Elaboration of thin foils in copper and zinc by self-induced ion plating

The aim of this work was to determine the ability to produce thin metallic foils by self-induced ion plating. Foils of pure copper and pure zinc with a thickness of 35 μm have been successfully produced and their characteristics have been compared to foils obtained by conventional techniques (i.e. electroplating and rolling). Results show the following: (i) more or less compact microstructures can be obtained by self-induced ion plating depending on gas pressure and substrate temperature; (ii) microstructures obtained by self-induced ion plating are quite different from those obtained by electroplating and rolling; (iii) Young’s modulus depends on foils roughness; (iv) hardness depends on grain size by exhibiting a Hall-Petch behavior in the case of copper foils and an “inverse” Hall-Petch behavior in the case of zinc foils

The Interstellar Gas Experiment: Analysis in progress

The Interstellar Gas Experiment (IGE) exposed thin metallic foils aboard the LDEF spacecraft in low Earth orbit in order to collect neutral interstellar particles which penetrate the solar system due to their motion relative to the sun. By mechanical penetration these atoms were imbedded in the collecting foils along with precipitating magnetospheric ions and, possibly, with ambient atmospheric atoms. During the entire LDEF mission, seven of these foils collected particles arriving from seven different directions as seen from the spacecraft. After the foils were returned to Earth, a mass spectrometric analysis of the noble gas component of the trapped particles was begun. The isotopes of He-3, He-4, Ne-20, and Ne-22 were detected. We have given a first account of the experiment. In order to infer the isotopic ratios in the interstellar medium from the concentrations found in the foils, several lines of investigation had to be initiated. The flux of ambient atmospheric noble gas atoms moving toward the foils due to the orbital motion of LDEF was estimated by detailed calculations. Any of these particles which evaded the baffles in the IGE collector could be entrapped in the foils as a background flux. However, the calculations have shown that this flux is negligible, which was the intent of the experiment hardware design. This conclusion is supported by the measurements. However, both the concentration of trapped helium and its impact energy indicate that the flux of magnetospheric ions which was captured was larger than had been expected. In fact, it appears that the magnetospheric particles constitute the largest fraction of the particles in the foils. Since little is known about this particle flux, their presence in the IGE foils appears fortunate. The analysis of these particles provides information about their isotropic composition and average flux

Compton Scattered Transition Radiation from Very High Energy Particles

X-ray transition radiation can be used to measure the Lorentz factor of relativistic particles. At energies approaching gamma = E/mc^2 = 10^5, transition radiation detectors (TRDs) can be optimized by using thick (sim 5 - 10 mil) foils with large (5-10 mm) spacings. This implies X-ray energies >100 keV and the use of scintillators as the X-ray detectors. Compton scattering of the X-rays out of the particle beam then becomes an important effect. We discuss the design of very high energy detectors, the use of metal radiator foils rather than the standard plastic foils, inorganic scintillators for detecting Compton scattered transition radiation, and the application to the ACCESS cosmic ray experiment.Comment: To be published, Astroparticle Physic

Influence of Process Parameters on the Deformation of Copper Foils in Flexible-Pad Laser Shock Forming

This paper investigates a new microforming technique, Flexible-Pad Laser Shock Forming (FPLSF), to produce mi-crofeatures on metallic foils without rigid punches and dies. FPLSF uses the laser-induced shock pressure and a flexi-ble-pad to plastically deform metal foils into hemispherical microcraters. In order to understand the deformation characteristics of metal foils in FPLSF, it is necessary to analyze the influence of process parameters on the foil deformation. In this paper, the effects of parameters such as the flexible-pad thickness, confinement layer medium, confinement layer thickness and the number of laser pulses on the depth, diameter and shape of the craters formed on copper foils were investigated. It is found that the flexible-pad thickness should be greater than its threshold value to maximize the deformation of foils. By comparing two different confinement media, namely water and glass, it is observed that hemispherical craters were formed on the copper foils at different laser fluence values tested when using water as the confinement; whereas shockwave ripples were formed on the copper foil at higher laser fluence while using the glass confinement. Using water as confinement medium, an increase in confinement thickness from 4 mm to 7 mm resulted in 48% increase of the crater depth at 7.3 J/cm2. However, at 13.6 J/cm2, reduction in crater depth was observed for thickness greater than 6 mm after an initial increasing trend. Regarding the number of pulses, it is found that increasing the number of pulses from 1 to 3 resulted only in a small increase (less than 1%) in crater depth at 7.3 J/cm2 and 13.6 J/cm2 laser fluence whereas 19.3% increase in depth was observed at larger laser fluence (20.9 J/cm2). It is also observed that the optimum number of pulses to achieve maximum deformation is varying with the laser fluence

Flexible thin polymer waveguide Bragg grating sensor foils for strain sensing

This paper demonstrates that epoxy-based single mode polymer waveguides with Bragg gratings can be realized in very thin (down to 50 micron) polymer foils which are suitable for strain sensing when integrated inside glass fiber reinforced polymer composite materials. The single mode waveguides were fabricated using laser direct-write lithography and the gratings were realized using nanoimprint lithography. These steps were performed on a temporary rigid carrier substrate and afterwards the functional layers were released yielding the thin, flexible sensor foils which can be laser-cut to the required dimensions. The Bragg grating-based polymer waveguide sensor foils were characterized before and after embedding into the composite. As expected, there was a blue shift in the reflection spectrum because of residual strain due to the embedding process. However, the quality of the signal did not degrade after embedding, both for 50 and 100 micron thick sensor foils. Finally, the sensitivity to strain of the embedded sensors was determined using a tensile test and found to be about 1 pm / microstrain

Scaling the propulsive performance of heaving and pitching foils

Scaling laws for the propulsive performance of rigid foils undergoing oscillatory heaving and pitching motions are presented. Water tunnel experiments on a nominally two-dimensional flow validate the scaling laws, with the scaled data for thrust, power, and efficiency all showing excellent collapse. The analysis indicates that the behaviour of the foils depends on both Strouhal number and reduced frequency, but for motions where the viscous drag is small the thrust closely follows a linear dependence on reduced frequency. The scaling laws are also shown to be consistent with biological data on swimming aquatic animals.Comment: 11 page

Ultrasmall divergence of laser-driven ion beams from nanometer thick foils

We report on experimental studies of divergence of proton beams from nanometer thick diamond-like carbon (DLC) foils irradiated by an intense laser with high contrast. Proton beams with extremely small divergence (half angle) of 2 degree are observed in addition with a remarkably well-collimated feature over the whole energy range, showing one order of magnitude reduction of the divergence angle in comparison to the results from micrometer thick targets. We demonstrate that this reduction arises from a steep longitudinal electron density gradient and an exponentially decaying transverse profile at the rear side of the ultrathin foils. Agreements are found both in an analytical model and in particle-in-cell simulations. Those novel features make nm foils an attractive alternative for high flux experiments relevant for fundamental research in nuclear and warm dense matter physics.Comment: 11 pages, 5 figure

Finite Element Modelling of Bends and Creases during Folding Ultra Thin Stainless Steel Foils

Finite Element Modelling of an ultra thin foil of SUS 304 stainless steel is carried out. These foils are 20 mm and below in thickness. The development of stresses and strains during folding of these foils is studied. The objective of this study is to induce qualities of paper in the foils of stainless steel such that a public sculpture of origami can be built with the foil. Finite Element modelling of the fold, reverse fold, junctions of multiple folds as well as the finger-dents are carried out to quantify the extent of straining the steel foil would undergo while an object of origami is folded with it. It is important to know the extent of straining the foil would undergo during folding operation. With this knowledge, the through-thickness microstructure and microtexture can be studied which influence the fracture toughness and low cycle fatigue properties of the steel foil. The foil with the requisite qualities of paper can then be manufactured