High-speed Radiography Research Articles

3D observations provide striking findings in rubber elasticity

The mechanical response of rubbers has been ubiquitously assumed to be only a function of the imposed strain. Using innovative X-ray measurements capturing the three-dimensional spatial volumetric strain fields, we demonstrate that rubbers and indeed many common engineering polymers undergo significant local volume changes. But remarkably, the overall specimen volume remains constant regardless of the imposed loading. This strange behavior which also leads to apparent negative local bulk moduli is due to the presence of a mobile phase within these materials. Combining X-ray tomographic observations with high-speed radiography to track the motion of the mobile phase, we have revised classical thermodynamic frameworks of rubber elasticity. The work opens broad avenues to understand not only the mechanical behavior of rubbers but a large class of widely used engineering polymers.

(Invited) Benchmarking and Predicting the Risks of Commercial Li-Ion Cells Undergoing Thermal Runaway

The performance of commercial Li-ion batteries increases year after year. New mechanical designs of cells as well as changing electrolyte and active material compositions continually push performance boundaries forward. With such changes, the risks associated with thermal runaway of cells change too and a challenge persists in recording and benchmarking risks to determine whether increased performance comes at the expense of increased risk in the event of thermal runaway. The Battery Failure Databank provides a record of thermal and mass ejection behaviors of past and present commercial cells and provides a valuable resource for benchmarking behaviors and determining the predictability of risks associated with thermal runaway.A Fractional Thermal Runaway Calorimeter (FTRC), developed by the NASA Johnson Space Center in collaboration with the National Renewable Energy Laboratory (NREL), distinctly measures heat emitted from the body of commercial cells and heat that is ejected from the cell. The FTRC also facilitates in-situ high-speed radiography to link phenomena occurring inside the cell with external thermal measurements. The FTRC was used for all tests recorded in the Battery Failure Databank and high-speed radiographs accompany each thermal dataset. Having thermal, mass ejection, and internal dynamics behaviors from hundreds commercial cells under mechanical and thermal abuse conditions facilitates statistical analyses of cell behaviors and evaluation of the efficacy of machine learning methods for predicting risks associated with thermal runaway.Using data from the Battery Failure Databank, the following three topics will be covered in this talk: Correlations between heat generation and mass ejection: The total heat output from cells showed a strong correlation with the quantity of material ejected. An explanation for this based on distinct heat measurements from ejected and non-ejected materials will be discussed. Potential causes of outlier cells that produce exceptionally high heat: Upon conducting numerous repeat tests for each cell, outlier cells that produce exceptionally high quantities of heat were observed. High-speed radiography data revealed that internal dynamic phenomena can lead to extreme variations in thermal and ejection behavior observed externally. The predictability of thermal runaway outcomes using machine learning methods and limited data: With limited data on thermal behavior, mass ejection, and cell specifications, the accuracy of zero- and one-shot approaches to predicting the variation and distribution of heat output during thermal runaway of a new cell type, based on training data in the Battery Failure Databank, will be discussed. The analyses and open-access resources provided with this work are expected to provide a foundation for benchmarking the behavior and predictability of risks associated with thermal runaway of past and present commercial Li-ion cells. In addition to providing a valuable resource for designing safe battery systems, it is expected that this data will be imperative as we evaluate next generation cell designs and assess their respective failure mechanisms and associated risks.

Laser isotope separation of 192Ir

The following two-step isotope selective photoionization process has been studied for the separation of 192Ir isotope from natural Iridium irradiated in a medium flux reactor for 28 days.5d76s2F9/240.0cm−1→247.5871nm5d76s6p40389.83cm−1J=9/2→307.9nmIr+Density matrix formalism has been used for the investigation of laser isotope separation process. Optimum system parameters such as peak power densities of the excitation and ionization lasers, bandwidth of the excitation laser, angular divergence limit to the atomic ensemble have been derived. Effects of number density and ion travel distance prior to collection on charge exchange probability have also been studied. It has been shown that it is possible produce ∼98% enriched 192Ir at rate of 82 μg/h (27.9 GBq/h or 0.76 Ci/h) which can provide activity of 334 TBq/g or 9027 Ci/g. The enriched 192Ir can be used in both high-dose brachytherapy and high speed radiography. This is the first ever study on the laser based enrichment of Iridium isotopes.

Automatic melt pool recognition in X-ray radiography images from laser-molten Al alloy

Size and shape of the melt pool play an important role in the microstructure formation in materials additively manufactured by laser powder bed fusion (LPBF) techniques. It is an enormous challenge to determine them automatically in radiography image series taken during LPBF when the melt pool has a very low contrast to the surrounding base material. In this work, an approach solving this problem for Al alloys is presented. The melt pool is detected by a combination of different image processing methods and boundary conditions. The method developed in this work is demonstrated on high-speed radiography images taken at a synchrotron beamline during an in-situ LPBF experiment using an Al-Si alloy.

The impact of self-lacing technology on foot containment during dynamic cutting

The sport of basketball requires repeated dynamic side-to-side movements that can cause foot sliding and place excessive stress on the athlete. Footwear that provides containment to reduce the motion of the foot relative to the shoe may have performance and injury prevention advantages. Foot containment can vary significantly across different types of footwear due to its dependence on the interaction between the shoe lacing system of the upper and specific design features within the shoe. This study used high-speed stereo radiography to assess the impact of a self-lacing system with three conditions of increasing lace tension compared to a control basketball shoe on foot containment by measuring foot–shoe motion during cutting and jab step activities. Twenty healthy athletes performed dynamic cutting activities in view of a unique stereo radiography system positioned to measure motion of specific foot bones while motion capture and perception data were also collected. By tracking bead positions on the foot and shoe, relative motion of the foot inside the shoe was measured along shoe planes during activity. The self-lacing system showed statistically significant reductions in foot–shoe motion of as much as 75.2% while performing dynamic basketball cuts. Controlling tension with the lacing system provides athletes flexibility in containment to go from a loose fit to a tight fit and reduce in-shoe motion by up to 39.3%. Furthermore, perception data showed athletes had 20.1% greater confidence to perform cutting tasks with increases in lace tension. Reduction of in-shoe foot motion with a self-lacing system is an important consideration in the design of footwear for performance athletes.

Thermal Runaway of Li-Ion Cells: How Internal Dynamics, Mass Ejection, and Heat Vary with Cell Geometry and Abuse Type

Thermal runaway of lithium-ion batteries can involve various types of failure mechanisms each with their own unique characteristics. Using fractional thermal runaway calorimetry and high-speed radiography, the response of three different geometries of cylindrical cell (18650, 21700, and D-cell) to different abuse mechanisms (thermal, internal short circuiting, and nail penetration) are quantified and statistically examined. Correlations between the geometry of cells and their thermal behavior are identified, such as increasing heat output per amp-hour (kJ Ah−1) of cells with increasing cell diameter during nail penetration. High-speed radiography reveals that the rate of thermal runaway propagation within cells is generally highest for nail penetration where there is a relative increase in rate of propagation with increasing diameter, compared to thermal or internal short-circuiting abuse. For a given cell model tested under the same conditions, a distribution of heat output is observed with a trend of increasing heat output with increased mass ejection. Finally, internal temperature measurements using thermocouples embedded in the penetrating nail are shown to be unreliable thus demonstrating the need for care when using thermocouples where the temperature is rapidly changing. All data used in this manuscript are open access through the NREL and NASA Battery Failure Databank.

Syris: a flexible and efficient framework for X-ray imaging experiments simulation

An open-source framework for conducting a broad range of virtual X-ray imaging experiments, syris, is presented. The simulated wavefield created by a source propagates through an arbitrary number of objects until it reaches a detector. The objects in the light path and the source are time-dependent, which enables simulations of dynamic experiments, e.g. four-dimensional time-resolved tomography and laminography. The high-level interface of syris is written in Python and its modularity makes the framework very flexible. The computationally demanding parts behind this interface are implemented in OpenCL, which enables fast calculations on modern graphics processing units. The combination of flexibility and speed opens new possibilities for studying novel imaging methods and systematic search of optimal combinations of measurement conditions and data processing parameters. This can help to increase the success rates and efficiency of valuable synchrotron beam time. To demonstrate the capabilities of the framework, various experiments have been simulated and compared with real data. To show the use case of measurement and data processing parameter optimization based on simulation, a virtual counterpart of a high-speed radiography experiment was created and the simulated data were used to select a suitable motion estimation algorithm; one of its parameters was optimized in order to achieve the best motion estimation accuracy when applied on the real data. syris was also used to simulate tomographic data sets under various imaging conditions which impact the tomographic reconstruction accuracy, and it is shown how the accuracy may guide the selection of imaging conditions for particular use cases.

Foot Posture and Mobility in Normal and Pronated Feet during Gait using High-Speed Stereo Radiography

Foot Posture and Mobility in Normal and Pronated Feet during Gait using High-Speed Stereo Radiography

Possible application of compact electronics for multilayer muon high-speed radiography to volcanic cones

Abstract. Compact data-taking electronics were developed for high-speed multilayer muon radiography in order to minimize operation failure rates. By requiring a linear trajectory within the position sensitive detectors (PSDs), the background (BG) events produced by vertical electromagnetic (EM) showers are effectively reduced. In order to confirm the feasibility of this method, the system comprising four PSD layers was tested by imaging the internal structure of a parasitic cone and the adjacent craterlets formed in the 1910 eruption at the base of the Usu volcano, Hokkaido with a conventional (MURG08) readout system (Kusagaya et al., 2012; Uchida et al., 2009). The new mountain is believed to be a cryptodome since its formation. As knowledge on lava domes is accumulated at various volcanoes, the definition of "cryptodome" is now doubted in its validity. The results of the preliminary 290 h muon radiographic survey revealed that the "cryptodome" is not underlain by any lava mass and that a main craterlet is accompanied by magma intrusions at shallow depths. The former verifies that the new mountain is not a cryptodome but a volcanogenetic mound, and the latter interprets the phreatic explosions forming the craterlets as intrusions of magma into the aquifer. However, a higher data taking failure rate was observed with a software-based MURG08 system when the size of the active area of the detection system was enlarged to improve the detection ability of the system. The newly developed MURG12 is a complete electronics system that can simultaneously process signals from 192 scintillation counters with a data size of 600 kbps ch−1 without operation failure. We anticipate that the observation speed would be further improved by employing MURG12. At the base of the Usu volcano, in the 20th century, four eruptions occurred. Some of them demonstrated three characteristic stages of magma intrusions. First, a magma branch remained at a depth leaving an upheaval of the ground; second, it rose and reached aquifers causing phreatic explosions without extrusions; and third, it reacted with aquifers causing phreatic explosions and further extruded over the ground forming a lava dome. In order to clarify the eruption mechanism of Usu, it is necessary for us to image many parasitic cones. Based on the result of the test measurement, we anticipate that MURG12 would be a strong tool for high-speed muon radiography.

A compact pulsed X-ray source for high-speed radiography

A pulsed source of hard X rays for high-speed radiography is described. The source is composed of a line pulse transformer, which is discharged into an accelerating tube with a vacuum diode, producing a high-voltage pulse across the tube with an amplitude of up to 750 kV. The effective energy of X-ray quanta, determined by attenuation in a 5-mm-thick steel plate, is 125 keV. The X-ray dose at a distance of 1 m from the anode is 10 and 15 mR at a 40- and 60-ns full width at half-maximum of the X-ray pulse, respectively. The diameter of the X-ray emitting spot is <2 mm. Photographic images of a steel step wedge 5–15 mm thick and steel beads ≥0.5 mm in diameter have been obtained.

Restoration and Enhancement of X-Ray Images of Molten Pool during Laser Deep Penetration Welding

Owing to a strong capability of penetration, the radiography can be used to observe and analyze the formation of a molten pool inside weldments during laser deep penetration welding. The shape of a molten pool and the thermal transmit of laser through keyhole can be monitored and analyzed in real-time. During a high-power fiber laser bead on plate welding of Type 304 stainless steel, a high-speed radiography camera was employed to capture the molten pool images. These captured X-ray images were degraded by the disturbance and noises from the welding process and radiography devices. This paper proposes an efficient arithmetic to restore and enhance the X-ray images of molten pools. The point spread function (PSF) of X-ray image degeneration was obtained through blind deconvolution, And the PSF was applied as a parameter to implement the constrained least squares filtering of X-ray image of a molten pool. Also, the X-ray image was enhanced by contrast stretching transformation. Experimental results showed that the proposed arithmetic of image restoration and enhancement could improve the quality of X-ray images efficiently and protrude the contour feature of a molten pool.

Automated measurement of neural foramen cross-sectional area during in vivo functional movement

An automated technique to measure neural foramen cross-sectional area during in vivo, multi-planar movements is presented. This method combines three-dimensional (3D) models of each vertebra obtained from CT scans with in vivo movement data collected using high-speed biplane radiography. A novel computer algorithm that automatically traces a path around the bony boundary that defines the neural foramen at every frame of X-ray data is described. After identifying the neural foramen boundary, the cross-sectional area is calculated. The technique is demonstrated using data collected from a patient with cervical radiculopathy who is tested before and after conservative treatment. The technique presented here can be applied when 3D, dynamic, functional movements are performed. Neural foramen cross-sectional area can be quantified at specific angles of intervertebral rotation, allowing for matched comparisons between two trials or two test sessions. The present technique is ideal for longitudinal studies involving subjects who receive conservative or surgical treatments that may affect spine motion.

Suppression of Afterglow in CsI(Tl) by Codoping With ${\rm Eu}^{2+}$: Fabrication of Microcolumnar Films for High-Resolution High-Speed Imaging

Although CsI:Tl is one of the brightest and most efficient scintillator materials ever developed, its applicability for high speed imaging is limited by its persistent afterglow. We have demonstrated that much of this afterglow can be suppressed by the addition of Eu2+ to the CsI host lattice. The magnitude of the effect depends strongly on the duration of the excitation pulse, but is virtually independent of its intensity. Our observations indicate that the presence of Eu2+ ions introduces a set of electron traps that fundamentally alter the decay kinetics, making the material useful for such applications as high speed radiography and, perhaps, X-ray CT. At RMD several single crystals of CsI:Tl, Eu with Eu2+ concentrations between 0.05 to 0.5 mole percent have been grown using the Bridgman technique. Here we report on our fabrication of microcolumnar films of the material using thermal vapor deposition for high-resolution digital radiography applications. Our data suggests that the afterglow suppression effect has a profound impact on high speed imaging performance, allowing rapid data acquisition with substantially reduced persistence from previous frames. The latest results on the effect of the codopant on the luminescence from CsI:Tl crystals as well as microcolumnar films will be reported.

MENISCI DISPLACEMENT UNDER JOINT LOAD

MENISCI DISPLACEMENT UNDER JOINT LOAD

High flux neutron imaging for high-speed radiography, dynamic tomography and strongly absorbing materials

We present NEUTROGRAPH, a new instrument for high-flux neutron radiography and tomography at the Institut Laue-Langevin in Grenoble, France. It has been operational since October 2002. With a high-intensity thermal neutron beam of about 3×10 9 n cm −2 s −1, NEUTROGRAPH is dedicated to real-time, snapshot and stroboscopic radiography with time resolution down to a few microseconds, as well as dynamic tomography on a sub-minute time scale. The high intensity also allows the visualization of thick and strongly absorbing materials. This allows investigation of larger samples with extremely low contrast, as in some fields of material science and archaeology. Various experiments have been carried out during the last 2 years. We present the large spectrum of applications and we describe the properties of a detector system dedicated to these types of experiments. Furthermore, we describe an algorithm to eliminate the effects of scintillator degradation in intense neutron fluxes.

Base-Metal Saturation of Refractory Carbide Coatings Produced by Enhanced Ceramic Jets in Electrothermally Exploded Powder Spray

Tungsten carbide and tantalum carbide were sprayed onto substrates of mild steel by the electrothermally exploded powder spray (ELTEPS) process. High-speed x-ray radiography revealed that tungsten-carbide jets of molten particles guided inside a nozzle exhibited denser flow than unguided jets at the substrate. The velocity of the jet was approximately 800 m/s at the early stage of jetting. The ceramic coatings obtained from the guided spray consisted of carbides of a few to tens of micrometers in size, which were saturated by the base metal up to the top of the coating. The coatings exhibited diffusion of the sprayed ceramics and base metal at the interface of the deposit and substrate. The enhancement of the jet flow formed a microstructure of the ceramic coating, which was saturated by the base metal even without post heat treatment.

63. キロヘルツパルスX線装置(4機種)の試作と応用

63. キロヘルツパルスX線装置(4機種)の試作と応用

MOMENTUM TRANSFER IN THE MIXING OF PARTICLE CLOUDS PLUNGING INTO WATER

Abstract This work discusses certain fundamental aspects in the mixing of particle clouds plunging into water. In particular, the momentum transfer in the isothermal interaction is considered here, as part of a broader investigation involving very high-temperature particles and thus heat transfer and phase change, as related to the premixing phase of steam explosions. The focus is on the multifield behaviour, and the investigation is carried out experimentally in the MAGICO-2000 facility: we observe front advancements, mixing region evolution and water displacements. The effect of particle volume fraction, density, inlet velocity and pool geometry are analyzed. Measurements are taken by means of high-speed videos and X-ray radiography: the latter allows us to map the interior of the mixing region, highlighting interesting features of the interaction. All results are compared to the numerical simulations obtained with the PM-ALPHA code, and the exercise reveals good predictive capabilities for it.

63.キロヘルツパルスX線装置(4機種)の試作と応用(第24回秋季学術大会 一般研究発表予稿集)

63.キロヘルツパルスX線装置(4機種)の試作と応用(第24回秋季学術大会 一般研究発表予稿集)

Sub-kilohertz flash X-ray generator utilising a glass-enclosed cold-cathode triode.

The construction and fundamental studies are described for a sub-kilohertz X-ray generator for producing low-dose rate flash X-rays. The X-ray tube was a glass-enclosed cold-cathode triode, composed of a tungsten plate target, a rod-shaped graphite cathode, a mesh-type trigger electrode made of tungsten wires, and a glass tube body. The coaxial condenser was charged up to 60 kV by a power supply, and the electric charges in the condenser were discharged to the X-ray tube repetitively when a negative high-voltage pulse was applied to the trigger electrode. The maximum tube voltage before the discharging was equivalent to the initial charged voltage of the condenser, and the maximum tube current was about 0.3 kA with a charged voltage of 60 kV. The X-ray durations were about 1 microsecond, and the X-ray intensity was about 0.47 microC kg-1 at 0.5 m per pulse with a charged voltage of 60 kV. The maximum repetition rate of the X-rays was about 0.4 kHz, and high-speed radiography was performed.