Beam Scanning Research Articles

A 1-bit passive reconfigurable metasurface for wide-angle scanning and broad-beam reflection

ABSTRACT A reconfigurable reflective metasurface design is proposed in this letter, allowing for beam scanning capabilities. This paper integrates a tunable capacitor into the metasurface unit. This paper integrates a tunable capacitor into the metasurface unit. The resonant characteristics of the metasurface unit are controlled by the tunable capacitor, which can be adjusted by changing the rotation angle of the metal plate on the tunable capacitor. By rotating the metal plate of the capacitor, it achieves state 1 at maximum capacitance and state 0 at minimum capacitance, resulting in a phase difference of 180° ± 20° between the states, thereby enabling 1-bit phase control. Leveraging the principle of phase compensation, the phase distribution of the array is designed to exhibit directional radiation characteristics. A reflective metasurface composed of a 20 × 20-element array is designed and simulated with these characteristics. The simulation results indicate that the scanning angle of the array-reflected beam can reach ± 50°, with a peak gain exceeding 14.6 dBi, an average gain of 13.8 dBi, and a gain loss of 1.5 dB. The beam’s 3 dB beamwidth exceeds 15°, enabling broader coverage. Joint simulations in typical indoor scenarios confirm the improved signal strength, highlighting the array’s versatility. This design allows the reflective array to function as a passive reflector relay, effectively improving signal coverage in indoor NLOS.

Preliminary Design and Thermal-Hydraulic Study of a 250-kW LBE Experimental Spallation Target for CiADS

The CiADS (China initiative Accelerator Driven System) project plans to build a 250-kW experimental target before construction of the 2.5-MW spallation target. In this paper, the effect of proton beam distribution on the performance of the 250-kW target is studied. Hence, a hollow beam distribution, formed by a Gaussian beam scanning around the center of the beam window, is proposed. Then, combined with the orthogonal test method and the CRITIC (Criteria Importance through Intercriteria Correlation) method, four key geometric parameters of the target flow channel are analyzed to simultaneously achieve optimization of the target performance from the viewpoints of both the maximum temperature and velocity under steady-state condition. Finally, transient analysis of the initiation of the Gaussian beam scanning is conducted; the calculation time was 15s. The results show that the temperature on the window rose gradually until reaching its maximum value corresponding to the steady-state analysis. Detailed analyses showed that the optimized target design is capable of meeting the thermal-hydraulic and mechanical requirements.

Application of intraoral scanning registration implant robot in dental implant surgery.

This paper aims to investigate the application of intraoral scanning and cone beam computed tomography (CBCT) registration implant robot in dental implant surgery. The data of 40 cases with dental defect of robot-assisted implantation from November 2023 to May 2024 were retrospectively analyzed. Before the operation, the intraoral scan data and CBCT data of the positioning markers were automatically fused with the initial CBCT images, and the registration error was calculated. The average registration error of positioning markers was determined during the operation, and the implantation accuracy was analyzed after the operation. The intraoral scan data and CBCT data of 40 patients with dental defect wearing positioning markers were successfully registered with the initial CBCT image, and the registration errors were (0.157±0.026) mm and (0.154±0.033) mm, respectively. Statistical analysis showed no statistical significance between them. The registration errors of the marker was (0.037 3±0.003 6) mm. A total of 55 implants were performed, and the total deviations of the implant point and the apical point were (0.78±0.41) and (0.89±0.28) mm, respectively. The transverse deviations of the implant point and the apical point were (0.44±0.36) and (0.58±0.25) mm, respectively. The depth deviations of the implant point and the apical point were (0.51±0.32) and (0.54±0.36) mm, respectively. The deviation of the implant angle was 1.24°±0.67°. The fusion technology based on intraoral scanning and CBCT registration can meet the accuracy requirements of preoperative registration of oral implant robots. The technology increases the choice of registration methods before robot-assisted dental implant surgery and reduces the multiple radiation exposuresof the patient.

Commissioning a clinical proton pencil beam scanning beamline for pre-clinical ultra-high dose rate irradiations on a cyclotron-based system

Commissioning a clinical proton pencil beam scanning beamline for pre-clinical ultra-high dose rate irradiations on a cyclotron-based system

Validity of Thermal Simulation Models for Different Laser Beam Shapes in Bead-on-Plate Melting

AbstractComputational models that predict melt pool shapes and temperature evolution in laser-based powder bed fusion of metals (PBF-LB/M) can range from simple thermal simulation models to more advanced models that incorporate more detailed physics of the process. While advanced models can accurately predict thermal fields and melt pool fluid dynamics, they are computationally more expensive and, thus, less suited for part-scale simulations or numerical optimization, where repeated model evaluations are necessary. On the other hand, thermal simulations are computationally efficient and attractive for their simplicity, but their accuracy is mainly limited to conduction-dominated processes. Moreover, the conduction model’s validity range is not fully understood for non-Gaussian laser beam shapes. This paper demonstrates that predictions of melt pool depth and width carried out by a heat conduction model are accurate to within 20 % for all investigated laser profiles, provided that the simulated maximum temperature does not exceed a certain threshold value for stainless steel 316L. This is established by thoroughly investigating the validity range of the heat conduction model through comparisons with over 200 single-track experiments on bare plates. The temperature predictions from the model are compared with multi-physics simulations using smoothed particle hydrodynamics (SPH). Through detailed analysis and validation for three laser beam shapes, this contribution provides valuable insights into the accuracy and applicability of heat conduction models in bead-on-plate melting simulations and offers a path to optimize process parameters, such as laser beam shape, scanning strategy, and other processes for diverse applications aimed at PBF-LB/M.

Effects of spot size errors in DynamicARC pencil beam scanning proton therapy planning

Objective.Spot size stability is crucial in pencil beam scanning (PBS) proton therapy, and variations in spot size can disrupt dose distributions. Recently, a novel proton beam delivery method known as DynamicARC PBS scanning has been introduced. The current study investigates the dosimetric impact of spot size errors in DynamicARC proton therapy for head and neck (HNC), prostate, and lung cancers.Approach.Robustly optimized DynamicARC proton therapy plans were created for HNC (n= 4), prostate (n= 4), and lung (n= 4) cancer patients. Spot size errors of ±10%, ±15%, and ±20% were introduced, and their effects on target coverage (D95%andD99%), homogeneity index (HI), and organ-at-risk doses were analyzed across different cancer sites.Main Results.HNC and lung cancer plans showed greater vulnerability to spot size errors, with reductions in target coverage of up to 4.8% under -20% spot size errors. Dose homogeneity was also more affected in these cases, with HI degrading by 0.12 in lung cancer. Prostate cancer demonstrated greater resilience to spot size variations, even under errors of ±20%. For spot size errors ±10%, the oral cavity, parotid glands, and constrictor muscles experiencedDmeandeviations within ±1.2%, while deviations were limited to ±0.5% forD10%of the bladder and rectum and ±0.3% forV20 Gy(RBE)of the lungs. The robustness analysis indicated that lung cancer plans were most susceptible to robustness reductions caused by spot size errors, while HNC plans demonstrated moderate sensitivity. Conversely, prostate cancer plans demonstrated high robustness, experiencing only minimal reductions in target coverage.Significance.While the ±10% spot size tolerance is appropriate in majority of the cases, lung cancer plans may require more stringent criteria. As DynamicARC becomes clinically available, measuring spot size errors in practice will be essential to validate these findings and refine tolerance thresholds for clinical use.

The Study of Effectiveness of Combined Proton-Neutron Irradiation of Tumor Cells In Vitro.

Combined proton-neutron therapy can be the best opportunity for neutron radiation therapy due to highly conformal proton irradiation and high relative biological effectiveness of neutrons. The study compares 4 schemes of sequential in vitro exposure of Chinese hamster fibrosarcoma cells B14-150 to 14.5 MeV neutrons and a scanning beam of protons. Treatment efficiency increased with increasing the contribution of the neutron component to the total dose from 30 to 40% and the delivery of the neutron dose as the first fraction in the two-fraction proton-neutron exposure.

Low-profile dual-polarized ultra-wideband phased antenna array based on metasurface

This paper presents what we believe to be a novel design for tightly coupled antenna arrays aimed at addressing the challenges associated with low-profile designs and dual polarization in ultra-wideband applications. The design features an innovative dual-polarized dipole arrangement and employs a cross-arranged methodology to construct the tightly coupled broadband antenna array. This approach achieves a working bandwidth ranging from the C-band to the Ku-band while maintaining a low-profile design. By incorporating a metasurface onto the tightly coupled array, this design significantly extends the effective working bandwidth while enhancing radiation performance throughout the beam coverage range. A 400-element dual-polarized array with an integrated phased array system is designed, fabricated, and measured. The antenna array is capable of ±60∘ beam scanning, with a relative bandwidth of 100% and a profile height of 0.38 wavelengths (at 18 GHz). This dual-polarized shared-aperture broadband phased array antenna not only facilitates flexible polarization synthesis but also offers a working bandwidth suitable for diverse application scenarios. Additionally, the implementation of an aperture reuse design minimizes the required aperture area. Collectively, these advancements enhance the overall performance of contemporary communication and radar systems, highlighting substantial application potential.

Spatially Fractionated Radiotherapy with Very High Energy Electron Pencil Beam Scanning.


To evaluate spatially fractionated radiation therapy (SFRT) for very-high-energy electrons (VHEEs) delivered with pencil beam scanning. Radiochromic film was irradiated at the CERN Linear Electron Accelerator for Research (CLEAR) using 194 MeV electrons with a step-and-shoot technique, moving films within a water tank. Peak-to-valley dose ratios (PVDRs), depths of convergence (PVDR≤1.1), peak doses, and valley doses assessed SFRT dose distribution quality. A Monte Carlo (MI) model of the pencil beams was developed using TOPAS and applied to a five-beam VHEE SFRT treatment for a canine glioma patient, compared to a clinical 6 MV VMAT plan. The plans were evaluated based on dose-volume histograms, mean dose, and maximum dose to the planning target volume (PTV) and organs at risk (OARs).
Main Results:
Experimental PVDR values were maximized at 15.5 ± 0.1 at 12 mm depth for 5 mm spot spacing. A depth of convergence of 76.5 mm, 70.7 mm, and 56.6 mm was found for 5 mm, 4 mm, and 3 mm beamlet spacings, respectively. MC simulations and experiments showed good agreement, with maximum relative dose differences of 2% in percentage depth dose curves and less than 3% in beam profiles. Simulated PVDR values reached 180 ± 4, potentially achievable with reduced leakage dose. VHEE SFRT plans for the canine glioma patient showed a decrease in mean dose (>16%) to OARs while increasing the PTV mean dose by up to 15%. Lowering beam energy enhanced PTV dose homogeneity and reduced OAR maximum doses. The presented work demonstrates that pencil beam scanning SFRT with VHEEs could treat deep-seated tumors such as head and neck cancer or lung lesions, though small beam size and leakage dose may limit the achievable PVDR.&#xD.

Correlating Heterogeneities in Support Fragmentation to Polymer Morphology in Metallocene‐Based Propylene Polymerization Catalysis

AbstractIn the field of olefin polymerization catalysis, metallocenes are heterogenized with methylaluminoxane onto silica supports to yield active catalysts. During olefin polymerization, these silica supports act as a framework to control the fragmentation stage, thereby influencing the final polymer product and preventing reactor fouling and fines formation. This study investigates the influence of different silica supports induced on the final polymer product. To study a broad range of silica supports from an industrial silica database, we utilize a hierarchical clustering method to cluster the supports based on their physical properties. From the clustering method, five supports representing the clusters and an industrial benchmark were analyzed at different polymerization stages using focused ion beam–scanning electron microscopy (FIB–SEM) and microcomputed tomography (microCT). This combined FIB‐SEM/microCT methodology revealed differences in both fragmentation behavior and polymer morphologies based on structural features, including macropores, mesopores, spray‐dried shells, spray‐dried spheres, and denser shells. The heterogeneity and ideal fragmentation behavior was further assessed by calculating the replication factor of each support, indicating that silica materials containing macropores and spray‐dried shells have an almost ideal replication phenomenon. This multiscale analysis revealed new understanding of catalyst fragmentation for different supports. This understanding could in the future be further developed by the addition of more supports or additional analysis of the supports to the industrial database.

Twisted Metasurfaces for On‐Demand Focusing Localization

AbstractDynamic focusing of electromagnetic (EM) waves is a cornerstone in various applications, encompassing aerospace communication, sensing, and high‐resolution imaging. Recently, the advent of intelligent metasurfaces, hailed as the next evolutionary step, has revolutionized self‐adaptive functionalities. However, their extensive embeddings of active components pose a great challenge associated with escalated costs, heightened power consumption, and increased complexity, thus hindering large‐scale implementation. Here, a cost‐effective approach for dynamic EM focusing utilizing a twisted metasurface is introduced, which integrates a transmissive layer with a reflective layer in a cascade fashion. This innovative design leverages the mutual rotation between two layers to enable the precise manipulation of beam propagation and scanning area, allowing for the flexible localization of the focal point across a wide range, spanning −44.17° to 44.17° in elevation and 0° to 360° in azimuth. This capability is underpinned by the strategic fusion of multiple phase profiles, including gradient and Gaussian phase. In the experiment, a goal‐oriented system is built up whose outcomes demonstrate a striking alignment with the simulated results, achieving a correlation coefficient of 96.7%. This work presents a streamlined pathway toward dynamic EM focusing and the related applications constrained by space and power limitations.

Dynamic response characteristics and linearization of liquid crystal cladding waveguide beam scanner

Dynamic response characteristics and linearization of liquid crystal cladding waveguide beam scanner

Crack-free manufacture of single weld tracks on aluminum alloy 6013 with the usage of laser beam shaping and oscillation strategies

The present paper investigates the application of laser beam shaping and laser beam oscillations (wobbling) for laser processing of the crack-prone aluminum alloy 6013, used in automotive and aerospace applications. A comparison of different laser beam profiles, such as the commonly used Gaussian profile, a ring-core distribution with the intensity of 50 % in the ring and 50 % in the core, and a ring-shaped beam profile shows different cracking behavior of the material. The ring-shaped beam profile shows the most promising results due to a reduction of the thermal gradient G and an enhancement of the growth rate R, which isalso stated by the state of the art. A combination of laser beam shaping and laser beam oscillations shows reproducible crack-free processing of Al6013 sheets at all three beam profiles at different parameter combinations. The crack elimination can be attributed to the emergence of a more pronounced equiaxed grain structure in the fusion zone of the weld with the application of laser beam oscillations and laser beam shaping. Thus, the temperature gradient G, the growth rate R and, therefore, the cooling rate can be controlled with the presented variation of the laser beam shapes and scanning strategies. Furthermore, the penetration depth of the laser at a Gaussian beam profile can be reduced using laser beam shaping, showing shallower melt pools with a lower depth-to-width aspect ratio, also suitable for the process of powder bed fusion of metals using a laser-based system (PBF-LB/M).

A Dual-Band Leaky Wave Antenna With Dual-Bi-Directional Continuous Beam Scanning for Large Space Radiation Coverage

A Dual-Band Leaky Wave Antenna With Dual-Bi-Directional Continuous Beam Scanning for Large Space Radiation Coverage

Impact of Pre-pectoral Implant Placement and Radiation Modalities (Protons/Photons) in Mastectomy Patients undergoing Immediate Direct-to-Implant Breast Reconstruction

BackgroundFor breast cancer patients receiving mastectomy with direct-to-implant (DTI) immediate breast reconstruction, placing the implant in the pre-pectoral or subpectoral plane remains debatable; especially in settings of postmastectomy radiotherapy (PMRT). Materials/MethodsWe reviewed 3,039 patients who underwent mastectomy and reconstruction at our institution between 2005 and 2020. Patients receiving DTI with and without PMRT were included. PMRT was delivered either with photon (3D-conformal or VMAT) or proton therapy mainly with pencil beam scanning. All patients received conventional fractionation (50-50.4Gy in 25-28fractions). Primary endpoints were reconstruction complications defined as infection/necrosis requiring debridement; capsular-contracture requiring capsulotomy; absolute-reconstruction-failure entailing permanent removal of the implant without replacement (i.e: no salvage reconstruction) and overall-reconstruction-failure (removal of implant for any complication with and without salvage reconstruction). Different subgroups analyses were done. Results815 patients met inclusion criteria, with an overall median follow-up of 6.2 years. We found that there is no significant difference between pre-pectoral vs sub-pectoral for infection/necrosis (OR:1.5, p=0.3); capsular-contracture (OR:0.97, p=0.9); absolute-reconstruction-failure (OR:1.9, p=0.12) and overall-reconstruction-failure (OR:1.2, p=0.5). Findings were confirmed using both logistic regression, time-to-event analysis and multivariable analyses for the entire cohort and subgroups with and without PMRT. There was no significant difference between Protons and Photons in terms of infection/necrosis (OR:1.6, p=0.4) and absolute-reconstruction-failure (OR: 1.2, p=0.7), but significantly higher risks for capsular-contracture with protons (OR:4.4, p<0.001) and overall-reconstruction-failure when compared to photon(OR:2.0, p=0.05). We did not find significant correlation pattern between different dosimetry factors (Dmean, Dmax, volume in cc) in either reconstructed-chest-wall target or the skin structure, to reconstruction complications; whether for protons or photons patients. ConclusionFor patients receiving single-stage DTI reconstruction with and without PMRT, pre-pectoral implant placement had similar rates of complications and reconstruction failure compared to subpectoral reconstruction. Protons compared to Photons did not increase the risk of infection/necrosis but significantly increased capsular-contracture risks.

Assessment of pencil beam scanning proton therapy beam delivery accuracy through machine learning and log file analysis

PurposeComprehensive Quality Assurance (QA) protocols are necessary for complex beam delivery systems like Pencil Beam Scanning (PBS) proton therapy. This study focuses on automating the evaluation of beam delivery accuracy using irradiation log files and machine learning (ML) models. MethodsIrradiation log files of 935 clinical treatment fields and routine QA beams were analysed to evaluate spot parameters and Monitor Unit (MU) accuracy. ML models predicted spot size along the X, Y, major, and minor axes. In-house scripts automated log file analysis and spot size predictions. Predicted spot sizes were compared with expected baselines, and the accuracy of spot position, symmetry, and MU for each spot in the beam was evaluated. ResultsMore than 99.5 % of spot positions were accurate within a 1 mm. The mean and Standard Deviation (SD) of X positional error were −0.021 mm (SD: 0.181 mm), and for Y positional error, they were −0.002 mm (SD: 0.132 mm). ML models accurately predicted spot sizes, with over 95 % of spots demonstrating size variations within 10 % of the baseline. The Root Mean Squared Error (RMSE) of X and Y spot size differences were 0.15 mm and 0.16 mm, respectively. Spot symmetry was within 10 %, and MU accuracy showed 95 % of spots with MU per spot variation less than 2 %. ConclusionThis method can validate the vendor’s beam delivery safety interlock system and serve as a quick alternative to patient-specific QA in adaptive treatment, where time is limited, as well as for routine QA spot parameter evaluations.

Anisotropic programmable metasurfaces with individually controllable 2-bit elements

Programmable metasurfaces capable of manipulating electromagnetic (EM) waves in real time provide new opportunities for various exciting applications. However, most previous programmable metasurfaces only work in a single polarization mode and their elements are controlled in a whole or one-dimensional way, which limits functionality and adaptability to complex environments. Here, an anisotropic programmable metasurface with individually controllable elements is proposed to realize real-time and independent dual-polarized EM control in the two-dimension direction. The anisotropic metasurface element is designed using the ingenious cross-over resonant structure integrated with two sets of varactors to achieve 2-bit phase modulation in the respective polarization direction. As a demonstration, an anisotropic programmable metasurface prototype with 21×20 such elements is simulated, fabricated, and measured. Real-time beam scanning and vortex wave generation are verified respectively under two different polarized wave incidences, which indicates that the realized anisotropic programmable metasurface can achieve totally distinct functionalities for two orthogonal polarizations. Our work could push programmable metasurfaces one step closer towards more advanced information devices and complicated applications in communication and imaging.

REAL TIME LUMINESCENT DOSIMETRY SYSTEM FOR PRODUCT PROCESSING AT AN ELECTRON ACCELERATOR

Quality control in industrial product processing at an electron accelerator requires continuous monitoring of critical parameters of the irradiation regime, first of all, of absorbed dose. The method of contact-free on-line measuring the surface distribution of absorbed dose in a processed object is described. The novel technique is based on the use of optical radiation induced in the object with the electron beam (cathodoluminescence, CL). It is shown, that the intensity of CL is proportional to the absorbed dose rate. An automated system for online measurement of the CL signal and determination of the scanning beam parameters (profile, width, offset) has been developed. The results of calibration of the absorbed dose by the CL signal in the industrial dose range are obtained. In contrast to the well-known methods of luminescent dosimetry based on thermo- or optically stimulated luminescence, the new approach does not require a special material for detector, as well as its extra stimulation to read out the dosimetry information.

A microwave/millimeter-wave triple-band shared-aperture antenna integrating differentially-fed patch and transmitarray

This paper presents a microwave (MW)/millimeter-wave (MMW) triple-band shared-aperture antenna. It is implemented by integrating a differentially-fed patch (3.6 GHz) and a dual-band transmitarray (TA) (26 GHz and 39 GHz) through structure reuse. To realize an efficient integration, the patch antenna is evolved from a single-layer structure to a multi-layer one, with an extended ring-shaped patch added in each layer to obtain a proper transmitting surface (TS) size. For the TA, it adopts a unit cell (UC) consisting of two interleaved slots. By adjusting the lengths of the slots, independent dynamic phase shifts covering 360∘ can be attained for the 26 GHz and 39 GHz bands, respectively. To achieve an appropriate focal-to-diameter ratio (F/D) for the TA, a frequency selective surface (FSS) is employed to replace the ground plane of the patch antenna. Thanks to the spatial feeding architecture of the TA, the proposed antenna eliminates the need of complicated feeding network and features low feeding loss and high gain in the MMW bands. To validate the design idea, a prototype is fabricated and measured. The experimental results demonstrate that the proposed antenna can successfully operate in the three bands with peak gain of 7.6 dBi, 19.3 dBi and 19.5 dBi, respectively. In the 26 GHz and 39 GHz bands, beam scanning ranges of ±25∘ and ±13∘ can be obtained, respectively. The proposed antenna can be a promising candidate for 5G multi-band applications.

Application of Advanced Microscopy Techniques to the Characterization of Mixed Matrix Membranes.

Mixed matrix membranes (MMMs) have emerged as promising materials for various separation processes due to their tunable properties, enhanced separation performance and reproducibility. In this review paper, we provide a comprehensive overview of the methodologies, challenges, and applications associated with the characterization of MMMs using two advanced imaging techniques: Focused Ion Beam Scanning Electron Microscopy (FIB-SEM) and Transmission Electron Microscopy (TEM). We begin by outlining the principles and capabilities of FIB-SEM and TEM, emphasizing their suitability for studying the microstructure, morphology, and composition of MMMs at nanoscale resolution. Subsequently, we discuss the specific challenges and limitations encountered in the characterization of MMMs using these techniques, including sample preparation, image acquisition, and data interpretation. Furthermore, we review the diverse applications of FIB-SEM and TEM in elucidating the structure-property relationships of MMMs. Through illustrative examples, we highlight the valuable insights gained from these imaging techniques in optimizing MMMs for various separation applications. Finally, we propose future directions and emerging trends in MMM characterization, including the integration of lasers into FIB-SEM and in situ characterization techniques, to address current challenges and push the boundaries of MMM design and performance. Overall, this review provides a comprehensive overview of the state-of-the-art methodologies for characterizing MMMs using FIB-SEM and TEM, identifies key challenges, and offers insights into future research directions aimed at harnessing the full potential of MMMs for sustainable separation technologies.