Energy Loss Measurements Research Articles

Synthesis of yellow persistent phosphor garnet by mixed fuel solution combustion synthesis and its characteristic

Persistent phosphor Gd3Al2Ga3O12:Ce3+-Cr3+ (GAGG:Ce3+-Cr3+) has been synthesized by solution combustion synthesis (SCS) incorporating mixed organic fuels of glycine and urea at 773 K. Using only single fuel can lead to incomplete combustion and amorphous products. Without additional heat treatment, a porous and pulverized GAGG:Ce3+-Cr3+ powders can be obtained when the fuel ratio ϕ = 1. The products exhibited yellow color emission in visible light photoluminescence. This emission is originated from Ce3+. Photoluminescence excitation spectra indicated that GAGG:Ce3+-Cr3+ can be well excited by blue light, marking its potential for white LED lights application. In comparison with green luminescence Y3Al2Ga3O12 doped with Ce3+-Cr3+ (YAGG:Ce3+-Cr3+), the yellow color in GAGG:Ce3+-Cr3+ is due to crystal field splitting when Y is substituted by Gd. Also, electron energy-loss spectroscopy measurement using scanning electron microscopy (STEM-EELS) showed that the band gap decreased in 6.14 eV, 6.05 eV and 5.93 eV order when Ga content (x = 2.5, 3, 3.5) increased. The bandgap change showed that the trap level produced by Cr3+ ions affected the persistent luminescence. In this study, when Ga content x = 3, Gd3Al5-xGaxO12:Ce3+-Cr3+ exhibited the longest persistent luminescence.

Influence of the structure of cylindrical mobile flumes on hydraulic performance characteristics in U-shaped channels

Small U-shaped channels are widely used in irrigation districts. Accurate flow measurement in U-shaped channels is an important aspect to field water management. In open channels, mobile flumes are widely used for flow measurement because of many advantages such as low cost, no sedimentation and moveable. However, how the structure of the flume influences hydraulic performance is still unclear. The principles for designing or optimizing mobile flumes are also lacking. In this study, FLOW-3D software was used to numerically simulate the flow pattern of three cylindrical mobile flumes that are most often used in U-shaped channels, including circular cylinder, elliptical cylinder and V-tailed cylinder mobile flumes. The hydraulic characteristics including backwater height, energy loss and flow measurement accuracy were analyzed. The results showed that under the same working conditions, the fluctuations of the stagnation point depth in the elliptical flume were the smallest. The backwater height and the energy loss in the V-tailed flume were the lowest. The contraction section of the cylinder could be designed as a curve with large curvature to make the upstream water flow more stable. The diffusion section could be designed as V-tail to improve flow pattern and reduce energy loss. Under a safe backwater height, the throat length could be increased to improve the submergence degree.

Energy loss of laser-accelerated ions in dense ionized matter

SynopsisKnowledge about the energy loss of heavy ion in dense ionized matter is of great importance in fields such as inertial confinement fusion, fast ignition as well as intense heavy ion beam driven high energy density physics. The energy loss of 3.4 MeV proton in TAC foam plasma was measured on the XGIII laser facility. It was found that the measured energy loss is far above the Beth prediction.

Exergetic Analysis of a Refrigeration System with Mechanical Vapors Compression

The main purpose of this study is to improve the energy efficiency of a refrigerated facility by means of exergetic analysis. In order to achieve this goal, we have evaluated the input exergy flows of the whole system to deduce the exergetic yields, which are compared to the degree of irreversibility in order to have a qualitative measurement of energy losses. The concept of exergy is the part of energy that is virtually converted into work. The exergetic analysis was performed on a refrigeration unit ZR22K3E Copeland Scroll. The results of this analysis are consistent with the condition, that the exergetic performance, which is: 36.57% and it is approximately equal to the degree of irreversibility which is 37.50%. This approach provides a comprehensive, standard and rigorous framework for the analysis of energy systems, and thus for the understanding and systemic management of the energy challenge.

Production and characterization of thin, self-supporting Si foils for use as targets in radioactive beam experiments

Development of thin, self-supporting silicon foils (both natural and isotopically-enriched) for use as targets in reaction studies with radioactive beams is detailed. Foils with a thickness of ∼220μg/cm2 were produced using vapor deposition and were floated onto aluminum frames with 10–15 mm diameter holes. During their production, the foil thickness was measured using a quartz crystal monitor. Subsequently, the foil thickness was characterized by α particle energy loss measurements and Rutherford backscattering (RBS). These measurements demonstrated that the thickness could be determined to within a 0.5% uncertainty. The elemental purity of the foils was assessed using RBS and X-ray photoelectron spectroscopy. This analysis demonstrated that the foils have 87%–90% silicon abundance.

Anisotropic plasmons due to carrier electrons in Cs-doped hexagonal WO3 studied by momentum transfer resolved electron energy-loss spectroscopy

Cs-doped hexagonal WO3 (CWO) is used as a solar heat-shielding material for windows, in which plasma oscillation due to carrier electrons (carrier plasmon) plays an important role for near infrared scattering. Despite the hexagonal crystal structure of CWO, the anisotropic properties of the carrier plasmons have not been investigated. This study reports the momentum transfer resolved electron energy-loss spectroscopic measurements of CWO to investigate the anisotropic properties of carrier plasmons. The experimental results clarified that the two plasma oscillation modes at 1.2 and 1.8 eV have different excitation properties in CWO. One plasma oscillation at 1.2 eV was excited for q along the ab plane with a large damping effect, which indicated that electron excitations occur for the q//ab plane. Another mode at 1.8 eV was an oscillation excited for q along the c-axis with a small damping effect, i.e., a long plasmon relaxation time. These two modes can be interpreted by the anisotropic energy dispersion of the electronic states around the Fermi level of CWO. Such anisotropic properties of the carrier plasmons led to an accurate understanding of the heat-shielding mechanism.

Metallic edge states in zig-zag vertically-oriented MoS2 nanowalls

The remarkable properties of layered materials such as MoS2 strongly depend on their dimensionality. Beyond manipulating their dimensions, it has been predicted that the electronic properties of MoS2 can also be tailored by carefully selecting the type of edge sites exposed. However, achieving full control over the type of exposed edge sites while simultaneously modifying the dimensionality of the nanostructures is highly challenging. Here we adopt a top-down approach based on focus ion beam in order to selectively pattern the exposed edge sites. This strategy allows us to select either the armchair (AC) or the zig-zag (ZZ) edges in the MoS2 nanostructures, as confirmed by high-resolution transmission electron microscopy measurements. The edge-type dependence of the local electronic properties in these MoS2 nanostructures is studied by means of electron energy-loss spectroscopy measurements. This way, we demonstrate that the ZZ-MoS2 nanostructures exhibit clear fingerprints of their predicted metallic character. Our results pave the way towards novel approaches for the design and fabrication of more complex nanostructures based on MoS2 and related layered materials for applications in fields such as electronics, optoelectronics, photovoltaics, and photocatalysts.

Neutron Time-of-Flight Measurements of Charged-Particle Energy Loss in Inertial Confinement Fusion Plasmas.

Neutron spectra from secondary ^{3}H(d,n)α reactions produced by an implosion of a deuterium-gas capsule at the National Ignition Facility have been measured with order-of-magnitude improvements in statistics and resolution over past experiments. These new data and their sensitivity to the energy loss of fast tritons emitted from thermal ^{2}H(d,p)^{3}H reactions enable the first statistically significant investigation of charged-particle stopping via the emitted neutron spectrum. Radiation-hydrodynamic simulations, constrained to match a number of observables from the implosion, were used to predict the neutron spectra while employing two different energy loss models. This analysis represents the first test of stopping models under inertial confinement fusion conditions, covering plasma temperatures of k_{B}T≈1-4 keV and particle densities of n≈(12-2)×10^{24} cm^{-3}. Under these conditions, we find significant deviations of our data from a theory employing classical collisions whereas the theory including quantum diffraction agrees with our data.

First AMS measurements of 60Fe/Fe isotopic ratios at the Cologne 10 MV tandem accelerator

The measurement capabilities of the new accelerator mass spectrometry (AMS) system at the 10 MV FN tandem accelerator of CologneAMS has been extended with AMS measurements of 60Fe/Fe in the range of 10-8, 10-10 and 10-12. The measurements were conducted combining a 135° gas-filled magnet and a subsequent energy loss measurement in a 5 anode gas ionization chamber. This technique allows a good separation of the stable isobar 60Ni resulting in a suppression by a factor of 107 for the high energy mass spectrometer. With this a limit for the background level of 7·10-14 was achieved. The calculation of the error normalized sensitivity allowed a first comparison to other AMS laboratories.

Solar-Blind Self-Powered Photodetector Using Solution-Processed Amorphous Core–Shell Gallium Oxide Nanoparticles

Solution-processed deep ultraviolet (DUV) photodetectors based on wide band gap oxide semiconductors (WBGS) working in the <280 nm wavelength range are drawing increasing attention of the research community because of their cost-effective production and potential use in diverse applications. Here, we report on the synthesis of novel core-shell amorphous gallium oxide nanoparticles (NPs) (a-Ga2Ox/GaOx NPs) that have not been previously obtained. The amorphous gallium oxide NPs were synthesized from gallium nitride using the femtosecond laser ablation in liquid technique. Transmission electron microscopy and electron energy-loss spectroscopy measurements revealed the amorphous NP nature with a Ga-rich core and oxide-rich shell. Optical properties of these core-shell amorphous gallium oxide NPs were investigated by time-resolved spectroscopy and photoluminescence. As a proof of concept, the amorphous gallium oxide NPs were used as an active layer in a solar-blind DUV photodetector with high responsivity (778 mA/W) at 244 nm, which is the highest responsivity recorded to date for any solution-processed DUV photodetector. This work on a high-performance solution-processed device paves the way for large-scale industrial application of the WBGS.

Assessing the potentiality of the 250kV-SSAMS for stopping power measurements at low energies

Abstract Since 2012, a compact 250 kV Single Stage accelerator (250 kV-SSAMS) has been installed at Instituto de Fisica, Universidade Federal Fluminense, for radiocarbon analysis of natural samples. The system presents two magnets, for mass selection prior and post the gas stripper, and an electrostatic spherical analyzer (ESA). The overall performance of the machine makes it suitable for experimental researches in atomic collisions, in particular for studies of the stopping power of atomic projectiles at energies below 25 keV/u. Here we report on the energy loss measurements of 12C + and 16O + ions in a thin carbon foil at energies in the range of 10 to 25 keV/u. Energies of the ions after the foil are determined from the high-voltage applied to the ESA in order to recover the maximum intensity reading in a Faraday Cup (FC) after the ESA. Energies of the ions after the foil are determined from the high-voltage applied to the ESA. With this technique, experimental data for the stopping power within a precision of about 0.5%.

Measurements of 252Cf fission product energy loss through thin silicon nitride and carbon foils, and comparison with SRIM-2013 and MCNP6.2 simulations

Gas ionization detectors are very widely used for radiation detection and measurement, but for external sources an entrance window is used which can reduce particle energy. For heavy ions this energy loss can be significant enough to affect measurements and very thin windows, such as those composed of silicon nitride (SiN), may be utilized to minimize this effect. For fission spectroscopy, carbon conversion foils are also common in measurements. In the current work, energy losses were measured for 252Cf spontaneous fission products passing through thin foils of carbon and of silicon nitride. The foils ranged in from 22.5 to 131.0 µg/cm2 for C and from 56.4 to 402.2 μg/cm2 for SiN. For comparison, simulations were performed with the TRIM program in SRIM-2013 and with MCNP6.2. To understand calculation differences, effective charge from partial ionization was predicted by several methods and compared with results directly using the Bethe stopping power formula.

High-Efficiency Dual-Frequency Reflective Linear Polarization Converter Based on Metasurface for Microwave Bands

A dual-broadband and high-efficiency reflective linear polarization converter based on an anisotropic metasurface is presented. The device consists of two symmetrical, double-slotted metallic split-rings and one criss-cross structure, a dielectric layer, and a completely reflective metallic ground. The converter exhibits four resonances and can near-perfectly convert x- or y-polarized incident waves into cross-polarized waves in the frequency ranges of 9.38–13.36 GHz and 14.84–20.36 GHz. The polarization conversion ratios (PCRs) of the two bands are 98.21% and 99.32%, respectively. The energy conversion ratio (ECR) for energy loss measurement is almost 100% in these frequency bands. The polarization conversion principle is studied. The bandwidths and PCRs of the two bands are determined by varying the dielectric layer thickness. The simulation results are consistent with experimental observations. The designed dual-broadband and high-efficiency metasurface has great potential in the application of electromagnetic polarization control.

Use of Polarization Curves to Determine Kinetics Parameters in K–O2 batteries

Metal–O2 batteries have shown great potential as energy storage devices and are foreseen as one of the potential successors to lithium ion batteries. Unlike either batteries or fuel cells, however, metal-O2 batteries form an insoluble product that diminishes cathode capacity. Cathode capacity is related to the electrochemically-accessible surface area and product accumulation results in a loss of that surface area, which then contributes to the total overpotential during discharge. While typically used to determine the effect of varying load levels on the performance of energy producing devices (i.e. batteries, fuel cells), polarization, or current-potential, measurements are also an indirect measure of the different energy losses that contribute to the total overpotential associated with a particular redox process. Each region of the curve is affected by a specific overpotential that is dominant within a certain potential range. Polarization curves therefore allow for the determination of certain properties that are important for understanding and improving the performance of electrochemical energy devices. As shown in Figure 1, the short steep, but curving, slope at the start of the current-potential curve is attributed to the activation overpotential, which is the energy required to overcome the potential barrier associated with the discharge reaction. The overpotential responsible for the long sloping line is attributed to the ohmic resistance, which is dominated by electrolyte resistance. Finally, the limiting current—sharp decline in the cell potential at higher current densities—is generally attributed to mass-transfer limitations. Using derived analytical expressions, essential kinetic parameters have been determined for fuel cells from the data obtained from polarization analyses.1,2 Proceeding from that previous work involving fuel cells, analytical expressions were derived that can be applied to the data obtained from polarization analyses of metal-O2 batteries. Due to the unique single-electron redox process (K+ + O2 + e− → KO2) in the cathode (oxygen) electrode, the K–O2 superoxide battery provided an ideal case for developing and evaluating those expressions.3,4 Polarization analyses were performed on K–O2 batteries and the data obtained was evaluated using the derived expressions to determine kinetic values essential to the operation and performance of the K–O2 battery.

Evaluation of hemodynamics in patients with hypertrophic cardiomyopathy by vector flow mapping: Comparison with healthy subjects.

The present study investigated the role of energy loss assessed by vector flow mapping (VFM) in patients with hypertrophic cardiomyopathy (HCM). VFM analysis was performed in 42 patients with HCM and in 40 control subjects, which were matched for age, sex and left ventricular (LV) ejection fraction. The intra-LV and left atrial blood flow were obtained from the apical 3-chamber view, and the energy loss (EL) during the systolic and diastolic phases was calculated. The measurements were averaged over three cardiac cycles and indexed to body surface area. Compared with the controls, the left ventricular energy loss (LVEL)-total value was significantly decreased in patients with HCM during the diastolic phase (P1, P2 and P3; all P<0.05). A tendency for increased systolic LVEL-total values was observed in the patients with HCM compared with the controls (P>0.05). LVEL-base values were decreased in the patients with HCM during P1 and P2 (slow filling time). Compared with the controls, patients with HCM had lower LVEL-mid values during the diastolic phases (P0, P1, P2 and P3; all P<0.05). However, the LVEL-mid value of patients with HCM was higher compared with that of the controls during systolic P5 (P<0.05). LVEL-apex was decreased in patients with HCM during P0, P2 and P3. Compared with the controls, the left atrial energy loss (LAEL) of all three phases in patients with HCM were lower (each P<0.01). The diastolic LVEL values were significantly lower in patients with HCM compared with the controls; however, the systolic LVEL levels tended to be higher in HCM. The LAEL of the reservoir phase, conduit phase and atrial systolic phase were decreased in HCM compared with controls. The present study demonstrated that measurement of EL by VFM is a sensitive method of determining subclinical LV dysfunction in patients with HCM. The value of EL has been considered to be a quantitative parameter for the estimation of the efficiency of intraventricular blood flow.

AGILE development and silicon detector

In the years 1980s and 1990s, a very fast and important progress on position and energy loss measurements of elementary particles was obtained by the use of Si strip detector in high energy (HE) experiments. The number of strips has been increasing at any improvement of the tracker device. The high number of strip density also pushed the power reduction of the readout electronic amplifiers. The Si tracker became at certain moment a challenging substitute of the classical spark chambers (Fichtel et al. NASA-TM-X-70761, 1995; Thompson arXiv:e:0811.0738, 2008), in use for tracking particles in space experiments. In particular in HE $$\gamma $$-strophysics, the photon direction was derived by measuring that of the positron electron pair produced in high Z material interlaid in the planes of the spark chamber. See for instance the EGRET figure in the text. AGILE and GLAST (renamed Fermi after launch) are the most successful examples of the Si revolution.

Theory of momentum-resolved phonon spectroscopy in the electron microscope

We provide a theoretical framework for the prediction and interpretation of momentum dependent phonon spectra due to coherent inelastic scattering of electrons. We complete the approach with first principles lattice dynamics using periodic density functional theory and compare to recent electron energy loss measurements on cubic and hexagonal boron nitride performed within a scanning transmission electron microscope (STEM). The combination of theory and experiment provides the ability to interpret momentum dependent phonon spectra obtained at nanometer spatial resolution in the electron microscope.

Energy Losses in Soft Magnetic Materials Under Symmetric and Asymmetric Induction Waveforms

Magnetic losses under triangular symmetric and asymmetric induction waveforms have been measured over a broad range of frequencies and predicted starting from standard results obtained with sinusoidal induction. Nonoriented Fe-Si and Fe-Co sheets, nanocrystalline Finemet–type ribbons, and Mn-Zn ferrites have been investigated up to f = 1 MHz and duty cycles ranging between 0.5 and 0.1. The intrinsic shortcomings of the popular approach to loss calculation of inductive components in power electronics, based on the empirical Steinmetz equation and its numerous modified versions, are overcome by generalized application of the statistical theory of losses and the related concept of loss separation. While showing that this concept applies both to ferrites and metallic alloys and extracting the hysteresis (quasi-static), excess, and classical loss components, we relate in a simple way the magnetic energy losses under symmetric triangular induction (square wave voltage) and sinusoidal induction. The loss behavior under asymmetric triangular induction is retrieved from the symmetric one, by averaging the energy losses pertaining to the two different semiperiods. Good comparison with the experimentally measured energy loss versus frequency behavior is demonstrated in all materials.

Energy loss measurements of inclined muon bundles in the Cherenkov water detector

An experiment on the measurements of the energy deposit of inclined cosmic ray muon bundles is being conducted at the experimental complex NEVOD (MEPhI). The complex includes the Cherenkov water calorimeter with a volume of 2000 m3 and the coordinate-tracking detector DECOR with a total area of 70 m2. The DECOR data are used to determine the local muon densities in the bundle events and their arrival directions, while the energy deposits (and hence the average muon energy loss) are evaluated from the Cherenkov calorimeter response. Average energy loss carries information about the mean muon energy in the bundles. The detection of the bundles in a wide range of muon multiplicities and zenith angles gives the opportunity to explore the energy range of primary cosmic ray particles from about 10 to 1000 PeV in the frame of a single experiment with a relatively small compact setup. Experimental results on the dependence of the muon bundle energy deposit on the zenith angle and the local muon density are presented and compared with expectations based on simulations of the EAS muon component with the CORSIKA code.

Non Rutherford elastic scattering to measure energy loss of H2 ions in aluminium

In this contribution, the presence of vicinage effects is demonstrated for H2+ ions slowing down in 20 nm thick aluminium target, using the 1.735 MeV resonance of 12C(p, p)12C elastic scattering. The stopping power ratio is deduced from the measured Elastic Backscattering Spectrometry (EBS) energy spectra of H+ and H2+ ions using the simulation code IBA DataFurnace. An enhancement of 30% is found in the energy loss of the H2+ ions as compared to the atomic ones. The influence of the Coulomb explosion on the energy loss straggling was also examined. This is evaluated for 100 nm thick target by adjusting the energy loss and the straggling parameters while processing the experimental data. A theoretical treatment, based on the Lindhard dielectric formalism generalized by N.R. Arista to molecular ions, was used to calculate the stopping power ratio for aluminium for comparison.