Beam Characteristics Research Articles

Improving Rotational Doppler Velocimetry Accuracy and Spectral Characteristics of Vortex Beam in Maritime Atmospheric Turbulence

Improving Rotational Doppler Velocimetry Accuracy and Spectral Characteristics of Vortex Beam in Maritime Atmospheric Turbulence

Investigation of the relationship between the structural and material composition and band gap characteristics of periodic metal composite beams

Investigation of the relationship between the structural and material composition and band gap characteristics of periodic metal composite beams

A scintillator detector for spatio-spectral characterization of proton beams at high repetition rate

A scintillator detector for spatio-spectral characterization of proton beams at high repetition rate

Tailoring transverse beam characteristics with the new CERN PS Booster charge-exchange injection system

A key aspect of the LHC Injectors Upgrade project is the connection of the PSB to the newly built Linac4 and the related installation of a new 160 MeV charge-exchange injection system. The new injection system was commissioned in winter 2020/21 and is now used operationally to tailor the transverse characteristics for the various beam types at CERN, such as high-intensity fixed target beams, LHC single bunch beams, and high-brightness beams for LHC. This contribution outlines the different injection strategies for producing the various beam types and discusses the application of numerical optimization algorithms to adjust injection settings in operation efficiently.

The Simons Observatory: Beam Characterization for the Small Aperture Telescopes

We use time-domain simulations of Jupiter observations to test and develop a beam reconstruction pipeline for the Simons Observatory Small Aperture Telescopes. The method relies on a mapmaker that estimates and subtracts correlated atmospheric noise and a beam fitting code designed to compensate for the bias caused by the mapmaker. We test our reconstruction performance for four different frequency bands against various algorithmic parameters, atmospheric conditions, and input beams. We additionally show the reconstruction quality as a function of the number of available observations and investigate how different calibration strategies affect the beam uncertainty. For all of the cases considered, we find good agreement between the fitted results and the input beam model within an ∼1.5% error for a multipole range ℓ = 30–700 and an ∼0.5% error for a multipole range ℓ = 50–200. We conclude by using a harmonic-domain component separation algorithm to verify that the beam reconstruction errors and biases observed in our analysis do not significantly bias the Simons Observatory r-measurement

Application of COMSOL Multiphysics for Fiber Beam Profiling

Fiber optic beam profiling is essential across scientific and engineering realms, demanding precise characterization of light beams for optimized system performance, accurate alignment, and efficient resource utilization. This study employs COMSOL Multiphysics to comprehensively analyze single-mode and multimode fiber beam profiles, encompassing diverse parameters such as wavelengths and modal distributions. The investigation of beam profiles is based on 850nm, 1310nm and 1550nm wavelengths; with three different modes (1, 5, and 20). COMSOL Multiphysics enhances beam profiling by providing precise numerical techniques, multiphysics modeling, and flexible parameter analysis. Its user-friendly interface facilitates efficient research, while validation and innovative possibilities underscore its value in photonics advancements. The research addresses the need for advanced profiling techniques, offering a robust methodology that captures intricate modal interactions and boundary conditions. Key findings include distinctive beam waist evolution, mode distribution patterns, and beam shaping behaviors, impacting data transmission, medical procedures, and manufacturing. By integrating computational power, this study advances our understanding of photonics, providing practical insights for future fiber optic technologies and their broader implications.

Numerical analysis of the dynamic characteristics of a fractional-order viscoelastic beam with fixed supports at both ends

In this paper, we present a generalized model of a viscoelastic beam, which takes into account the influence of axial forces and incorporates a fractional constitutive relationship. In addition, we propose a novel numerical calculation method for analyzing fractional-order viscoelastic beams. This method takes the transverse displacement and bending moment of the beam as state variables, transforms the beam model into a discrete state space equation through the application of the central difference method, and utilizes an improved precise integration algorithm to solve the equation. To evaluate the performance of the method, the responses of the beam under two types of excitations, namely uniformly distributed transverse load and the motion of the support at both ends, are calculated under fixed hinge conditions. The results demonstrate that the present method has excellent accuracy and convergence, and also reveal some nonlinear phenomena of the system.

Out-of-plane characteristics of cross-laminated bamboo and timber beams under variable span three-point loading

Given the exceptional mechanical properties of cross-laminated bamboo and timber (CLBT) and its ability to efficiently utilize bamboo and timber resources, CLBT holds considerable potential for applications in modern sustainable timber and bamboo structures. CLBT panels, when used as floors or roofs, typically experience out-of-plane loads. This study investigates the out-of-plane bending and shear characteristics of 5-layer CLBT and cross-laminated timber (CLT) specimens using the variable span three-point loading test method. The results indicated that the developed CLBT exhibited superior mechanical properties compared to CLT, offering a preliminary demonstration of its value in engineering applications. In addition, factors such as the span and outermost lamination influenced the failure modes, vertical deflections, strain distributions, ductility indices, and energy absorption characteristics of CLBT and CLT specimens. This study provides a foundational reference for using CLBT as floor and roof panels subjected to out-of-plane loads and lays the foundation for further research.

Flexural behaviour of bamboo scrimber beams with different composite and reinforced technology: A literature review

Bamboo scrimber (BS) is a novel renewable biocomposite material with excellent mechanical performance and stability that is suitable for load-bearing structural members. Beam-type components are among the most widely used members in structural engineering, and their flexural behaviour is crucial for the safety and applicability of structures. Based on a review of the existing literature, this article presents a comprehensive overview and discussion of the research and development of various forms of beam-type BS members with the aim of reaching a clearer understanding of the bending mechanisms and mechanical characteristics of BS beams. The members highlighted in this review include general BS beams, reinforced BS beams (with steel bars and fibre-reinforced polymer plates), composite BS beams (with profile steel and concrete), and strengthened damaged BS beams. Moreover, the factors affecting the flexural performance of BS beams, such as span-depth ratios, their mechanical properties, and reinforcing materials, are analysed quantitatively. Finally, the calculation models for the flexural bearing capacity and stiffness of BS beams are summarised and compared. This review aims to illustrate the potential of BS in the field of structural engineering and provide references for future research and design methods for BS flexural members.

Mutual aid instead of mutual restraint: interactive probing for topological charge and phase of a vortex beam of large aberrations

An imperfect propagation environment or optical system would introduce wavefront aberrations to vortex beams. The phase aberrations and orbital angular momentum in a vortex beam are proved to be mutually restrictive in parameter measurement. Aberrations make traditional topological charge (TC) probing methods ineffective while the phase singularity makes phase retrieval difficult due to the aliasing between the wrapped phase jump and the vortex phase jump. An interactive probing method is proposed to make measurements of the aberrated phase and orbital angular momentum in a vortex beam assist rather than hinder each other. The phase unwrapping is liberated from the phase singularity by an annular shearing interference technique while the TC value is determined by a Moiré technique immune to aberrations. Simulation and experimental results proving the method effective are presented. It is of great significance to judge the characteristics of vortex beams passing through non-ideal environments and optical systems.

Influence of extraction voltage on electron and ion behavior characteristics

The characteristics of the extracted ion current have a significant impact on the design and testing of ion source performance. In this paper, a 2D in space and 3D in velocity space particle in cell (2D3V PIC) method is utilized to simulate plasma motion and ion extraction characteristics under various initial plasma velocity distributions and extraction voltages in a Cartesian coordinate system. The plasma density is of the order of 1015 m−3–1016 m−3 and the extraction voltage is of the order of 100 V–1000 V. The study investigates the impact of various extraction voltages on the velocity and density distributions of electrons and positive ions, and analyzes the influence of different initial plasma velocity distributions on the extraction current. The simulation results reveal that the main reason for the variation of extraction current is the space-charge force formed by the relative aggregation of positive and negative net charges. This lays the foundation for a deeper understanding of extraction beam characteristics.

Nonlinear post-compression of a hybrid vortex mode in a gas-filled capillary.

We demonstrate nonlinear temporal compression of a vortex beam by propagation in a gas-filled capillary. Starting from an ytterbium-based laser delivering 700 μJ 640 fs pulses at a 100 kHz repetition rate, the vortex beam is generated using a spiral phase plate and coupled to a capillary where it excites a set of four modes that have an overlap integral of 97% with a Laguerre-Gauss LG10 mode. Nonlinear propagation of this hybrid, orbital angular momentum (OAM)-carrying mode results in temporal compression down to 74 fs at the output. Beam and pulse characterizations are carried out to determine the spatial profile and temporal duration of compressed pulses. This result in multimode nonlinear optics paves the way towards the generation of OAM-carrying few-cycle pulses, isolated attosecond XUV pulses, and tunable UV pulses through resonant dispersive wave emission.

Nonlinear transmission dynamics of mutual transformation between array modes and hollow modes in elliptical sine-Gaussian cross-phase beams

In this paper, based on the nonlocal nonlinear Schrödinger equation, the nonlinear transmission characteristics of elliptical sine-Gaussian cross-phase (ESGCP) beams in strongly nonlocal nonlinear media are researched, and propagation expression of ESGCP beams in transmission process is given. One of the characteristics of beams is that the array mode and the hollow mode can be transformed into each other during the transmission process, which can produce more abundant light intensity modes. Numerical simulation is used to determine how the parameters in the initial propagation equation affect the beam width. In addition, evolution laws of light intensity, phase, and critical power are explored. The results show that the evolution of the beams is controlled by the parameters of the sine term and the cross-phase term in the initial propagation expression. The relationship between initial incident power and evolution period is introduced, and the reason is explained. The beams have great potential for development in the fields of optical communication and light capture.

Characteristics of breathing-adapted gating using surface guidance for use in particle therapy: A phantom-based end-to-end test from CT simulation to dose delivery.

To account for intra-fractional tumor motion during dose delivery in radiotherapy, various treatment strategies are clinically implemented such as breathing-adapted gating and irradiating the tumor during specific breathing phases. In this work, we present a comprehensive phantom-based end-to-end test of breathing-adapted gating utilizing surface guidance for use in particle therapy. A commercial dynamic thorax phantom was used to reproduce regular and irregular breathing patterns recorded by the GateRT respiratory monitoring system. The amplitudes and periods of recorded breathing patterns were analysed and compared to planned patterns (ground-truth). In addition, the mean absolute deviations (MAD) and Pearson correlation coefficients (PCC) between the measurements and ground-truth were assessed. Measurements of gated and non-gated irradiations were also analysed with respect to dosimetry and geometry, and compared to treatment planning system (TPS). Further, the latency time of beam on/off was evaluated. Compared to the ground-truth, measurements performed with GateRT showed amplitude differences between 0.03±0.02mm and 0.26±0.03mm for regular and irregular breathing patterns, whilst periods of both breathing patterns ranged with a standard deviation between 10 and 190ms. Furthermore, the GateRT software precisely acquired breathing patterns with a maximum MAD of 0.30±0.23mm. The PCC constantly ranged between 0.998 and 1.000. Comparisons between TPS and measured dose profiles indicated absolute mean dose deviations within institutional tolerances of±5%. Geometrical beam characteristics also varied within our institutional tolerances of 1.5mm. The overall time delays were<60ms and thus within both recommended tolerances published by ESTRO and AAPM of 200 and 100ms, respectively. In this study, a non-invasive optical surface-guided workflow including image acquisition, treatment planning, patient positioning and gated irradiation at an ion-beam gantry was investigated, and shown to be clinically viable. Based on phantom measurements, our results show a clinically-appropriate spatial, temporal, and dosimetric accuracy when using surface guidance in the clinical setting, and the results comply with international and institutional guidelines and tolerances.

Simulation study of protoacoustics as a real-time in-line dosimetry tool for FLASH proton therapy.

Applying ultra-high dose rates to radiation therapy, otherwise known as FLASH, has been shown to be just as effective while sparing more normal tissue compared to conventional radiation therapy. However, there is a need for a dosimeter that is able to detect such high instantaneous dose, particularly in vivo. To fulfill this need, protoacoustics is introduced, which is an in vivo range verification method with submillimeter accuracy. The purpose of this work is to demonstrate the feasibility of using protoacoustics as a method of in vivo real-time monitoring during FLASH proton therapy and investigating the resulting protoacoustic signal when dose per pulse and pulsewidth are varied through multiple simulation studies. The dose distribution of a proton pencil beam was calculated through a Monte Carlo toolbox, TOPAS. Next, the k-Wave toolbox in MATLAB was used for performing protoacoustic simulations, where the initial proton dose deposition was inputted to model acoustic propagations, which were also used for reconstructions. Simulations involving the manipulation of the dose per pulse and pulsewidth were performed, and the temporal and spatial resolution for protoacoustic reconstructions were investigated as well. A 3D reconstruction was performed with a multiple beam spot profile to investigate the spatial resolution as well as determine the feasibility of 3D imaging with protoacoustics. Our results showed consistent linearity in the increasing dose-per-pulse, even up to rates considered for FLASH. The simulations and reconstructions were performed for a range of pulsewidths from 0.1 to 10μs. The results show the characteristics of the proton beam after convolving the protoacoustic signal with the varying pulsewidths. 3D reconstruction was successfully performed with each beam being distinguishable using an 8cm×8cm planar array. These simulation results show that measurements using protoacoustics has the potential for in vivo dosimetry in FLASH therapy during patient treatments in real time. Through this simulation study, the use of protoacoustics in FLASH therapy was verified and explored through observations of varying parameters, such as the dose per pulse and pulsewidth. 2D and 3D reconstructions were also completed. This study shows the significance of using protoacoustics and provides necessary information, which can further be explored in clinical settings.

Effect of self-healing behavior and self-healing technologies on the structural characteristics of cracked RC/ECC composite beams

The improving potential of self-healing behavior and self-healing technology to degradation of structural characteristics of cracked reinforced concrete structures was explored at the member level. Reinforced concrete/engineered cementitious composite (RC/ECC) composite beams were prepared by three self-healing technologies, including crystalline additives (CA), two types of superabsorbent polymers (SAP), and beam without self-healing technology was used as reference specimens. The self-healing properties of structural characteristics of beams were studied by four-point bending tests, including bear capacity, stiffness, ductility index, energy absorption capacity (EAC), and failure mode. The self-healing behavior of damage was evaluated by ultrasonic wave test and damage identification test based on natural frequency. Self-healing behavior of four types of RC/ECC composite beams improved the structural characteristics after cracking to varying degrees. The stiffness of CB-0, CB-S, CB-C, and CB-SH after self-healing increased by 10.80%, 22.88%, 36.71%, and 28.80% compared to that without self-healing, respectively. Recovery ability of structural characteristics of RC/ECC composite beam is enhanced by self-healing technologies. Moreover, CA exhibits a superior improvement in the recovery ability of the structural characteristics compared with two types of SAP. Moreover, the natural frequency and ultrasonic velocity of pre-cracked beams after self-healing were higher than those without self-healing, especially when self-healing technologies were applied. There is a positive correlation between the recovery ability of ultrasonic velocity and self-healing behavior of the structural characteristics of RC/ECC composite beams. This also explains why the structural characteristics of pre-cracked beams have been improved to varying degrees due to different self-healing techniques.

Free vibration of three-layered piezoelectric semiconductor rectangular beam

In this paper, the free vibration of a three-layered piezoelectric semiconductor (PS) rectangular beam is studied within the framework of the theory of Timoshenko beam and the theory of piezoelectric semiconductor. The perturbations of displacement, electric potential and electron concentration are given according to the theory of Timoshenko beam. By introducing the assumption of plane stress, the governing equations are integrated along the beam thickness direction, and the governing equations including motion equation, Gauss law and current continuity condition are obtained. The vibration of a simply supported three-layered piezoelectric semiconductor rectangular beam is realized by solving the governing equations. The effects of the ratio of layer thickness, length to thickness ratio, width to thickness ratio and length on the vibration of three-layered piezoelectric semiconductor rectangular beam are shown by numerical examples. The results show that there is an initial electron concentration range where the natural frequency of PS beam decreases sharply with the increase of the initial electron concentration. The damping characteristic of PS beams increases with the increase of the layer thickness ratio. For different length dimensions and length to thickness ratios, the damping characteristics of PS beams decrease with the increase of length and length to thickness ratio.

LOW INTENSITY BEAMS OF ELECTRONS AND POSITRONS IN THE ENERGY RANGE UP TO 100 MeV AT IHEPNP FACILITY

The article considers possible characteristics of low-intensity secondary positron and electron beams, which can be obtained using an electron accelerator with energy of ~100 MeV and average current of some μA. Preliminary simulation shows that using a tungsten converter of 2X0 thick and collimation of secondary particles beam, such accelerator allows one to get electron and positron secondary beams with energy of ~ 5…70 MeV, intensity of ~10-6-8 from the primary electron beam intensity, and energy spread of about some percent. Such low-intensity beams can be used for researches in the field of interaction of radiation with amorphous ubstances and crystals, testing detectors and scintillation materials.

Essential stressing state characteristics of H-section steel beams in fire revealed by modeling tested response data

This study finds out the essential behavior features of H-section steel beams in fire by analyzing the response data applying structural stressing state theory. Firstly, the deformation data are transformed into the generalized work of force (GWF) values called the state variables. Then, the state variables are used to build the stressing state mode and the parameter characterizing the mode called the stressing state characteristic pair. Next, the characteristic points in the evolution curve of the characteristic parameter are distinguished by the Mann-Kendall criterion. Further, the investigation into the evolution curve of the stressing state mode verifies the characteristic points. Thus, the starting points of the beams’ failure processes are revealed from the tested data and the corresponding loads are defined as the failure loads. Also, the other characteristic point called the elastoplastic branch (EPB) point is revealed from the evolution curves of the stressing state characteristic pair. Both characteristic points are the embodiment of the natural law from quantitative change to qualitative change of any system, which provides the new reference to update the analysis and design of H-section steel beams in fire. Finally, the formulas are fitted to calculate the failure loads and the EPB loads of the beams in fire with a verification.

Flexural Characterization of Concrete Beams Reinforced with 3D-Printed Formworks

3D printing has been on the rise in recent times and the civil engineering industry has adopted this technology due to its various advantages. However, printing is largely restricted to concrete members while the reinforcement is introduced manually. The current work looks at the possibility of using 3D printed thermoplastics as formwork and reinforcement for concrete beams. Three different polymeric materials, namely PETG, PLA, and TPU were utilized in this research to fabricate formwork-like reinforcement for 150×150×500 mm concrete beams. The reinforcements were 3D-printed using a fused deposition modelling (FDM) printer in the shape of a formwork to serve as moulds and external reinforcement. The reinforcing formwork geometry was designed with trapezoidal corrugations to ensure strong bonding with the concrete. The beams were tested in four-point bending configuration, and their flexural behaviour was characterized and compared with plain and steel reinforced concrete (RC) reference beams. Results indicate that all 3D printed beams reached a load capacity of around 30 kN. The post-peak behaviour of these beams was dependent on the type of polymer used. The PLA and TPU reinforced beams exhibit large post-peak deflection however their load carrying capacity was compromised, while the PETG exhibited a strain hardening behaviour but with much lower deflections. Overall, the results indicate that 3D-printed thermoplastics are a promising economical alternative to the conventional steel reinforcement.