Standard Foil Research Articles

Augmentation of the step-by-step Energy-Scanning EXAFS beamline BL-09 to continuous-scan EXAFS mode at INDUS-2 SRS

An innovative scheme to carry out continuous-scan X-ray absorption spectroscopy (XAS) measurements similar to quick-EXAFS mode at the Energy-Scanning EXAFS beamline BL-09 at INDUS-2 synchrotron source (Indore, India), which is generally operated in step-by-step scanning mode, is presented. The continuous XAS mode has been implemented by adopting a continuous-scan scheme of the double-crystal monochromator and on-the-fly measurement of incident and transmitted intensities. This enabled a high signal-to-noise ratio to be maintained and the acquisition time was reduced to a few seconds from tens of minutes or hours. The quality of the spectra (signal-to-noise level, resolution and energy calibration) was checked by measuring and analysing XAS spectra of standard metal foils. To demonstrate the energy range covered in a single scan, a continuous-mode XAS spectrum of copper nickel alloy covering both Cu and Ni K-edges was recorded. The implementation of continuous-scan XAS mode at BL-09 would expand the use of this beamline in in situ time-resolved XAS studies of various important systems of current technological importance. The feasibility of employing this mode of measurement for time-resolved probing of reaction kinetics has been demonstrated by insitu XAS measurement on the growth of Ag nanoparticles from a solution phase.

Near Zero Volt Tolerant Lithium Ion Cells: Benefits for Safe Storage, Shipping, and Medical Implants

There are inherent safety risks associated with lithium ion batteries leading to greater restrictions and regulations on shipping and inactive storage. Maintaining the cell(s) of a lithium ion battery at a near zero voltage with an applied fixed load is one promising approach which can lessen (and potentially eliminate) the risk of entering thermal runaway when in an inactive state. However, a near zero lithium ion cell voltage can be damaging if the anode potential increases to above ~3.1 V vs. Li/Li+ where dissolution of the anode copper current collector and other side reactions occur. Approaches using alternative anode current collectors (e.g. titanium) which are stable at higher electrochemical potentials vs. Li/Li+ have had success in mitigating anode substrate dissolution during storage of cells at near zero voltage. However, several anticipated tradeoffs exist with titanium current collectors including increased foil thickness, increased cost, and lower bulk conductivity compared to standard copper foils. An alternative approach to prevent copper current collector dissolution during near zero volt storage is to ensure that the anode electrochemical potential remains less than the copper dissolution potential during near zero volt storage. Past approaches to achieve this have included secondary electrode active materials with intermediate discharge potentials and high first cycle loss cathode additives. However, addition of secondary active materials or additives to the electrodes that may not contribute to the discharge energy of the cell during normal cycling will reduce cell energy density. Additionally, secondary materials may have other operational concerns such as gassing or instability in the operational potential range of the electrode they are added to. In the present work, the anode potential of a lithium ion cell is maintained less than the copper dissolution potential during near zero volt storage using anode pre-lithiation prior to cell assembly. Specifically, pouch cells were fabricated with a LiCoO2 cathode and a mesocarbon microbead (MCMB) anode that was cycled and partially pre-lithiated with active lithium. Three electrode tests with a lithium metal reference and 1.2 M LiPF6 3:7 EC:EMC electrolyte showed that the electrochemical potential of the anode is less than the copper dissolution potential throughout a multiple day near zero volt storage period. Specifically, during the transient period of cell discharge to near zero volts under fixed load over the course of several hours, the anode potential is <1.9 V vs. Li/Li+. After the cell reaches near zero volts and a quasi-equilibrium state, the electrochemical potential that the electrodes asymptote to, the electrode asymptotic potential (EAP), is ~1.9 V vs. Li/Li+ which is less than the copper dissolution potential. The LiCoO2:MCMB pouch cell maintained 99% of its original capacity and average discharge voltage after three, 3-day storage periods at near zero volts cell voltage under fixed load at room temperature. In a second demonstration, a LiCoO2/MCMB cell with a pre-lithiated anode was stored for 7-day periods under a fixed load at near zero volts. The cell maintained 99% of its original capacity and average discharge voltage after three, 7-day storage periods at near zero volts cell voltage at room temperature. A third LiCoO2/MCMB cell with a pre-lithiated anode maintained >99% of its discharge capacity after a 3-day near zero volt storage period under fixed load at 45 °C. High temperature tolerance could impact the reliability of cells in medical implants, which can be inadvertently overdischarged due to patient non-compliance. Lowering the transient period anode potential and EAP of a cell with anode pre-lithiation is an emerging concept to achieve lithium ion cells with high tolerance to storage at near zero voltage at room temperature and elevated temperatures. The demonstrated cell modifications to achieve this performance utilized conventional materials and required no change of typical cell construction parameters. Thus, anode pre-lithiation is an attractive design for near zero volt storage-tolerant lithium ion cells.

ALD Protection of Li‐Metal Anode Surfaces – Quantifying and Preventing Chemical and Electrochemical Corrosion in Organic Solvent

Chemical and electrochemical instability of the Li metal interface with organic solvent has been a major impediment to use of Li‐metal anodes for next‐generation batteries. Here the character of Li surface degradation and the application of atomic layer deposition (ALD) as a protection layer to suppress the degradation are addressed. Using standard Li foil samples in organic solvent with and without in situ deposited ALD Al2O3 protective layers, results from in situ atomic force microscopy, mass spectrometry (including differential electrochemical mass spectrometry), X‐ray Photoelectron Spectroscopy (XPS), and ex situ scanning electron microscopy/energy dispersive X‐ray spectroscopy are reported. Despite the presence of a thin oxide/hydroxide/carbonate layer on the Li foil surface, degradation readily occurs in organic solvent, particularly at surface features such as ridges. Introduction of the ALD protective layer – deposited directly on this Li foil surface – dramatically suppresses the degradation.

A novel carbon coating technique for foil bolometers.

Naked foil bolometers can reflect a significant fraction of incident energy and therefore cannot be used for absolute measurements. This paper outlines a novel coating approach to address this problem by blackening the surface of gold foil bolometers using physical vapour deposition. An experimental bolometer was built containing four standard gold foil bolometers, of which two were coated with 100+ nm of carbon. All bolometers were collimated and observed the same relatively high temperature, ohmically heated plasma. Preliminary results showed 13%-15% more incident power was measured by the coated bolometers and this is expected to be much higher in future TCV detached divertor experiments.

Activation cross sections of longer-lived radionuclides produced in germanium by alpha particle irradiation

The cross sections of alpha particles induced nuclear reactions on natural germanium were investigated by using the standard stacked foil target technique, the activation method and high resolution gamma spectrometry. Targets with thickness of about 1μm were prepared from natural Ge by vacuum evaporation onto 25μm thick polyimide (Kapton) backing foils. Stacks were composed of Kapton-Ge-Ge-Kapton sandwich target foils and additional titanium monitor foils with nominal thickness of 11μm to monitor the beam parameters using the natTi(α,x)51Cr reaction. The irradiations were done with Eα=20.7 and Eα=51.25MeV, Iα=50nA alpha particle beams for about 1h. Direct or cumulative activation cross sections were determined for production of the 72,73,75Se, 71,72,74,76,78As, and 69Ge radionuclides. The obtained experimental cross sections were compared to the results of theoretical calculations taken from the TENDL data library based on the TALYS computer code. A comparison was made with available experimental data measured earlier. Thick target yields were deduced from the experimental cross sections and compared with the data published before.

The hydrogen anomaly in neutron Compton scattering: new experiments and a quantitative theoretical explanation

No consensus has been reached so far about the hydrogen anomaly problem in Compton scattering of neutrons, although strongly reduced H cross-sections were first reported almost 20 years ago. Over the years, this phenomenon has been observed in many different hydrogen-containing materials. Here, we use yttrium hydrides as test objects, YH2, YH3, YD2 and YD3, Y(HxD1−x)2 and Y(HxD1−x)3, for which we observe H anomalies increasing with transferred momentum q. We also observe reduced deuteron cross-sections in YD2 and YD3 and have followed those up to scattering angles of 140° corresponding to high momentum transfers. In addition to data taken using the standard Au-197 foils for neutron energy selection, the present work includes experiments with Rh-103 foils and comparisons were also made with data from different detector setups.The H and D anomalies are discussed in terms of the different models proposed for their interpretation. The ‘electron loss model’ (which assumes energy transfer to excited electrons) is contradicted by the present data, but it is shown here that exchange effects in scattering from two or more protons (or deuterons) in the presence of large zero-point vibrations, can explain quantitatively the reduction of the cross-sections as well as their q-dependence. Decoherence processes also play an essential role. In a scattering time representation, shake-up processes can be followed on the attosecond scale. The theory also shows that large anomalies can appear only when the neutron coherence lengths (determined by energy selection and detector geometry) are about the same size as the distance between the scatterers.

Design, construction and characterization of a new neutron beam for neutron radiography at the Tehran Research Reactor

To obtain a thermal neutron beam for neutron radiography applications, a neutron collimator has been designed and implemented at the Tehran Research Reactor (TRR). TRR is a 5MW open pool light water moderated reactor with seven beam tubes. The neutron collimator is implemented in the E beam tube of the TRR. The design of the neutron collimator was performed using MCNPX Monte Carlo code. In this work, polycrystalline bismuth and graphite have been used as a gamma filter and an illuminator, respectively. The L/D parameter of the facility was chosen in the range of 150–250. The thermal neutron flux at the image plane can be varied from 2.26×106 to 6.5×106ncm−2s−1. Characterization of the beam was performed by ASTM standard IQI and foil activation technique to determine the quality of neutron beam. The results show that the obtained neutron beam has a good quality for neutron radiography applications.

Comparative Study of a New IR-absorbing Film to Improve Solar Shading and Thermal Comfort for ETFE Structures

Standard ETFE foils have a very high solar transmission. This can result in serious problems with overheating and also cause a high degree of thermal discomfort. A new material by Nowofol (Nowoflon ET 6235 Z-IR) uses a new approach: infra-red absorbing (solar IR). Another company is currently developing a multilayer film that maintains high visible light transmission while blocking infrared heat by reflection. Also, the authors are currently working on new options that are not only relying on printing, tinting or colouring of foils. Compared to the state of technology, the new material Nowoflon ET 2356 Z-IR will be examined to quantify their energy saving potential in different application scenarios including different climate zones by using dynamic thermal simulations. Also, the effect on thermal comfort will be investigated.

Pressure Response of Aanderaa and Sea-Bird Oxygen Optodes

AbstractThis study investigated the effect of hydrostatic pressure of up to 6000 dbar on Aanderaa and Sea-Bird oxygen optodes both in the laboratory and in the field. The overall pressure response is a reduction in the O2 reading by 3%–4% per 1000 dbar, which is closely linear with pressure and increases with temperature. Closer inspection reveals two superimposed processes with an opposite effect: an O2-independent pressure response on the luminophore that increases optode O2 readings and an O2-dependent change in luminescence quenching that decreases optode O2 readings. The latter process dominates and is mainly due to a shift in the equilibrium between the sensing membrane and seawater under elevated pressures. If only the dominant O2-dependent process is considered, then the Aanderaa and Sea-Bird optodes differ in their pressure response. Compensation of the O2-independent process, however, yields a uniform O2 dependence for Aanderaa optodes with standard foil and fast-response foil as well as for Sea-Bird optodes. A new scheme to calculate optode O2 from raw data is proposed to account for the two processes. The overall uncertainty of the optode pressure correction amounts to 0.3% per 1000 dbar, which is mainly due to variability between the sensors.

Synthesis of Large Area Graphene for High Performance in Flexible Optoelectronic Devices.

This work demonstrates an attractive low-cost route to obtain large area and high-quality graphene films by using the ultra-smooth copper foils which are typically used as the negative electrodes in lithium-ion batteries. We first compared the electronic transport properties of our new graphene film with the one synthesized by using commonly used standard copper foils in chemical vapor deposition (CVD). We observed a stark improvement in the electrical performance of the transistors realized on our graphene films. To study the optical properties on large area, we transferred CVD based graphene to transparent flexible substrates using hot lamination method and performed large area optical scanning. We demonstrate the promise of our high quality graphene films for large areas with ~400 cm2 flexible optical modulators. We obtained a profound light modulation over a broad spectrum by using the fabricated large area transparent graphene supercapacitors and we compared the performance of our devices with the one based on graphene from standard copper. We propose that the copper foils used in the lithium-ion batteries could be used to obtain high-quality graphene at much lower-cost, with the improved performance of electrical transport and optical properties in the devices made from them.

New data on cross-sections of deuteron induced nuclear reactions on gold up to 50 MeV and comparison of production routes of medically relevant Au and Hg radioisotopes

Investigations of cross-sections of deuteron induced nuclear reactions on gold were extended up to 50MeV by using the standard stacked foil irradiation technique and high resolution gamma-ray spectrometry. New cross-sections are reported for the 197Au(d,xn)197m,197g,195m,195g,193m,193gHg and 197Au(d,x)198m,198g,196m,196g,195,194Au nuclear reactions. The application for production of the medically relevant isotopes 198Au and 195m,195g,197m,197gHg is discussed, including the comparison with other charged particle induced production routes. The possible use of the 197Au(d,x)197m,197g,195m,193mHg and 196m,196gAu reactions for monitoring deuteron beam parameters is also investigated.

Assessing the feasibility of low temperature XAFS experiments at Indus-2, India: First results

In this work, we report installation of displex cryostat XAFS sample holder at XAFS beamline (BL-09) of Indus-2 synchrotron facility, India and make critical assessment of feasibility of low-temperature XAFS experiments in terms of data quality and reproducibility, temperature range, calibration and attainable resolution. We adopted the Debye Model-based calibration method by measuring XAFS of standard Au foil with known Debye temperature (ΘDebye)Autheory=165K. The data is of good quality and reproducible with international data. By fitting Debye Waller Factor (σexpt2(T)), we deduced (ΘDebye)Auexpt=163K which implies calibration within 2K. Error bars for σexpt2(T) correspond to temperature uncertainty ΔT≤5K, which defines the temperature resolution for low temperature XAFS experiments. Thus, from both calibration and resolution points-of-view, this work demonstrates the feasibility of low temperature XAFS experiments at BL-09, Indus-2. Feasibility of extending XAFS experiments to lower temperature and unknown samples is discussed.

Evaluation of the sensitivity and fatigue performance of embedded piezopolymer sensor systems in sandwich composite laminates

It has been claimed that embedding piezoceramic devices as structural diagnostic systems in advanced composite structures may introduce mechanical impedance mismatches that favor the formation of intralaminar defects. This and other factors, such as cost and their high strain sensitivity, have motivated the use of thin-film piezopolymer sensors. In this paper, we examine the performance of sandwich composite panels fitted with embedded piezopolymer sensors. Our experiments examine both how such thin-film sensors perform within a structure and how the inclusion of sensor films affects structural performance. Strain-controlled tests on sandwich panels subjected to three-point bending under wide-ranging static and dynamic strains lead us to conclude that embedding thin piezopolymer films has no marked reduction on the tensile strength for a wide range of strain loading paths and magnitudes, and that the resilience of the embedded sensor is itself satisfactory, even up to the point of structural failure. Comparing baseline data obtained from standard surface-mounted sensors and foil gauges, we note that whereas it is possible to match experimental and theoretical strain sensitivities, key properties—especially the pronounced orthotropic electromechanical factor of such films—must be duly considered before an effective calibration can take place.

Optical quality assurance of GEM foils

An analysis software was developed for the high aspect ratio optical scanning system in the Detector Laboratory of the University of Helsinki and the Helsinki Institute of Physics. The system is used e.g. in the quality assurance of the GEM-TPC detectors being developed for the beam diagnostics system of the SuperFRS at future FAIR facility. The software was tested by analyzing five CERN standard GEM foils scanned with the optical scanning system. The measurement uncertainty of the diameter of the GEM holes and the pitch of the hole pattern was found to be 0.5μm and 0.3μm, respectively. The software design and the performance are discussed. The correlation between the GEM hole size distribution and the corresponding gain variation was studied by comparing them against a detailed gain mapping of a foil and a set of six lower precision control measurements. It can be seen that a qualitative estimation of the behavior of the local variation in gain across the GEM foil can be made based on the measured sizes of the outer and inner holes.

Experimental Measurement of Neutron Flux Distribution Inside The Water-Filled Howitzer Using Isotope Sources In The Nuclear Research Institute, Vietnam

The water-filled Howitzer had been studied and made in the Nuclear Research Institute (Dalat). It has been the specialized system with multi-function and the unique in Vietnam, that has been used to study experimentally characteristics of neutron in water medium, neutron flux distribution and dose-rate, neutron activation analysis using isotope sources. This report presents the first researches on experimental measurements of neutron flux distributions for sources of 252 Cf and 241 Am-Be (according to horisontal-radius direction) by the technique of neutron activation analysis using the standard foils of gold with cadmium covers and without ones. The experimental results were shown that thermal and epi-thermal neutron fluxes decreased gradually with distances from the source center. This study has been very useful for trainees carrying out measurements of neutron flux distributions and other characteristics using isotope sources.

Excitation function of 3He-particle induced nuclear reactions on natural palladium

Excitation functions of 3He-particle induced nuclear reactions on natural palladium were measured using the standard stacked foil technique and high resolution γ-ray spectroscopy. From their threshold energies up to 27MeV, cross-sections for natPd(3He,x)103,104,105,106m,110m,111,112Ag and natPd(3He,x)104,105,107,111mCd reactions were measured. The nuclear model codes TALYS-1.4, and EMPIRE-3.1 were used to describe the formation of these products. The present data were compared to theoretical results and to the available experimental data. Integral yields for some important radioisotopes were determined.

Robust energy enhancement of ultrashort pulse laser accelerated protons from reduced mass targets

This paper reports on a systematic investigation of the ultrashort pulse laser driven acceleration of protons from thin targets of finite size, so-called reduced mass targets (RMTs). Reproducible series of targets, manufactured with lithographic techniques, and varying in size, thickness, and mounting geometry, were irradiated with ultrashort (30 fs) laser pulses of intensities of about 8 × 1020 W cm−2. A robust maximum energy enhancement of almost a factor of two was found when comparing gold RMTs to reference irradiations of plain gold foils of the same thickness. Furthermore, a change of the thickness of these targets has less influence on the measured maximum proton energy when compared to standard foils, which, based on detailed particle-in-cell simulations, can be explained by the influence of the RMT geometry on the electron sheath. The performance gain was, however, restricted to lateral target sizes of greater than 50 µm, which can be attributed to edge and mounting structure influences.

Capacitive strain gauges on flexible polymer substrates for wireless, intelligent systems

Abstract. This paper presents a novel capacitive strain gauge with interdigital electrodes, which was processed on polyimide and LCP (liquid crystal polymer) foil substrates. The metallization is deposited and patterned using thin-film technology with structure sizes down to 15 μm. We determined linear strain sensitivities for our sensor configuration and identified the most influencing parameters on the output signal by means of an analytical approach. Finite-element method (FEM) simulations of the strain gauge indicated the complex interaction of mechanical strains within the sensitive structure and their effect on the capacitance. The influence of geometry and material parameters on the strain sensitivity was investigated and optimized. We implemented thin films on 50 μm thick standard polymer foils by means of a temporary bonding process of the foils on carrier wafers. The characterization of the strain sensors after fabrication revealed the gauge factor as well as the cross sensitivities on temperatures up to 100 °C and relative humidity up to 100%. The gauge factor of a sensor with an electrode width of 45 μm and a clearance of 15 μm was −1.38 at a capacitance of 48 pF. Furthermore, we achieved a substantial reduction of the cross sensitivity against humidity from 1435 to 55 ppm %−1 RH when LCP was used for the sensor substrate and the encapsulation instead of polyimide. The gauge factor of a sensor half-bridge consisting of two orthogonal capacitors was 2.3 and the cross sensitivity on temperature was reduced to 240 ppm K−1. Finally, a sensor system was presented that utilizes a special instrumentation Integrated Circuit (IC). For this system, performance data comprising cross sensitivities and power consumption are given.

Excitation functions of natPb(d,x) 206,205,204,203,202Bi, 203cum,202m,201cumPb and 202cum,201cumTl reactions up to 50 MeV

Cross-sections of deuteron induced nuclear reactions on lead were measured up to 50 MeV using the standard stacked foil irradiation technique and high resolution $\gamma$-ray spectrometry. Experimental cross-sections and derived integral yields are presented for the $^{nat}$Pb(d,x)$^{206,205,204,203,202}$Bi, $^{203cum,202m,201cum}$Pb and $^{202cum,201cum}$Tl reactions. The experimental data were compared with the results from literature and with the data in the TENDL-2013 library (obtained with TALYS code). The cross-section data were analyzed also with the theoretical results calculated by using the ALICE-IPPPE-D and EMPIRE-D codes.

Experimental investigation and theoretical calculation of 3He-particle induced nuclear reactions on cadmium up to 27 MeV

Excitation functions of 3He-particle induced nuclear reactions on natural cadmium were measured using the standard stacked foil technique and high resolution gamma-ray spectroscopy. From their threshold energies up to 27MeV, cross-sections for natCd(3He,xn)117m,113,111,110Sn, natCd(3He,xnp)117m,g,116m,115m,114m,113m,111,110m,g,109,108,107In, and natCd(3He,X)115g,111mCd reactions were measured. The nuclear codes TALYS, and EMPIRE-3,1 were used to describe the formation of these products. The present data were compared to theoretical results and to the available experimental data. Integral yields for some important radioisotopes were determined.