Two Time-of-flight Research Articles

Soft tissue material properties based on human abdominal in vivo macro-indenter measurements

Simulations of human-technology interaction in the context of product development require comprehensive knowledge of biomechanical in vivo behavior. To obtain this knowledge for the abdomen, we measured the continuous mechanical responses of the abdominal soft tissue of ten healthy participants in different lying positions anteriorly, laterally, and posteriorly under local compression depths of up to 30 mm. An experimental setup consisting of a mechatronic indenter with hemispherical tip and two time-of-flight (ToF) sensors for optical 3D displacement measurement of the surface was developed for this purpose. To account for the impact of muscle tone, experiments were conducted with both controlled activation and relaxation of the trunk muscles. Surface electromyography (sEMG) was used to monitor muscle activation levels. The obtained data sets comprise the continuous force-displacement data of six abdominal measurement regions, each synchronized with the local surface displacements resulting from the macro-indentation, and the bipolar sEMG signals at three key trunk muscles. We used inverse finite element analysis (FEA), to derive sets of nonlinear material parameters that numerically approximate the experimentally determined soft tissue behaviors. The physiological standard values obtained for all participants after data processing served as reference data. The mean stiffness of the abdomen was significantly different when the trunk muscles were activated or relaxed. No significant differences were found between the anterior-lateral measurement regions, with exception of those centered on the linea alba and centered on the muscle belly of the rectus abdominis below the intertubercular plane. The shapes and areas of deformation of the skin depended on the region and muscle activity. Using the hyperelastic Ogden model, we identified unique material parameter sets for all regions. Our findings confirmed that, in addition to the indenter force-displacement data, knowledge about tissue deformation is necessary to reliably determine unique material parameter sets using inverse FEA. The presented results can be used for finite element (FE) models of the abdomen, for example, in the context of orthopedic or biomedical product developments.

An extreme ultraviolet 2e-ARPES setup based on dual time-of-flight analyzers

Measuring the momentum and energy distribution of photoemitted correlated electron pairs is a promising approach to directly probe the nature of electron–electron interactions in quantum materials. In this work, we present a two electron angle resolved photoemission spectroscopy (2e-ARPES) setup based on two time-of-flight (TOF) analyzers and a gas fiber high-harmonic generation (HHG) extreme ultraviolet (XUV) source. For each incident XUV pulse, the system is capable of recording six-dimensional coincidence datasets (kinetic energy and two orthogonal momenta for each electron) with an unprecedented double photoemission energy resolution of < 25 meV. The two TOF analyzers permit measurements of correlated electron pairs with momentum separation of ∼2Å−1. The performance of the setup is demonstrated by both single and double photoemission measurements, with an emphasis on the coincidence acquisition electronics and data extraction procedure for isolating correlated pair emission.

Design and Evaluation of a Wearable Biofeedback Training System to Reduce Trip-Related Falls During Level Walking

Trip-related falls are a major concern especially for older adults and individuals with gait impairments as they can lead to serious injuries, hospitalizations and negatively impact the quality of life. A low Minimum Toe Clearance (MTC) can be a predictor of tripping risk and thus, increasing the MTC is a possible way to reduce trip-related falls. In this paper, a wearable system is proposed that can measure the MTC in real-time using two Time-of-Flight (ToF) sensors on the shoe and provide auditory biofeedback using a piezo buzzer. Ten healthy female adults were recruited to walk in four conditions: baseline, biofeedback, short retention (same day), and long retention (next day) to design and validate our gait training tool. Average MTC values were compared pre-feedback, post-feedback, and post-retention, and our analysis revealed significant differences between the feedback and retention sessions for the training system. Therefore, the proposed system has the potential to be used as a wearable training system to minimize tripping risks in older adults and gait-impaired populations.

ToFカメラを用いた低速風洞通風中の展開型柔軟エアロシェル形状計測

Deployable flexible aeroshells have the potential to innovate atmospheric entry systems and space transportation technology. This study constructed and validated a shape measurement system for deployable flexible aeroshells during low-speed wind tunnel ventilation. The system consists of two Time of Flight (ToF) cameras with a wide measurement range and a high sampling rate. By software control, these can simultaneously capture and store depth images at 30 fps. A post-analysis method for ToF camera data with moving objects is proposed, and the obtained front projected area of the flexible aeroshell was verified. The proposed method could provide reasonable results and adapt to the object's position changes without readjusting parameters. The front projected area of the flexible aeroshell estimated from the ToF measurement data was consistent with trends that can be visually observed and with the results of structural strength tests. A positive correlation between aerodynamic forces and the front projected area was also confirmed.

A segmented total energy detector (sTED) for (n, γ) cross section measurements at n_TOF EAR2

The neutron time-of-flight facility n_TOF is characterised by its high instantaneous neutron intensity, high-resolution and broad neutron energy spectra, specially conceived for neutron-induced reaction cross section measurements. Two Time-Of-Flight (TOF) experimental areas are available at the facility: experimental area 1 (EAR1), located at the end of the 185 m horizontal flight path from the spallation target, and experimental area 2 (EAR2), placed at 20 m from the target in the vertical direction. The neutron fluence in EAR2 is ˜ 300 times more intense than in EAR1 in the relevant time-of-flight window. EAR2 was designed to carry out challenging cross-section measurements with low mass samples (approximately 1 mg), reactions with small cross-sections or/and highly radioactive samples. The high instantaneous fluence of EAR2 results in high counting rates that challenge the existing capture systems. Therefore, the sTED detector has been designed to mitigate these effects. In 2021, a dedicated campaign was done validating the performance of the detector up to at least 300 keV neutron energy. After this campaign, the detector has been used to perform various capture cross section measurements at n_TOF EAR2.

Determination of the Plasma Delay Time in PIPS detectors for fission fragments at the LOHENGRIN spectrometer

The VElocity foR Direct particle Identification spectrometer (VERDI) is a 2E-2v fission spectrometer that allows the measurement of the total mass distribution of secondary fission fragments with a resolving power of 1-2 u. It consists of two time-of-flight (ToF) arms, with one Micro Channel Plate (MCP) detector and up to 32 Silicon PIPS (Passive Implanted Planar Silicon) detectors per arm. The MCPs provide the start timing signals and the PIPS detectors provide both the energy and the stopping ToF signals. In real conditions, the PIPS signals are affected by the formation of plasma from the interaction between the heavy ions and the detector material. The plasma contributes to a reduction in signal amplitude, resulting in a Pulse Height Defect (PHD), and introduces a signal delay, known as Plasma Delay Time (PDT). An experiment to characterize the PDT and PHD was performed at the LOHENGRIN recoil separator of the Institut Laue Langevin (ILL). Characteristic fission fragments from the 239Pu(n,f) reaction were separated based on their A/Q and E/Q ratios, allowing the measurement of a wide range of energies from 21 to 110 MeV and masses between 80 and 149 u. Six PIPS detectors were characterized to study their individual responses to the PDT and PHD effects. The signals were recorded in a digital acquisition system to completely exploit the offline analysis capabilities. Achieved combined timing and energy resolutions for fission fragments varied between 72(2) ps and 100(4) ps and 1.4% - 2% (FWHM), respectively. Preliminary PHD and PDT data are presented from the masses A=85, 95, 130 and 143. The PHD trends are strongly correlated with both the ion energy and mass. The PDT, on the other hand, shows a strong variation as a function of the ion kinetic energy but a smaller dependence on the ion mass.

An 80 × 60 Flash LiDAR Sensor With In-Pixel Delta-Intensity Quaternary Search Histogramming TDC

This article presents a flash light detection and ranging (LiDAR) sensor featuring an in-pixel histogramming time-to-digital converter (hTDC) based on a delta-intensity quaternary search (DIQS) technique. The proposed 12-b DIQS hTDC is a two-step converter consisting of a 6-b coarse hTDC and a 7-b fine hTDC with 1-b redundancy. The DIQS hTDC synthesizes depth maps with three subframes from the coarse mode and a single subframe from the fine mode, achieving 100-ps resolution without a clock frequency of a few gigahertz. The DIQS repeats dividing the time range of a current step into four periods and finding the location where a target object is placed by comparing the number of events in each period, which is similar to the binary search method but doubles its operating speed. Two time-of-flight (ToF) bits are consecutively determined in every coarse step, and seven ToF bits are estimated by the indirect ToF technique with photon counts. An up–down counter is employed to reduce the memory size by half and enable the delta-intensity technique that can extend the dynamic range by suppressing the uniform background light. The prototype LiDAR with an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$80\times60$ </tex-math></inline-formula> pixel array was fabricated in a 110-nm CMOS image sensor (CIS) process and fully characterized. The maximum detectable range is measured to 45 m with a success rate of 100% at night and 60% under 70-klux background light. The depth accuracy and precision are 2.5 and 1.5 cm from 3 to 4.5 m indoor, respectively, and the precision is maintained to 1.8 cm for the target located at a 1.5-m distance under 60-klux background light. Inherent time-gating and differential signaling of the DIQS hTDC effectively suppress common-mode noise, accomplishing real-time acquisition of depth images with 30 frames/s in a 9-m range at 30-klux background light.

Precision measurement of the transition energy [formula omitted] versus magnetic rigidity for storage-ring isochronous mass spectrometry

The transition energy, γt, of a heavy-ion storage ring is an important machine parameter. The variation of γt versus the magnetic rigidity, Bρ, over the acceptance of the ring directly affects the mass resolving power achievable in the high-precision isochronous mass spectrometry (IMS). With two time-of-flight (TOF) detectors installed in a straight section of the ring, revolution frequency (revolution time) and velocity of each stored ion can simultaneously be measured. By using these quantities, a method for fast and precise γt determinations has been developed. The dependence of γt on the orbit length (or Bρ) has been obtained. The newly developed method does not require particle identification and is thus suitable for real-time monitoring of the ion optical setting during experiment.

Untargeted Analysis of Lemna minor Metabolites: Workflow and Prioritization Strategy Comparing Highly Confident Features between Different Mass Spectrometers.

Metabolomics approaches provide a vast array of analytical datasets, which require a comprehensive analytical, statistical, and biochemical workflow to reveal changes in metabolic profiles. The biological interpretation of mass spectrometric metabolomics results is still obstructed by the reliable identification of the metabolites as well as annotation and/or classification. In this work, the whole Lemna minor (common duckweed) was extracted using various solvents and analyzed utilizing polarity-extended liquid chromatography (reversed-phase liquid chromatography (RPLC)-hydrophilic interaction liquid chromatography (HILIC)) connected to two time-of-flight (TOF) mass spectrometer types, individually. This study (introduces and) discusses three relevant topics for the untargeted workflow: (1) A comparison study of metabolome samples was performed with an untargeted data handling workflow in two different labs with two different mass spectrometers using the same plant material type. (2) A statistical procedure was observed prioritizing significant detected features (dependent and independent of the mass spectrometer using the predictive methodology Orthogonal Partial Least Squares-Discriminant Analysis (OPLS-DA). (3) Relevant features were transferred to a prioritization tool (the FOR-IDENT platform (FI)) and were compared with the implemented compound database PLANT-IDENT (PI). This compound database is filled with relevant compounds of the Lemnaceae, Poaceae, Brassicaceae, and Nymphaceae families according to analytical criteria such as retention time (polarity and LogD (pH 7)) and accurate mass (empirical formula). Thus, an untargeted analysis was performed using the new tool as a prioritization and identification source for a hidden-target screening strategy. Consequently, forty-two compounds (amino acids, vitamins, flavonoids) could be recognized and subsequently validated in Lemna metabolic profile using reference standards. The class of flavonoids includes free aglycons and their glycosides. Further, according to our knowledge, the validated flavonoids robinetin and norwogonin were for the first time identified in the Lemna minor extracts.

Design of a Novel Wearable System for Foot Clearance Estimation.

Trip-related falls are one of the major causes of injury among seniors in Canada and can be attributable to an inadequate Minimum Toe Clearance (MTC). Currently, motion capture systems are the gold standard for measuring MTC; however, they are expensive and have a restricted operating area. In this paper, a novel wearable system is proposed that can estimate different foot clearance parameters accurately using only two Time-of-Flight (ToF) sensors located at the toe and heel of the shoe. A small-scale preliminary study was conducted to investigate the feasibility of foot clearance estimation using the proposed wearable system. We recruited ten young, healthy females to walk at three self-selected speeds (normal, slow, and fast) while wearing the system. Our data analysis showed an average correlation coefficient of 0.94, 0.94, 0.92 for the normal, slow, and fast speed, respectively, when comparing the ToF signals with motion capture. The ANOVA analysis confirmed these results further by revealing no statistically significant differences between the ToF signals and motion capture data for most of the gait parameters after applying the newly proposed foot angle and offset compensation. In addition, the proposed system can measure the MTC with an average Mean Error (ME) of −0.08 ± 3.69 mm, −0.12 ± 4.25 mm, and −0.10 ± 6.57 mm for normal, slow, and fast walking speeds, respectively. The proposed affordable wearable system has the potential to perform real-time MTC estimation and contribute to future work focused on minimizing tripping risks.

Investigation of Energy and Density of Laser-Ablated Si and Ge Plasma Ions Along With Surface Modifications

The energy and density of laser-generated Si and Ge plasma ions have been investigated by using Faraday cup (FC). Nd: YAG laser (532 nm, 6 ns) at different irradiances ranging from 4 to 7.1 GWcm−2 has been employed as an irradiation source. FC measurements reveal two time-of-flight (TOF) ion signal peaks. From the observed TOF signals of ions, the kinetic energy and density of laser induced Si and Ge plasma ions have been evaluated. With increasing the laser irradiance from 4 to 7.1 GWcm−2, the Si ions density varies from $4.9\times 10^{20}$ cm−3 to $5.62\times 10^{20}$ cm−3, whereas for Ge ions, it varies from $11\times 10^{20}$ cm−3 to $12\times 10^{20}$ cm−3. Similarly, the evaluated values of Si ion energy range from 156 to 166 eV, whereas for Ge ion, energy varies from 108 to 124 eV. It was also revealed that both energy and density of plasma ions are strongly dependent on FC distance from the target surface as well as the angle of FC with respect to the target surface normal. By employing an electric probe, self-generated electric field (SGEF) of laser-induced plasmas of both Si and Ge has also been measured and it varies from 94 to 122 and 101 to 158 V/m, respectively, with increasing the laser irradiances from 4 to 6 GWcm−2. The observation of SGEF confirms the existence of double layer potential in laser-induced Si and Ge plasmas. Scanning electron microscope (SEM) analysis has been performed to establish a correlation between number density of the Si spikes and the periodicity of laser-induced periodic surface structure of Ge grown after ablation with evaluated corresponding ion density of Si and Ge plasmas. Surface structures grown on Si and Ge after laser ablation enhance their optical, electrical, and field emission properties to make them useful in solar cells, LED displays, electronic device, as well as for the fabrication of nanograting.

Characterization of a double Time-Of-Flight detector system for accurate velocity measurement in a storage ring using laser beams

The Isochronous Mass Spectrometry (IMS) is a powerful tool for mass measurements of exotic nuclei with half-lives as short as several tens of micro-seconds in storage rings. In order to improve the mass resolving power while preserving the acceptance of the storage ring, the IMS with two Time-Of-Flight (TOF) detectors has been implemented at the storage ring CSRe in Lanzhou, China. Additional velocity information beside the revolution time in the ring can be obtained for each of the stored ions by using the double TOF detector system. In this paper, we introduced a new method of using a 658 nm laser range finder and a short-pulsed ultra-violet laser to directly measure the distance and time delay difference between the two TOF detectors which were installed inside the $10^{-11}$ mbar vacuum chambers. The results showed that the distance between the two ultra-thin carbon foils of the two TOF detectors was ranging from 18032.5 mm to 18035.0 mm over a measurable area of 20$\times$20 mm$^2$. Given the measured distance, the time delay difference which comes with signal cable length difference between the two TOF detectors was measured to be $\Delta t_{delay1-2}=99$(26) ps. The new method has enabled us to use the speed of light in vacuum to calibrate the velocity of stored ions in the ring. The velocity resolution of the current double TOF detector system at CSRe was deduced to be $\sigma(v)/v=4.4\times 10^{-4}$ for laser light, mainly limited by the time resolution of the TOF detectors.

Experimental investigation of the transition energy [formula omitted] in the isochronous mode of the HIRFL-CSRe

The Isochronous Mass Spectrometry (IMS) based on storage rings is a powerful technique for mass measurement of short-lived exotic nuclei. The transition energy γt of the storage ring is a vital parameter of the IMS technique. It is difficult to measure the γt and its relation to momentum spread or circulating length, especially to monitor the variation of γt during experiments. An experimental investigation on the γt has been performed for the IMS experiment at the Cooler Storage Ring of the Heavy Ion Research Facility in Lanzhou (HIRFL-CSRe). With the velocity measured by two time-of-flight (TOF) detectors, the γt as a function of orbital length can be determined. The influences of higher order magnetic field components on the γt function were inferred for isochronous correction. This paper introduces and investigates the influence of dipole magnetic fields, quadrupole magnetic fields and sextupole magnetic fields on the γt function. With the quadrupole magnets and sextupole magnets corrections, a mass resolution of 171332 (FWHM) and σ(T)∕T=1.34×10−6 were reached, which shall be compared with 31319 (FWHM) and σ(T)∕T=7.35×10−6 obtained without correction.

A method to measure the transition energy [formula omitted] of the isochronously tuned storage ring

The Isochronous Mass Spectrometry (IMS) is a powerful technique developed in heavy-ion storage rings for measuring masses of very short-lived exotic nuclei. The IMS is based on the isochronous setting of the ring. One of the main parameters of this setting is the transition energy γt. It has been a challenge to determine the γt and especially to monitor the variation of γt during experiments. In this paper we introduce a method to measure the γt online during IMS experiments by using the acquired experimental data. Furthermore, since the storage ring has (in our context) a relatively large momentum acceptance, the variation of the γt across the ring acceptance is a source of systematic uncertainty of measured masses. With the installation of two time-of-flight (TOF) detectors, the velocity of each stored ion and its revolution time are simultaneously available for the analysis. These quantities enabled us to determine the γt as a function of orbital length in the ring. The presented method is especially important for future IMS experiments planned at the new-generation storage ring facilities FAIR in Germany and HIAF in China.

A data analysis method for isochronous mass spectrometry using two time-of-flight detectors at CSRe**Supported by the 973 Program of China (2013CB834401), National Nature Science Foundation of China (U1232208, U1432125, 11205205,11035007) and the Helmholtz-CAS Joint Research Group (Group No. HCJRG-108)

The concept of isochronous mass spectrometry (IMS) applying two time-of-flight (TOF) detectors originated many years ago at GSI. However, the corresponding method for data analysis has never been discussed in detail. Recently, two TOF detectors have been installed at CSRe and the new working mode of the ring is under test. In this paper, a data analysis method for this mode is introduced and tested with a series of simulations. The results show that the new IMS method can significantly improve mass resolving power via the additional velocity information of stored ions. This improvement is especially important for nuclides with Lorentz factor γ-value far away from the transition point γt of the storage ring CSRe.

Electron pair emission detected by time-of-flight spectrometers: Recent progress

We present results for electron coincidence spectroscopy using two time-of-flight (ToF) spectrometers. Excited by electron impact, the energy and momentum distribution of electron pairs emitted from the Cu(111) surface are resolved and a spectral feature related to the Shockley surface state is identified. By combining the two ToF spectrometers with a high-order harmonic generation light source, we demonstrate double photoemission spectroscopy in the laboratory that required synchrotron radiation in the past. Utilizing this setup, we report results for (γ,2e) on NiO(001) on Ag(001) excited with light at 30 eV photon energy.