Cylindrical Target Research Articles

Calibration Method for Line-Structured Light Three-Dimensional Measurement Based on a Simple Target

Line-structured light three-dimensional (3D) measurement is apt for measuring the 3D profile of objects in complex industrial environments. The light-plane calibration, which is a crucial link, greatly affects the accuracy of measurement results. This paper proposes a novel calibration method for line-structured light 3D measurement based on a simple target, i.e., a single cylindrical target (SCT). First, the line-structured light intersects with the target to generate a light stripe. Meanwhile, the camera captures the calibration images, extracts the refined subpixel center points of the light stripe (RSCP) and detects the elliptic profiles of the two ends of the cylindrical target (EPCT). Second, two elliptical cones defined by the EPCT and the camera optical center are determined. Combining the two defined elliptical cones and the known radius of the SCT, we can uniquely solve the axis equation of the SCT. Finally, because the coordinates of RSCP in the camera coordinate system fulfill both the camera model and the cylindrical equation, these coordinates can be solved and used to obtain the optimal solution of the light-plane equation. The results of simulations and experiments verify that our proposed method has higher accuracy and effectiveness.

Two-mirror compact system for ideal concentration of diffuse light.

We introduce a simple, compact two-mirror system for diffuse light concentration. The design principle is based on local conservation of optical brightness. The system design is flexible, and we are able to compute mirror shapes given arbitrary incident beam direction and target cross-sectional shape. As illustration, we showcase our design for flat and cylindrical target geometries, and we also demonstrate that our system is able to concentrate efficiently along one or two dimensions. We perform numeric experiments that confirm our theoretical results and provide diffuse light concentration very close to the thermodynamic limit in all cases we considered.

The Dynamics and Nonequilibrium Ionic Composition of a Highly Ionized Plasma Сreated by Interaction of a High-Power Laser-Radiation Pulse with a Cylindrical Plasma Target

The Dynamics and Nonequilibrium Ionic Composition of a Highly Ionized Plasma Сreated by Interaction of a High-Power Laser-Radiation Pulse with a Cylindrical Plasma Target

On the initiation and evolution of dielectric breakdown in auto-magnetizing liner experiments

Auto-magnetizing (AutoMag) liners are cylindrical tubes composed of discrete metallic helices encapsulated in insulating material; when driven with a ∼2 MA, ∼100-ns prepulse on the 20 MA, 100-ns rise time Z accelerator, AutoMag targets produced >150 T internal axial magnetic fields [Shipley et al., Phys. Plasmas 26, 052705 (2019)]. Once the current rise rate of the pulsed power driver reaches sufficient magnitude, the induced electric fields in the liner cause dielectric breakdown of the insulator material and, with sufficient current, the cylindrical target radially implodes. The dielectric breakdown process of the insulating material in AutoMag liners has been studied in experiments on the 500–900 kA, ∼100-ns rise time Mykonos accelerator. Multi-frame gated imaging enabled the first time-resolved observations of photoemission from dynamically evolving plasma distributions during the breakdown process in AutoMag targets. Using magnetohydrodynamic simulations, we calculate the induced electric field distribution and provide a detailed comparison to the experimental data. We find that breakdown in AutoMag targets does not primarily depend on the induced electric field in the gaps between conductive helices as previously thought. Finally, to better control the dielectric breakdown time, a 12–32 mJ, 170 ps ultraviolet (λ = 266 nm) laser was implemented to irradiate the outer surface of AutoMag targets to promote breakdown in a controlled manner at a lower internal axial field. The laser had an observable effect on the time of breakdown and subsequent plasma evolution, indicating that pulsed UV lasers can be used to control breakdown timing in AutoMag.

Double cylinder target design for study of hydrodynamic instabilities in multi-shell ICF

Cylindrical implosions are used to study hydrodynamic instability growth for inertial confinement fusion (ICF) applications, as the cylindrical geometry allows for easier diagnostic access while retaining convergence effects. In this work, we use the established cylindrical implosion platform [Palaniyappan et al., Phys. Plasmas 27, 042708 (2020)] to inform the double shell ICF campaign [Montgomery et al., Phys. Plasmas 25, 092706 (2018)]. We present a design for a double cylindrical target as an analogue to the double shell ICF capsule in order to study hydrodynamic instability growth on the high-Z inner shell. Our design work is done with two-dimensional (2D) Eulerian radiation-hydrodynamics simulations, considering the axial uniformity of the implosion and feasibility of measuring the instability growth of pre-seeded single mode sinusoidal perturbations. We discuss in depth the design for a target to be directly driven at the OMEGA laser facility [Boehly et al., Opt. Commun. 133, 495 (1997)]. We evaluate the design for axial implosion symmetry and visibility of instability growth using synthetic radiographs constructed from the simulations, as the instability growth on the inner cylinder is experimentally measured using x-ray radiography of the implosion. We find that the seeded perturbation growth on the inner cylinder should be visible in an experiment, even with axial implosion asymmetry and preheat. We compare our 2D simulations with linear theory predictions for perturbation growth and show that a cylinder with lower azimuthal mode number (mode-20) perturbations compares more favorably with linear theory, while a cylinder with higher azimuthal mode number (mode-40) perturbations at the same starting amplitude saturates and is over-predicted by linear theory.

Fluorescence strobo-stereoscopy for specular reflection-suppressed full field of view imaging

This paper introduces fluorescence strobo-stereoscopy (FSS) to suppress strong specular reflection and enable the full field of view (FFOV) 3D surface imaging while the part is rotating. Specular reflection off the target surface significantly degrades the image quality and becomes critical for highly reflective surface measurements. In FSS, the fluorescent dye-doped fluid applied on the machined surface is excited upon incident ultra-violet light and becomes a new light source by Stokes' Law. Thus, specular reflection off of smooth surface can be suppressed by separating the fluorescent light from the excitation light. The developed FSS comprises a pair of imaging cameras, spatial filters, and an excitation light source. As a result, FSS effectively rejected the specular reflection and improved the FFOV 3D surface image quality of the machined part by enhancing contrast in the rotating target surface. Such enhancements in 3D imaging allowed to identify manufacturing tolerance of the part and to detect the surface features. The axial and lateral accuracy errors of FSS were 2.3% and 1.4% with the target size of 4.07 mm and 0.215 mm, respectively. A whole view reconstruction of the cylindrical target sample was performed, and the corresponding cylindricity and diameter deviation were assessed. The fluid media effect and the target surface quality effect were discussed.

Engineering in-plane mechanics of electrospun polyurethane scaffolds for cardiovascular tissue applications

Effective cardiovascular tissue surrogates require high control of scaffold structural and mechanical features to match native tissue properties, which are dependent on tissue-specific mechanics, function heterogenicity, and morphology. Bridging scaffold processing variables with native tissue properties is recognized as a priority for advancing biomechanical performance of biomedical materials and, when translated to the clinical practice, their efficacy. Accordingly, this study selected electrospinning on a rotating cylindrical target as an apparatus of broad application and mapped the relationship between key processing variables and scaffold mechanics and structure. This information was combined with mechanical anisotropy ranges of interest for the three main categories of tissue surrogated in cardiovascular tissue engineering: heart valve leaflets, ventricle wall, and large diameter blood vessels. Specifically, three processing variables have been considered: the rotational velocity and the rastering velocity of the mandrel and the dry (single nozzle – polymer only) vs wet (double nozzle – polymer plus phosphate buffer saline solution) fabrication configuration. While the dry configuration is generally utilized to obtain micro-fiber based polymeric mats, the wet fabrication is representative of processing conditions utilized to incorporate cells, growth factors, or micro-particles within the fibrous scaffold matrix. Dry and wet processed electrospun mats were fabricated with tangential and rastering velocities within the 0.3–9.0 m/s and 0.16–8 cm/s range respectively. Biaxial mechanics, fiber network, and pore micro-architectures were measured for each combination of velocities and for each fabrication modality (dry and wet). Results allowed identification of the precise combination of rotational and rastering velocities, for both dry and wet conditions, that is able to recapitulate the native cardiovascular tissue anisotropy ratio. By adopting a simple and broadly utilized electrospinning layout, this study is meant to provide a repeatable and easy to access methodology to improve biomimicry of the in plane-mechanics of heart valve leaflets, ventricular wall, and large diameter blood vessels.

Planetary physics research at the Facility for Antiprotons and Ion Research using intense ion beams

Intense particle beams offer a new efficient driver to produce extended samples of high energy density (HED) matter with extreme physical conditions that are expected to exist in the planetary interiors. In this paper, we present two-dimensional hydrodynamic implosion simulations of a multi-layered cylindrical target that is driven by an intense uranium beam. The target is comprised of a sample material (which is water in the present case) that is enclosed in a cylindrical tungsten shell. This scheme is named LAPLAS that stands for Laboratory Planetary Science, and it leads to a low entropy compression. This means that the water sample is compressed to super-solid densities, ultra-high pressures, but relatively low temperatures. Such exotic conditions are predicted to exist in the cores of water-rich solar, as well as extrasolar planets. The beam parameters are chosen to match the characteristics of the particle beam that will be delivered by the heavy ion synchrotron, SIS100, at the Facility for Antiprotons and Ion Research (FAIR), at Darmstadt. It is to be noted that the LAPLAS scheme is an important part of the HED physics program at FAIR, which is named HEDP@FAIR. The simulations predict that the LAPLAS experiments will produce a wealth of information on the Equation-of-State properties of the exotic matter that forms the planetary cores. This information can be very helpful in understanding the formation, evolution and the final structure of the planets.

Calibration of line-structured light vision sensor based on free-placed single cylindrical target

This paper proposes a novel calibration method for the Line-structured Light Vision Sensor (L-LVS) based on a straight cylindrical target that can be free placed. The cylindrical target is placed at least once in the measurement space. The camera captures the image of the cylindrical target and the light stripe. Based on the geometric properties of the cylinder and vanishing points, we calculate the 3D centers of the cylindrical end circles and reconstruct the cylindrical quadric surface. Then, multiple 3D points on the cylindrical surface are obtained according to the perspective projection relationship, which finally allows for the reconstruction of the light plane. Both simulation and real experiments show that the proposed method is effective. In the real experiments, the measurement accuracy of a L-LVS based on the proposed calibration method achieves 0.056 mm, when the measuring distance is about 400 mm. Due to the small-size and pose-unconstrainted target, our calibration method is superior to be applied in the confined measurement space in the wild.

Exploring extreme magnetization phenomena in directly driven imploding cylindrical targets

This paper uses extended-magnetohydrodynamics (MHD) simulations to explore an extreme magnetized plasma regime realizable by cylindrical implosions on the OMEGA laser facility. This regime is characterized by highly compressed magnetic fields (greater than 10 kT across the fuel), which contain a significant proportion of the implosion energy and induce large electrical currents in the plasma. Parameters governing the different magnetization processes such as Ohmic dissipation and suppression of instabilities by magnetic tension are presented, allowing for optimization of experiments to study specific phenomena. For instance, a dopant added to the target gas-fill can enhance magnetic flux compression while enabling spectroscopic diagnosis of the imploding core. In particular, the use of Ar K-shell spectroscopy is investigated by performing detailed non-LTE atomic kinetics and radiative transfer calculations on the MHD data. Direct measurement of the core electron density and temperature would be possible, allowing for both the impact of magnetization on the final temperature and thermal pressure to be obtained. By assuming the magnetic field is frozen into the plasma motion, which is shown to be a good approximation for highly magnetized implosions, spectroscopic diagnosis could be used to estimate which magnetization processes are ruling the implosion dynamics; for example, a relation is given for inferring whether thermally driven or current-driven transport is dominating.

Shot peen forming pattern optimization to achieve cylindrical and saddle target shapes: The inverse problem

The inverse problem of determining how to shot peen a plate such that it deforms into the desired target shape is a challenge in the peen forming industry. While peening thick plates uniformly on one side results in a spherical shape, with the same curvature in all directions, complex peening patterns are required to form other shapes, such as cylinders and saddles found on fuselages and wing skin panels. In this study, we present an optimization procedure to automatically compute shot peening patterns. This procedure relies on an idealized model of the peen forming process, where the effect of the treatment is modeled by in-plane expansion of the peened areas, and on an off-the-shelf optimization algorithm. For validation purposes, we peen formed three 305 × 305 × 4.9 mm and two 762 × 762 × 4.9 mm 2024–T3 aluminium alloy plates into cylindrical and saddle shapes using the same peening treatment. The obtained shapes qualitatively match simulations. For 305 × 305 × 4.9 mm plates, the relative differences had the same distribution and were of the same order of magnitude as initial out-of-plane deviations measured on the as-received plates.

一個流しスパッタリング成膜のためのターゲット‐基材間短縮が成膜レートや膜質に及ぼす影響

A magnetron sputtering device was prototyped for forming a thin film from the entire circumference of a rod-shaped substrate, which was placed coaxially in the inner space of a cylindrical sputtering target. The deposition rate of TiN by employing the coaxial sputtering was as slow as 1.33 μm/h when DC discharge was used, and the deposition rate required for small-volume, ultra-high-speed deposition technology was not obtained. Therefore, we came up with the idea of realizing ultra-high-speed deposition with the coaxial sputtering by reducing target-substrate distance, and as a first step, we investigated the relationship between the target-substrate distance and the deposition rate using a planar magnetron sputtering device. As a result, the deposition rate of Ti thin film exceeded 50 μm/h at a target-substrate distance of 10 mm. It was suggested that decreasing target-substrate distance could provide a deposition rate required for low-volume, ultra-high-speed deposition technology.

A Forward Scattering Model in Two-Dimensional Half-Space for Scatterers’ Size Estimation Using Linear Inversion

Analytic expressions of scattered electric fields for different categories of cylindrical targets buried in the half-space have been developed. In all the cases, investigation domains have been considered two-dimensional and are infinitely long in the remaining dimension. The investigation domains have been excited by the fields generated by a z-directed line source of constant amplitude, operating in the microwave frequencies. The usefulness and validity of these scattering models have been examined by inversion of the scattered electric field generated by the same. The inversion is based on the fact that the scattered field is mapped by a linear operator containing the induced current density and Green’s function of the investigation domain. On application of the incident field, the presence of a discontinuity in half-space induces the current density. By using the information retrieved from the reconstruction of current density by inversion and analytical expressions of the scattered electric field, information about the diameter and the type of the scatterer have been obtained. In addition, the performance of the linear sampling method for shape reconstruction of the scatterer in half-space is also explored.

On the Limitations of Hyperbola Fitting for Estimating the Radius of Cylindrical Targets in Nondestructive Testing and Utility Detection

Hyperbola fitting is a mainstream interpretation technique used in ground penetrating radar (GPR) due to its simplicity and relatively low computational requirements. Conventional hyperbola fitting is based on the assumption that the investigated medium is a homogeneous half-space, and that the target is an ideal reflector with zero radius. However, the zero-radius assumption can be easily removed by formulating the problem in a more generalized way that considers targets with arbitrary size. Such approaches were recently investigated in the literature, suggesting that hyperbola fitting can be used not only for estimating the velocity of the medium, but also for estimating the radius of subsurface cylinders, a very challenging problem with no conclusive solution to this day. In this paper, through a series of synthetic and laboratory experiments, we demonstrate that for practical GPR survey, hyperbola fitting is not suitable for simultaneously estimating both the velocity of the medium and the size of the target, due to its inherent non-uniqueness, making the results unreliable and sensitive to noise.

Reactivity worth measurement of the lead target on VENUS-II light water reactor and validation of evaluated nuclear data

In this paper, the benchmark experiment of the lead reactivity worth was introduced in detail, which has been carried out under a super-critical state at the light water reactor of the VENUS-II experimental facility. The reactivity worth of the cylindrical lead target was measured and processed as 142.0 ± 11.3 pcm by the period method. In simulations, the reactivity worth of the lead target was calculated by MCNP with the five libraries, i.e., ENDF/B-VII.1, ENDF/B-VII.0, JENDL-4.0, CENDL-3.1 and JEFF-3.2. By comparisons, the MCNP simulated results of the lead reactivity worth with ENDF/B-VII.1, ENDF/B-VII.0, CENDL-3.1 and JEFF-3.2 libraries are underestimated, and that of JENDL-4.0 shows slight better agreement with the experiment data within errors. Through the perturbation analysis, the (n, el) reaction channel is most related to the positive reactivity worth of the lead target. Additionally, the reaction rates of the (n, el), (n, inl) and (n, γ) channels were calculated by FM card in MCNP. It is observed that the (n, γ) reaction rates from different libraries show the maximum difference, which is due to the discrepancy of the (n, γ) cross sections in the thermal neutron region. In conclusion, the lead cross sections from the main libraries in the world have been preliminarily validated based on the measurements, which lays the foundation for the engineering design of CIADS.

Rayleigh scattering of a cylindrical sound wave by parallel, infinite cylinders

Scattering of sound by a target can be described as a wave radiated by virtual point sources inside the target. In the Rayleigh scattering regime, the strength of the virtual sources can be calculated analytically, and the number of linear sources is finite. When a target is located close to the ocean surface or another reflecting boundary, reflections of the incident and single-scattered waves from the boundary lead to multiple scattering from the target, with the target being insonified by nearby virtual sources. The virtual source method has recently been applied to study low-frequency acoustic fields in the vicinity of cylindrical targets near a pressure release surface or a hard bottom. This method is extended here to study the acoustic field in the near- and far-field of parallel cylindrical targets for arbitrary positions of the sound source. Multiple scattering solutions for scattering from soft, hard, and fluid targets are considered.

Reflection of Detonation Wave from the Symmetry Plane within a Cylindrical Target for Controlled Thermonuclear Fusion

Reflection of Detonation Wave from the Symmetry Plane within a Cylindrical Target for Controlled Thermonuclear Fusion

A feasibility study of time of flight cone beam computed tomography imaging.

The time of flight (TOF) cone beam computed tomography (CBCT) was recently shown to reduce the X-ray scattering effects by 95% and improve the image CNR by 110% for large volume objects. The advancements in X-ray sources like in compact Free Electron Lasers (FEL) and advancements in detector technology show potential for the TOF method to be feasible in CBCT when imaging large objects. To investigate the feasibility and efficacy of TOF CBCT in imaging smaller objects with different targets such as bones and tumors embedded inside the background. The TOF method used in this work was verified using a 24 cm phantom. Then, the GATE software was used to simulate the CBCT imaging of an 8 cm diameter cylindrical water phantom with two bone targets using a modeled 20 keV quasi-energetic FEL source and various TOF resolutions ranging from 1 to 1000 ps. An inhomogeneous breast phantom of similar size with tumor targets was also imaged using the same system setup. The same results were obtained in the 24 cm phantom, which validated the applied CBCT simulation approach. For the case of 8 cm cylindrical phantom and bone target, a TOF resolution of 10 ps improved the image contrast-to-noise ratio (CNR) by 57% and reduced the scatter-to-primary ratio (SPR) by 8.63. For the case of breast phantom and tumor target, image CNR was enhanced by 12% and SPR was reduced by 1.35 at 5 ps temporal resolution. This study indicates that a TOF resolution below 10 ps is required to observe notable enhancements in the image quality and scatter reduction for small objects around 8 cm in diameter. The strong scattering targets such as bone can result in substantial improvements by using TOF CBCT.

Estimation of the neutron generation in the combined magneto-inertial fusion scheme

The results of calculating the combined effects of intense laer beams and plasma jets on a cylindrical target located in external magnetic field are presented. Parameters of compressed plasma are demonstrated and the capability to create neutron source with combined scheme—the number of neutrons per unit length N fus ≈ 1015 n · cm−1 by the time the exposure is completed, is shown. The conclusion is drawn about the prospects of the combined use of laser radiation and pulsed jets in interaction with a magnetized target.

The role of target closure in detachment in Magnum-PSI

A cylindrical target with a high degree of closure was exposed to ITER divertor-relevant plasmas with typical electron temperatures of 2 eV, electron densities of 5⋅1020 m−3, and heat fluxes up to 20 MWm−2 in the linear device Magnum-PSI. By terminating the plasma in an unpumped closed volume, neutral pressures were enhanced from about 0.5 to 20 Pa without any increase in the neutral flux returning to the plasma. Such pressures were sustained largely by the pressure exerted by the incoming plasma. By means of hydrogen gas injection, internal neutral pressures of up to 40 Pa were reached during plasma exposure. We find that at these high neutral pressures, a < 1 eV recombination front forms and expands from the back of the cylinder, so that downstream density drops dramatically. Furthermore, in these scenarios, heat deposition to the back plate vanishes and is redirected to the upstream part of the cylinder and to hot neutrals, which can carry 50% of the plasma input power. A power balance analysis reveals that even without additional gas puffing, only about 10% of the incoming heat load reaches the back plate for the 20 MWm−2 plasma. These results demonstrate the important role of closed target configurations and local gas puffing in mitigating plasma heat loads and indicate that the gained experience should be taken into account in next-generation divertor designs.