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Forbes Faulkner posted an update 6 months ago
A variable-area exhaust nozzle for an aeroengine, utilizing a flexible shape memory alloy (SMA) actuator, has been created, tested, and thoroughly investigated to determine its performance properties as a proof-of-concept. The experiments captured the exhaust nozzle’s movement trajectory using image recognition, a method also employed to quantify the changes in the exhaust nozzle’s area. The actuator’s flexibility is evident in the results, which demonstrate its ability to bend at any angle within the -90 to +90 degree range. The flexible SMA actuator’s actuating displacement is adjustable via an increase or decrease in the number of its hinged components. In contrast to prior studies on SMA-actuated exhaust nozzles, which documented a maximum area change of 40%, the current study observed a 644% change in the exhaust nozzle’s area.
Experiments in inertial confinement fusion (ICF) and high-energy-density physics produce MeV-range ions, which contain significant data points regarding the fusion reaction yield, rate and spatial emission characteristics, the implosion areal density, the electron temperature and mix, and the presence and magnitude of electric and magnetic fields. This analysis explores the theoretical underpinnings of data extraction, coupled with an examination of the presently accessible charged particle diagnostic instrumentation at major US inertial confinement fusion facilities for conducting these measurements. Time-integrating instruments utilizing image plates, radiochromic film, or CR-39 detectors in different configurations are described for ion counting, spectroscopy, and emission profile determination. In addition, detectors, using chemically vapor-deposited diamonds coupled to oscilloscopes or scintillators coupled to streak cameras, are detailed for the timing analysis of ion emission. A description of radiography setups, using charged particles, to probe plasma experiments, is also provided. This paper endeavors to present to the reader a broad summary of available functionalities, with references to sources offering more specific and detailed information.
X-ray phase contrast imaging (XPCI) achieves heightened image contrast, surpassing absorption-based x-ray imaging, through the exploitation of refractive and diffractive phenomena arising from the varying density of the object material. Density variations, encompassing minor inconsistencies like internal voids, cracks, grains, defects, and material flow, as well as substantial fluctuations similar to those from a shock wave, render it sensitive. XPCI, initially a tool in biological and material science research, is now widely applied in inertial confinement fusion (ICF) and high energy density (HED) studies. It is first employed in characterizing ICF capsules and targets, later extending to dynamic experiments, which require coherent X-ray sources, ultrafast X-ray pulses, and exquisite temporal and spatial resolution. This review piece presents the XPCI image formation theory, discusses its diverse applications in ICF and HED research, outlines the specific requirements for ultrafast XPCI imaging, and examines the current challenges and hurdles within its implementation.
Thin films’ optical properties and thicknesses are meticulously ascertained using spectroscopic ellipsometry, a widely employed optical technique in both industry and academic research. The technical hurdles of lateral resolution and data acquisition rate curtail the effective application of spectroscopic ellipsometry to microstructures. Our newly developed spectroscopic micro-ellipsometer (SME) allows for the simultaneous recording of spectrally resolved ellipsometric data at multiple incident angles within a single measurement of only a few seconds, and its lateral resolution in the visible spectral region is down to 2 meters. The SME’s integration into generic optical microscopes is facilitated by the addition of a handful of standard optical components. Using the SME, we demonstrate complex refractive index and thickness measurements that closely match those from a commercial spectroscopic ellipsometer. High lateral resolution is displayed in the detailed mapping of refractive index and thickness over micron-scale areas. The SME’s accuracy and high lateral resolution allow for the characterization of the optical properties and layer numbers in exfoliated transition-metal dichalcogenides and graphene, which are present in structures only a few microns in size.
In the field of inertial confinement fusion (ICF) research, the neutron yield and related experimental data often elude precise prediction by one- or two-dimensional models. This inconsistency points to potentially significant three-dimensional effects. The origins of these effects lie in flaws within the shells themselves, including flaws at shell interfaces, the capsule’s filling tube, and the connecting elements of double-shelled targets. The ability of x rays to penetrate materials makes them suitable for revealing the internal structure of objects. Computational tomography leverages x-ray radiographs, captured from hundreds of projections, to model the object in three dimensions. The National Ignition Facility and Omega-60, representative of experimental environments, showcase a scarcity of these views, often with only a single line of sight available. The mathematical reconstruction of a 3-dimensional object from a small set of views suffers from the ill-posedness of the inverse problem. AMPK signals receptor Employing pre-existing information is a common approach to resolving these kinds of problems. For 3D reconstruction, neural networks are suitable because of their capability to encode and utilize existing information. To generate diverse 3D representations of ICF implosions from experimental data, half a dozen distinct convolutional neural networks are employed. Deep supervision is employed in the training of a neural network, resulting in high-resolution reconstructions. The ablator, inner shell, and the connection between the hemispheres of the shell, among other 3D capsule features, are tracked using these representations. Different priors augmenting machine learning presents a promising approach to 3D reconstructions in ICF and x-ray radiography.
A fresh approach to model position sensing is presented for levitation of models with a small length-to-diameter ratio in magnetic suspension and balance systems (MSBS). The MSBS model-support device, proving invaluable for wind-tunnel testing, enables the study of flow fields around blunt bodies free from the influence of mechanical supports. This methodology provides aerodynamic force measurements derived from a pre-calibrated magnetic force relation. The new method in wind tunnel experiments, thanks to a low fineness ratio model, allows for the complete removal of mechanical supports. The method adopts the use of two line sensors positioned parallel to the central axis of the model image. This enables position measurements with a resolution exceeding 0.006 mm or degrees, even for extremely thin model geometries. The camera’s depth measurements were further refined by compensating for the second-order term in the depth axis. Calibration of the sensors preceded the levitation of a circular cylinder model with a low fineness ratio. Model operation was tested both with and without the stream of free flowing air. Applying this position measurement method extended to a reentry capsule model. Maintaining a stable position and attitude near the origin, the model experienced levitation.
On the Mars 2020 vehicle’s MEDLI2 sensor suite and in the Low-Earth Orbit Flight Test of an Inflatable Decelerator (LOFTID) mission, passively cooled Schmidt-Boelter gauges are the method for heat flux sensing. Experiments have consistently illustrated that the output of the sensors is tied to the temperature of the sensor element. The outcomes of the experiment are in agreement with a model that considers the temperature-sensitivity of material properties, notably the Seebeck coefficient. In advance of mounting the MEDLI2 and LOFTID flight heat flux sensors onto the vehicles, a complete thermal calibration was absent, due to the unknown nature of the temperature dependence. The designs, being proprietary, prevent the knowledge of the material properties. These factors necessitated the derivation of an approximate correction factor. The presented temperature-dependent correction factor’s applicability and associated uncertainty are discussed in this document. Temperature-related inaccuracies could reach 95% for the MEDLI2 and 16% for the LOFTID total heat flux sensors if such effects are not considered during the measurement process. A critical step for future flight and ground applications that incorporate passively cooled heat flux sensors is the individualized calibration of each sensor at all relevant temperatures, allowing for the consideration of inherent sensor variations and minimizing measurement error.
To investigate 3D pyroelectric distributions in thin vinylidene fluoride-trifluoroethylene copolymer films, a laser scanning microscope employing the Laser Intensity Modulation Method was created. The setup is built from the following components: a laser unit, a laser driver, an xyz-stepper motor unit, a transimpedance amplifier, and a lock-in amplifier. Magnetic levitation secures the focus lens within the laser unit, enabling correction of system defocusing or sample surface tilt. Across a range of samples, the system’s lateral resolution for evaluating the topological surface structure or pyroelectric distribution patterns has been demonstrated to be one meter. Measurements of small pyroelectric currents and their variations within a pyroelectric sample are facilitated by a system comprising a self-designed laser driver, a transimpedance amplifier, and a fast lock-in amplifier, with a sensitivity of roughly 1 pA. A 4 MHz maximum frequency and rapid lock-in facilitate high-resolution measurements of 3D pyroelectric distributions. A 3-day procedure involves scanning 30 distinct layers within the sample, each possessing depths ranging from 100 nanometers to 5 meters. Within each layer, 100 x 100 points are measured along the xy-plane.
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