Transmission Geometry Research Articles

In Situ Observation of the Structure of Crystallizing Magnesium Sulfate Heptahydrate Solutions with Terahertz Transmission Spectroscopy.

Terahertz time-domain spectroscopy in a transmission geometry combined with visual analysis was used to investigate the crystallization process of MgSO4 solution. Careful spectral analysis of both a feature at 1.6 THz and the overall magnitude of absorption allowed the extraction of information about the liquid phase before and during crystallization, aiding the investigation of solvation dynamics and the behavior of molecular species at phase boundaries. The method was reproducibly applied to a number of measurements on a series of solutions of three chosen concentrations at different temperatures. When increasing temperature at the end of the measurement, the dissolution of crystals was observed as well. The temperature-dependent absorption data of the semicrystalline systems were converted to the solvent concentrations using a recently developed method. Solutions of a series of concentrations were also investigated in the temperature range of 4–25 °C. The results were compared to the theoretical calculated values, and the consistent differences proved the existence of a hydration shell around the salt ions whose behavior is different from bulk water. Future work will focus on triggering nucleation at specific positions in order to study the very beginning of the crystallization process. MgSO4 heptahydrate is used as a model system in this study, while the concept and the setup can be applied to other systems.

Broadband terahertz time-domain polarimetry based on air plasma filament emissions and spinning electro-optic sampling in GaP.

We report on a time-domain polarimetry (TDP) system for generating and detecting broadband terahertz (THz) waves of different polarization angles. We generate THz waves from two-color laser filaments and determine their polarization states with a detection bandwidth of up to 8 THz using a spinning gallium phosphide crystal. The polarization of THz emission can be controlled by adjusting the position and tilt angle of the β-barium borate crystal. We characterize the precision of this system for polarimetric measurements at fixed time delay to be and for complete time-domain waveforms. We also demonstrate the feasibility of our TDP system by measuring broadband optical properties of anisotropic samples in both transmission and reflection geometries. The THz-TDP technique can be easily integrated in conventional THz time-domain spectroscopy setups using nonlinear crystal detectors.

Generalized pole figures from post-processing whole Debye-Scherrer patterns for microstructural analysis on deformed materials.

Debye-Scherrer patterns, obtained from X-ray diffraction experiments using synchrotron light in transmission geometry, were analysed to construct generalized pole figures, and further used as input for an orientation distribution function inversion algorithm. By using Langford's method for separating strain and size contributions to peak broadening, it was possible, for the first time, to obtain full domain size and dislocation density generalized distribution functions (GDFs). This method was applied to cold-rolled and annealed interstitial-free steel. The predictions made using GDFs were corroborated by electron backscatter diffraction measurements and were also consistent with what was previously known for this kind of material under these conditions.

Performance Optimization of Underwater Communication Links at Different Ranges for AIS Relay to AUV

Autonomous Underwater Vehicles (AUVs) are becoming increasingly popular for large number of civil and military applications, such as environmental monitoring, oceanography, archaeology, or mine warfare. Operational safety issue still prevents the exploitation of the full potential of AUVs. Operations of AUVs are limited by constraints including the need to guarantee no collision with manned surface vehicles. To avoid collisions, a solution is to relay surface vessel positions to the AUVs by an underwater communication link. The communication must be optimized to establish a robust and reliable link at various range and depth. Commercial underwater acoustic modems are often dedicated for specific distances and bit rates with performances strongly dependent on the environmental conditions. For the considered application, the modem must be adaptive at the time and frequency selectivity of the channel which is varying according to the operation context. In this work, we propose an adaptive underwater acoustic waveform optimized to exploit at the best the time and frequency diversity the channel. To show the potential gain obtained by using diversity, the performance of the designed modem is evaluated using theoretical and realistic underwater channels. In addition, we propose a method for adapting the waveform based only on the knowledge of the transmission geometry. Finally, the proposed modem is tested to relay Automatic Identification Systems (AIS) picture of an area to AUVs.

High crystal quality of vertical Bridgman and edge-defined film-fed growth β-Ga2O3 bulk crystals investigated using high-resolution X-ray diffraction and synchrotron X-ray topography

High crystal quality of vertical Bridgman (VB)-grown (001) β-Ga2O3 single-crystal was confirmed in comparison with edge-defined film-fed growth (EFG)-grown (001) β-Ga2O3 single-crystal. The FWHMs of VB were lower than FWHMs of EFG from X-ray diffraction rocking curve analysis. VB and EFG crystal curvatures were measured as 232.24 m and 45.83 m, respectively. By using transmission and reflection geometry in synchrotron X-ray topography, we unambiguously determined the Burgers vector ( b ) = [010] and [001]. For the VB crystal, screw dislocations with b = [010] and dislocation direction ( t ) = [010] were observed. For the EFG crystal, edge dislocations with b = [001] and t = [010] were observed. In addition, wandering dislocations on the (001) plane with b = [010] for EFG and b = [001] for both EFG and VB were observed. These phenomena indicate that the wandering dislocations were formed by a slip motion on the (001) slip plane.

Spectral-sensitive proton radiography of thin samples with the pixel detector Timepix3

We evaluate a high-resolution contrast-enhanced method for energy-sensitive radiography of thin samples with low-energy protons at the light-ion Tandetron accelerator of the NPI-CAS in Rez near Prague. We make use of the high-sensitivity of the hybrid semiconductor pixel detectors Timepix enabled by integrated per-pixel signal processing electronics. For this work we use the Timepix3 ASIC chip equipped with a 500 µm Si sensor operated with the fast data rate AdvaPix readout electronics interface. Measurements are performed in air with a 2.9 MeV proton microbeam on thin samples (<100 µm thick). As referential and testing sample we use a set of aluminum foils stacked into a closely packed assembly of varying layers of well-defined thickness. This and other samples were imaged and placed in front of the detector in transmission geometry. Radiographies were collected with focused beam (few mm size) and a microbeam (few µm size). The imaging principle is based on high-resolution spectrometry of single transmitted particles. Contrast is obtained by registration of small differences in the deposited energy of the proton after passing through the sample. This can be measured in wide-range by detailed spectral-tracking analysis of the pixelated clusters in the pixel detector. We examine and evaluate various cluster-track parameters sensitive for imaging contrast such as deposited energy, cluster area (number of pixels) and cluster height (maximum energy value of the pixels in the cluster). The position of interaction in the detector is registered in sub-pixel resolution down to few µm scale for the particles and geometry used. Radiographies are reconstructed based on these individual parameters imaged in image bins of adjustable size (few µm up to few tens of µm). The technique developed with different cluster parameters is presented together with evaluation of image contrast sensitivity on various types of samples and beam energies.

Photon radiation shielding properties of germanate glass systems containing Bi2O3, PbF2, and B2O3

AbstractIn this study, we studied the gamma radiation shielding properties of ternary germanate glass systems containing Bi2O3, PbF2, and B2O3. The glass samples were synthesized by using the traditional melt‐quenching method. X‐ray Diffraction (XRD) measurements were performed to confirm the glassy nature of the synthesized materials. A narrow‐beam transmission geometry equipped with a NaI(Tl) scintillation detector was used to measure experimentally measurable shielding parameters of the samples, like mass attenuation coefficient, linear attenuation coefficient, half‐value layer, and effective atomic number. Measurements were performed at gamma‐ray energies of 662, 1173, and 1332 keV emitted from 137Cs and 60Co radioactive sources. Additionally, all the above parameters were also calculated theoretically in the .015–15 MeV energy region by employing the WinXCOM software to verify the experimental findings. The experimental and theoretical results were found to be in good agreement. The results showed that the 70Ge20Bi10Pb glass system has competitive shielding properties among the studied glass systems and could be a good candidate for radiation shielding applications.

Terahertz Measurements on Subwavelength-Size Samples Down to the Tunneling Limit

For terahertz spectroscopy on single crystals, the wavelength lambda often is comparable to the size of the studied samples, emphasizing diffraction effects. Using a continuous-wave terahertz spectrometer in transmission geometry, we address the effect of the sample size on the achievable accuracy of the optical properties, focusing in particular on the phase data. We employ alpha-lactose monohydrate as a paradigmatic example and compare data that were measured using apertures with diameters D in the range from 10 to 0.2 mm. For small D, strong diffraction typically invalidates a quantitative analysis of the transmitted amplitude at low frequencies. The phase data, however, can be evaluated to lower frequency and show a more systematic dependence on D. For a quantitative analysis, we employ a waveguide picture for the description of small apertures with a cylindrical bore. For D as small as 0.2 mm, corresponding to 1/D = 50 cm^{-1}, a circular waveguide does not support propagating waves below its cut-off frequency 1/lambda _c = omega _c/2pi c approx 29 cm^{-1}. Experimentally, we confirm this cut-off for cylindrical apertures with a thickness d_{text {ap}} = 1 mm. Close to omega _c, the measured phase velocity is an order of magnitude larger than c, the speed of light in vacuum. The cut-off is washed out if a sample is mounted on a thin aperture with a conical bore. In this case, the phase data of alpha-lactose monohydrate for D = 0.2 mm can quantitatively be described down to about 10 cm^{-1} if the waveguide-like properties of the aperture are taken into account in the analysis.

Experimental investigation of contaminated clay slabs for X-ray shielding

The advent of radiation is a challenge to the human race therefore; a suitable material is a solution to effective radiation shielding. This research aims to investigate the effectiveness of clay slabs mixed with some heavy metals in radiation shielding. Thereafter, absorption coefficients (mass and linear) were calculated from both incident and transmitted intensity measured with a detector at different energies: 40 keV, 60 keV, 80 keV, 100 keV,120 keV, 150 KeV and 200 Kev. The following procedures were taken: the clay was mixed with heavy metals (Lead, Nickel Cadmium, Zinc and Copper) using the ion exchange capacity technique and then slabs were moulded using a wooden frame of dimensions 4 cm x 4 cm x 1 cm. A narrow collimated beam transmission geometry condition was used for the measurements. The measured values of these parameters were in good agreement with the literature. At selected energies, the values of linear and mass attenuation for lead were 2.29 cm-1 and 0.466 gcm-2, 1.58 cm-1 and 0.392 gcm-2, 1.23 cm- 1 and 0.281 gcm-2, 1.09 cm-1 and 0.216 gcm-2, 0.88 cm-1 and 0.180 gcm-2, 0.74 cm-1 and 0.168 gcm-2 and 0.57 cm-1 and 0.161 gcm-2, respectively. The results obtained were compared with concrete. The clay slabs mixed with heavy metal showed good shielding properties for moderate radiation energy. Hence, these slabs are feasible and cost effective compared with traditional concrete used for construction.

Bifunctional spoof surface plasmon polariton meta-coupler using anisotropic transmissive metasurface

Abstract Tailoring the wavefronts of spoof surface plasmon polaritons (SSPPs) at will, especially with multifunctional integration, is of great importance in near-field photonics. However, conventional SSPP devices suffer from the issues of bulk configurations, limited functionalities, and single operating modes, which are unfavorable for electromagnetic (EM) integration. Here, a novel scheme is proposed to design bifunctional SSPP meta-devices based on the polarization dependent property via satisfying the comprehensive phase distributions and multi-mode momentum matching in a transmission geometry. As proof of the concept, we experimentally demonstrate a bifunctional SSPP meta-device in the microwave regime that can convert incident x- and y-polarized waves to transverse magnetic (TM)-mode SSPP Bessel beams and transverse electric (TE)-mode SSPP focusing beams, respectively. Our findings open a door to achieve near-field manipulation of SSPPs with multi-function and multi-mode integration, which can stimulate the applications of SSPP functional devices, such as near-field sensing, imaging, and on-chip photonics.

Energy deposition by H and He ions at keV energies in self-supporting, single crystalline SiC foils

The specific energy deposition of H and He ions in SiC has been studied for both random and channeling orientations. The experiments were carried out in transmission geometry using the Time-of-Flight Medium Energy Ion Scattering System at the 350 keV Danfysik Implanter at Uppsala University. The target was a self-supporting, single crystalline cubic 3C–SiC (100) foil with nominal thickness of 200 nm. The measured stopping cross sections are compared with data available from the literature and theoretical predictions. The results for random geometries reveal slightly lower values than predicted by SRIM for H projectiles whereas for He projectiles good agreement was observed over the whole energy range studied. Higher specific energy loss is observed along random trajectories in comparison to channeling geometry, for all measured energies and for both H and He ions. For H ions, however, differences are minor, whereas for He ions, they are found generally more pronounced.

Precipitation-hardening stainless steels: Potential use radiation shielding materials

In this study, it was focused on the research of new materials with high attenuation efficiency that can be used as radiation shielding material due to the incapability of conventional materials. In accordance with this purpose, the radiation shielding capabilities of four different precipitation-hardening stainless steels (PH-SSs), which are symbolized 15-5PH, 15-7PH, 17-4PH and 17-7PH, were determined both experimentally and theoretically in a wide range of radiation energy. For experimental measurements, two different detectors (Si(Li) and Na(Tl)) and twenty-three different photon energies (from 22.1 to 1332.5 keV) emitted from seven different radionuclides were used in narrow-beam transmission geometry. Phy-X/PSD software were used for theoretical calculations. The theoretically calculated parameters were determined both in the photon energies emitted by the radionuclides used in the experiment and in the continuous energy range of 0.015–15 MeV. Furthermore, in order to make a remarkable assessment of the integration of PH-SSs to nuclear energy applications, the all results obtained have been compared with the corresponding values of Fe-based steel concretes (steel-scrap (SS) and steel-magnetite (SM)), which are widely used as conventional shield materials in nuclear power plants. Moreover, in order to choose the best material to be used in nuclear applications among the PH-SSs, the results were evaluated comparatively in terms of both the characteristics of the materials and the magnitude of the radiation shielding parameters. Consequently, it was concluded that the material with the best radiation shielding performance among the examined PH-SSs was 15-7PH and the radiation shielding performance ranking was generally in the form of 15-7PH ≥ 15-5PH > 17-4PH > 17-7PH > SM > SS. Due to both high attenuation efficiency and superior properties for radiation shielding, it was determined that the PH-SSs can be used as new shielding materials in nuclear applications.

Method for in situ texture investigation of recrystallization of Cu and Ti by high-energy synchrotron X-ray diffraction

Abstract High-energy synchrotron radiation has been used to study in situ annealing of cold-rolled Cu and Ti. The measurements were performed using a high-vacuum furnace in transmission geometry and an area detector. The diffraction images were subsequently processed to extract the orientation distribution. The recrystallization process could be followed with a time resolution of the order of 10 s, and good pole figures could be obtained from the very limited amount of data in single diffraction images. The pole figures compare favorably with pole figures of the same material measured ex situ with a conventional pole figure goniometer. For Cu, a rapid and complete change from a typical rolling texture to a cube texture was observed after annealing for 20 min at 650 °C. For Ti, changes were more subtle with a tendency for c-axes to diminish near the normal direction, as well as for a-axes to become aligned with the rolling direction. The method makes it feasible to study the kinetics of recrystallization with quantitative texture analysis.

Infrared Laser Ablation Microsampling with a Reflective Objective.

A Schwarzschild reflective objective with a numerical aperture of 0.3 and working distance of 10 cm was used for laser ablation sampling of tissue for off-line mass spectrometry. The objective focused the laser to a diameter of 5 μm and produced 10 μm ablation spots on thin ink films and tissue sections. Rat brain tissue sections 50 μm thick were ablated in transmission geometry, and the ablated material was captured in a microcentrifuge tube containing solvent. Proteins from ablated tissue sections were quantified with a Bradford assay, which indicated that approximately 300 ng of protein was captured from a 1 mm2 area of ablated tissue. Areas of tissue ranging from 0.01 to 1 mm2 were ablated and captured for bottom-up proteomics. Proteins were extracted from the captured tissue and digested for liquid chromatography tandem mass spectrometry (LC–MS/MS) analysis for peptide and protein identification.

The linear phase correction of modulation of intensity emerging from zero effort (MIEZE) with magnetic Wollaston prisms

This study proposes the use of two magnetic Wollaston prisms (MWPs) to correct for the linear Larmor phase aberration of modulation of intensity emerging from zero effort (MIEZE), introduced by the transverse size of the sample. With this approach, the contrast of the intensity modulation can be maximized at any scattering angle of interest such that the same contrast as the direct transmission geometry can be fully recovered. The optimum magnetic fields required for the MWPs depend only on the scattering angle and the frequencies of the radio-frequency flippers, and they are independent of the neutron wavelength and beam divergence, which makes the approach suitable for both pulsed and continuous neutron sources.

Review: The evolution of chemometrics coupled with near infrared spectroscopy for fruit quality evaluation

Short wave near infrared (NIR) spectroscopy operated in a partial or full transmission geometry and a point spectroscopy mode has been increasingly adopted for evaluation of quality of intact fruit, both on-tree and on-packing lines. The evolution in hardware has been paralleled by an evolution in the modelling techniques employed. This review documents the range of spectral pre-treatments and modelling techniques employed for this application. Over the last three decades, there has been a shift from use of multiple linear regression to partial least squares regression. Attention to model robustness across seasons and instruments has driven a shift to machine learning methods such as artificial neural networks and deep learning in recent years, with this shift enabled by the availability of large and diverse training and test sets.

Методика расчета на прочность глобоидной червячной передачи

Worm gears are widely used in mechanical engineering. Recently, worm gears with a globoid worm attract a considerable interest. To improve the quality characteristics of globoid gears, their geometric dimensions and parameters, as well as the production technologies are being improved. It is also important to have a methodology for calculating the strength, which is, however, currently unavailable, and the state standards cover the issue of determining and calculating only the transmission geometry. In this regard, the development of the technique for calculating the contact and bending strength of a globoid worm gear appears relevant. The basic areas of the research are gear enhancement, production technology improvement, the gearing pattern study, working surfaces mathematical simulation, 3-D modeling, and the transmission calculation. The contact strength calculation is based on the Hertz’s formula taking into account the geometric features of globoid worm gears. The authors developed the calculation of the bending strength of the worm gear teeth based on the helical gear calculation method. The paper presents data on the influence of the mechanical properties of the materials of a worm and a worm gear wheel on the gear contact strength, gives the computed coefficients estimated values. The authors note that the dynamic load factor can increase significantly with the wear of the gear working surfaces. The research findings can be used to develop the design calculation technique, as well as to improve it to take into account the effect of transmission wear and working temperature on the operation duration.

Operando X-Ray Diffraction in Transmission Geometry « at Home » from Tape Casted Electrodes to All-Solid-State Battery

Operando X-Ray Diffraction in Transmission Geometry « at Home » from Tape Casted Electrodes to All-Solid-State Battery

Limits in enhancement factor in near-brewster angle reflection pump-probe two-dimensional infrared spectroscopy

In this work, we simulated 2D infrared spectroscopy (IR) spectroscopy in both transmission geometry and Brewster-angle reflection geometry. Light dispersion and the leakage of s-polarized light are considered in simulating the enhancement factor of the reflection mode. Our simulation shows that the dispersion in reflection will only alter the 2D IR lineshape slightly and can be corrected. Leaking spolarized light due to imperfectness of IR polarizers in the reflection geometry may limit the enhancement factor, but such limit is above what a typical experiment can reach. In the current experiment, the enhancement factor is mainly limited by the precision of incident angle, for which ordinary rotation stages are probably not adequate enough. Moreover, traditional energy ratio of pump and probe pulses, which is 9:1, may not be ideal and could be changed to 2:1 in the reflection geometry. Considering all the above factors, the enhancement on the order of 1000 is possible in the current experiment. Nevertheless, near-Brewster angle reflection will enhance both the signal and the noise caused by the signal itself, therefore this method only works if the noise is unrelated to the signal, particularly if the noise is caused by the fluctuation in the probe. It cannot improve the signal to noise ratio when the dominate noise is from the signal itself. The theoretical results here agree reasonably well with published experiment results and pave way for realizing even higher enhancement at nearer-Brewster angle.

Material Classification for Terahertz Images Based on Neural Networks

Terahertz time-domain spectroscopy enables the extraction of electrical properties from materials. An extraction of the complex permittivity can be carried out with measurements in transmission or reflection geometry enabling the identification of materials. To perform an exact identification, the sample thickness and the angle of incidence of the terahertz radiation must be known. However, when those parameters are unknown and additionally the materials show strong absorbances, a precise differentiation between materials is challenging. A promising approach is the use of a neural network for automated material classification of terahertz images from different materials. Here, we show that a trained neural network can differentiate between 16 3D printed dielectric materials with a high accuracy of 98 % from measurements taken in transmission mode. As the constitution of the dataset has a big impact on the accuracy, various data preparations were investigated as well as the number of traces needed for achieving a well-trained network was determined. Finally, the trained neural network was evaluated with different sample thicknesses, revealing the huge impact of the materials absorbance on the extrapolation ability. This approach can be used in security application to classify harmful substances as well as for the automated generation of material maps.