation standards. The preparation procedure employs active charcoal as the microwave susceptor, using a domestic microwave oven without a setup for special gases. The MASS method drastically reduced the synthesis time and energy consumption (up to 97% in nominal power) over previous reports using conventional solid-state methods. A single-step synthesis of 10 min is enough to yield highly crystalline powders starting from Gd2O3 and Tb4O7 precursors and elemental sulfur. In order to obtain 100% pure materials with superior scintillation efficiency, two microwave treatments of 25 min each are required. Due to the reducing CO atmosphere generated in situ by the active charcoal during the microwave synthesis, no Tb4+ impurity was found according to Synchrotron Radiation X-ray Absorption (SR-XAS) experiments. Spectroscopic studies were carried out using SR Vacuum-Ultraviolet (VUV) photoluminescence and SR X-ray Excited Optical Luminescence (XEOL). The material prepared by two-step synthesis exhibited a better scintillation performance owing to higher crystal purity and emission intensity, presenting versatility for technological applications such as X-ray imaging and scintillation bio-probing.
关键词： Synchrotron Radiation,Gd2O2S:Tb3+,Microwave-assisted solid-state synthesis,X-ray scintillation
更新于2025-09-23 15:21:01
-
Indirect predissociation of highly excited singlet states of N <sub/><b>2</b> </sub>
摘要： Indirect predissociation of the b(cid:2) 1(cid:1)+u (v = 20) level of N2 is studied experimentally by vacuum-ultraviolet photoabsorption employing synchrotron radiation and a Fourier-transform spectrometer, and interpreted with the aid of a quantitative model of interacting 1(cid:2)u and 1(cid:1)+u, bound and unbound states which solves the coupled Schr?dinger equation. An observed rotationally-localised peak in the b(cid:2)(20) predissociation linewidths is identi?ed by the model as arising from an interaction with a strongly predissociated and unobserved bound level of the mixed c3 1(cid:2)u and o3 1(cid:2)u Rydberg states. This leads to the dissociation of b(cid:2)(20) into the continuum of the b 1(cid:2)u valence state. The residual observed predissociation of b(cid:2) 1(cid:1)+u (v = 20) apart from the rotationally-localised peak cannot be explained by a mechanism of 1(cid:2)u and 1(cid:1)+u interaction, and must involve states of higher multiplicity.
关键词： Fourier-transform spectrometer,coupled Schr?dinger equation,vacuum-ultraviolet photoabsorption,N2,Indirect predissociation,synchrotron radiation
更新于2025-09-23 15:21:01
-
Diagnostics of polarization purity of x rays by means of Rayleigh scattering
摘要： Synchrotron radiation is commonly known to be completely linearly polarized when observed in the orbital plane of the synchrotron motion. Under actual experimental conditions, however, the degree of polarization of the synchrotron radiation may be lower than the ideal 100%. We demonstrate that even tiny impurities of polarization of the incident radiation can drastically affect the polarization of the elastically scattered light. We propose to use this effect as a precision tool for the diagnostics of the polarization purity of the synchrotron radiation. Two variants of the diagnostics method are proposed. The ?rst one is based on the polarization measurements of the scattered radiation and relies on theoretical calculations of the transition amplitudes. The second one involves simultaneous measurements of the polarization and the cross sections of the scattered radiation and is independent of theoretical amplitudes.
关键词： polarization purity,diagnostics,Rayleigh scattering,x rays,synchrotron radiation
更新于2025-09-23 15:21:01
-
Operation and performance of the JUNGFRAU photon detector during first FEL and synchrotron experiments
摘要： JUNGFRAU is a hybrid pixel photon detector developed at the Paul Scherrer Institut for free electron laser (FEL) and synchrotron applications. A charge integrating detector, JUNGFRAU features three automatically switching gains per pixel which adjust the amplification factor to the amount of deposited charge. This enables single photon sensitivity, while ensuring a dynamic range over four orders of magnitude. Each detector module consists of eight 256 × 256 pixel ASICs bump-bonded to a single 320 μm thick silicon sensor, resulting in half a million pixels of 75 μm pitch arranged in 1024 × 512 arrays for a sensitive area of approximately 8 × 4 cm2. Modules can be combined in various configurations to produce larger systems. These proceedings present the required steps, both operational and in terms of data processing, necessary to perform experiments with the JUNGFRAU detector. This includes the calculation and application of pedestal and gain corrections and the geometric arrangement of the recorded image. Examples of these techniques in action will be presented from the first experiments performed with JUNGFRAU detectors; the pilot experiment of the SwissFEL Bernina beamline and proof-of-principle macromolecular crystallography measurements from the X06SA beamline of the Swiss Light Source. Successful operation and data processing methods from FEL and synchrotron facilities will be compared and contrasted, and experience of overcoming challenges in the two scenarios will be shared. Finally, the capability of JUNGFRAU for FEL and synchrotron applications will be demonstrated.
关键词： Instrumentation for synchrotron radiation accelerators,X-ray detectors,Instrumentation for FEL
更新于2025-09-23 15:21:01
-
Hard X Rays from Laser-Wakefield Accelerators in Density Tailored Plasmas
摘要： Betatron x-ray sources from laser-plasma accelerators reproduce the principle of a synchrotron at the millimeter scale. They combine compactness, femtosecond pulse duration, broadband spectrum, and micron source size. However, when produced with terawatt class femtosecond lasers, their energy and flux are not sufficient to compete with synchrotron sources, thus limiting their dissemination and its possible applications. Here we present a simple method to enhance the energy and the flux of betatron sources without increasing the laser energy. The orbits of the relativistic electrons emitting the radiation were controlled using density tailored plasmas so that the energetic efficiency of the betatron source is increased by more than one order of magnitude.
关键词： laser-plasma accelerators,synchrotron radiation,Betatron x-ray sources,density tailored plasmas
更新于2025-09-23 15:19:57
-
A Spectroscopic Study of Changes in the Secondary Structure of Proteins of Biological Fluids of the Oral Cavity by Synchrotron Infrared Microscopy
摘要： On the basis of the data of infrared spectroscopy with synchrotron radiation, the secondary structure of proteins of the dentinal and gingival fluids during the development of cariosity in deep dentin tissues is studied. It is shown that the change in the shape of the profile of the amide I band in the region of 1700?1605 cm–1 is associated both with a change in the ratio of the integrated absorption intensities of the α-helix and β-sheet secondary structures and with the position of the β-coil and β-sheet components in the spectrum. It is established that the α-helix/β-sheet ratio for both dentinal and gingival fluids is below the threshold level, at which significant changes in the secondary structure of proteins of biological fluids are observed, unequivocally indicating the development of pathology in hard dental tissues. The features that we discovered in the profile of the amide I band of biological fluids of the oral cavity, together with the spectral markers of the development of cariosity in dentin, are reliable spectroscopic signatures of the pathology and can be detected using the gingival fluid.
关键词： synchrotron radiation,IR microscopy,spectroscopic signatures of pathological processes,dentin caries
更新于2025-09-23 15:19:57
-
On symmetry of rare-earth scandium borate RESc3(BO3)4 (RE = Ce, Nd) laser crystals
摘要： Symmetry, structural features, and point defects in the Czochralski-grown single crystals with the initial compositions CeSc3(BO3)4 (CSB-1.0) and Nd1.25Sc2.75(BO3)4 (NSB-1.25) are studied by the full-profile Rietveld method on synchrotron X-ray powder data. The space group P321 is first established and confirmed for CSB-1.0 and NSB-1.25 crystals, respectively. The features of synchrotron diffraction patterns that distinguish the space group Р321 from the R32 one are given. The site occupancies in both structures are refined and resulted in the stoichiometric composition for CeSc3(BO3)4, which coincides with the nominal composition, and the composition [Nd0.455(1)Sc0.045(39)(1)]Nd0.500(2)Sc3(BO3)4 ((Nd0.955Sc0.045(39))Sc3(BO3)4), which differs from the initial Nd1.25Sc2.75(BO3)4 one, with partial occurrence of Sc ions in one of the trigonal-prismatic sites. An analysis of literature data on single crystals with the general formula RESc3(BO3)4 (RE ? Ce, Pr, Nd) together with the results of present study of powdered single crystals gives reason to exclude a crystallization of these compounds and solid solutions based on them in the space group R32. The correlation between the refined compositions of RESc3(BO3)4 crystals (RE ? La, Ce, Pr, Nd), having a specific space group, and compositions of initial charge is given.
关键词： Crystal structure,Czochralski technique,Optical materials,Point defects,Synchrotron radiation
更新于2025-09-23 15:19:57
-
Synchrotron infrared spectral regions as signatures for foodborne bacterial typing
摘要： Fourier-transform infrared (FTIR) spectroscopy has emerged as a viable alternative to biochemical and molecular biology techniques for bacterial typing with advantages such as short analysis time, low cost and laboratorial simplicity. In this study, synchrotron radiation-based FTIR (SR-FTIR) spectroscopy with higher spectral quality was successfully applied to type 16 foodborne pathogenic bacterial strains. Combined with principal component analysis (PCA) and hierarchical cluster analysis (HCA), we found that the specific spectral region 1300–1000 cm-1, which reflects the information of phosphate compounds and polysaccharides, can be used as the signature region to cluster the strains into groups similar with genetic taxonomic method. These findings demonstrated that FTIR spectra combined with HCA have a great potential in quickly typing bacteria depending on their biochemical signatures.
关键词： FTIR,PCA,Bacterial typing,Spectral signature,HCA,Synchrotron radiation
更新于2025-09-19 17:15:36
-
HgCdTe Detector Saturation Using Infrared Free Electron Laser and Infrared Synchrotron Radiation
摘要： Recently, the high-brilliance infrared synchrotron radiation source out of various infrared sources has become popular, and it is widely used in many fields of studies. For spectroscopy, the mercury cadmium telluride (MCT) detector is often used. It covers a wide mid-infrared region and has high sensitivity, but saturates easily. In this work, the detector saturation behavior was investigated in detail using infrared synchrotron radiation and infrared free electron laser. We found that the saturation and its elimination show various patterns depending on the amplifier gain, light intensity and the time structure of the light. The influence of the saturation to the spectral shape is also discussed.
关键词： Saturation,Infrared Synchrotron Radiation,Infrared FEL,MCT Detector
更新于2025-09-19 17:13:59
-
Mapping the geometry of Ti-6Al-4V: From martensite decomposition to localized spheroidization during selective laser melting
摘要： The influence that complex component geometries can have on microstructure formation is investigated in a rocket engine impeller fabricated of a Ti-6Al-4V alloy by selective laser melting (SLM). The SLM melt pool monitoring, indicative of the component’s thermal history during processing, is linked to the bulk mapping of martensite decomposition obtained by high energy synchrotron X-ray diffraction. In addition to the martensitic and lamellar microstructures typically obtained during SLM of Ti-6Al-4V, spheroidization is identified to take place in the component’s down-skin regions. Grain boundary migration may contribute to the latter effect. Small recrystallized grains form along grain boundaries.
关键词： Titanium alloys,X-ray diffraction,Microstructure,Selective laser melting,Synchrotron radiation
更新于2025-09-19 17:13:59