Multibeam Configuration Research Articles

On the Performance of a Horizontally Mounted ADCP in an Energetic Tidal Environment for Floating Tidal Turbine Applications.

Incident flow measurement is key in the tidal industry for conducting power performance assessments. This paper explores the use of a horizontally mounted Nortek Signature 500 Acoustic Doppler Current Profiler (ADCP) as a means for incident flow measurement onboard a utility-scale tidal turbine. This study shows that the measurement range of an ADCP mounted horizontally in highly dynamic tidal flow (up to 4 m/s) is less than the maximum range stated by the manufacturer. The ability for the horizontal ADCP to accurately resolve velocities in a multi-beam configuration is also analysed. Effects from both vertical shear and beam selection result in incident flow velocities that differ from a single horizontal beam recording. The maximum measurement range of the instrument is found to depend on current speed and on the proportion of data loss that is acceptable to the user. The ability of the ADCP to record data from the free-stream velocity two equivalent diameters upstream of the O2, as set out by IEC TS 62600-200, is considered. It is found that at this distance, there is 90% data loss. Accepting only 10% data loss across all flow speeds resulted in a maximum range of 31 m for a Nortek Signature 500 in this study. While some limitations of an ADCP deployed horizontally in highly energetic tidal flow are identified, the benefits of mounting the sensor close to the rotor facing horizontally into the incoming flow mean that valuable data are still produced for tidal turbine operators.

Reconstructing turbulent wind-fields using inverse-distance-weighting interpolation and measurements from a pulsed mounted-hub lidar

This study evaluates a numerical multi-beam pulsed lidar mounted on the hub of the NREL 5MW reference wind turbine using the HAWC2 v13.1 numerical sensor for synthetic lidar measurement generation. While initially designed for single-beam operations, it facilitates multi-beam configuration simulations. We conducted an analysis of full-rotor longitudinal wind speed reconstruction by combining inverse-distance-weighting with synthetic sensor data from HAWC2. Utilizing a Mann-generated turbulence box for wind input at U = 11.4 m/s, we examined three lidar configurations for efficacy. The hub-mounted lidar proved efficient in capturing the incoming flow towards the turbine, showing a 60% improvement in overall reconstruction accuracy across the plane compared to the baseline, where hublidar measurements are simple average across the rotor plane. The rotor average wind speed showed a 30% enhancement compared to the baseline. Crucially, the lidar configuration, which impacted the spatial distribution across the rotor plane, emerged as a pivotal factor for effective reconstruction. Proper configuration assessment is essential, especially given the implications of rotational sampling and its impact under various wind conditions, for optimal performance. The proposed method, combining inverse-distance weighting with hub-lidar data for high spatial resolution measurements across the rotor plane, shows significant potential for real-time windflow estimation and lidar-assisted control applications.

Control of laser-plasma instabilities by non-collinear polychromatic light

Normal broadband lasers with collinear polychromatic components have immense potential for mitigating laser plasma instabilities (LPIs). However, the projection complexity of collinear polychromatic light (CPL) is a significant challenge owing to the demand for a large bandwidth and beamlet number. Here, we propose a theoretical LPI model and optical design for non-collinear polychromatic light (NCPL), which has a small angle ∼4∘ and large frequency difference ∼1% between the double-color beamlets. LPI models of the NCPL demonstrate a decoupling threshold for the shared daughter waves under a multibeam configuration. Compared with the CPL, the wavevector couplings of LPIs are further reduced by the introduced angle. Therefore, both the growth rate and saturation level of LPIs are greatly mitigated by using the NCPL. The two- and three-dimensional simulation results indicate that the NCPL reduces the absolute and convective decoupling thresholds of the CPL and is sufficient to effectively mitigate the reflectivity, hot-electron generation, and intensity of cross-beam energy transfer. An optical design for the efficient generation of ultraviolet NCPL has been presented based on the unsaturated optical parametric amplification and non-collinear sum-frequency generation.

Vacuum Breakdown in Multibeam Configuration of a Magnetic Dipole Wave

Vacuum Breakdown in Multibeam Configuration of a Magnetic Dipole Wave

Electronic‐Resonance‐Enhanced Coherent Raman Spectroscopy with a Single Femtosecond Laser Beam

AbstractCoherent Raman scattering (CRS) spectroscopy holds versatile applications in many fields ranging from measuring temperature and concentration in reacting flows to imaging biological molecules in living cells. Although the powerful spectroscopic technique has been studied for a few decades, significant attention is still paid to developing state‐of‐the‐art CRS spectroscopy with the simpler design and higher sensitivity for practical applications in harsh or complex environments. Herein, a novel electronic‐resonance‐enhanced coherent Raman scattering (ERE‐CRS) technique is developed with a single femtosecond laser beam. Such single‐beam ERE‐CRS scheme is accomplished with the narrowband air lasing signal naturally generated in the interaction region as a probe source. The developed technique not only avoids fine spatio‐temporal control in the conventional multibeam configuration, but also accomplishes 1–2 orders of magnitude enhancement of Raman signal due to the resonance of air lasing with electronic transition of the target gas. The dramatic enhancement effect is also manifested through the comparative measurements in CO2 isotopes. The single‐beam ERE‐CRS spectroscopy shows an unprecedented opportunity for the high‐sensitivity standoff detections of gas‐phase molecules and plasmas.

Filtering Photon Cloud Data in Forested Areas Based on Elliptical Distance Parameters and Machine Learning Approach

The Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2) was successfully launched. Due to its small spot size, multibeam configuration, high sampling rate, and strong immunity to terrain slopes, it has been regarded as a powerful tool for forest resources surveying and managing. However, the ICESat-2 photon cloud data contain considerable background photons, which discretely distribute in the background space of signal photons. Therefore, it is necessary to filter these noise photons. In this study, photons are divided into three categories: signal photons, noise photons far away from signal photons, and noise photons adjacent to signal photons. Based on the existing research, forward and backward elliptical distances were used to express the spatial relationship between two photons, and backward local density (BLD) was used to describe the density distribution of the photons. However, the single statistical parameter cannot clearly distinguish three types of photon cloud. Therefore, forward local density (FLD) and neighboring forward local density difference (NFLDD) also were defined to describe the density distribution of the photons. Finally, by combining the support vector machine (SVM), the above three density parameters were used to classify the photons by signal and noise photons. The proposed method was validated with photon cloud data acquired by the Simulated Advanced Terrain Laser Altimeter System (MATLAS), the Multiple Altimeter Beam Experimental Lidar (MABEL), and the ICESat-2 systems over different forested areas. The results demonstrated that the proposed method can well remove the noise photons and retain the signal photons without depending on any statistical assumptions or thresholds. The comprehensive accuracy of the three test sites was 0.99, 0.98, and 0.99, respectively, which was higher than those of the existing method. In addition, the total errors corresponding to the three test sites were about 0.4%, 0.5%, and 1.0% respectively, which were lower than those of the existing method.

A Novel Linear Energy Transfer Integrated Spot-Scanning Proton Arc Therapy Algorithm: Feasibility Study and Clinical Potential

To develop a novel dose-averaged linear energy transfer (LETd) integrated spot-scanning proton arc therapy (SPArc) optimization algorithm and to exploit its feasibility and potential clinical benefits. An open-source proton planning platform has been modified to incorporate LETd into optimization for both SPArc and multi-field intensity-modulated proton therapy (IMPT) treatment planning. SPArc and multi-field IMPT plans with multi-beam configurations (2, 4, 6, and 8 equally spacing fields) for a prostate patient were generated to investigate the feasibility of LETd-based optimization using SPArc in terms of spatially distributing LETd and plan delivery efficiency. One liver and one brain case were also studied to further evaluate the advantages of SPArc over multi-field IMPT. With similar dose distributions, the efficacy of spatially optimizing LETd distributions improves with increasing number of beams. Compared with multi-field IMPT, SPArc shows substantial improvement in spatially LETd distributions while keeping similar delivery efficiency. Specifically, for the liver case, the average LETd in the GTV was 4.88 and 2.35 keV/μm for the SPArc and 2-field IMPT plans respectively. Compared with the 2-field non-LETd optimized IMPT plan, the LETd increased by 129% for SPArc plan, and only 12% for the LETd optimized IMPT plan due to the limited number of beams. In case of LET optimization in brain case, the average LETd for the SPArc plan was increased by 29% for CTV, and was decreased by 22%, 30%, 28%, and 17% for brainstem, chiasm, left, and right optical nerves, respectively, compared to the 3-field non-LETd optimized IMPT plan. Subsequently, smaller improvement was observed in the 3-field LETd optimized IMPT plan (4%, 12%, 22%, 21%, and -3%, respectively). This work demonstrates the feasibility and significant advantages of using SPArc with LETd-based optimization, which could maximize the LETd distribution wherever is desired inside the target and averts the high LETd away from the adjacent critical organs-at-risk.

Broadband Linear-to-Circular Polarizing Reflector for Space Applications in Ka-Band

This article presents a novel low-profile broadband polarizing reflector to convert dual linear polarization (LP) into dual circular polarization (CP). The polarizing cell is based on printed dipole technology and presents a wideband performance in Ka-band. The dimensions of the printed dipoles are adjusted cell by cell to improve the reflection phase performance against variations in the incidence angles or in the cell dimensions. A 25 cm flat polarizing reflector demonstrator has been designed, fabricated, and tested. The design has been optimized for transmit (19.2-20.2 GHz) and receive (29-30 GHz) frequencies in Ka-band, but the broadband behavior of the cell provides satisfactory results also at the intermediate frequencies. The measured patterns show a good agreement with the simulations, with an axial ratio lower than 1.8 dB within the 19.2-30 GHz band. The proposed polarizing reflector can be used for novel multibeam antenna configurations to produce multispot coverage in Ka-band with a smaller number of apertures.

ARCTURUS laser: a versatile high-contrast, high-power multi-beam laser system

With the latest configuration, the Ti:Sa laser system ARCTURUS (Düsseldorf University, Germany) operates with a double-chirped pulse amplification (CPA) architecture delivering pulses with an energy of 7 J before compression in each of the two high-power beams. By the implementation of a plasma mirror system, the intrinsic laser contrast is enhanced up to $10^{-12}$ on a time scale of hundreds of picoseconds, before the main peak. The laser system has been used in various configurations for advanced experiments and different studies have been carried out employing the high-power laser beams as a single, high-intensity interaction beam ( $I\approx 10^{20}~\text{W}/\text{cm}^{2}$ ), in dual- and multi-beam configurations or in a pump–probe arrangement.

A tesselation-based model for intensity estimation and laser plasma interactions calculations in three dimensions

A three-dimensional laser propagation model for computation of laser-plasma interactions is presented. It is focused on indirect drive geometries in inertial confinement fusion and formulated for use at large temporal and spatial scales. A modified tesselation-based estimator and a relaxation scheme are used to estimate the intensity distribution in plasma from geometrical optics rays. Comparisons with reference solutions show that this approach is well-suited to reproduce realistic 3D intensity field distributions of beams smoothed by phase plates. It is shown that the method requires a reduced number of rays compared to traditional rigid-scale intensity estimation. Using this field estimator, we have implemented laser refraction, inverse-bremsstrahlung absorption, and steady-state crossed-beam energy transfer with a linear kinetic model in the numerical code Vampire. Probe beam amplification and laser spot shapes are compared with experimental results and pf3d paraxial simulations. These results are promising for the efficient and accurate computation of laser intensity distributions in holhraums, which is of importance for determining the capsule implosion shape and risks of laser-plasma instabilities such as hot electron generation and backscatter in multi-beam configurations.

Towards attosecond-scale highly directed GeV gamma-ray sources with multipetawatt-class lasers

We consider a possibility of constructing a gamma-ray source based on the multibeam configuration of a multipetawatt laser system which we simulate using a converging dipole wave. It is shown that such a configuration of fields allows the generation of gamma radiation with narrow directivity of about 1 mrad in the form of pulse trains or isolated pulses on the attosecond timescale. The influence of quantum electrodynamic cascade development on the parameters of generated gamma bursts is studied.

Microwave Radiometers for Fire Detection in Trains: Theory and Feasibility Study.

This paper introduces the theory of fire detection in moving vehicles by microwave radiometers. The system analysis is discussed and a feasibility study is illustrated on the basis of two implementation hypotheses. The basic idea is to have a fixed radiometer and to look inside the glass windows of the wagon when it passes in front of the instrument antenna. The proposed sensor uses a three-pixel multi-beam configuration that allows an image to be formed by the movement of the train itself. Each pixel is constituted by a direct amplification microwave receiver operating at 31.4 GHz. At this frequency, the antenna can be a 34 cm offset parabolic dish, whereas a 1 K brightness temperature resolution is achievable with an overall system noise figure of 6 dB, an observation bandwidth of 2 GHz and an integration time of 1 ms. The effect of the detector noise is also investigated and several implementation hypotheses are discussed. The presented study is important since it could be applied to the automatic fire alarm in trains and moving vehicles with dielectric wall/windows.

Multibeam 3D Underwater SLAM with Probabilistic Registration.

This paper describes a pose-based underwater 3D Simultaneous Localization and Mapping (SLAM) using a multibeam echosounder to produce high consistency underwater maps. The proposed algorithm compounds swath profiles of the seafloor with dead reckoning localization to build surface patches (i.e., point clouds). An Iterative Closest Point (ICP) with a probabilistic implementation is then used to register the point clouds, taking into account their uncertainties. The registration process is divided in two steps: (1) point-to-point association for coarse registration and (2) point-to-plane association for fine registration. The point clouds of the surfaces to be registered are sub-sampled in order to decrease both the computation time and also the potential of falling into local minima during the registration. In addition, a heuristic is used to decrease the complexity of the association step of the ICP from to . The performance of the SLAM framework is tested using two real world datasets: First, a 2.5D bathymetric dataset obtained with the usual down-looking multibeam sonar configuration, and second, a full 3D underwater dataset acquired with a multibeam sonar mounted on a pan and tilt unit.

Orthogonal Vector Approach for Synthesis of Multi-Beam Directional Modulation Transmitters

An orthogonal vector approach is proposed for the synthesis of multi-beam directional modulation (DM) transmitters. These systems have the capability of concurrently projecting independent data streams into different specified spatial directions while simultaneously distorting signal constellations in all other directions. Simulated bit error rate (BER) spatial distributions are presented for various multi-beam system configurations in order to illustrate representative examples of physical layer security performance enhancement that can be achieved.

Adaptive multibeam laser cutting of thin steel sheets with fiber laser using spatial light modulator

Laser cutting with multibeam diffraction pattern using an adaptive optics is studied. Infrared (IR) continuous single-mode fiber laser with maximum power of 200 W is applied to laser cutting of thin metal sheets, together with liquid crystal on silicon spatial light modulator (SLM). SLM can be used as the adaptive diffractive optical element, which can modify intensity profile of the laser beam almost arbitrary. In studies single Gaussian laser beam was divided into multiple spots. It was found out that with this way it is possible to enhance the cutting quality and also decrease pressure of the needed assist gas. Multibeam configuration enabled to laser cut burr free with 50% less protection gas pressure compared to single beam laser cutting with conventional optics.

An approach for simplifying a multiple beam-forming network for concentric ring arrays using CORPS

This research work deals with a innovative way to simplify the design of beam-forming networks (BFNs) for multi-beam steerable concentric ring arrays based on coherently radiating periodic structures (CORPS) technology. Mono- and multi-beam design configurations of CORPS-BFN for steerable concentric ring arrays are proposed and analyzed. The complex inputs of the feeding network for these configurations are optimized with the differential evolution algorithm. Simulation results reveal a significant simplification of the feeding network based on CORPS for concentric ring arrays reducing drastically the number of input ports to control each beam in both configurations analyzed.

A Robust MUSIC Based Scheme for Interference Location in Satellite Systems with Multibeam Antennas

In this paper, we investigate methods for interference location in satellite communication system using satellite multi-beam antenna with subspace based schemes. A novel MUSIC based approach is proposed for estimating the direction of arrival of the interfering sources. The proposed method provides super resolution and asymptotic maximum likelihood estimates of the direction of arrivals even at low SNR values. Simulations were performed using typical satellite multi-beam antenna configurations and results show that the proposed scheme can effectively estimates the direction of arrival in the azimuth and elevation spectra. Compared to the support vector regression method, the proposed approach offer improved estimation accuracy at low SNR values.

Performance Analysis of Optimum Tilt Angle and Beam Configuration to Derive Horizontal Wind Velocities by Postset Beam Steering Technique

Software beam synthesis by postset beam steering (PBS) technique is used to derive the horizontal wind velocities from multireceiver phased-array radar data. In order to improve the efficiency of beam synthesis, the Capon beamforming method is used to synthesize time series signals in the desired line-of-sight angle within the radar transmit beam volume (3.6 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> beamwidth). This paper describes beam synthesizing in optimum directions to reduce the error in the measurement of horizontal wind velocities using the PBS technique. For this purpose, beams are synthesized at various tilt angles with multibeam configuration. From the synthesized beam, power spectral distribution is obtained by one of the subspace methods, i.e., eigenvector (EV). The mean Doppler frequency and radial wind velocity at the desired line-of-sight angle are derived by an adaptive-moment estimation method from an EV-produced power spectrum. Using the moments obtained in various radial directions, horizontal wind components are derived by the conventional method for wind profiler radars. Also, an analysis is done for the required number of beams to improve PBS-based wind estimation. The statistical comparisons of performances of various tilt angles and beam configurations are being studied using the data collected from a multireceiver phased-array radar system (middle and upper atmosphere radar, Shigaraki, Japan). The analyzed results show that beam synthesis at the tilt angle from 1.5 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> to 2.0 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> using a 16-beam configuration minimize the error in horizontal wind estimation by PBS technique.

Performance Analysis of Optical Wireless Communication System Employing Neuro-Fuzzy Based Spot-Diffusing Techniques

The spot-diffusing technique provides better performance compared to conventional diffuse system for indoor optical-wireless communication (OWC) system. In this paper, the performance of an OW spot-diffusing communication system using Neuro-Fuzzy (NF) adaptive multi-beam transmitter configuration has been proposed. The multi-beam transmitter generates multiple spots pointed in different directions, hence, forming a matrix of diffusing spots based on position of the receiver and receiver mobility. Regardless of the position of the transmitter and receiver, NF controller target the spots adaptively at the best locations and allocates optimal power to the spots and beam angle are adapted in order to achieve better signal-to-noise plus interference ratio (SNIR). Maximum ratio combining (MRC) is used in the imaging receiver. The proposed OW spot-diffusing communication system is compared with other spot-beam diffusion methods proposed in literature. Performance evaluation revels that the proposed NF based OW spot-diffusing communication system outperforms other spot-beam diffusion methods.

Monte Carlo simulation of a compact microbeam radiotherapy system based on carbon nanotube field emission technology

Microbeam radiation therapy (MRT) is an experimental radiotherapy technique that has shown potent antitumor effects with minimal damage to normal tissue in animal studies. This unique form of radiation is currently only produced in a few large synchrotron accelerator research facilities in the world. To promote widespread translational research on this promising treatment technology we have proposed and are in the initial development stages of a compact MRT system that is based on carbon nanotube field emission x-ray technology. We report on a Monte Carlo based feasibility study of the compact MRT system design. Monte Carlo calculations were performed using EGSnrc-based codes. The proposed small animal research MRT device design includes carbon nanotube cathodes shaped to match the corresponding MRT collimator apertures, a common reflection anode with filter, and a MRT collimator. Each collimator aperture is sized to deliver a beam width ranging from 30 to 200 μm at 18.6 cm source-to-axis distance. Design parameters studied with Monte Carlo include electron energy, cathode design, anode angle, filtration, and collimator design. Calculations were performed for single and multibeam configurations. Increasing the energy from 100 kVp to 160 kVp increased the photon fluence through the collimator by a factor of 1.7. Both energies produced a largely uniform fluence along the long dimension of the microbeam, with 5% decreases in intensity near the edges. The isocentric dose rate for 160 kVp was calculated to be 700 Gy∕min∕A in the center of a 3 cm diameter target. Scatter contributions resulting from collimator size were found to produce only small (<7%) changes in the dose rate for field widths greater than 50 μm. Dose vs depth was weakly dependent on filtration material. The peak-to-valley ratio varied from 10 to 100 as the separation between adjacent microbeams varies from 150 to 1000 μm. Monte Carlo simulations demonstrate that the proposed compact MRT system design is capable of delivering a sufficient dose rate and peak-to-valley ratio for small animal MRT studies.