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Possibilities for serial femtosecond crystallography sample delivery at future light sourcesa)
摘要： Serial femtosecond crystallography (SFX) uses X-ray pulses from free-electron laser (FEL) sources that can outrun radiation damage and thereby overcome long-standing limits in the structure determination of macromolecular crystals. Intense X-ray FEL pulses of sufficiently short duration allow the collection of damage-free data at room temperature and give the opportunity to study irreversible time-resolved events. SFX may open the way to determine the structure of biological molecules that fail to crystallize readily into large well-diffracting crystals. Taking advantage of FELs with high pulse repetition rates could lead to short measurement times of just minutes. Automated delivery of sample suspensions for SFX experiments could potentially give rise to a much higher rate of obtaining complete measurements than at today’s third generation synchrotron radiation facilities, as no crystal alignment or complex robotic motions are required. This capability will also open up extensive time-resolved structural studies. New challenges arise from the resulting high rate of data collection, and in providing reliable sample delivery. Various developments for fully automated high-throughput SFX experiments are being considered for evaluation, including new implementations for a reliable yet flexible sample environment setup. Here, we review the different methods developed so far that best achieve sample delivery for X-ray FEL experiments and present some considerations towards the goal of high-throughput structure determination with X-ray FELs.
关键词： automation,serial femtosecond crystallography,X-ray free-electron laser,sample delivery,high-throughput
更新于2025-09-23 15:22:29
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Study of the depletion depth in a frontside biased CMOS pixel sensors
摘要： Depletion of the sensitive volume for semiconductor based detectors is a key to achieve high performance. It is for instance required for charged particle detection in highly radiative environment and for X-ray spectroscopy. PIPPER-2 is a CMOS pixel sensor featuring an architecture that allows the application of the reverse bias of the pn junction from the frontside (cathode), on the electronic side, without process modification. Biasing voltages up to 45 V have been applied to sensor prototypes fabricated on two different high resistivity substrates: a thin epitaxial layer (1 kW cm) and a 40 μm thick bulk substrate (600 W cm). Calculations from a simplified analytical model and 3D-TCAD simulations were conducted to predict the evolution of the depletion depth with the bias voltage. These expectations were compared to measurements of PIPPER-2 illuminated with two X-ray energies. We conclude that the frontside biasing method allows the full-depletion of the thin epitaxial layer. In contrast, depletion of the bulk substrate reaches about half-depth but X-rays are still detected over the full depth.
关键词： X-ray detectors,Particle tracking detectors (Solid-state detectors)
更新于2025-09-23 15:22:29
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Development and evaluation of polycrystalline cadmium telluride dosimeters for accurate quality assurance in radiation therapy
摘要： For quality assurance in radiation therapy, several types of dosimeters are used such as ionization chambers, radiographic films, thermo-luminescent dosimeter (TLD), and semiconductor dosimeters. Among them, semiconductor dosimeters are particularly useful for in vivo dosimeters or high dose gradient area such as the penumbra region because they are more sensitive and smaller in size compared to typical dosimeters. In this study, we developed and evaluated Cadmium Telluride (CdTe) dosimeters, one of the most promising semiconductor dosimeters due to their high quantum efficiency and charge collection efficiency. Such CdTe dosimeters include single crystal form and polycrystalline form depending upon the fabrication process. Both types of CdTe dosimeters are commercially available, but only the polycrystalline form is suitable for radiation dosimeters, since it is less affected by volumetric effect and energy dependence. To develop and evaluate polycrystalline CdTe dosimeters, polycrystalline CdTe films were prepared by thermal evaporation. After that, CdTeO3 layer, thin oxide layer, was deposited on top of the CdTe film by RF sputtering to improve charge carrier transport properties and to reduce leakage current. Also, the CdTeO3 layer which acts as a passivation layer help the dosimeter to reduce their sensitivity changes with repeated use due to radiation damage. Finally, the top and bottom electrodes, In/Ti and Pt, were used to have Schottky contact. Subsequently, the electrical properties under high energy photon beams from linear accelerator (LINAC), such as response coincidence, dose linearity, dose rate dependence, reproducibility, and percentage depth dose, were measured to evaluate polycrystalline CdTe dosimeters. In addition, we compared the experimental data of the dosimeter fabricated in this study with those of the silicon diode dosimeter and Thimble ionization chamber which widely used in routine dosimetry system and dose measurements for radiation therapy.
关键词： X-ray detectors,Dosimetry concepts and apparatus,Solid state detectors,Materials for solid-state detectors
更新于2025-09-23 15:22:29
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Characterization of ECR plasma by means of radial and axial X-ray diagnostics
摘要： This work presents the X-ray characterization of the plasma generated in a simple mirror axis symmetric trap as a function of the magnetic field profile. A Si-Pin detector has been used to characterize warm electron population in axial and radial directions at 6.83 GHz. Moreover, the hot electrons emitted in axial direction has been measured by means of a HyperPure Germanium (HpGe) detector. Results show that X-ray emission is not homogenous, and its homogeneity and temperature depend strongly on the magnetic field profile, and especially on the Bmin/BECR ratio.
关键词： Ion sources (positive ions, negative ions, electron cyclotron resonance (ECR), electron beam (EBIS)),Solid state detectors,X-ray detectors
更新于2025-09-23 15:22:29
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Specific Features of the Molecular Structure of A New 3-(Benzo[d]Oxazole-2-Yl)- 1-(2-(1,3,3-Trimethylindoline-2-Ylidene) Ethylidene)Naphthalene-2(1H)-One Zinc Chloride Complex
摘要： X-ray diffraction is used to determine the structure of a new 3-(benzo[d]oxazole-2-yl)-1-(2-(1,3,3-trimethylindoline-2-ylidene)ethylidene)naphthalene-2(1H)-one zinc chloride complex 1. It is demonstrated that the ligand molecule in complex 1 has a trans–trans–cis conformation in which the indoline nitrogen atom is oriented in the same direction as the chelate ring, which could promote an additional coordination with the complexing atom.
关键词： 3-trimethylindoline-2-ylidene)ethylidene)naphthalene-2(1H)-one zinc chloride,3,3-(benzo[d]oxazole-2-yl)-1-(2-(1,spiropyrans,X-ray diffraction study
更新于2025-09-23 15:22:29
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Correlation Between Currents, X-ray Diffraction Patterns and Transfer Characteristics of SnO <sub/>2</sub> Thin Film Transistor
摘要： SnO2 thin film transistor (TFT) was prepared with SiOC as a gate insulator on n-type Si and the correlation between bonding structures, the contact properties of SnO2 thin films and the transfer characteristics of TFTs was researched. The current of SnO2 thin films increased with increasing the crystallinity and the crystallinity of SnO2 was increased by annealing. The SnO2 deposited with much oxygen gas flows became an amorphous structure after annealing due to lowered crystallinity. On the other hand, the current decreased in the amorphous structure SnO2 with high oxygen vacancies. However, the ambipolar transfer characteristics of SnO2/SiOC TFT with an amorphous structure had higher stability-mobility than that of TFT with the crystallinity, because of the increment effect of the diffusion current at the depletion layer as the amorphous structure with high Schottky barrier (SB).
关键词： Amorphous Structure,SnO2,Capacitance,TFT,X-ray Diffraction
更新于2025-09-23 15:22:29
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Stress and Microstructure Study of W/Si X-ray Multilayers with Different Structural Parameters
摘要： X-ray Timing and Polarimetry (XTP) telescope is proposed by using nested focusing optics with a large effective area for studies in the field of high energy physics (energy region of 1–30 keV). High-reflectance and low-stress W/Si multilayers are required for this telescope to improve the spectral response and maintain the figure quality of the mirrors simultaneously. In this paper, we focused on the study of stress and layer structure of W/Si periodic multilayers at different d-spacings (thickness of period), thickness ratios, and bilayer numbers. The results show that the stress of the multilayer increased from ?73.3 to ?465.5 MPa with increase in the d-spacing from 2.7 to 5.5 nm, while the change in the average interface width was negligible, from 0.31 to 0.36 nm. For the multilayers prepared with different thickness ratios of W, from 0.3 to 0.67 (d = 3.7 nm), the lowest stress appeared at the ratio of ～0.46, and the average interface width was unchanged. The number of bilayers (N = 80–160) had negligible effects on both the layer structure and the stress, and the multilayers exhibited a very smooth surface morphology with a root-mean-square roughness of 0.19 nm. To further study the microstructural changes of the multilayer, X-ray diffraction measurements of the samples with different d-spacings and thickness ratios were performed. An increased crystallization along with phase changes were observed in the samples prepared with thicker W layers, which can increase the compressive stress of the multilayer.
关键词： W/Si Multilayer,Stress,X-ray,Crystallization,Interface Width
更新于2025-09-23 15:22:29
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[IEEE 2018 China International SAR Symposium (CISS) - Shanghai (2018.10.10-2018.10.12)] 2018 China International SAR Symposium (CISS) - Coherent Scattering and PolinSAR Imaging Simulation of Fractal Trees
摘要： A 3-D deterministic spatial structure of forest was built and used to calculate the coherent electromagnetic scattering. The trees were generated based on the rule-based growth algorithm. The trunks, branches and leaves in the trees were simplified as a cluster of cylinders and disks, in which every scatterer has its deterministic location and orientation. The generalized Rayleigh-Gans (GRG) approximation and the infinite cylinder approximation are used to calculate the scattering matrix of cylinders and disks. A scatterer above a dielectric plane mainly contributes four scattering components, and the scattering of each component was added coherently. The effects of attenuation and phase change in each component were taking into account using Foldy’s approximation. The scattering coefficient of one tree and a forest were both calculated, which was used to simulate PolinSAR images.
关键词： fractal tree,vegetation scattering simulation,coherent scattering,multi-ray approach
更新于2025-09-23 15:22:29
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The development of new image receptor-holding instruments with appropriate horizontal X-ray beam angulation for periapical radiographs
摘要： Objectives: This study aimed to develop new image receptor-holding instruments with appropriate horizontal X-ray beam angulation, based on the anatomical data of posterior region interproximal surfaces derived from archived CT images. Methods: CT images of 92 patients with sound upper and lower dental arches were collected from our CT database and analyzed to determine the angles between the tangential interproximal contact line and the central groove line of posterior teeth. The average angle for each site was calculated and used to modify instruments using a three-dimensional printer. The utilities of the conventional and the modified instruments for viewing proximal surfaces were compared using two dry skulls. Results: The right and left sides of each site, except for the lower second premolar and first molar sites, did not differ significantly. The difference between the sites was 2.0°; hence, we calculated mean values for the two sides at each site. In the maxilla, the angles of the first and second premolar, second premolar and first molar, and first and second molar to the groove line were 83.9° (±5.4°), 84.4° (±3.9°), 81.6° (±5.1°), while those in the mandible were 85.0° (±9.2°), 85.0° (±4.0°), and 90.6° (±4.9°), respectively. The holding instruments modified to 80° demonstrated better proximal viewing ability in the upper molar region than conventional instruments. conclusions: The mean angles of the interproximal surfaces were determined from CT data. The image receptor holding-instruments were modified according to these angles to allow appropriate X-ray angulation, which facilitated improved observation of the proximal surfaces of teeth in the posterior region in this pilot in vitro study.
关键词： dental radiography,X-ray beam,holding instruments,periapical radiograph
更新于2025-09-23 15:22:29
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[IEEE 2018 41st International Conference on Telecommunications and Signal Processing (TSP) - Athens, Greece (2018.7.4-2018.7.6)] 2018 41st International Conference on Telecommunications and Signal Processing (TSP) - Depth Estimation and Ray Tracing Model Selection of Buried Utilities on Ground Penetrating Radar Data
摘要： When assessing a target depth from a Ground Penetrating Radar (GPR) image, one typically assumes a certain wave propagation model as well as the model parameters (typically the dielectric of the medium). While much work has been conducted on the automatic inference of the model parameters, not much work has been performed testing the validity of the model itself. The work presented here closes this gap for a low-frequency GPR system (350 MHz center frequency). It compares the measurement, taken from known targets at known depths, with different ray propagation models. It also presents a novel method for efficiently estimating the depth of a target without using any knowledge of the medium's wave propagation speed, or even the time of the signal's emission from the transmitter (time zero). Experiments on 26 targets of varying depths showed an averaged estimation error of less than 0.5%, with a standard deviation of 3% using this robust and efficient method.
关键词： GPR,Wave Propagation,Ray Tracing Models,Target Depth Estimation
更新于2025-09-23 15:22:29