Precise Beam Research Articles

Preliminary beam formations after the upgrade of the TIARA two microbeam systems

This paper presents a comprehensive study on the enhancements made to the heavy-ion microbeam (H-MB) and light-ion microbeam (L-MB) systems at the Takasaki Institute for Advanced Quantum Science, part of the National Institutes for Quantum Science and Technology (QST), and their implications for future research in ion microbeam technology. Our work addresses the critical need for submicron beam sizes in advanced ion microbeam applications, a challenge previously unmet due to limitations in the original system designs and aging components. The manuscript details the extensive upgrades undertaken for both the H-MB and L-MB systems, including the implementation of new quadruple magnets, refined demagnification strategies, and advanced control systems, culminating in the successful formation of submicron ion beams. The meticulous alignment procedures for both the H-MB and L-MB have enabled precise ion beam focusing. The current beam sizes have been measured at 1.0 × 1.1 µm2 with a beam current of approximately 10 pA for the H-MB, and 500 × 600 nm2 with a beam current of approximately 50 pA for the L-MB at a 3 MeV H+ beam.

A Novel Topology of a 3 × 3 Series Phased Array Antenna with Aperture-Coupled Feeding.

This paper presents a novel 3 × 3 phased array antenna optimized for 4 GHz operation, achieving a realized gain of 13.2 dBi and enabling 30-degree beam steering with a minimal capacitance variation of 1.5 pF. The design features a series aperture-coupled feeding mechanism that not only reduces the antenna's size but also simplifies the fabrication process, making the device both cost-effective and compact. Integrating cost-efficient quadrature-hybrid phase shifters and novel power splitters with cascaded quadrature hybrids ensures uniform power distribution and precise beam steering. The innovative use of these components addresses common challenges in phased array systems, such as space constraints, high costs, and complex power distribution.

Reducing treatment time for robotic radiosurgery by considering path efficiency during node selection.

Robotic radiosurgery treatments allow for precise non-coplanar beam delivery by utilizing a robot equipped with a linac that traverses through a set of predetermined nodes. High quality treatment plans can be produced but treatment times can grow large, with one substantial component being the robot traversal time. The aim of this study is to reduce the treatment time for robotic radiosurgery treatments by introducing algorithms for reducing the robot traversal time. The algorithms are integrated into a commercial treatment planning system. First, an optimization framework for robotic radiosurgery planning is detailed, including a heuristic optimization method for node selection. Second, two methods aimed at reducing the traversal time are introduced. One utilizes a centrality measure focusing on the structure of the node network, while the other is based on the direct computation of traversal times during optimization. A comparison between plans with and without the time-reducing algorithms is made for three brain cases and one liver case with basis in treatment time, plan quality, monitor units, and network structure of the selectednodes. Large decreases in traversal times are obtained by the traversal time reducing algorithms, with reductions of up to 49 % in the brain cases and 31 % in the liver case. The resulting reductions in treatment times are up to 30 % and 13 %, respectively. Small differences in plan quality are observed, with similar dose-volume histograms, dose distributions, and conformity/gradientindices. The total treatment time of the robotic radiosurgery treatments can be reduced by selecting nodes with more efficient robot traversal paths, while maintaining planquality.

Research on angular displacement detection technology of inter-satellite laser communication based on coherent system

With the rapid development of spatial information networks technologies, inter-satellite laser communication links have played an important role in the satellite Internet. High-precision relative angular displacement detection is the foundation for achieving real-time tracking of laser communication links, and its accuracy directly impacts the tracking performance and communication quality of the laser communication link. Traditional laser communication systems utilize intensity-based position detection methods to calculate angular displacement, requiring setting separate Charge Coupled Device (CCD) or Four-quadrant Detector (QD) as well as independent optical tracking branches. This setup makes it difficult to integrate with high-speed coherent communication systems. Additionally, the method employing intensity detection to determine angular displacement based on spot position has lower accuracy in theory. A angular displacement detection of coherent-based inter-satellite laser communication is proposed in this paper. Firstly, real-time calculation of phase differences at different positions of the beam is achieved through heterodyne coherent array detection and dual high-precision phase-locked loops. Then, a model correlating wave front phase difference with relative angular displacement is established, phase noise during beam transmission and detection processes is analyzed, and algorithm for detecting angular displacement in coherent systems is studied. Finally, a laser communication link is constructed under laboratory condition, and experimental validation work is carried out. When the relative angle deviation is 1°, the phase difference changes by 0.089049795 rad, and the angular displacement detection error of 0.66697μrad(σ). When the relative angle error is 0.603873μrad(σ), the detection sensitivity is −43.93dBm. The experimental results show that in the coherent system, the relative angular displacement detection with high precision can be realized by using the wavefront phase difference of beam, which can support the laser communication tracking system to achieve higher precision beam tracking.

Conditional guided generative diffusion for particle accelerator beam diagnostics

Advanced accelerator-based light sources such as free electron lasers (FEL) accelerate highly relativistic electron beams to generate incredibly short (10s of femtoseconds) coherent flashes of light for dynamic imaging, whose brightness exceeds that of traditional synchrotron-based light sources by orders of magnitude. FEL operation requires precise control of the shape and energy of the extremely short electron bunches whose characteristics directly translate into the properties of the produced light. Control of short intense beams is difficult due to beam characteristics drifting with time and complex collective effects such as space charge and coherent synchrotron radiation. Detailed diagnostics of beam properties are therefore essential for precise beam control. Such measurements typically rely on a destructive approach based on a combination of a transverse deflecting resonant cavity followed by a dipole magnet in order to measure a beam’s 2D time vs energy longitudinal phase-space distribution. In this paper, we develop a non-invasive virtual diagnostic of an electron beam’s longitudinal phase space at megapixel resolution (1024 × 1024) based on a generative conditional diffusion model. We demonstrate the model’s generative ability on experimental data from the European X-ray FEL.

PVDF/Al2O3/Gd2O3 layers splitter with first-order suppression functionality

In the realm of optical component design, the proposed multilayer grating splitter represents a significant breakthrough. For the triple-layered grating in this paper, it combines the outstanding optical properties of polyvinylidene fluoride (PVDF), aluminum oxide (Al2O3), and gadolinium oxide (Gd2O3) to achieve high-efficiency outputs for both the 0th and −2nd orders under secondary Bragg angle incidence conditions. The diffraction efficiencies for both TE and TM polarizations exceed 97%, with energy uniformity surpassing 99%. These results highlight the potential of this design in precision beam control applications. The splitter's performance benefits from the intrinsic material properties and optimally designed structural dimensions, which enhance transparency and thermal stability under operational conditions. Through rigorous design and optimization, including modal methods and simulated annealing algorithms, the device achieves exceptional uniformity in diffraction efficiency, which is crucial for high-resolution spectroscopy and precision optical measurement applications.

Impact of Scattering Foil Composition on Electron Energy Distribution in a Clinical Linear Accelerator Modified for FLASH Radiotherapy: A Monte Carlo Study.

This study investigates how scattering foil materials and sampling holder placement affect electron energy distribution in electron beams from a modified medical linear accelerator for FLASH radiotherapy. We analyze electron energy spectra at various positions-ionization chamber, mirror, and jaw-to evaluate the impact of Cu, Pb-Cu, Pb, and Ta foils. Our findings show that close proximity to the source intensifies the dependence of electron energy distribution on foil material, enabling precise beam control through material selection. Monte Carlo simulations are effective for designing foils to achieve desired energy distributions. Moving the sampling holder farther from the source reduces foil material influence, promoting more uniform energy spreads, particularly in the 0.5-10 MeV range for 12 MeV electron beams. These insights emphasize the critical role of tailored material selection and sampling holder positioning in optimizing electron energy distribution and fluence intensity for FLASH radiotherapy research, benefiting both experimental design and clinical applications.

Multiplicative Basis Function Based Adaptive DOA Estimation in Optimal MIMO Sparse Antenna Reconfiguration Model

Direction of arrival (DOA) estimation using sparse signal representation has gained significant attention in recent decades. The spatial signals utilized for DOA estimation are reconstructed through a novel compressive sensing (CS) approach. In this study, we used a CS approach to ascertain the adaptive underdetermined DOA for multiple inputs and multiple output (MIMO) sparse media. Accurate DOA estimation through the CS approach contributes to enhanced signal investigation and the suppression of undesired noise in a sparse channel. The method proposed herein encompasses the development and execution of a novel multiplicative basis function known as the multi-kernel supported non-negative sparse Bayesian learning (NNSBL) algorithm, which is implemented on predefined grid values. Concurrently, stochastic grey wolf optimization (GWO) is virtually applied to increase the degrees of freedom (DOF) on a minimum redundancy array (MRA) while considering an optimal antenna reconfiguration model. The advantages of this proposed approach include the generation of a distinct manifold matrix for precise beam steering, resulting in improved DOA estimation accuracy. Additionally, an augmentation of DOF using GWO was observed, with low computational complexity. The simulated result of proposed algorithm leads to the attainment of optimal minimum root mean square error (RMSE) across various optimal wavelengths of the stochastic sources. Finally, a comparative analysis of RMSE and convergence plots confirms the superior performance and high potentiality of the proposed method in comparison to existing techniques across different SNR values. Notably, there is significant reduction in RMSE which is suitable for precise DOA estimation in signal processing applications.

Steering Mirror System with Closed-Loop Feedback for Free-Space Optical Communication Terminals

Precision beam pointing plays a critical role in free-space optical communications terminals in uplink, downlink and inter-satellite link scenarios. Among the various methods of beam steering, the use of fast steering mirrors (FSM) is widely adopted, with many commercial solutions employing diverse technologies, particularly focusing on small, high-bandwidth mirrors. This paper introduces a method using lightweight, commercial off-the-shelf components to construct a custom closed-loop steering mirror platform, suitable for mirror apertures exceeding 100 mm. The approach involves integrating optical encoders into two off-the-shelf open-loop actuators. These encoders read the signal reflected on purposefully diamond-machined knurled screw knobs, providing maximum contrast between light and dark lines. The resulting steering mirror has the potential to complement or replace FSM in applications requiring a larger stroke, at the expense of motion speed. In the presented setup, the mirror tilt resolution achieved based on the encoder closed-loop signal feedback is 45 μrad, with a mean slew rate of 1.5 mrad/s. Importantly, the steering assembly is self-locking, requiring no power to maintain a steady pointing angle. Using the mirror to actively correct for a constantly moving incoming beam, a 5-fold increase in concentration of the beam spot on the center of the detector was obtained compared to a fixed position mirror, demonstrating the mirrors ability to correct for satellite platform jitter and drift.

Evaluation of the thin film polyimide‐based holographic metasurface inspired leaky‐wave antenna

AbstractThe proposed paper presents the design of a leaky‐wave antenna inspired by holographic metasurfaces employing thin film. Leveraging the holographic principle, this metasurface showcases its transformative capacity by converting an omnidirectionally radiating monopole into a highly directional antenna emitting leaky waves. The holographic metasurface is constructed using a thin film of polyimide (PI) (Df = 0.008; Dk = 3.5), measuring 50 μm in thickness. The antenna structure comprises multiple layers, commencing with the top PI layer, succeeded by a 40 μm thick adhesive layer (Df = 0.004; Dk = 6). Subsequent layer includes the Rogers RT/duroid 5880 substrate (Df = 0.0009; Dk = 2.20), grounded at the bottom and has a thickness of 1.6 mm. The meticulously tailored design of the proposed antenna ensures optimal performance at 15 GHz, facilitating directional radiation and precise beam steering at 10 degrees (ϴ = 10°). This innovative design, incorporating the holographic metasurface on thin film, significantly enhances the antenna's performance, increasing gain from 1.5 dBi to 13.8 dBi.

Multipurpose Additives Toward Improving the Polymer Cold Spray Process

Polymers have proven to be challenging to cold spray, particularly with high efficiency and quality when using inexpensive nitrogen (N2) and air propellants. Helium (He), when used as a process propellant, can improve spray deposit properties but is often undesirable due to its limited availability and high cost. In this study, additives of multiple particle sizes and materials were mixed with polymer powder in an effort to improve the performance of polymer sprays using mainly N2 as a process propellant. The effects of hard-phase additives on deposit microstructure were investigated by precise ion beam polishing of deposit cross sections and subsequent electron microscope imaging. Additional metrics including the density and post-spray composition of deposits were investigated to quantify the peening effect and the amount of embedded additive. Additives, regardless of size, were observed to embed in the spray deposits. Additionally, hard-phase additives demonstrated nozzle cleaning properties that continually remove polymer fouling on the nozzle walls. Inversely, sprays with polymer powder and no additives tended to clog the nozzle throat and diverging section because of continual fouling.

A Variable Fractional Delay Filter Based True-Time-Delay Array Architecture for Wideband Beamforming

True-time delay (TTD) units are critical in Wideband Large-Scale Antenna Systems (LSASs) for resolving beam squint and frequency selective fading. In this paper, we propose a TTD array architecture for wideband beamforming that addresses the challenges posed by LSASs by utilizing variable fractional delay (VFD) filters and time delay estimations (TDEs). This study introduces a convex optimization problem to develop a novel method for designing VFD filters that can achieve high precision time delay resolution while maintaining an acceptable frequency response peak error. Using these VFD filters, we present a TDE approach with Newton-Raphson iteration update that corrects the difference in arrival time between sensors. Due to the implementation of VFD filters and fast TDE modules, the new architecture can complete beam steering and tracking in 10 ms with MATLAB simulation. Furthermore, an example was designed to demonstrate that the proposed architecture is capable of producing precise beam pointing while maintaining the bit error rate (BER) that is extremely close to the theoretical curve over the entire bandwidth.

A Convolutional Neural Network for Beam Prediction in 5G and Beyond Massive MIMO Systems

This paper presents an innovative Convolutional Neural Network (CNN) architecture designed for the prediction of beamforming vectors in Massive Multiple-Input Multiple-Output (MIMO) systems, a cornerstone technology in 5G and emerging wireless communication networks. As mmWave frequencies become central to modern MIMO systems, ensuring precise beam alignment amid susceptibility to blockages is imperative for maintaining robust communication links. Traditional beamforming algorithms, challenged by high complexity and sluggish adaptation to dynamic environmental conditions, are outperformed by the proposed CNN, which effectively captures complex channel patterns for accurate beam prediction. Leveraging a rich dataset from the DeepSense 6G scenarios, the study meticulously preprocesses the data through normalization and scaling before dividing it into training and testing subsets. The CNN, evaluated against real-world signal propagation behaviors, demonstrates a high prediction accuracy in beam indices, particularly in clear line-of-sight scenarios. The paper concludes with an assessment of the model's predictive performance, using Mean Absolute Error as a key metric, and proposes future enhancements to the model's architecture and training process. The implications of this work are significant, heralding a new era of intelligent, self-optimizing wireless networks that can adapt autonomously to environmental changes and user mobility

Detection of Silica in Rice Husks Using Laser-Induced Plasma and Studying the Effect of Laser Energy on the Parameters of the Produced Plasma

This study aims to analyze the spectral properties of plasma produced from rice husk(Rh) using the laser breakdown spectroscopy (LIBS) method. The plasma generation process used the fundamental harmonic (1064 nm) of a Q-switched Nd:YAG laser. Yttrium aluminum garnet (YAG) is a man-made crystalline material. The laser fired pulses with a duration of 10 ns and a repetition rate of 6 Hz. Thus, the energy outputs achieved were 50–200 mJ at the wavelength of 1064 (nm). The silica content in the rice hulls was verified using an XRF measurement, which revealed the presence of silica in the rice hulls in a high percentage. Precise beam focusing was achieved by focusing the laser on the target material. This target material is placed within an atmospheric environment at standard pressure settings. The electron temperature was derived using the Boltzmann diagram method by harnessing experimental data for the linear properties associated with the neutral lines (Si II), (O II), and ion lines (Si I). The use of analytical methodology led to the determination of electron temperature values from 0.79 eV to 1.16 eV for the fundamental harmonic of the laser. At the same time, the electron (ne) density was determined by analyzing the Stark broadening profile associated with the neutral silica line. Furthermore, the study included an additional dimension by determining the plasma properties (electron temperature and electron density) by adjusting the laser energy on the target surface longitudinally along the path of the plasma plume.

A Graphene Geometric Diode with the Highest Asymmetry Ratio and Three States Gate‐Tunable Rectification Ability

AbstractGraphene geometric diodes, with applications in THz detection, energy harvesting, and high‐speed rectification, have been previously constrained by graphene quality and geometry feature size. This study presents significant advancements in graphene geometric diodes by employing the h‐BN/monolayer graphene/h‐BN heterojunction and extremely precise electron beam lithography. Two distinct designs of graphene geometric diodes with neck widths of 23 and 26 nm are fabricated, the superior of which demonstrated an asymmetry ratio of 1.97, a zero bias current responsivity of 0.6 A W−1, and a voltage responsivity of 12,000 V W−1, setting new benchmarks for such devices. Integrating this device into a rectification circuit, the experimentally validate that the rectified DC output voltage can be dynamically modulated and even inverted through adjustments to the diode's gate voltage. This behavior aligns seamlessly with graphene's intrinsic tunability of charge carriers, implying promising prospects for the device's application in advanced logic circuits, bidirectional switches, and signal modulation/demodulation techniques.

A Review of Mechanical Fine-Pointing Actuators for Free-Space Optical Communication

This paper presents a state-of-the-art overview of fine beam steering mechanisms for free-space optical communication on satellites. Precise beam pointing is a critical task for the successful operation of free-space optical communication systems. Based on past research and ongoing projects, the use of fast steering mirrors (FSMs) is still the most popular solution for free-space optical communication applications. Although a variety of commercial off-the-shelf (COTS) FSM solutions exist, there is limited publicly available data on these solutions in the space environment. Three main actuation principles are considered (electro-static force actuated, magnetic force actuated, piezo-effect actuated) and reviewed using available data from past space missions. The article describes the most important criteria in the choice of a fine beam steering solution for free-space optical communication in space.

A Method to Locally Irradiate Specific Organ in Model Organisms Using a Focused Heavy-Ion Microbeam.

The functions of organisms are performed by various tissues composed of different cell types. Localized irradiation with heavy-ion microbeams, which inactivate only a portion of the constituent cells without destroying the physical intercellular connections of the tissue, is a practical approach for elucidating tissue functions. However, conventional collimated microbeams are limited in the shape of the area that can be irradiated. Therefore, using a focused heavy-ion microbeam that generates a highly precise beam spot, we developed a technology to uniformly irradiate specific tissues of an organism with a defined dose, which conventional methods cannot achieve. The performance of the developed paint irradiation technology was evaluated. By irradiating the CR-39 ion track detector, we confirmed that the new method, in which each ion hit position is placed uniformly in the irradiated area, makes it possible to uniformly paint the area at a specified dose. The targeted irradiation of the pharynx and gonads of living Caenorhabditis elegans demonstrated that the irradiated ions were distributed in the same shape as the targeted tissue observed under a microscope. This technology will elucidate biological mechanisms that are difficult to analyze with conventional collimated microbeam irradiation.

Wide-angle beam scanning from binary amplitude-modulated conformal meta-surface dense array with precise beam granularity

We propose a binary amplitude-modulated conformal meta-surface with every meta-element capable of functioning as the leaky wave passage or the null radiating spot through dynamically tuning the PIN diodes over the meta-elements with ON or OFF states. In particular, the staggered arrangement of the meta-elements forms a dense radiating array with 0.1 wavelength periodicity and every radiating patch consists of dual hourglass shaped slots stacked over the coupled feed of substrate integrated waveguide slits. Such a design, on the basis of binary amplitude-modulated conformal meta-surface frames, can achieve wide-angle steerable fan-beam scanning, while possessing the precise beam direction with less than one tenth of the 3 dB beamwidth. Thus, this should pave the way for building up more advanced contemporary conformal wireless communication systems over different platforms.

Inhomogeneous thermal analysis of microlayer mold for glass molding of fast-axis collimation lens array

Fast-axis collimation (FAC) lens arrays play a crucial role in laser systems, offering precise beam shaping and focusing for applications such as laser marking, and optical communication. Achieving high precision in these applications requires a FAC lens array with a long Rayleigh range. While precision glass molding with nickel-phosphorus (Ni-P) microlayer molds has revolutionized the mass production of FAC lens arrays, the extreme conditions during the molding process can lead to poor profile accuracy. To address this issue, we developed an optical collimation system to derive the final characteristic parameters and obtain the beam waist radius and Rayleigh range of the collimated laser. Additionally, we conducted a thorough analysis of the inhomogeneous thermal expansion process of the microlayer mold and established a mathematical solution for thermal compensation to modify the mold's shape. We validated the proposed method by fabricating an FAC lens array mold and measuring the profile error and waist radius of a molded FAC lens array. We also calculated the profile error of this method using a finite element (FE) model in ABAQUS. The results indicate that incorporating the inhomogeneous thermal expansion reduces the shape error of the FAC lens array from 0.577 μm to 0.135 μm. Moreover, using inhomogeneous thermal compensation significantly improves the Rayleigh range of the FAC lens array from 1.285 μm to 9.8 × 104 μm.

Scalable and robust beam shaping using apodized fish-bone grating couplers.

Efficient power coupling between on-chip guided and free-space optical modes requires precision spatial mode matching with apodized grating couplers. Yet, grating apodizations are often limited by the minimum feature size of the fabrication approach. This is especially challenging when small feature sizes are required to fabricate gratings at short wavelengths or to achieve weakly scattered light for large-area gratings. Here, we demonstrate a fish-bone grating coupler for precision beam shaping and the generation of millimeter-scale beams at 461 nm wavelength. Our design decouples the minimum feature size from the minimum achievable optical scattering strength, allowing smooth turn-on and continuous control of the emission. Our approach is compatible with commercial foundry photolithography and has reduced sensitivity to both the resolution and the variability of the fabrication approach compared to subwavelength meta-gratings, which often require electron beam lithography.