Thin Metal Wires Research Articles

Anomalous transparency at 1064 nm of a freely expanding gas cylinder in vacuum during fast electric explosion of thin metal wires

Laser shadowgrams of exploding metal wires in a vacuum show the anomalous transparency of a completely evaporated wire core for a probe beam with a wavelength of 1064 nm. Simultaneous shadowgrams at 532 nm show significant light attenuation. The anomalous transparency for laser radiation at a wavelength of 1064 nm is highly likely due to the Rayleigh scattering of the probing beam by metal atoms. Our experimental results can be explained under the assumption of a strongly non-equilibrium state of an expanding gas cylinder with a non-uniform density.

INFRARENAL PREAORTIC FOREIGN BODY - AN UNFORESEEN CASE OF MYSTERIOUS ORIGIN

Time and again in medical literature, extra-luminal foreign bodies have been documented in different parts of the body. However, the occurrence of non-rearm, non-explosive, non-iatrogenic foreign bodies are rare. Most foreign bodies are seen in high-risk populations such as paediatric age groups, psychiatric patients, alcoholics and are usually found incidentally while screening for some other medical condition. Most swallowed foreign bodies; depending on their shape and size are generally passed out naturally, a few tend to get lodged along the tract, causing perforations and rarely may migrate to nearby organs or viscera. While symptoms may vary, a large number of these foreign bodies may go unnoticed for years, making it a challenge to accurately trace their incidence or the source of occurrence. Here, we present a case of a 58 year old man with a linear thin metallic wire in the infra-renal, pre-aortic region with no possible clue for origin or migration making its whole presence a mystery!

Metal-wire-embedded alumina insulating material using micro- and nanoscale 3D printing for surface flashover mitigation in a vacuum

A micro- and nanoscale 3D printing technique is applied to fabricate a functional insulating material that mitigates surface discharge in a vacuum based on microscopic electron multipactor suppression. The proposed alumina ceramic insulator design consists of surface-embedded thin metal wires that introduce a local gradient of secondary electron emission (SEE) yield, such that the trajectories of multipactor electrons are distorted by accumulated negative surface charge and the SEE avalanche across the insulator surface becomes intermittent. Considerable increases of surface flashover threshold and surface charging reduction are verified by the experiment. Also, additional efforts are made to determine the optimal size and spatial distribution of the metal wire. A convex-shape flashover voltage trace is observed when increasing the width of the wire, suggesting a trade-off between the multipactor mitigation and the insulator strength. The wire’s position between the adjacent cathode triple junction and the middle of the insulator is proved to be favorable for flashover mitigation. The physical details of surface flashover mitigation by the proposed insulator design are revealed by an ab initio particle-in-cell simulation code, corroborating the experiment from a microscopic aspect.

Anapole-enabled RFID security against far-field attacks

Abstract Radio frequency identification (RFID) is a widely used wireless technology for contactless data exchange. Owing to international standardization and one-way security nature of the communication protocol, RFID tags, holding sensitive information, may be a subject to theft. One of the major security loopholes is the so-called far-field attack, where unauthorized interrogation is performed from a distance, bypassing the user’s verification. This loophole is a penalty of using a dipole-like RFID tag antenna, leaking wireless information to the far-field. Here we introduce a new concept of anapole-enabled security, prohibiting far-field attacks by utilizing fundamental laws of physics. Our design is based on radiationless electromagnetic states (anapoles), which have high near-field concentration and theoretically nulling far-field scattering. The first property enables performing data readout from several centimeters (near-field), while the second prevents attacks from a distance, regardless an eavesdropper’s radiated power and antenna gain. Our realization is based on a compact 3 cm high-index ceramic core–shell structure, functionalized with a thin metal wire and an integrated circuit to control the tag. Switching scheme was designed to provide a modulation between two radiation-less anapole states, blocking both up and down links for a far-field access. The anapole tag demonstrates more than 20 dB suppression of far-field interrogation distance in respect with a standard commercial tag, while keeping the near-field performance at the same level. The proposed concept might significantly enhance the RFID communication channel in cases, where information security prevails over cost constrains.

Laser scattering by submicron droplets formed during the electrical explosion of thin metal wires

This paper presents the results of studying dispersed media formation during the electrical explosion of thin metal wires in vacuum by using low-current generators (∼1–10 kA). Particular attention is paid to the analysis of the composition and structure of the corresponding explosion products as well as to the problem of their visualization using simultaneous laser interferometry and shadow imaging at two wavelengths (1.064 µm and 0.532 µm). Our findings indicate the important role in the visualization of the explosion products that belongs to multiple scattering by submicron droplets of dense condensed matter, which are mixed with metal vapor. The hypothesis on the existence of submicron droplets in the products of exploding metal wires correlates with the results obtained by soft x-ray radiography combined with a laser probing technique. Taking into account the multiple scattering by submicron droplets, it is possible to significantly clarify the parameters of the explosion products visualized via laser probing techniques as well as to gain a deeper insight into the physics behind the electrical wire explosion.

Continuous wave terahertz imaging for NDT: Fundamentals and experimental validation

Continuous wave terahertz (CW THz) imaging, is a variant of terahertz imaging that has been gaining scientific and technological relevance in multiple areas. In this paper the fundamental phenomena of CW THz were studied and a mathematical model was developed that successfully describes the Fabry–Perot interference for such a system, opening the possibility for measurement of thicknesses and surface curvatures. The capabilities of the system were tested using different types of defects, such as voids, water infiltrations and thin metallic wires. The interactions between different materials, features and the radiation beam were numerically studied using finite element method and the results agreed with the experiments. By comparing the results with other Non-Destructive Testing methods, it was found that CW THz imaging is particularly interesting to image water infiltrations and composite materials that incorporate conductive wires.

Millimeter-Wave Waveguide-to-Microstrip Transition With a Built-In DC/IF Return Path

In this article, a novel waveguide-to-microstrip transition with a built-in dc/IF return path is proposed, in which a traditional E- plane probe is directly connected to the backshort by a thin metal wire along the axis of the waveguide. The proposed waveguide-to-microstrip transition implements an additional dc/IF return path while realizing mode conversion. Moreover, the presence of the dc/IF return path has little influence on the performance of the original E- plane probe. The operating principle is analyzed by theoretical analysis and full-wave simulation, and the design procedure of the transition is also presented. To implement the proposed dc/IF return path on different substrates, two approaches, including direct integration with planar circuits or with wire bonding technology, are developed. Furthermore, two back-to-back transition prototypes working in the millimeter and submillimeter bands were designed and characterized. The measured results are in excellent agreement with the simulations. Finally, as an application example, a 70-/140-GHz unbalanced frequency doubler adopting this structure for both dc biasing and dc grounding was designed and fabricated. Measured results show that the conversion loss of the fabricated doubler is less than 13 dB in the range from 125 to 145 GHz, and the minimum conversion loss is 11 dB at 140 GHz with 100-mW input power.

Non‐polymeric thin wires by drawing materials near room temperature

AbstractHerein, non‐polymeric thin cross‐sectional wires were fabricated by injecting materials into elastomeric hollow fibers with subsequent drawing. Once materials were injected into hollow elastic fibers, cores were drawn as fibers elongated. Solidifying the core and removing polymeric shell could form free‐standing wires with thin cross‐sections. In this work, two different thin wires, metallic wires (gallium), and SiCN ceramic wires, were fabricated. Although mechanical and physical properties of these wires completely differed, fabrication approaches were identical by drawing materials near room temperature. Solidified wires enhanced mechanical properties of fibers. Thus, fibers could store elastic energy and preserve deformed complex shapes with the assist of solidified cores. Although the wires with thin cross sections are inherently brittle, the relatively low melting point of gallium (29.8°C) allows it to heal easily upon body heating.

Effect of electrodes on microsecond explosion of thin metal wires in vacuum

An order of magnitude difference was observed in the energy deposition during a microsecond explosion of thin nickel wires in a vacuum, depending on the design of the wire-holding electrodes. In one case, cylindrical polished stainless steel (ss) electrodes with a rounded edge have a small axial hole of 0.3 mm to hold a thin wire. In the second case, these were the same polished electrodes without an axial hole, and the wire was attached to the side of the electrode with a kapton tape. For the electrodes with an axial hole, a voltage breakdown appears when the wire reaches a low temperature of ∼570 K due to the generation of the parasitic plasma discharges from the wire-holder contact. In a long timescale of ∼30 μs, wire resistive heating was interrupted by plasma generations 6 times up to the moment of melting. For the same electrodes without holes, the wire reaches a temperature of ∼1870 K during an ∼2 μs single-stage heating, and the shunting plasma was generated due to the evaporation of impurities from the hot metal surface and avalanche ionization by thermo-emitted electrons from the hot metal surface. We observe similar effects for Cu, Ti, and Pt wires. This effect is important for slow microsecond exploding wires in a vacuum and negligible for fast nanosecond explosions.

Temperature of metal wires for nanosecond and microsecond electrical explosions in vacuum

Experiments show an inverse correlation between temperature and heating time for the electrical explosion of thin metal wires in vacuum. Faster heating of the wire results in higher energy release in a short time, while slow heating lasts longer but releases less energy before breakdown. Breakdown is a natural barrier to the direct release of Joule energy and an increase in the metal temperature to an abnormally high value. An increase in the current rate from 0.07 to 170 A/ns leads to a decrease in the heating time from 5 μs to 5 ns and an increase in the wire temperature from 450 K to 4000 K before the voltage breakdown. This inverse correlation between the heating time and the temperature of the wire in a vacuum can be explained by the inertia of evaporation of the hydrocarbon impurity from the surface of the hot metal.

Observation of 2D omnidirectional invisibility from an electrically large cluster under TE polarization.

The concept of perfect invisibility in free space implies an object neither reflects nor refracts optical waves coming from arbitrary directions, regardless of its shape and size. An optimal solution to realize such a peculiar phenomenon is to tune the constitutive parameters of the object to be identical to air. In particular, to render zero extinction from an existing object by covering some additional structures, is of importance for practical implementations, which is challenging. Here, we demonstrate and propose that a thin metallic wire can be tuned to be air-like under TE polarization, with the aid of an external enclosure. This is achieved through a precise dispersion engineering with independently controllable electric and magnetic responses. Consequently, an electrically large cluster composed of multiple thin wires can be safely hidden in free space, without any macroscopic cloaking structure, which is verified by full-wave simulations and experiments. The measured results on an electrically large airplane-like sample show the excellent performance of 2D omnidirectional invisibility at the designed frequency. This proposed metamaterial would be helpful in enhancing the mechanical stability, electrical conduction, and heat dissipation of a device (or system) by extra wires (or pipes), without disturbing its electromagnetic characteristics.

Initiation of nitromethane deflagration promoted by the oxidation reaction of vaporized metal wire

The rapid construction of rescue routes following natural disasters is of global interest. Nitromethane (NM) is among the proposed means of creating such routes via controlled explosions. However, the use of NM typically requires a highly energetic input when tungsten is employed to initiate deflagration. In this study, a high-current pulse passing through a thin metal wire was used to initiate the deflagration and heating of NM. We found that light-metal elements vaporized by the electrical explosion of a wire chemically reacted with the oxygen in NM, and when the energy density applied to the light metal wire increased, NM began the deflagration process via heating within several microseconds. If the metal wire was partially vaporized, the deflagration reaction began at the point where this occurred because of selective heating. Heating NM with solid or liquid tungsten failed to achieve an instantaneous NM deflagration reaction. The oxidation reaction of vaporized metal elements was found to accelerate the deflagration of NM. We demonstrated that Al and Mg could successfully replace tungsten in electric-discharge impulse crushing systems, as they have lower energy-input requirements for initiating the deflagration reaction. The heat of the oxidation reaction that initiates NM deflagration can be controlled by varying the diameter of the light-metal wire.

Negative Effective Mass in Plasmonic Systems II: Elucidating the Optical and Acoustical Branches of Vibrations and the Possibility of Anti-Resonance Propagation.

We report the negative effective mass metamaterials based on the electro-mechanical coupling exploiting plasma oscillations of free electron gas. The negative mass appears as a result of the vibration of a metallic particle with a frequency ω which is close to the frequency of the plasma oscillations of the electron gas , relative to the ionic lattice . The plasma oscillations are represented with the elastic spring constant , where is the plasma frequency. Thus, the metallic particle vibrating with the external frequency ω is described by the effective mass , which is negative when the frequency approaches from above. The idea is exemplified with two conducting metals, namely Au and Li embedded in various matrices. We treated a one-dimensional lattice built from the metallic micro-elements connected by ideal springs with the elastic constant representing various media such as polydimethylsiloxane and soda-lime glass. The optical and acoustical branches of longitudinal modes propagating through the lattice are elucidated for various ratios , where and represents the elastic properties of the medium. The 1D lattice, built from the thin metallic wires giving rise to low frequency plasmons, is treated. The possibility of the anti-resonant propagation, strengthening the effect of the negative mass occurring under ω = ωp = ω1, is addressed.

Radio Frequency Coil for Dual-Nuclei MR Muscle Energetics Investigation Based on Two Capacitively Coupled Periodic Wire Arrays

In this letter, we describe a dedicated radio frequency (RF) coil for magnetic resonance imaging and spectroscopy at 4.7 T optimized for investigation of muscle energetics in a human forearm. The coil operating at the Larmor frequencies of protons $^1$ H (200.1 MHz) and phosphorous $^{31}$ P (81 MHz) is based on two cylindrical periodic structures made of thin metal wires with tips interconnected through structural capacities of printed overlapping patches and sliding electric contacts. By independently exciting two orthogonal eigenmodes of the structure, the coil can be tuned and matched at both frequencies without lumped capacitors and cover the target region of interest for the forearm flexor muscles.

Etching sharp tips from thin metallic wires for tuning-fork-based scanning probe microscopy

Sharp tips are critical for obtaining high resolution images in scanning probe microscopy (SPM), particularly in samples with large variations in topography. For tuning-fork-based SPM, such tips are commonly obtained by electrochemical etching of metallic wires (e.g., tungsten). Electrochemical etching of metallic wires is the preferred means of preparing tips for scanning tunneling microscopy (STM), and techniques for obtaining sharp tips have been investigated extensively. However, the requirements for STM and tuning-fork-based SPM are different. In particular, the wires used in STM are typically 250−500μm in diameter, while the wires used for tuning-fork-based SPM are usually an order of magnitude narrower in order to minimize loading of the tuning fork: 25−50μm and sometimes down to a few micrometers in diameter. Consequently, many of the recipes developed for etching thicker metallic wires for STM tips do not give optimal results for smaller diameter wires. The authors describe here a modification of the etching circuit of Ibe et al. that significantly improves the reproducibility and reliability of the etching process for thin wires, and discuss the parameters that affect the aspect ratio of produced tips.

Reversed-slit spectroscopy method for in situ measurement of H isotopes on plasma facing material

Optic spectroscopy methods are employed for plasma facing component (PFC) material diagnostics and H isotopes retention on various platforms. A common issue of those spectroscopy methods is the measurement sensitivity. Various improvement methods have been investigated. In the current work, a 'reversed-slit' method is explored, aiming to maximise signal input while retain a reasonably good line resolution. A thin metal wire with a diameter that is comparable to a normal slit width is placed in front of an open slit. By opening the slit the input of the emission light is maximised. The thin wire casts a line of shadow on the spectral image. The shadow line is used as the 'characteristic line' to identify and separate the spectral line of each H isotope. The result shows that an open slit of 3 mm width can bring an intensity increase of 20–30 times compared to a 100 μm wide normal slit without compromising the resolution.

On anomalous absorption of electromagnetic radiationby a subwave metal wire

Background: The effect of anomalously strong absorption, scattering and attenuation of microwave electromagnetic radiation by thin conductive wires is considered. The investigated effect can be used in the development of radio-absorbing and radio-masking materials for various purposes. The aim of the work is to clarify the physical nature of the effect. Materials and methods:. On the basis of the generalized Lorentz-Mi theory the mathematical model of diffraction interaction of microwave radiation with a cylindrical object which material is characterized by a complex refractive index is constructed. The case of normal incidence of a plane electromagnetic wave of E- and H-polarizations on a cylinder is considered. Numerical calculations of the field distribution were performed in the MathCard environment. Results: It is shown that for thick cylinders with a diameter greater than the wavelength, characteristic resonant peaks of absorption and scattering of wave energy are observed. For very thin cylinders, the diameter of which is much smaller than the wavelength, there are maxima of absorption and scattering of energy of incident radiation, which cannot be explained by resonant phenomena. Simplified analytical expressions for the efficiency coefficients of attenuation, absorption and scattering of electromagnetic radiation by thin cylinders are obtained. The field distributions inside and outside the dielectric and metal cylinders at different ratios of their diameter and wavelength of incident radiation are calculated. The efficiency of radiation absorption by a thin wire at different ratios of its diameter and skin-layer thickness for wire material has been studied. Conclusion: It was found that the effect of abnormally strong absorption of microwave radiation by very thin metal wires is due to the existence of a skin effect for conductive materials that interact with microwave radiation. It is obtained that the maximum efficiency of radiation absorption is achieved when the diameter of the wire is twice less than the thickness of the skin layer. The observed effect of anomalous absorption is nonresonant.

Analysis of Thin Truncated Cylinder Scatterers Using Incomplete Hankel Functions and Surface Impedance Boundary Conditions

The incomplete Hankel functions (IHFs) are employed to evaluate the scattered field from thin truncated cylinders excited by uniform plane waves or by arbitrarily oriented elemental current sources. Metallic and dielectric lossy structures are modeled by means of impedance boundary conditions (IBCs) including surface curvature effects. The scattering currents, expanded in triangular basis functions, are determined upon solving electrical field integral equations (EFIEs) by means of the point-matching method of moments (MoM). The scattered field is then expressed in closed analytical form in terms of IHFs, thus yielding highly accurate numerical results. Furthermore, accurate IHFs approximants are also derived to reduce the computational burden in the analysis of large electrical structures. The proposed approach is demonstrated in practical applications involving cylindrical dielectric structures used in planar lenses, lossy dielectric cylinders suitable to model cane-like vegetation, as well as polarization rotators featuring multiple stages composed of thin metallic wire arrays.

Fast and Slow Electromagnetic Waves in a Longitudinally Magnetized Thin-Film Ferromagnetic Metamaterial

We present the results of a theoretical study of the electrodynamic characteristics of fast and slow electromagnetic waves (EMWs) propagating in a metamaterial consisting of a ferromagnetic film inside which there is a periodic lattice of thin metal wires. The ferromagnetic thin-film metamaterial possesses the properties of a left-handed medium at frequencies of slow electromagnetic waves. In a ferromagnetic metamaterial, in comparison with a conventional ferromagnetic film, the cutoff frequencies of fast and slow electromagnetic waves shift to a higher frequency range and the electromagnetic waves themselves become very slow.

Mesh-Grounded Monopolar Hexagonal Microstrip Antenna for Artillery-Launched Observation Round

This paper presents a novel low-profile microstrip antenna with an omnidirectional radiation pattern for an artillery-launched observation round. The proposed antenna consists of one centered hexagonal patch for a feeding network and six periodic arrays of a trapezoid patch for a radiator. The trapezoid patch is equal to a half-sized hexagonal patch based on geometrical symmetry. A gap-coupled one-hexagonal patch and six trapezoid patches are supported on a nonfundamental TM02 mode for vertically polarized omnidirectional radiation patterns. In addition, a meshed ground structure for the proposed antenna is employed to improve the impedance bandwidth. The thin metal wires that are formed by the meshed ground structure yield six trapezoid slot arrays for the feeding network and three triangular slot arrays for the radiator on the ground plane. To verify the feasibility of the meshed ground structure, the mesh width, denoted by w, was investigated theoretically and optimized carefully to enlarge the impedance bandwidth of the proposed antenna. Finally, the proposed antenna, with a mesh width of 0.2 mm, successfully demonstrated excellent monopolar radiation at a resonant frequency of 5.84 GHz, a realized gain of 5.27 dBi, and an impedance bandwidth of 452 MHz from 5.583 GHz to 6.035 GHz with respect to 7.78% at a center frequency of 5.809 GHz.