High-speed Measurement Research Articles

Squeezed dual-comb spectroscopy.

Optical frequency combs have enabled unique advantages in broadband, high-resolution spectroscopy and precision interferometry. However, quantum mechanics ultimately limits the metrological precision achievable with laser frequency combs. Quantum squeezing has led to significant measurement improvements with continuous wave lasers, but experiments demonstrating metrological advantage with squeezed combs are less developed. Using the Kerr effect in nonlinear optical fiber, a 1 GHz frequency comb centered at 1560 nm is amplitude-squeezed by >3 dB over a 2.5 THz bandwidth. Dual-comb interferometry yields mode-resolved spectroscopy of hydrogen sulfide gas with a signal-to-noise ratio nearly 3 dB beyond the shot-noise limit. The quantum noise reduction leads to a two-fold quantum speedup in the determination of gas concentration, with impact for high-speed measurements of multiple species in dynamic chemical environments.

Capillary infiltration measurements by finite size drop method: wetting, spreading and infiltration of liquid silver in porous iron

The study proposes a direct method for studying capillary infiltration of porous media using high-speed measurements of the shape of an imbibited droplet of finite size. The method assumes isotropic infiltration, and the change in the droplet volume on the surface is equated to the volume of imbibited liquid. The shape of the imbibited volume in the case of a droplet of finite volume is assumed to be a flattened spheroid. In the mathematical model, the rate of change of the apparent volume obtained in the experiment is reduced to the rate of movement of the liquid front in the porous media.Measurements of capillary processes in the silver (melt)-iron (porous or dense solid) system were carried out at various temperatures in a vacuum of 10-3Pa to verify the model. Time dependencies of the wetting contact angle and the contact diameter of pure silver melt on the surface of dense solid iron, the imbibition rate of silver melt into porous iron, and the kinetics of sintering of iron powder were measured. All measurements were conducted using direct methods of high-speed video and thermal imaging. As a result, in addition to the application of the proposed imbibition model, kinetic dependencies of the mentioned processes at various temperatures in the range from 1000 to 1150 °C were obtained and their activation energies were determined.

High-speed tissue metabolism measurement using a combination of diffuse speckle contrast analysis and near-infrared spectroscopy

This study presents and validates a multimodal optical system combining diffuse speckle contrast analysis (DSCA) and near-infrared spectroscopy (NIRS) with a unique system design for high-speed tMRO2 monitoring. The optical system for simultaneous dual-wavelength illumination and detection by a single camera is constructed using dichroic mirrors without an external trigger device. Phantom experiments and in-vivo arterial occlusion tests are conducted by varying the camera exposure time from 0.5 ms to 10 ms to validate system performance. We analyze and compare the results according to the exposure time to acquire the optimal relative tMRO2 (rtMRO2) signal by dual-exposure time control. The in-vivo experiment confirmed that the relative blood flow (rBF) and tissue oxygenation index (TOI) signals from the two modalities had a trade-off with the camera exposure time. We obtained the optimal rtMRO2 using dual-exposure time control. We conclude that the proposed DSCA/NIRS provides real-time rtMRO2 assessment, which can provide biomarkers for diagnosing vascular diseases.

Confinement-sensitive volume regulation dynamics via high-speed nuclear morphological measurements

Diverse tissues in vivo present varying degrees of confinement, constriction, and compression to migrating cells in both homeostasis and disease. The nucleus in particular is subjected to external forces by the physical environment during confined migration. While many systems have been developed to induce nuclear deformation and analyze resultant functional changes, much remains unclear about dynamic volume regulation in confinement due to limitations in time resolution and difficulty imaging in PDMS-based microfluidic chips. Standard volumetric measurement relies on confocal microscopy, which suffers from high phototoxicity, slow speed, limited throughput, and artifacts in fast-moving cells. To address this, we developed a form of double fluorescence exclusion microscopy, designed to function at the interface of microchannel-based PDMS sidewalls, that can track cellular and nuclear volume dynamics during confined migration. By verifying the vertical symmetry of nuclei in confinement, we obtained computational estimates of nuclear surface area. We then tracked nuclear volume and surface area under physiological confinement at a time resolution exceeding 30 frames per minute. We find that during self-induced entrance into confinement, the cell rapidly expands its surface area until a threshold is reached, followed by a rapid decrease in nuclear volume. We next used osmotic shock as a tool to alter nuclear volume in confinement, and found that the nuclear response to hypo-osmotic shock in confinement does not follow classical scaling laws, suggesting that the limited expansion potential of the nuclear envelope might be a constraining factor in nuclear volume regulation in confining environments in vivo.

A high-speed camera-based measurement system for monitoring and controlling the induced jet break-up fabrication of advanced ceramic breeder pebbles

The production of lithium-rich ceramic pebbles is crucial for future fusion reactors, as they are one of the most important components of the tritium-breeding blankets. In order to produce high-quality pebbles, a melt-based fabrication process KALOS (KArlsruhe Lithium OrthoSilicate) has been developed at the Karlsruhe Institute of Technology (KIT), which produces pebbles utilising the break-up of a molten laminar jet. Since the production of the pebbles is very precise (with diameters of hundreds of micrometres) and significantly influenced by process parameters, a system that monitors and regulates the fabrication in real-time is essential. This paper elaborates on a high-speed camera-based measurement system for automatically monitoring and controlling the production process. Experimental proof demonstrates that the presented measurement system can provide the real-time sizes, locations and distance distribution of the molten ceramic droplets accurately. In addition, the system is also designed to enable the control of the pebble production by adjusting a production parameter, i.e. the driving frequency, based on the real-time output of the proposed measurement system.

High-speed blood flow measurement based on a continuous laser-assisted nonlinear photoacoustic

High-speed blood flow measurement based on a continuous laser-assisted nonlinear photoacoustic

Researches on projectile muzzle velocity measurement system based on high-speed camera binocular intersection measurement and laser illumination

Abstract In order to reduce the impact of muzzle flame and smoke blurring on the flight trajectory imaging quality of projectile when measuring muzzle velocity in current weapon testing systems, a projectile velocity measurement system based on sequential pulsed laser illumination was studied. The wavelength of the pulsed laser is 532nm and the narrow-band filters with the same center wavelength were put in front of the camera lens which was used to suppress the influence of the flame. The pulsed laser and the filter helped the system to capture the images of the muzzle projectile wrapped in flames. The spatial movement distance of the projectile was calculated based on the principle of binocular intersection. The flying time of the projectile was determined by the high-speed camera shooting rate and the image frames intervals. The system was used to test the muzzle velocity of the projectile fired from a 12.7mm ballistic gun. The experiment results show that laser illumination effectively suppressed the influence of muzzle flames on projectile imaging. According to the calibration and binocular vision imaging algorithms, the muzzle velocity of the projectile was calculated with an accuracy of better than 0.3%. The method can measure the initial velocity of the projectile with the help of sequential pulsed laser illumination and short exposure time (as short as 1.1μs), which has great application value for range testing.

Depth-Resolved Structure Change of LiNi0.8Co0.2O2 Cathode during Battery Operation

Ni-rich layered oxides, which are isostructural to LiCoO2, are regarded as promising cathode materials alternative to LiCoO2 for lithium-ion batteries, since partial substitution of Ni with Co leads to a higher capacity and lower materials cost. However, increasing the Ni content causes a relatively rapid capacity fading, which is a challenge to overcome. It is considered that many factors are involved in the instability, such as irreversible crystal structure evolutions, degradation of morphological structures, and interface instabilities. To clarify the underlying mechanism the structure changes have been studied by various analysis techniques [1,2]. Regarding the structure evolutions near interfaces, the analyses were limited to static observations and dynamic observation during battery operation is lacking.In this study, we observed depth-resolved structure evolutions of LiNi0.8Co0.2O2 cathode near the interface to a solid electrolyte during battery operation using synchrotron X-ray crystal truncation rod (CTR) scattering. In order to realize the real-time atomic scale analysis, we utilized following two unique techniques. (i) A thin film battery with an epitaxial LiNi0.8Co0.2O2 cathode layer grown by pulsed-laser-deposition (PLD) was used as the specimen (Fig. 1(a)), which had a very sharp electrolyte/cathode interface suited to the atomic scale analysis [3,4]. (ii) A high-speed CTR measurement technique was used, which realized the operando observation of depth-resolved structure changes of thin films with a temporal resolution of 1 s [5,6].Fig. 1(b) shows a change of specular reflection CTR scattering profile observed during a discharge-charge. Since the LiNi0.8Co0.2O2 cathode layer was (001)-orientated, the CTR profile represents the structure along the [001] direction (c-axis). Fig. 1(c) shows the distribution of c-axis length obtained by analyzing the CTR scattering profiles. The H1, H2, H3, and M represent the crystal phases assigned based on the c-axis lengths, referring to previous reports [1,7]. When the Li content x in Li x Ni0.8Co0.2O2was larger than 0.9, the hexagonal H1 phase was uniformly formed. With decreasing x the variation of c-axis length along the depth direction was observed, and eventually a spatially separated two phases were observed in the range 0.3 < x < 0.6: hexagonal H2 and H3 phases were formed at the surface side and bottom side, respectively. The structure distribution indicates that the thermodynamically unstable H3 phase [1] was nucleated at the bottom.

Electrical spectra characterization of mode-locked fiber laser and application for high-speed optoelectronic devices measurement

A calibration-free and three-in-one electro-optic frequency sweeping-based method is proposed for the electrical spectra and frequency response characterization of mode-locked fiber laser (MLFL) MLFL, intensity modulators (IMs), and photodetectors (PDs) with a shared measurement scheme. By carefully setting the frequency relationship between the swept frequency, the extra influence from other assisted devices besides device under test (DUT) is fully cancelled out by analyzing the power ratio between the single-tone driving signal and electrical signals of the MLFL after photodetection. Moreover, the wideband requirement of the assistant devices is reduced by half to that of the DUT in the cases of the MLFL, IM, and PD measurement, respectively. The microwave characterization of the MLFL, IM and PD are experimentally extracted with the proposed method and the measured results are compared to those obtained with the traditional electro-optic frequency sweeping method to check the consistency and accuracy.

High-precision automated processing of sequential images for high-speed videogrammetric measurement

Abstract High-speed videogrammetric measurement is widely used in fields of structural health monitoring. However, it is difficult to perform efficient and accurate automation for the copious sequential images data. This paper proposes a novel high-precision automated sequential images processing method for high-speed videogrammetric measurement. First, a precision circular marker detection network model is proposed to detect circular marker, which can effectively address recognition challenges associated with small, dense, and deformed markers in complex scenarios with a precision of 99.37 and recall of 98.86. Second, a circular center tracker, utilizing Kalman filtering and the Hungarian matching algorithm, is presented to achieve highly automated sub-pixel tracking of marker centers with an root mean square error of 0.092 pixel. At last, a global confidence optimization matching strategy is put forward to attain precise automated stereo images matching with an accuracy of 94.48%. The results show that the proposed method can significantly advance the intelligence of high-speed videogrammetric measurement.

Stochastic Emission in Passively Fed Single-Emitter Porous-Media Ionic Liquid Ion Sources

Ionic liquid ion sources are a promising form of efficient thrust for power- and mass-constrained satellites. Flight performance requirements necessitate large arrays of emitters; however, the fundamental behaviors of the ion emission process are obscured by the simultaneous operation of multiple emitters. One such behavior is the stochastic nature of Taylor cone formation and ion emission from the emitter. To examine these phenomena, a single-emitter electrospray using a conventionally machined porous borosilicate emitter cone was operated using the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate. Repeated performance curves of the same emitter, measuring the emitter and extractor electrode currents as a function of the emitter voltage, vary significantly between tests. Ion current density spatial distribution maps of the plume and time-resolved emitter current and plume current while retarding potential energy analyzer sweeps are also presented. High-speed current measurements on a collector plate downstream of a different single-emitter electrospray were collected to examine the variation in the onset delay time of the Taylor cone. The onset delay time decreased with increasing emitter voltage and was effectively eliminated using bipolar switching. In monopolar mode, the onset delay rate was not sensitive to changes in the emitter voltage switching frequency across the range of tested values.

Eulerian multi-fluid simulations of local liquid distribution in a bed packed with cylindrical particles

Packed bed reactors (PBRs) are extensively used in chemical process industries to perform solid-catalyzed gas–liquid reactions. Their performance is significantly influenced by liquid distribution which is a strong function of particle shape and size. In the present work, we simulated the steady-state local liquid distribution, pressure drop (ΔP/L), and overall liquid holdup (〈εL〉) for the beds packed with spherical and cylindrical particles using a three-dimensional (3D) Eulerian multifluid model and validated the predictions using corresponding high-speed imaging measurements performed in pseudo-2D packed beds. We showed that the Eulerian model with existing closures significantly underpredicts the liquid distribution for the bed randomly packed with cylindrical particles. To address this, we proposed a modification in existing mechanical dispersion force (F→D) model as a function of average particle orientation angle (θ). The modification significantly improved agreement between the predictions and the corresponding measurements. Using the modified model, we showed that the increased magnitude of F→D in the lateral direction leads to higher lateral liquid spreading for cylindrical particles as compared to that for the spherical particles. Importantly, the modified model also predicted the local liquid distribution and ΔP/L for beds packed manually with cylindrical particles oriented at different θ in a satisfactory agreement with the corresponding measurements. On increasing θ, the F→D in lateral direction (i.e., perpendicular to flow) as well as liquid–solid interaction force (F→LS) in axial direction (i.e., parallel to flow) found to increase significantly. As a result, the lateral liquid spreading as well as ΔP/L decrease substantially on increasing θ.

Effect of dilution and Lewis number of the fuel in the fuel-air mixture on the heat flux during flame wall interaction (FWI)

Most combustion systems where flame is bounded by walls encounter Flame-wall interactions (FWI). Heat losses during FWI are in the magnitude of MW/m2 leading to concern about inefficiency, and thermal stresses. Hence, FWI is a topic of significant interest. With the goals of climate change pushing us toward renewable fuels with least carbon emissions, it is imperative to understand the FWI of renewable fuels like hydrogen-air mixture. In this study, FWI in a head-on-quenching configuration is carried out in a constant volume chamber. High-speed surface temperature measurement is carried out to compute instantaneous wall heat flux. Adding inert diluents to methane-air mixtures, the effect of dilution on the peak of heat flux during FWI is studied. Dilution affects the peak of heat flux predominantly by changing the adiabatic flame power of the fuel-air mixture. Furthermore, a large variation in flame power is carried out by changing the dilution fraction in the methane-air mixture to quantify its effect. It is found that the peak of heat flux and non-dimensional heat flux follows a nonlinear decrease with an increase in flame power. Knowing this effect, FWI of three different fuels, that is, methane, hydrogen, and a mixture of acetylene and hydrogen, having different Lewis numbers ( Le) of fuel in a fuel-oxidizer mixture are studied at equivalent flame power. This comparison shows that FWI of hydrogen-air mixtures in HOQ configuration have a lower peak of heat flux compared to other fuels which may be due to the preferential diffusion of hydrogen-air mixture.

Gradient transformation-weighted centroid: enhancing peak localization precision in the line chromatic confocal sensing system

Line chromatic confocal imaging (LCI) is an advanced system used for quick and accurate three-dimensional surface imaging without vertical mechanical scanning. It is extensively employed for fast industrial inspection. For high-speed and accurate measurement characteristics of the LCI technique, a rapid and accurate peak localization method is important. In this paper, we propose a gradient transform weight centroid method (GTWC) to improve the accuracy of peak positioning, without compromising high-speed characteristics. This method helps reconstruct the 3D profile at a higher axial resolution by reducing the full width at half maximum (FWHM) without altering the original structure of the LCI system. Both simulations and experiments show the feasibility and good performance of this method.

New high-precision measurement system for electron–positron pairs from sub-GeV/GeV gamma-rays in the emulsion telescope

The GRAINE project observes cosmic gamma-rays, using a balloon-borne emulsion-film-based telescope in the sub-GeV/GeV energy band. We reported in our previous balloon experiment in 2018, GRAINE2018, the detection of the known brightest source, Vela pulsar, with the highest angular resolution ever reported in an energy range of >80MeV. However, the emulsion scanning system used in the experiment was designed to achieve a high-speed scanning, and it was not accurate enough to ensure the optimum spatial resolution of the emulsion film and limited the performance. Here, we report a new high-precision scanning system that can be used to greatly improve the observation result of GRAINE2018 and also be employed in future experiments. The scanning system involves a new algorithm that recognizes each silver grain on an emulsion film and is capable of measuring tracks with a positional resolution for the passing points of tracks of almost the same as the intrinsic resolution of nuclear emulsion film (∼70 nm). This resolution is approximately one order of magnitude smaller than that obtained with the high-speed scanning system. With this scanning system, an angular resolution for gamma-rays of 0.1° at 1GeV is expected to be achieved. Furthermore, we successfully combine the new high-precision scanning system with the existing high-speed scanning system, enabling the high-speed and high-precision measurements. Employing these techniques, we reanalyze the gamma-ray events detected previously by only the high-speed scanning system in GRAINE2018 and obtain an about three times higher angular resolution (0.22°) in the 500–700MeV energy range. Adopting this technique in future observations may provide new insights into the gamma-ray emission from the Galactic center region and may realize polarization measurements of high-energy cosmic gamma-rays.

Coexistence of H-MAR and N-MAR in divertor simulation experimental module of GAMMA 10/PDX

In a divertor simulation experimental module (D-module) of GAMMA 10/PDX, additional hydrogen seeding induces molecular-activated recombination (H-MAR). However, when seeding of hydrogen and nitrogen is combined, Nitrogen MAR (N-MAR) is observed in D-module. In this work, we experimentally investigate plasma detachment processes in D-module by seeding hydrogen-only and hydrogen + nitrogen in order to de-couple MARs contribution to the measured particle flux reduction. Nitrogen is seeded after the electron density, measured with Langmuir probes installed in D-module, begins to decrease due to hydrogen seeding. In both cases, the electron temperature near the V-shaped target decreases from ∼23 eV to ∼2 eV. A clear rollover is observed in the ion flux to the V-shaped target. When only hydrogen is seeded, the Balmer lines emission ratio (i.e. the intensity of Hα emission line (IHα)/the intensity of Hβ emission line (IHβ)), an indicator of H-MAR, is observed to increase between V-shaped targets installed in D-module as the amount of hydrogen gas increases. However, when both hydrogen and nitrogen are seeded, IHα/ IHβ increase is suppressed, and the region of the largest IHα/ IHβ signal shifts upstream of D-module, as observed by a high-speed camera. These results show for the first time the transition from H-MAR-dominated phase to N-MAR-dominated phase and the coexistence of both MARs in D-module. It is found that nitrogen seeding increases plasma detachment even at already relatively low Te (∼5 eV). The high-speed camera measurements suggest this effect to be related to the increase of NHx neutral density, in line with previous modeling works.

The effect of temperature-dependent drug viscosity on needle-free jet injection

Highly viscous drugs cannot be delivered through a needle. Typically, this means that these drugs are formulated at lower concentrations, demanding higher delivery volumes, which often must be delivered intravenously. Jet injection may provide an important solution for viscous drug delivery. Jet injection is a needle-free drug delivery technique whereby a liquid drug is formed into a hair-thin (∼200 µm) high-speed (>100 m/s) jet that penetrates and delivers itself into tissue. While it may seem that it would be just as difficult to form a viscous drug into a high-speed jet as it is to force it down a needle, this is not the case. Recent work has revealed that ‘viscous-heating’ during jet injection can result in significant temperature increase, and resultant viscosity decrease, in a thin outer-layer of the jet; this phenomenon effectively results in the drug ‘self-lubricating’ as it passes through a jet injection orifice. Despite the potential for this finding to revolutionise the subcutaneous delivery of high-viscosity drugs, little further work in this area has since been reported on. In this work we develop finite element models of needle-free injection to investigate how viscous heating affects jet production, how heat exchange with the orifice material influences this process, and to what extent jet production is affected by the initial temperature of the fluid. We then conduct novel high-speed measurements of jet and orifice temperature changes due to viscous heating. We find that viscous heating is responsible for approximately doubling the speed of jets that can be produced with very viscous fluid (1 Pa·s) at room temperature. The thermal conductivity of the orifice can transfer heat away from the perimeter of the jet, and thus reduce the lubricating effect of viscous heating. We then show that by preheating 99 % glycerol (1 Pa·s) from 7 °C to 37 °C the jet speed can be increased 6-fold. We also demonstrate the successful delivery of a very viscous glycerol solution using preheated jet injection into ex vivo porcine tissue. Given that 99 % glycerol is 10- to 100-fold more viscous than current protein therapeutics, our findings demonstrate the potential for jet injection, with or without additional drug preheating, to deliver drug formulations, needle-free, that are much more viscous than those currently delivered through needles.

Impact of polarization pulling on optimal spectrometer design for stimulated Brillouin scattering microscopy.

Brillouin spectroscopy has become an important tool for mapping the mechanical properties of biological samples. Recently, stimulated Brillouin scattering (SBS) measurements have emerged in this field as a promising technology for lower noise and higher speed measurements. However, further improvements are fundamentally limited by constraints on the optical power level that can be used in biological samples, which effectively caps the gain and signal-to-noise ratio (SNR) of SBS biological measurements. This limitation is compounded by practical limits on the optical probe power due to detector saturation thresholds. As a result, SBS-based measurements in biological samples have provided minimal improvements (in noise and imaging speed) compared with spontaneous Brillouin microscopy, despite the potential advantages of the nonlinear scattering process. Here, we consider how a SBS spectrometer can circumvent this fundamental trade-off in the low-gain regime by leveraging the polarization dependence of the SBS interaction to effectively filter the signal from the background light via the polarization pulling effect. We present an analytic model of the polarization pulling detection scheme and describe the trade-space unique to Brillouin microscopy applications. We show that an optimized receiver design could provide >25× improvement in SNR compared to a standard SBS receiver in most typical experimental conditions. We then experimentally validate this model using optical fiber as a simplified test bed. With our experimental parameters, we find that the polarization pulling scheme provides 100× higher SNR than a standard SBS receiver, enabling 100× faster measurements in the low-gain regime. Finally, we discuss the potential for this proposed spectrometer design to benefit low-gain spectroscopy applications such as Brillouin microscopy by enabling pixel dwell times as short as 10 μs.

High-Speed Train Impedance Measurement Approach Based on Adaptive Multifrequency Voltage Disturbance

High-Speed Train Impedance Measurement Approach Based on Adaptive Multifrequency Voltage Disturbance

SPArch: A Hardware-oriented Sketch-based Architecture for High-speed Network Flow Measurements

Network flow measurement is an integral part of modern high-speed applications for network security and data-stream processing. However, processing at line rate while maintaining the required data structure within the on-chip memory of the hardware platform is a challenging task for measurement algorithms, especially when accuracy is of primary importance, such as in network security applications. Most of the existing measurement algorithms are no exception to such issues when deployed in high-speed networking environments and are also not tailored for efficient hardware implementation. Sketch-based measurement algorithms minimize the memory requirement and are suitable for high-speed networks but possess a low memory-accuracy trade-off and lack the versatility of individual flow mapping. To address these challenges, we present a hardware-friendly data structure named Sketch-based Pseudo-associative array Architecture (SPArch). SPArch is highly accurate and extremely memory-efficient, making it suitable for network flow measurement and security applications. The parallelism in SPArch ensures minimal and constant memory access cycles. Unlike other sketch architectures, SPArch provides the functionality of individual flow mapping similar to associative arrays, and the optimized version of SPArch allows the organization of counters in multiple buckets based on the flow sizes. An in-depth analysis of SPArch is carried out in this article and implemented SPArch on the Alveo data center accelerator card, demonstrating its suitability for high-speed networks.