Transmission Setup Research Articles

Note: Radio frequency inductance-capacitance band-stop filter circuit to perform contactless conductivity measurements in pulsed magnetic fields

We present a new technique to perform radio frequency (rf) contactless conductivity measurements in pulsed magnetic fields to probe different ground states in condensed matter physics. The new method utilizes a simple analog band-stop filter circuit implemented in a radio frequency transmission setup to perform contactless conductivity measurements. The new method is more sensitive than the other methods (e.g., the tunnel diode oscillator and the proximity detector oscillator) due to more sensitive dependence of the circuit resonance frequency on the tank circuit inductance (not the transmission line). More important, the new method is more robust than other methods when used to perform measurements in very high magnetic fields, works for a wide range of temperatures (i.e., 300 K-1.4 K) and is less sensitive to noise and mechanical vibrations during pulse magnet operation. The new technique was successfully applied to measure the Shubnikov-de Haas effect in Bi(2)Se(3) in pulsed magnetic fields of up to 60 T.

Wireless Power Transmission Using Ultrasonic Guided Waves – Electric Circuit Measurement and Simulation

A project investigating the possibility to transmit electrical power (several mW) along the structure of an aircraft by using an intermediate medium of ultrasonic Lamb waves is being carried out at Cardiff University in conjunction with Airbus. This power supply method is aimed at wireless, surface-bonded sensor packages, primarily for the aircraft structural health monitoring (SHM) applications. It is expected to replace conventional batteries or energy harvesting devices. This paper presents methods of piezoelectric transducer characterisation, electric power measurement and electric circuit simulation that were developed in support of the ultrasonic power transmission project. The unique combination of low power and a high AC frequency range (up to 200 kHz) precluded the use of conventional power measurement instruments and called for a tailored system and software to be developed. Two approaches were developed: one relying on the measurement of the ultrasonic transducers impedance characteristics and their subsequent use in a circuit simulation; and another relying on the direct measurement of voltage waveforms in the power transmission setup. The two methods were found to be capable of producing closely matching results up to 300 kHz. Results of early power transmission trials are also presented. The optimum approach resulted in 1 mW of power transmission over a distance of 74 cm in a 1.5 mm thick aluminium plate.

Non-destructive evaluation of thick glass fiber-reinforced composites by means of optically excited lock-in thermography

Optically excited lock-in thermography (OLT) has been exploited for quantitative assessment of simulated subsurface defects in thick glass fiber reinforced polymer (GFRP) composite laminates routinely employed for the manufacturing of luxury yachts. The paper investigates the detection limits associated to defects geometry and depth as well as recognition of barely visible impact damage over the external gel-coat finish layer. The obtained results demonstrated the effectiveness of lock-in infrared thermography as a powerful and non-contact full-field measurement technique for the inspection of large GFRP structures. In particular, results showed that, by using a transmission set-up instead than a reflection one, accurate assessment (standard uncertainty < 1.4%) of impact damages could be attained, whereas estimation of delaminations depth is critically influenced by the actual area and aspect ratio of the discontinuity. A simple model to account for this dependency has been proposed.

An experimental evaluation of two effective medium theories for ultrasonic wave propagation in concrete

This study compares ultrasonic wave propagation modeling and experimental data in concrete. As a consequence of its composition and manufacturing process, this material has a high elastic scattering (sand and aggregates) and air (microcracks and porosities) content. The behavior of the "Waterman-Truell" and "Generalized Self Consistent Method" dynamic homogenization models are analyzed in the context of an application for strong heterogeneous solid materials, in which the scatterers are of various concentrations and types. The experimental validations of results predicted by the models are carried out by making use of the phase velocity and the attenuation of longitudinal waves, as measured by an immersed transmission setup. The test specimen material has a cement-like matrix containing spherical inclusions of air or glass, with radius close to the ultrasonic wavelength. The models are adapted to the case of materials presenting several types of scattering particle, and allow the propagation of longitudinal waves to be described at the scale of materials such as concrete. The validity limits for frequency and for particle volume ratio can be approached through a comparison with experimental data. The potential of these homogenization models for the prediction of phase velocity and attenuation in strongly heterogeneous solids is demonstrated.

Artificially disordered birefringent optical fibers

We develop and experimentally verify a theory of evolution of polarization in artificially-disordered multi-mode optical fibers. Starting with a microscopic model of photo-induced index change, we obtain the first and second order statistics of the dielectric tensor in a Ge-doped fiber, where a volume disorder is intentionally inscribed via UV radiation transmitted through a diffuser. A hybrid coupled-power & coupled-mode theory is developed to describe the transient process of de-polarization of light launched into such a fiber. After certain characteristic distance, the power is predicted to be equally distributed over all co-propagating modes of the fiber regardless of their polarization. Polarization-resolved experiments, confirm the predicted evolution of the state of polarization. Complete mode mixing in a segment of fiber as short as ∼ 10cm after 3.6dB insertion loss is experimentally observed. Equal excitation of all modes in such a multi-mode fiber creates the conditions to maximize the information capacity of the system under e.g. multiple-input-multiple-output (MIMO) transmission setup.

Experimental analysis of singularity-avoidance techniques for CMA equalization in DP-QPSK 112-Gb/s optical systems

We experimentally investigate the singularity problem in DP-QPSK 112-Gb/s receivers using the CMA. Three algorithms are compared: Constrained, Two-Stage, and Multi-User. Although these algorithms have been individually evaluated, they have not been compared by extensive experiments. The transmission setup emulates amplifier noise; first-order PMD; and chromatic dispersion. It is shown that all algorithms effectively mitigate singularities. However, under certain conditions, the Multi-User and the Constrained algorithms--both used for system startup--outperformed the Two-Stage, which does not distinguish between system operation and startup. In light of its effectiveness and low computational complexity, we recommend the Constrained algorithm.

Evaluation of a spectrally resolved scattering microscope

A scattering microscope was developed to investigate single cells and biological microstructures by light scattering measurements. The spectrally resolved part of the setup and its validation are shown in detail. The analysis of light scattered by homogenous polystyrene spheres allows the determination of their diameters using Mie theory. The diameters of 150 single polystyrene spheres were determined by the spectrally resolved scattering microscope. In comparison, the same polystyrene suspension stock was investigated by a collimated transmission setup. Mean diameters and standard deviations of the size distribution were evaluated by both methods with a statistical error of less than 1nm. The systematic errors of both devices are in agreement within the measurement accuracy.

Electromagnetic properties of polycrystalline diamond from 35 K to room temperature and microwave to terahertz frequencies

Dielectric resonators are key components for many microwave and millimeter wave applications, including high-Q filters and frequency-determining elements for precision frequency synthesis. These often depend on the quality of the dielectric material. The commonly used material for building the best cryogenic microwave oscillators is sapphire. However, sapphire is becoming a limiting factor for higher frequency designs. It is, then, important to find new candidates that can fulfill the requirements for millimeter wave low noise oscillators at room and cryogenic temperatures. These clocks are used as a reference in many fields, such as modern telecommunication systems, radio astronomy (very-long-baseline interferometry), and precision measurements at the quantum limit. High resolution measurements were taken of the temperature-dependence of the electromagnetic properties of a polycrystalline diamond disk at temperatures between 35 and 330 K at microwave to submillimeter wave frequencies. The cryogenic measurements were made using a TE01δ dielectric mode resonator placed inside a vacuum chamber connected to a single-stage pulse-tube cryocooler. The high frequency characterization was performed at room temperature using a combination of a quasi-optical two-lens transmission setup, a Fabry–Perot cavity, and a whispering gallery mode resonator excited with waveguides. Our CVD diamond sample exhibits a decreasing loss tangent with increasing frequencies. We compare the results with well known crystals. This comparison makes it clear that polycrystalline diamond could be an important material for generating stable frequencies at millimeter waves.

Nanoantenna-Assisted Extraordinary Optical Transmission Under Radial Polarization Illumination

We numerically study the extraordinary optical transmission of a plasmonic structure that combines a circular nanoantenna and a vertical annular nanoslit etched into a gold film under radially polarized illumination. The nanoantenna collects the incident field and localizes it in a horizontal Fabry-Perot cavity over the gold film. The vertical nanoslit positioned at the maximal field in the horizontal cavity couples the localized field and facilitates its transmission to the free space. Due to the symmetry matching between the structure and the illumination polarization, surface plasmons can be excited effectively and enhance the transmission. Through optimizing the structure parameters, the transmission efficiency can be greatly enhanced by 225 times for a resonant annular nanoslit and 251 times for a non-resonant annular nanoslit. This axisymmetric extraordinary optical transmission setup may be fabricated on the facet of an optical fiber for optical sensing applications.

Measurements of electron cloud density in the CERN Super Proton Synchrotron with the microwave transmission method

The electron cloud effect can pose severe performance limitations in high-energy particle accelerators as the CERN Super Proton Synchrotron (SPS). Mitigation techniques such as vacuum chamber thin film coatings with low secondary electron yields ($\mathrm{SEY}&lt;1.3$) aim to reduce or even suppress this effect. The microwave transmission method, developed and first applied in 2003 at the SPS, measures the integrated electron cloud density over a long section of an accelerator. This paper summarizes the theory and measurement principle and describes the new SPS microwave transmission setup used to study the electron cloud mitigation of amorphous carbon coated SPS dipole vacuum chambers. Comparative results of carbon coated and bare stainless steel dipole vacuum chambers are given for the beam with nominal LHC 25 ns bunch-to-bunch spacing in the SPS and the electron cloud density is derived.

Laser optoacoustic spectroscopy of gold nanorods within a highly scattering medium

We describe a spectroscopic comparative analysis based on the optoacoustic technique over the wavelength range from 410nm to 1000nm using a Q-switched Nd:YAG pumped optical parametric oscillator tunable source on a gold nanostructure solution located within a highly scattering medium. The advantages of this method over standard spectroscopy techniques are the possibility to localize and monitor the spectroscopic response of absorbing materials located within turbid media. The operation is confirmed using a comparative analysis with the spectroscopic results obtained from a reference measurement scheme, based on a highly sensitive collimated optical transmission setup in parallel and under the same experimental conditions as the optoacoustic technique.

Wireless digital data transmission at 300 GHz

Recently, analogue video signal transmission at 300 GHz has been demonstrated using a versatile Schottky mixer based measurement system designed for terahertz communication channel modelling and propagation studies. In this reported work, digital signal transmission at 300 GHz using this system is demonstrated and analysed. The performance of the digital transmission setup is characterised with respect to phase noise and modulation errors. For demonstration, high data rate digital video signals have been transmitted over a distance of up to 52 m.

Transparent Silver Microcrystals: Synthesis and Application for Nanoscale Analysis

Micrometer-sized atomically flat silver nanoplates with a thickness of 10-20 nm were obtained in a one-pot reduction of silver nitrate with hydrazine sulfate without surfactants or polymers. The optically transparent triangles and hexagons have been proven to be excellent substrates for experiments with a tip-enhanced Raman transmission setup.

Evidence of “crossed” transitions in dots-in-a-well structures through waveguide absorption measurements

In-plane absorption measurements were performed at room temperature by means of a waveguide transmission setup on a Stranski–Krastanov InAs dots-in-a-well system emitting at 1.3μm embedded in a p-i-n structure. The polarization dependence of quantum dot (QD) absorption was exploited to resolve its discrete and continuous spectral components and study them separately under reverse bias application. The quantum confined Stark effect observed in the discrete spectral component gave evidence of an upward built-in QD dipole of about 9.5×10−29Cm. The continuous component was found to originate from electronic transitions involving a QD state and a quantum well state.

PVB mechanical constants characterization in laminated glasses using low frequency ultrasound

To predict the behaviour of a partition made of laminated glasses, it's necessary to know the parameters of the layers composing it. These types of devices are composed by monolithic glass and an intermediate muffling layer usually made of PVB. In this study, we present a method to find the mechanical constants of PVB in laminated glasses. Mechanical constants characterization in these materials is studied using a model-based inverse problem and the data obtained from an ultrasonic transmission setup: a numerical simulation of the system is proposed using a lineal finite elements model of the ultrasonic propagation on the multilayered solid. Parameters are obtained by minimizing divergences between experimental and numerically predicted waveform.

Detection of Nematodes in Cod (Gadus morhua) Fillets by Imaging Spectroscopy

A promising method for detection of parasites in whitefish fillets has been developed. By use of imaging spectroscopy it is possible to record both spectral and spatial information from an object. In this work it is shown that by applying a white light transmission setup and imaging spectroscopy to cod (Gadus morhua) fillets, it is possible to make spectral images containing information to differentiate between fish muscle and parasites. The spectral images are analyzed by discriminant partial least square regression as well as image-filtering techniques. The method identifies parasites on the surface of the fillets as well as embedded parasites. One parasite was detected at 0.8 cm below the fillet surface, which is 2 to 3 mm deeper than what can be found by manual inspection of fish fillets. The method is nonintrusive and should thus be feasible for industrial purposes.

Subharmonic emissions from microbubbles: effect of the driving pulse shape

The aims of this work are to investigate the response of the ultrasonic contrast agents (UCA) insonified by different arbitrary-shaped pulses at different acoustic pressures and concentration of the contrast agent focusing on subharmonic emission. A transmission setup was developed in order to insonify the contrast agent contained in a measurement chamber. The transmitted ultrasonic signals were generated by an arbitrary wave generator connected to a linear power amplifier able to drive a single-element transducer. The transmitted ultrasonic pulses that passed through the contrast agent-filled chamber were received by a second transducer or a hydrophone aligned with the first one. The radio frequency (RF) signals were acquired by fast echographic multiparameters multi-image novel apparatus (FEMMINA), which is an echographic platform able to acquire ultrasonic signals in a real-time modality. Three sets of ultrasonic signals were devised in order to evaluate subharmonic response of the contrast agent respect with sinusoidal burst signals used as reference pulses. A decreasing up to 30 dB in subharmonic response was detected for a Gaussian-shaped pulse; differences in subharmonic emission up to 21 dB were detected for a composite pulse (two-tone burst) for different acoustic pressures and concentrations. Results from this experimentation demonstrated that the transmitted pulse shape strongly affects subharmonic emission in spite of a second harmonic one. In particular, the smoothness of the initial portion of the shaped pulses can inhibit subharmonic generation from the contrast agents respect with a reference sinusoidal burst signal. It also was shown that subharmonic generation is influenced by the amplitude and the concentration of the contrast agent for each set of the shaped pulses. Subharmonic emissions that derive from a nonlinear mechanism involving nonlinear coupling among different oscillation modes are strongly affected by the shape of the ultrasonic driving pulse.

Development of a microwave transmission setup for time-resolved measurements of the transient complex conductivity in bulk samples

We describe and characterize a microwave transmission setup for the measurement of radiation-induced transient conductivities in the frequency range between 26 and 38GHz (Q band). This technique combines the virtues of two already existing techniques. On one hand, the microwave transmission technique is well established for the determination of (quasi)static conductivities, but requires adaptations to be suitable to the determination of transient conductivities with 1ns temporal resolution. On the other hand, the transient conductivity technique is well established, too, but in its present form (using a reflection configuration) it suffers from a poor signal to noise ratio due to unwanted interferences. These interferences are due to the circulator, which diverts part of the incoming microwave flux directly to the detector. We characterized the transmission setup by measuring the real and imaginary components of the conductivity of pulse irradiated CO2 gas at different pressures, and compared these results to predictions of the Drude model. CO2 was chosen as a test sample because of its well characterized behavior when irradiated with MeV electron pulses, and the fact that a wide range of the ratios of imaginary to real components of the conductivity are obtainable by just controlling the pressure. For intrinsic bulk isolators (either powders or in solution) pulse-induced conductivity changes as small as 10−8S∕m can be measured with nanosecond time resolution. The ratio of the imaginary to real part of the conductivity can be measured in the range from 0.084 to 28, which means that the dynamic range has been increased more than 100-fold with respect to the customary reflection setup.

Micro particle-image velocimetry of bead suspensions and blood flows

We present and discuss velocity profiles of microflows obtained by micro particle-image velocimetry in a transmission setup. We have measured suspensions of beads in water and on human blood, using the red blood cells as a natural particle seeding. The limitations imposed by our optical system on the spatial resolution normal to the focal plane, the so-called focal depth, have also been analyzed. The first direct observations of the influence of the focal depth on the observed velocity profiles are presented. Good agreement is obtained between observations and calculated profiles modified by the finite focal depth through a weight function.

Analysis of neutron attenuation in boron-alloyed stainless steel with neutron radiography and JEN-3 gauge

This paper concerns the neutron attenuation behavior of boron-alloyed stainless steels, and quantitative estimations of secondary effects on the neutron transmission measurements, such as beam hardening, background and micro-structure of neutron absorber causing a decrease in the total macroscopic cross-sections. Systematic thermal neutron transmission measurements of boron-alloyed steel plates have been performed at different neutron radiography facilities and at a portable gauge called JEN-3, which is a practical neutron transmission setup for industrial demands in non-destructive material inspection. In addition, MCNP (Monte Carlo Neutron Particle transport) simulations were performed for a better understanding of the experimental results, the secondary factors affecting the total macroscopic cross-sections, and the characteristics of the JEN-3 gauge. The detectable thickness limit for 1.88 wt% natural boron-alloyed steel plates was determined as 1–1.5 cm depending on the contributions of the secondary factors in each facility.