Excitation Curves Research Articles

Activation cross-sections of proton induced reactions on vanadium in the 37–65 MeV energy range

Experimental excitation functions for proton induced reactions on natural vanadium in the 37–65MeV energy range were measured with the activation method using a stacked foil irradiation technique. By using high resolution gamma spectrometry cross-section data for the production of 51,48Cr, 48V, 48,47,46,44m,44g,43Sc and 43,42K were determined. Comparisons with the earlier published data are presented and results predicted by different theoretical codes (EMPIRE and TALYS) are included. Thick target yields were calculated from a fit to our experimental excitation curves and compared with the earlier experimental yield data. Depth distribution curves to be used for thin layer activation (TLA) are also presented.

Tunable white light and energy transfer of Dy3+ and Eu3+ doped Y2Mo4O15 phosphors

A series of Dy3+ or/and Eu3+ doped Y2Mo4O15 phosphors were successfully synthesized at a low temperature of 600°C via solid state reaction. The as-prepared phosphors were characterized by X-ray powder diffraction (XRD), scanning electronic microscope (SEM), photoluminescence (PL) excitation, emission spectra and PL decay curves. XRD results demonstrate that Y2Mo4O15: Dy3+, Eu3+ has the monoclinic structure with the space group of p21/C(14). Under the excitation of ultraviolet (UV) or near-UV light, the Dy3+ and Eu3+ ions activated Y2Mo4O15 phosphors exhibit their characteristic emissions in the blue, yellow and red regions. The emitting light color of the Y2Mo4O15: 0.08Dy3+, yEu3+ phosphors can be adjusted by varying the concentration ratio of Dy3+ to Eu3+ ions and a white light is achieved when the doping concentration of Eu3+ is 5%. In addition, the energy transfer from Dy3+ to Eu3+ is also confirmed based on the luminescence spectra and decay curves.

Proton induced gamma-ray production cross sections and thick-target yields for boron, nitrogen and silicon

The excitation functions for the reactions 14N(p,p′γ)14N, 28Si(p,p′γ)28Si and 29Si(p,p′γ)29Si were measured at an angle of 55° by bombarding a thin Si3N4 target with protons in the energy range of 3.6–6.9MeV. The deduced γ-ray production cross section data is compared with available literature data relevant for ion beam analytical work. Thick-target γ-ray yields for boron, nitrogen and silicon were measured at 4.0, 4.5, 5.0, 5.5, 6.0 and 6.5MeV proton energies utilizing thick BN and Si3N4 targets. The measured yield values are put together with available yield data found in the literature. The experimental yield data has been used to cross-check the γ-ray production cross section values by comparing them with calculated thick-target yields deduced from the present and literature experimental excitation curves. All values were found to be in reasonable agreement taking into account the experimental uncertainties.

Effects of Ce3 + sensitizer on the luminescent properties of Tb3 +-activated silicate oxyfluoride scintillating glass under UV and X-ray excitation

Novel Tb3+ or Ce3+ doped and Tb3+/Ce3+ codoped silicate oxyfluoride scintillating glasses were synthesized by melt-quenching method. The luminescent properties were studied by transmission spectra, photoluminescence excitation (PLE) and photoluminescence (PL) spectra, X-ray excited luminescence (XEL) spectra and luminescence decay curves in order to reveal the roles of Ce3+ sensitizer in the luminescence process of Tb3+-activated silicate oxyfluoride scintillating glass under UV and X-ray excitation. As for Tb3+/Ce3+ codoped scintillating glasses, the Ce3+ ions strongly sensitized the luminescence of the Tb3+ ions by energy transfer process from Ce3+ to Tb3+ ions under UV excitation. The optimal doping concentration of Ce2O3 in Tb3+/Ce3+ codoped scintillating glasses can be determined to be 0.6mol%. But under X-ray excitation, the enhancement of Tb3+ ions emission intensity caused by Ce3+ codoping is not as obvious as that under UV excitation, which is mainly due to the low energy transfer efficiency from host glass to Ce3+ ions. Under X-ray excitation, the intensity of 544nm emission in Tb3+/Ce3+ codoped scintillating glasses with 0.6mol% of Ce2O3 was 6 times than that of 500nm emission in the commercial Bi4Ge3O12 (BGO) crystals. The integral scintillation efficiency was about 83% of the BGO crystals. These results imply that the developed silicate oxyfluoride scintillating glasses in our case can be potential candidate for high-resolution medical X-ray imaging.

Experimental investigation and theoretical calculation for 3He induced nuclear reactions on vanadium

Using stacked-foil activation technique and gamma-ray spectrometry, excitation functions for 3He induced nuclear reactions on natV were measured. Cross-sections for natV(3He,xn)52m,gMn and natV(3He,pxn)51Cr nuclear reactions were measured up to 27MeV utilizing the MGC-20E cyclotron of ATOMKI. The measurements establish for the first time consistent excitation curves. Comparisons with results for values derived from different theoretical codes were included. Integral yield were calculated.

Yb3+/Tb3+ co-doped GdPO4 transparent magnetic glass-ceramics for spectral conversion

Tb3+ and Yb3+ ions co-doped transparent phosphate glass-ceramics containing monoclinic GdPO4 nanocrystals were successfully synthesized using a conventional high temperature melting quenching method in air atmosphere. The structure and morphology properties were systematically analyzed by recording X-ray diffraction patterns and transmission electron microscopy images, which indicate the GdPO4 glass-ceramics was well formed. The luminescent properties of the GdPO4: Yb3+, Tb3+ were investigated based on excitation, emission spectra and decay curves. All samples exhibited the emission of Tb3+ ions from 5D4 → 7FJ (J = 6, 5, 4 and 3) and 5D3 → 7FJ (J = 6, 5 and 4) under irradiation with ultraviolet and near infrared light. Specially, strong green up-conversion emission of Tb3+ at 543 nm (5D4 → 7F5) is observed. And the decay curves illustrate more efficient UC process in GdPO4 glass-ceramics rather than precursor glass. Energy transfer from Gd3+ to Tb3+ as well as cooperative energy transfer from Yb3+ pair to Tb3+ gives a dual mode luminescence. Laser power dependence of up-conversion shows that two-photon process is responsible for the green emission as expected. Additionally, the paramagnetic property of this material was discussed. The hysteresis plot (M−H) analysis results at room temperature indicate their good paramagnetic property. Based on the above results, the block GdPO4 glass-ceramics have potentials to serve as multifunctional materials applied in laser field materials.

Improving green emission of Tb3+ ions in BaO-B2 O3 -P2 O5 glasses by means of Al3+ ions.

BaO-B2 O3 -P2 O5 glasses doped with a fixed concentration of Tb3+ ions and varying concentrations of Al2 O3 were synthesized, and the influence of the Al3+ ion concentration on the luminescence efficiency of the green emission of Tb3+ ions was investigated. The optical absorption, excitation, luminescence spectra and fluorescence decay curves of these glasses were recorded at ambient temperature. The emission spectra of terbium ions when excited at 393nm exhibited two main groups of bands, corresponding to 5 D3 →7 Fj (blue region) and 5 D4 →7Fj (green region). From these spectra, the radiative parameters, viz., spontaneous emission probability A, total emission probability AT , radiative lifetime τ and fluorescent branching ratio β, of different transitions originating from the 5 D4 level of Tb3+ ions were evaluated based on the Judd-Ofelt theory. A clear increase in the quantum efficiency and luminescence of the green emission of Tb3+ ions corresponding to 5 D4 →7 F5 transition is observed with increases in the concentration of Al2 O3 up to 3.0mol%. The improvement in emission is attributed to the de-clustering of terbium ions by Al3+ ions and also to the possible admixing of wave functions of opposite parities. Copyright © 2016 John Wiley & Sons, Ltd.

Hydrothermal synthesis and multicolor luminescence properties of Dy3+/Eu3+ co-doped KLa(MoO4)2 phosphors

A series of Dy3+/Eu3+ co-doped KLa(MoO4)2 phosphors were synthesized by a hydrothermal method. The as-prepared samples were characterized by an X-ray diffraction (XRD), a field emission scanning electron microscope (FE-SEM), a photoluminescence (PL) excitation, emission spectra and decay curves. The samples have a single-phase monoclinic structure of KLa(MoO4)2 and consist of microspheres with the mean size of 1.5μm. Upon excitation at 389nm, KLa(MoO4)2:Dy3+ exhibits characteristic peaks at 485nm and 576nm. The optimal doping concentration of Dy3+ is about 7mol%. KLa0.93−y(MoO4)2:0.07Dy3+, yEu3+ samples show emission peaks of both Dy3+ and Eu3+ centered at 485, 576, 595 and 618nm under 389nm excitation. It can be found that the integrated emission intensity of Dy3+ is decreased and the lifetime of Dy3+ is declined with increasing Eu3+ concentration, which is due to the energy transfer from Dy3+ to Eu3+. Furthermore, according to Dexter's theory and Reisfeld's approximation, the quadrupole–quadrupole (q–q) interaction is the mechanism for energy transfer between Dy3+ and Eu3+. Moreover, the chromaticity color coordinates of KLa0.93−y(MoO4)2:0.07Dy3+, yEu3+ samples are tuned from the yellowish-white region to white light and eventually to the reddish-white region with increasing Eu3+ content. This kind of multicolor tunable phosphors exhibits the great potential applications in the fields of white light diodes, full-color displays and optoelectronic devices.

An Improved Differential Protection of Large Power Transformer using Fuzzy based Protective Relay for Inrush Current and Harmonic Components

This paper deals with the analysis of various operating conditions of power transformer such as energization, inrush current, over excitation and CT saturation. In this work a new relaying algorithm is used to enhance the fault detection sensitivities of conventional techniques by using a fuzzy logic approach. An improved differential protection scheme is proposed which uses voltages and current to detect the abnormalities in the different zone of protection. The magnetizing inrush current during transformer energization is taken with a simplified excitation curve. Discrete fourier transform is used for extraction of fundamental and higher harmonic components of the differential current. The fuzzy based protective relaying algorithm will analyze inrush current, residual flux, saturation flux, harmonics restraint and percentage differential characteristics curve. This method of fuzzy based protective relaying algorithm is tested with MATLAB simulink model and a performance comparison of conventional scheme and fuzzy logic based protection scheme is provided.

Relationship between Ga3+ concentration and luminescence properties of Eu2(MoO4)3 films at low annealing temperature

Ga3+-doped Eu2(MoO4)3 films were prepared by electron beam evaporation and annealed at 400°C–800°C in oxidizing atmosphere, and the relationship between Ga3+ concentration and luminescence properties of the films was explored combining the characterization methods of XRD, excitation, emission spectra and decay curves. It was found that intensity ratio I(5D0–7F2)/I(5D0–7F1) was extremely susceptible to Ga3+ concentration, and the luminescence intensity was significantly influenced by the doping of Ga3+. The intensity increased with Ga3+ concentration ranging from 0 to 0.65mol and reached a maximum at 0.3mol and decreased when exceeding 0.65mol. Finally, the effect of annealing temperature on photoluminescence was also obtained.

Spin and chirality effects in antler-topology processes at high energy $$\varvec{e^+e^-}$$ colliders

We perform a model-independent investigation of spin and chirality correlation effects in the antler-topology processes $e^+e^-\to\mathcal{P}^+\mathcal{P}^-\to (\ell^+ \mathcal{D}^0) (\ell^-\mathcal{\bar{D}}^0)$ at high energy $e^+e^-$ colliders with polarized beams. Generally the production process $e^+e^-\to\mathcal{P}^+\mathcal{P}^-$ can occur not only through the $s$-channel exchange of vector bosons, $\mathcal{V}^0$, including the neutral Standard Model (SM) gauge bosons, $\gamma$ and $Z$, but also through the $s$- and $t$-channel exchanges of new neutral states, $\mathcal{S}^0$ and $\mathcal{T}^0$, and the $u$-channel exchange of new doubly-charged states, $\mathcal{U}^{--}$. The general set of (non-chiral) three-point couplings of the new particles and leptons allowed in a renormalizable quantum field theory is considered. The general spin and chirality analysis is based on the threshold behavior of the excitation curves for $\mathcal{P}^+\mathcal{P}^-$ pair production in $e^+e^-$ collisions with longitudinal and transverse polarized beams, the angular distributions in the production process and also the production-decay angular correlations. In the first step, we present the observables in the helicity formalism. Subsequently, we show how a set of observables can be designed for determining the spins and chiral structures of the new particles without any model assumptions. Finally, taking into account a typical set of approximately chiral invariant scenarios, we demonstrate how the spin and chirality effects can be probed experimentally at a high energy $e^+e^-$ collider.

Mechanical Vibration Remote Laboratory Development using iLab Shared Architecture

This paper focuses on the implementation of the first remote laboratory in the mechanical field being used by the Higher Institute of Industrial Systems of Gabès (ISSIG)-Gabès University, Tunisia. The developed remote laboratory is achieved thanks to the e-Sience Tempus project. The control system for this remote laboratory was implemented using LabVIEW software. The experiment studies the forced vibrations system. The students access our platform via the internet to determine the resonance frequency of damping forced vibration from the amplitude vs. excitation frequency and the phase angle vs. excitation curves. The students also determined the damping ration for system via phase angle vs. excitation frequency curve. All online experiments were deployed on the interactive version of iLab Shared Architecture (ISA).

A new self-activated vanadate phosphor of Na2YMg2(VO4)3 and luminescence properties in Eu3+ doped Na2YMg2(VO4)3

A novel self-activated vanadate phosphor of Na2YMg2(VO4)3 was prepared using a sol–gel method. Phase formation was verified through X-ray diffraction studies. Luminescence characteristics such as photoluminescence excitation, emission spectra and decay curves were investigated. This host can be efficiently excited by ultraviolet (UV) light, and exhibits an intense green emission band in the regions from 400nm to 750nm with maximum at about 521nm, originating from VO43- groups. The band gap energy of Na2YMg2(VO4)3 is estimated to be an approximate value of 2.95eV by UV–visible absorption spectra. Intensities of host and Eu3+ emissions and their decay curves depend on Eu3+ doping concentration. Various luminescent colors, including warm white, can be easily tuned by adjusting concentrations. Spectrum analysis showed that energy transfer from host to Eu3+ ions occurred with low efficiency. Luminescence properties of as-prepared materials indicate to be as a potential candidate for application in near-UV exciting white LEDs.

Core-excitation from excited triplet states of organic molecules: X-ray absorption spectra and doubly excited potential curves

SynopsisSoft X-ray absorption spectra of the lowest excited triplet states of several organic molecules (quinones, benzaldehydes, and other carbonyls) and potential curves of valence- and core- doubly excited states are calculated for the O 1s region.

Influence of spinal cord lesion level and severity on H-reflex excitability and recovery curve.

Changes in spinal reflexes can result from alterations in the spinal cord and descending pathways. We studied whether H-reflex excitability and its recovery depend on the level and/or severity of spinal cord injury (SCI). The soleus Hmax and Mmax responses and the H-reflex recovery curve (HRC) at interstimulus intervals (ISIs) ranging from 50 to 1,000 ms were recorded in 38 SCI individuals and 18 healthy subjects. Amplitude of Mmax correlated with level and severity of lesion (smaller amplitude correlated with more severe SCI or with more caudal lesion). Hmax/Mmax correlated only with age in the SCI group. HRC was increased significantly in complete SCI at ISIs < 500 ms and in incomplete SCI at ISIs > 200 ms with respect to healthy subjects. The changes in spinal reflexes as measured by the H-reflex and its recovery curve after SCI depend on the severity, but not on the level of the lesion.

Efficient Quantum Cutting in Tb3+/Yb3+ Codoped $\alpha $ -NaYF4 Single Crystals Grown by Bridgman Method Using KF Flux for Solar Photovoltaic

Tb <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> /Yb <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> codoped α-NaYF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> single crystals with various Yb <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> concentrations and ~0.40 mol% Tb <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> are grown by Bridgman method using KF (Potassium fluoride) as flux with a temperature gradient of 70 °C/cm-90 °C/cm across the solid-liquid interface. The effect and mechanisms of KF in the growing process are studied. The crystal structure is characterized by means of XRD. The high transmission from 300 to 7350 nm and maximum phonon energy about 390 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> for the α-NaYF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> single crystal are obtained from the measured transmission and Raman spectra, respectively. The luminescent properties of the crystals are investigated through excitation, emission spectra, and decay curves. Downconversion with emission of two near-infrared photons about 1000 nm for each blue photon at 486-nm absorption is obtained in Tb <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> /Yb <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> codoped α-NaYF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> single crystals. Moreover, the energy transfer processes is studied based on the Inokuti-Hirayama model from the measured luminescent decay curves, and the results indicated that the interaction between Tb <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> and Yb <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> is electric dipole-dipole. The maximum quantum cutting efficiency approached 174.6% in α-NaYF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> single crystal with 0.42 mol% Tb <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> and 9.98 mol% Yb <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> , making it a potential candidate for applications in silicon-based solar cells.

Investigation on the precision cropping system with high-speed and centrifugal action

In view of the special shape of V-shaped notch on metal bar in course of low-stress bending blanking, a new-type of cropping method, which is a precision cropping system with high-speed and centrifugal action, is proposed by introducing the crack controlled expansion and the centrifugal technology into the low-stress blanking. The working principle of the cropping method is introduced, and the calculation method of critical initial loading force acted on the metal bar is given. By means of ADAMS software, the movement characteristic of the slide block is obtained. Based on the characteristic of low-stress blanking, five types of excited frequency control curves are designed and applied in the cropping experiments and influences of these control curves on the cropping cross-section quality and the cropping time are analyzed in detail. The cropping experimental results show that 1/2 cosine decrease control curve, by which the high-quality cross section is obtained and the cropping time is reduced to 3 s, is an ideal control mode compared with other control modes mentioned in this paper. Finally, influence of geometric parameters of V-shaped notch on the cropping time is analyzed and the ideal combination of geometric parameters of V-shaped notch is also determined.

Growth and spectral properties of Ho3+ doped α-NaYF4 single crystal

Ho3+ doped α-NaYF4 single crystal with size of ∼∅10mm×100mm was grown by an improved Bridgman method using KF as flux with the molar composition of raw materials NaF: KF: YF3: HoF3=30: 18: 51: 1. The X-ray powder diffraction, transmission spectrum from 2500nm to 8000nm, absorption spectrum, emission spectrum by 640nm excitation and fluorescence decay curves at 1190nm and 2040nm of the obtained single crystal were detected. The Judd–Oflet theory was applied to calculate the Judd–Oflet intensity parameters Ω2,4,6, radiative transition rate, branching ratio, radiative lifetime according to its measured absorption spectrum. The calculated maximum emission cross section by McCumber theory of Ho3+ doped α-NaYF4 crystal for ∼1.2μm and ∼2.0μm reached 0.42×10−20cm2 and 0.69×10−20cm2, respectively. The gain cross section spectra were calculated based on the absorption and emission cross section spectra. In the meantime, the fluorescent lifetime at 1190nm and 2040nm were also estimated to be 3.21ms and 18.12ms from their decay curves. The Ho3+ doped α-NaYF4 single crystal with ∼90% high transmittance in wide range of 300–8000nm and long lifetime of fluorescence may be considered as a potential candidate for applications in mid-infrared optical devices.

Near-infrared quantum cutting in Nd^3+ and Yb^3+ Doped BaGd_2ZnO_5 phosphors

Nd3+ and Yb3+ doped BaGd2ZnO5 phosphors were synthesized via high temperature solid-state method. The composition and structure have been investigated by the X-ray powder diffraction. The near-infrared quantum cutting for BaGd2ZnO5: Nd3+, Yb3+ is proved by the visible and near-infrared excitation, emission spectra and decay curves. Upon 359 nm excitation, visible and near-infrared emission of Nd3+ decrease with Yb3+ concentration increasing, and the intensities of 978 nm near-infrared emission of Yb3+ increase firstly and then decrease because of concentration quenching. The corresponding quantum cutting mechanism has been discussed through the energy level diagram. The maximum energy transfer efficiency calculated approaches 31.9%. Furthermore, the quenching concentration of Yb3+ is 7%. This study has prospect to be applied in the silicon-based solar cells to progress the conversion efficiency.

Cross-section measurement for the 206Pb(n, α)203Hg reaction induced by neutrons around 14 MeV

The cross section for the 206Pb(n, α)203Hg reaction has been measured in the neutron energy range of 13.5–14.7MeV using the activation technique and a coaxial HPGe γ-ray detector. The cross-section data of the 206Pb(n, α)203Hg reaction which are scaled to the evaluated values of the 93Nb(n, 2n) 92mNb reaction are reported to be 0.99±0.07, 1.23±0.11, and 1.39±0.12mb at 13.5±0.2, 14.4±0.2, and 14.7±0.2MeV incident neutron energies, respectively. The results are discussed and compared with experimental data found in the literatures, with the results of published empirical formulae and the evaluated values of the databases. The comparison shows that the value of our excitation curve at 14.5MeV is close to the estimation obtained from the published empirical formula based on the statistical model with dependence on the Q-value and odd–even effect taken into consideration.