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Electromagnetic ultrasonic detection technology utilizes the electromagnetic coupling method to generate and receive ultrasonic waves without a couplant, which is suitable for rapid detection. However, the detection can be affected by the spatial distribution of the acoustic field and the polarization direction of the shear wave, which can result in suboptimal detection performance. The acoustic field directivity of the shear wave generated by the butterfly coil electromagnetic acoustic transducer was measured using the transmission method. The data indicate that the acoustic pressure amplitude of the shear wave is maximized along the axis of the acoustic field, thereby meeting the requirements of synthetic aperture focusing technique imaging. We used the reflection method to detect the through-hole defects and investigated the effect of shear wave polarization direction. By comparing the experimental data and imaging results, it can be concluded that higher echo amplitudes are obtained when the polarization direction of the shear wave is perpendicular to the axis of the through-hole defects. Based on the explosive reflection model, the frequency domain phase shift migration (PSM) method converts the time-domain signal to the frequency domain for processing and uses a phase-shift factor for layer-by-layer imaging. We used the PSM method to process the experimental data, which not only produced high-resolution images but also had a high computational speed. [ABSTRACT FROM AUTHOR]

Photonic interconnects between quantum systems will play a central role in both scalable quantum computing and quantum networking. Entanglement of remote qubits via photons has been demonstrated in many platforms; however, improving the rate of entanglement generation will be instrumental for integrating photonic links into modular quantum computers. We present an ion trap system that has the highest reported free-space photon collection efficiency for quantum networking. We use a pair of in-vacuum aspheric lenses, each with a numerical aperture of 0.8, to couple 10(1)% of the 493 nm photons emitted from a 138Ba+ ion into single-mode fibers. We also demonstrate that proximal effects of the lenses on the ion position and motion can be mitigated. [ABSTRACT FROM AUTHOR]

To provide optimal depth resolution with a coded-aperture Laue diffraction microscope, an accurate position of the coded-aperture and its scanning geometry need to be known. However, finding the geometry by trial and error is a time-consuming and often challenging process because of the large number of parameters involved. In this paper, we propose an optimization approach to automate the focusing process after data is collected. We demonstrate the robustness and efficiency of the proposed approach with experimental data taken at a synchrotron facility. [ABSTRACT FROM AUTHOR]

The Synthetic Aperture Microwave Imaging (SAMI) system is a novel diagnostic consisting of an array of 8 independently phased antennas. At any one time, SAMI operates at one of the 16 frequencies in the range 10-34.5 GHz. The imaging beam is steered in software post-shot to create a picture of the entire emission surface. In SAMI's active probing mode of operation, the plasma edge is illuminated with a monochromatic source and SAMI reconstructs an image of the Doppler backscattered (DBS) signal. By assuming that density fluctuations are extended along magnetic field lines, and knowing that the strongest back-scattered signals are directed perpendicular to the density fluctuations, SAMI's 2-D DBS imaging capability can be used to measure the pitch of the edge magnetic field. In this paper, we present preliminary pitch angle measurements obtained by SAMI on the Mega Amp Spherical Tokamak (MAST) at Culham Centre for Fusion Energy and on the National Spherical Torus Experiment Upgrade at Princeton Plasma Physics Laboratory. The results demonstrate encouraging agreement between SAMI and other independent measurements. [ABSTRACT FROM AUTHOR]

The synthetic aperture microwave imaging diagnostic has been operating on the MAST experiment since 2011. It has provided the first 2D images of B-X-O mode conversion windows and showed the feasibility of conducting 2D Doppler back-scattering experiments. The diagnostic heavily relies on field programmable gate arrays to conduct its work. Recent successes and newly gained experience with the diagnostic have led us to modify it. The enhancements will enable pitch angle profile measurements, O and X mode separation, and the continuous acquisition of 2D DBS data. The diagnostic has also been installed on the NSTX-U and is acquiring data since May 2016. [ABSTRACT FROM AUTHOR]

Sixty-four neutral density filters constructed of metal plates with 88 apertures of varying diameter have been radiographed with a soft x-ray source and CCD camera at National Security Technologies, Livermore. An analysis of the radiographs fits the radial dependence of the apertures' image intensities to sigmoid functions, which can describe the rapidly decreasing intensity towards the apertures' edges. The fitted image intensities determine the relative attenuation value of each filter. Absolute attenuation values of several imaged filters, measured in situ during calibration experiments, normalize the relative quantities which are now used in analyses of neutron spectrometer data at the National Ignition Facility. [ABSTRACT FROM AUTHOR]

A 22 m diameter circular rail, outfitted with a mobile sonar tower trolley, was designed, fabricated, instrumented with underwater acoustic transducers, and assembled on a 1.5 m thick sand layer at the bottom of a large freshwater pool to carry out sonar design and target scattering response studies. The mobile sonar tower translates along the rail via a drive motor controlled by customized LabVIEW software. The rail system is modular and assembly consists of separately deploying eight circular arc sections, measuring a nominal center radius of 11 m and 8.64 m arc length each, and having divers connect them together in the underwater environment. The system enables full scale measurements on targets of interest with 0.1° angular resolution over a complete 360° aperture, without disrupting target setup, and affording a level of control over target environment conditions and noise sources unachievable in standard field measurements. In recent use, the mobile cart carrying an instrumented sonar tower was translated along the rail in 720 equal position increments and acoustic backscatter data were acquired at each position. In addition, this system can accommodate both broadband monostatic and bistatic scattering measurements on targets of interest, allowing capture of target signature phenomena under diverse configurations to address current scientific and technical issues encountered in mine countermeasure and unexploded ordnance applications. In the work discussed here, the circular rail apparatus is used for acoustic backscatter testing, but this system also has the capacity to facilitate the acquisition of magnetic and optical sensor data from targets of interest. A brief description of the system design and operation will be presented along with preliminary processed results for data acquired from acoustic measurements conducted at the Naval Surface Warfare Center, Panama City Division Test Pond Facility. [ABSTRACT FROM AUTHOR]

A new technique for the experimental characterization of electromagnetic chaff based on Inverse Synthetic Aperture Radar is presented. This technique allows for the characterization of as few as one filament of chaff in a controlled anechoic environment allowing for stability and repeatability of experimental results. This approach allows for a deeper understanding of the fundamental phenomena of electromagnetic scattering from chaff through an incremental analysis approach. Chaff analysis can now begin with a single element and progress through the build-up of particles into pseudo-cloud structures. This controlled incremental approach is supported by an identical incremental modeling and validation process. Additionally, this technique has the potential to produce considerable savings in financial and schedule cost and provides a stable and repeatable experiment to aid model valuation. [ABSTRACT FROM AUTHOR]

The microfluidic probe (MFP) consists of a flat, blunt tip with two apertures for the injection and reaspiration of a microjet into a solution-thus hydrodynamically confining the microjet-and is operated atop an inverted microscope that enables live imaging. By scanning across a surface, the microjet can be used for surface processing with the capability of both depositing and removing material; as it operates under immersed conditions, sensitive biological materials and living cells can be processed. During scanning, the MFP is kept immobile and centered over the objective of the inverted microscope, a few micrometers above a substrate that is displaced by moving the microscope stage and that is flushed continuously with the microjet. For consistent and reproducible surface processing, the gap between the MFP and the substrate, the MFP's alignment, the scanning speed, the injection and aspiration flow rates, and the image capture need all to be controlled and synchronized. Here, we present an automated MFP station that integrates all of these functionalities and automates the key operational parameters. A custom software program is used to control an independent motorized Z stage for adjusting the gap, a motorized microscope stage for scanning the substrate, up to 16 syringe pumps for injecting and aspirating fluids, and an inverted fluorescence microscope equipped with a charge-coupled device camera. The parallelism between the MFP and the substrate is adjusted using manual goniometer at the beginning of the experiment. The alignment of the injection and aspiration apertures along the scanning axis is performed using a newly designed MFP screw holder. We illustrate the integrated MFP station by the programmed, automated patterning of fluorescently labeled biotin on a streptavidin-coated surface. [ABSTRACT FROM AUTHOR]

A coded imaging and decoding (image reconstruction) scheme was developed for diagnosing a hot and dense region emitting hard x-rays and neutrons in laser-fusion plasmas. Because the imager was a uniformly redundant array of penumbral aperture (URPA) arranged in an M-matrix, URPA leads to N times (N: the total number of apertures) enhancement of signal intensity in comparison with a single penumbral aperture. A recorded penumbral image was reconstructed by a computer-based heuristic method to reduce artifacts caused by noises contained in a penumbral image. Applicability of this technique was investigated by imaging x-rays emitted from laser-produced plasmas, demonstrating a spatial resolution of 16 μm. Under the present conditions, the spatial resolution was determined dominantly by a detector resolution (10.5 μm) and a signal-to-noise ratio of the obtained penumbral image. [ABSTRACT FROM AUTHOR]

Uniformly redundant arrays (URA) is one coded aperture imaging technique. Since the URA camera can view the object with a large solid angle, it can provide some tomographic resolution for a three-dimensional object. The performance of a URA camera for three-dimensional imaging has been investigated in detail by computer simulations. The tomographic (depth) resolution of the camera has also been estimated quantitatively as a full width at half maximum of a depth point spread function, which is obtained by reconstructing a point source at different depths. We also show that the tomographic resolution can be improved by the use of small pinholes for URA aperture and fine sampling for decoding. [ABSTRACT FROM AUTHOR]

We present a new simple method for decoding penumbra image. Penumbral imaging is a coded aperture technique which uses a simple large circular aperture as coding aperture. Thus, the image of the object is coded and the information must be recovered through a decoding process. The proposed decoding method overcomes the classical problem related to the zero-crossing of the Fourier transform of the point spread function. This problem arises when using the usual methods based on inverse filtering in Fourier domain. Moreover, it allows to remove automatically the flat background which is often superimposed to the penumbra image, without requiring an evaluation of its mean level. Performance comparison with the classical pseudo-Wiener filtering are presented. The method has been applied to ICF neutron penumbra images recorded at the Omega Laser Facility of the LLE (University of Rochester, NY). Experimental results are presented. [ABSTRACT FROM AUTHOR]

Aperture, pin-hole and collimator detection systems are often used in plasma diagnostics, for example, in soft x-ray detection and bolometer systems. In this article the simultaneous optimization of viewing-beam overlap and light yield is considered in multi-channel aperture and collimator systems for two-dimensional (2D) tomography. This article briefly highlights the relation between beamwidth overlap and spatial aliasing in tomography, and how aliasing can be avoided in theory and in practice. Three-dimensional (3D) single-channel aperture and collimator systems can be approximated by a combination of two planar systems if the aperture is rectangular. Three ways to optimize beamwidth overlap and light yield for planar aperture and collimator systems are considered in detail: overlap of the angular éendue at the full width at half maximum (FWHM), overlap of the geometric function at the FWHM a certain distance from the aperture, and arbitrary overlap for a given maximum beamwidth. The combination of 2D effects from all three optimization methods were used in the design of 3D apertures for a new multi-channel bolometer camera on the Joint European Torus tokamak. The resulting apertures are complex, but the new camera has several advantages over previous cameras. [ABSTRACT FROM AUTHOR]

Calculates the acceleration-field for a structure-based laser-driven linear accelerator. Capability of the apertures of transmitting electrons; Computation of the acceleration field for a cylindrically focused, crossed laser-beam linear accelerator; Decrease of energy gain and width apertures.

We are incorporating a system of fast, variable apertures in our designs for the x-ray, neutral, and ion spectrometers for plasma diagnostics on Mirror Fusion Test Facility B (MFTF-B). The purpose of these apertures is to maintain optimized count rates, and thus optimized measurement statistics during an experimental shot, where flux variations as large as 10[sup 4]-10[sup 5] may occur in periods as short as 0.1 s. We shall discuss the application of the fast apertures to the x-ray spectrometer in particular, and to the other diagnostic instruments in general. The particular design requirements for the optimized aperture system will be discussed, as will be the influence the system has on the data-handling process. We have performed experiments to test this new concept and shall present the results, including the details of the closed-loop feedback circuit controlling the apertures, optimization of the loop gain, and the engineering issues of the system, such as the effect of vacuum feedthrough, position sensitivity, and alignment criteria. [ABSTRACT FROM AUTHOR]

This article presents a simple measurement setup for characterization of a combined near-field scanning optical and atomic force microscopy (NSOM/AFM) using an aperture Si based probe. A technological approach has been found for the fabrication of a miniature aperture at the apex of a SiO[sub 2] tip on a Si cantilever for NSOM using a "low temperature oxidation and selective etching" (LOSE) technique. The optical transmission efficiency (throughput) of the fabricated probe was measured to be about 10[sup -2] when the aperture size was approximately 100 nm, which is several orders of magnitude higher than that of conventional optical fibers and is also higher than other published throughput on micromachined tips due to a large curvature angle of the SiO[sub 2] tip. An extension of the LOSE technique for the fabrication of a tip with a tiny aperture having a metal nanowire at the center of the aperture for a multipurpose NSOM probe is also presented. Using the proposed measurement setup and the fabricated probe, NSOM and corresponding AFM images in contact and tapping modes of several surfaces are obtained. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]