Beam Scanning Method Research Articles

Determination of the optimal number of detectors for the multiangle wire beam scanning method

The implementation of control over the characteristics of the beam is an important stage in the conduct of experiments within the field of accelerator physics. The multiangle scanning method based on the reconstruction of the electron beam profile image from projection data can be used to determine the distribution of beam intensities in the transverse plane. In order to reduce the time required for measurement, it is proposed that a set of detecting elements be used in place of a single detecting element when employing this method. This work presents a scheme for optimized data collection using the multiangle scanning method and evaluates the applicability of the modernized approach. For this, a numerical experiment was conducted to determine the beam profile using different numbers of detecting elements. The results of this study demonstrate that the use of multiple detecting elements for the implementation of the multiangle scanning method reduces the measurement time and ensures high quality of the reconstructed beam profile images. It was demonstrated that the minimum number of detecting elements necessary to ascertain a specific beam profile is ten.

Cascaded-prism multi-mode beam scanning method for three-dimensional imaging lidar

Light detection and ranging (lidar) has emerged as an indispensable approach to three-dimensional (3D) perception, which probably suffers from performance limitations with traditional beam steering devices. In this paper, we investigate a cascaded-prism beam scanning method to enhance the versatility of 3D imaging lidar systems. The cascaded-prism-based 3D lidar architecture is theoretically developed with an emphasis on a rigorous beam scan model. By exploiting the additional flexibility of cascaded prisms, the lidar can achieve beam scanning through prism rotation in either step-motion or constant-speed mode, which exhibits superior agility and adaptability in multi-mode pattern analysis. Moreover, the cascaded-prism beam scanning lidar is demonstrated with a 3D imaging performance evaluation in terms of field of view, angular resolution and sampling density. It proves that the cascaded-prism beam scanner can offer lidar systems with flexible and configurable 3D imaging capability while balancing between a wide field of view and high angular resolution.

Development of a Front End Array for Broadband Phased Array Receiver

The receiver is a signal receiving device placed at the focus of the telescope. In order to improve the observation efficiency, the concept of phased array receiver has been proposed in recent years, which places a small phased array at the focal plane of the reflector, and flexible pattern and beam scanning functions can be achieved through a beamforming network. If combined with the element multiplexing, all beams within the entire field of view can be observed simultaneously to achieve continuous sky coverage. This article focuses on the front-end array of phased array receiver at 0.7–1.8 GHz for QiTai Telescope, and designs a Vivaldi antenna array of PCB structure with dual line polarization. Each polarization antenna is designed to arrange in a rectangle manner by 11 × 10. Based on the simulation results of the focal field, 32, 18, and eight elements were selected to form one beam at 0.7, 1.25, and 1.8 GHz. An analog beamforming network was constructed, and the measured gains of axial beam under uniform weighting were 19.32, 13.72, and 15.22 dBi. Combining the beam scanning method of reflector antenna, the pattern test of different position element sets required for PAF beam scanning was carried out under independent array. The pattern optimization at 1.25 GHz was carried out by weighting method of conjugate field matching. Compared with uniform weighting, the gain, sidelobe level, and main beam direction under conjugate field matching have been improved. Although the above test and simulation results are slightly different, which is related to the passive array and laboratory testing condition, the relevant work has accumulated experience in the development of the front-end array for the phased array receiver, and has good guiding significance for future performance verification after the array is installed on the telescope.

Оценка возможности определения поперечного профиля медицинского электронного пучка методом многоуглового сканирования для повышения точности проведения радиотерапевтических процедур

This study is aimed at assessing the applicability of the proposed method of multiangle beam scanning for determining the transverse profile of an electron beam. The application area of the proposed approach will be control of the therapeutic beams spatial and dose characteristics in order to increase the irradiation accuracy and, as a result, reduce the side effects of radiation therapy. One of the main applied problems to be solved by the proposed approach is to determine the beam characteristics during electron beam therapy. For carrying out of electron beam therapy procedures it is necessary to form electron beams with the complex shape of transverse profile. The need to precisely control beam shapes throughout all irradiation stages determines the relevance of this study. The integral transform method was used in this study to obtain distributions of medical electron beam intensity. For the study, we used electron beam transverse pro-files calculated on the basis of a radiation therapy planning system for real clinical cases. The method was applied both theoretical beam profiles with sharp edge and to ones experimentally obtained with real medical electron beams. Integral transforms were performed for a different number of scan projections. Due to this, the optimal number of projections was calculated for each considered profile. The results of the study demonstrate that the multiangle beam scanning method needs 12 scan projections which corresponds to an angular displacement of 15° to control the medical electron beam profile.

Synthetic Beam Scanning and Super-Resolution Coincidence Imaging Based on Randomly Excited Antenna Array

Nowadays, there is no good scheme for simultaneously achieving super-resolution imaging within a coherent beamwidth and beam scanning in microwave radar. In this paper, a synthetic beam scanning method based on a randomly excited antenna array, which possesses the ability of super-resolution coincidence imaging, is proposed. The beamwidth of the randomly excited array is comparable to that of the conventional phased array with the same size, and its steering angle can be adjusted by modulating the excitation signals. Firstly, the optimized covariance matrix of the proposed array to uniformly bunch the spatial radiation energy in a specific angle range is obtained by means of the sequential quadratic programming (SQP) algorithm. Accordingly, the partially correlated excitation signals restricted by the optimized covariance matrix are determined. Then, a secondary weighted modulation method is proposed to steer the main beam to the direction of interest. The excitation signals are weighted by the conjugated radiation fields in the direction of interest. Furthermore, the super-resolution ability of the proposed coincidence imaging system is analyzed based on the first-order statistical characteristics of the radiation fields. Simulations and experiments demonstrate that synthetic beam scanning can be realized by controlling the excitation signals. Besides, a 10 times super-resolution coincidence image can be reconstructed within a coherent beamwidth (3dB-beamwidth) when the signal-to-noise (SNR) is greater than 15 dB, assisted by the fast Bayesian learning (FBL) algorithm.

A review of microwave electronically scanned array: Concepts and applications

As the application of microwave to radar and 5G communication goes wider, the array beam scanning capability has become an important and popular issue in modern society. Appropriate implementation of beam scanning methods suitable for diverse conditions could provide better performance and help to save costs for a system. Moreover, electronically scanned array has the characteristics of fast beam switching rate, high measurement accuracy and low profile. Thus, discussions on typical electronic scanning approaches are particularly necessary. This paper first presents a review of typical electronic scanning approaches to microwave arrays, such as the phased array, the focused aperture array, the frequency scanning array, and the time modulated array. And then some latest designs in the industry have been introduced. In addition, problems appeared in the application of the phased array and relevant solutions have been put forward. For the rest, some discussions are briefly summarized, as well as some comments on future trend in this field.

IoT Sensor Network Using ESPAR Antenna Based on Beam Scanning Method for Direction Finding.

Wireless sensor networks (WSNs) systems based on Internet of Things (IoT) have developed rapidly in recent years. However, interference is a major obstacle to relatively long-distance communications in such networks. It is also very complicated and challenging to fix the exact location of tags in the IoT sensor networks. To overcome these problems, in this paper, an electronic steering parasitic array radiator (ESPAR) antenna used as a beamformer to handle the interference and extend the communication range from the sensors or tags is suggested. In addition, an efficient method, namely beam scanning (BS), is proposed to find the directions of tags. The beam scanning method (BSM) can be used for the selective beam switching (SBS) system by designing an ESPAR or array of ESPAR antennas with the help of CST studio. The antennas exhibit higher gain (8.17 dBi, 11.40 dBi) and proper radiation pattern at a particular direction. In addition, the MATLAB simulation findings indicate that the proposed BSM algorithm provides longer communication range, i.e., 25 m. In order to maximize range while avoiding interference, it is necessary to determine the direction and precise orientation of the tag in the WSN communication systems. Consequently, this work could be applied to an IoT sensor network such as an electrocardiogram system by providing better advantages such as higher localization accuracy and longer operating range.

Intelligent Reflecting Surfaces Adaptive Beamsteering and PSK Direct Modulation

Intelligent Reflecting Surfaces (IRS), a planar array consisting of a large number of low-cost and low-complexity metal patch elements, is predicted to be among the key technologies in future wireless communications. This is mainly due to its capability to improve wireless energy and spectrum efficiency by reconfiguring the wireless environment in a smart and flexible way. IRS is capable of shifting the phase, amplitude, frequency, or even polarity of the impinging electromagnetic (EM) wave. However, only the phase-shift type of IRS is widely adopted in most scenarios. In this paper, we exploit the property of such IRS to directly modulate an incident EM wave with phase shift keying (PSK) modulation. We consider one transmit antenna that transmits a continuous single-tone electromagnetic (EM) wave, which is then modulated by the IRS and reflected toward the receiver. In addition to the theoretical explanation, we present simulation results with different modulation orders. Moreover, we validated the simulation results by experiment. Furthermore, we also proposed a beam scanning method to obtain IRS patterns to steer the beam towards the desired direction in an adaptive manner. One optimal pattern that maximizes the received power is then selected from the beam scanning codebook. By doing so, a wireless path strength can be significantly improved.

Experimental investigation of total electron emission yield of polyimide film under various temperatures

As the thermal variation may change the total electron emission yield (TEEY) of materials and may ultimately result in unexpected surface charging, it is necessary to study the TEEY at various temperatures. In this research, we first updated the TEEY measurement system with a newly designed sample stage for different temperatures (−50, 25, and 100 °C) and the primary electron from 25 eV to 10 keV. By using the 30 μs/20 nA primary electron beam and sample scanning method to mitigate surface charging, the TEEY could be accurately obtained for dielectrics. Then, we chose a kind of polyimide film (Kapton 100H) used on spacecraft and a gold film sample to compare the TEEY at various temperatures. The results show that high temperature leads to higher TEEY of Kapton films, whereas 25 and −50 °C also leads to the same. On the other hand, the TEEY of gold remains the same at different temperatures. In the view of surface hole density and charge transportation, the TEEY variation of Kapton films was analyzed by bulk conduction, charge mobility, and the electron–hole recombination property. It is considered that the dissipation rate of holes is sensitive to temperature, and furthermore, the TEEY of Kapton films is dependent on temperature.

Novel Beam Scan Method of Fabry–Perot Cavity (FPC) Antennas

A new beam scanning method of a Fabry–Perot cavity (FPC) antenna is proposed. To obtain high gain in a target direction with a reduced sidelobe level (SLL), we devised a tapered partially reflective surface (PRS) as a superstrate. Moreover, to attain various beam scanning directions, a phase-controllable artificial magnetic conductor (AMC) ground plane with a broad reflection phase range and high reflection magnitudes was introduced. In the proposed method, a new formula to satisfy an FP resonance condition in a cavity for a scanned beam is also suggested. According to the formula, the FPC antenna can precisely scan the main beam in designed target directions with well-maintained high gain, which has been hardly achievable. In addition, our method demonstrates the potential of electrical beam-scanning antennas by employing active RF chips on the AMC cells. To validate the method, we fabricated a prototype FPC antenna for a scanned beam at θ = 30°. Furthermore, we conducted an additional simulation for a different beam scanning angle as well. Good agreement between the expected and experimental results verifies our design approach.

Unambiguous Direction-of-Arrival Estimation for Improved Scanning Efficiency in Subarray-Based Hybrid Array

Hybrid antenna array consisting of analog subarrays provides a low-cost solution to achieving high beamforming gain in millimeter-wave/terahertz communication systems. For beam adjustment, beam scanning can be readily applied to find the line-of-sight (LoS) path. Conventionally, the beam scanning process is inefficient because the number of grids, together with the scanning period, has to be large to achieve high resolution. To improve the beam scanning efficiency, in this paper we propose an off-gird direction-of-arrival (DoA) estimation method utilizing unequal-sized subarrays. Specifically, we first provide a new solution to overcome the ambiguity problem, i.e., the hybrid antenna array may render the DoA estimate non-unique. That new solution is formed by designing the antenna numbers in the subarrays and can be easily combined with the beam scanning process. We then propose a three-stage beam scanning strategy. At the first stage, coarse scanning is applied to roughly steer the subarrays along the LoS path. At the second stage, a simple DoA estimator is employed to obtain the candidate DoAs. Finally, beam scanning is performed again on the candidate DoAs to obtain the final DoA estimate. Simulation results demonstrate that the proposed method can achieve higher DoA estimation accuracy in shorter scanning period than the conventional beam scanning method; and compared with existing methods developed for equal-sized subarrays, the proposed method is more robust against multi-path interference.

A study on the removal of paint and oxide layer on the steel surface by laser beam scanning method

In this study, a laser cleaning method was developed in order to replace the existing manual work-based technologies. The experimental investigation analyzed the cleaning properties of the paint and the oxide layer on the steel surface according to the laser beam scanning method. Experiments showed that in the cleaning process, the line beam patterns with a moving stage showed differences in heat input depending on the area, and the square area beam patterns obtained with control of a Galvano scanner showed uniform cleaning performance. The results of this study demonstrated that through the prosed laser cleaning technique, oxide layers as well as paint on steel surfaces can be removed with excellent precision, which is expected to be useful in the development of eco-friendly surface cleaning techniques.

Laser-induced scanning transfer deposition of silver electrodes on glass surfaces: A green and scalable technology

A pulsed laser ablation backwriting technique with high repetitive rates is implemented for the fabrication of silver coatings on glass surfaces. This method enables geometrical constraint-free deposition of metallic coatings. These exhibit sufficiently low electrical resistance to be used as electrodes in dielectric barrier discharge (DBD) plasma elements.Ambient air deposition of metallic silver electrodes on standard glass slides is explored using a sub-ns UV laser source, combined with hybrid beam scanning methods. The green nature of the overall deposition process includes a preliminary irradiation scan to homogenise the target surface before the subsequent backwriting step. Metal transfer is achieved by combining two phenomena within a simple beam scanning process: LIRT (laser-induced reverse transfer) of silver from the target to the glass, with a partial and secondary LIFT (Laser-Induced Forward Transfer) of silver from the glass to the target.Appropriate selection of pulse energy and pulse repetition rates, beam scanning velocities and target motion enable the growth of sufficiently thick Ag deposits on glass with the required low electrical resistivity and nearly 2D constraint-free geometry. This method avoids the use of vacuum and liquids, resulting in a cheap, facile and green methodology for the deposition of silver electrodes onto transparent substrate surfaces.

Measurement and investigation of mechanical properties of a partial oxide dispersion strengthened Zircaloy-4 tube via an instrumented indentation test

The formation of a partial oxide dispersion strengthened (here denoted as P-ODS) layer on the surface of a Zircaloy-4 (Zry-4) tube is regarded as one of the effective ways to increase the strength of the Zry-4 tube at a bulk scale. This consequently enhances the resistance to ballooning and rupture under accident conditions. In this study, the mechanical properties such as the yield strength of a P-ODS Zry-4 tube at local scale were investigated by micro instrumented indentation testing (IIT). The P-ODS layer was formed on the surface of the Zry-4 tube by a laser beam scanning (LBS) method that uses Y2O3 particles. The IIT was performed at a cross-sectional plane of the P-ODS Zry-4 tube using a spherical indenter. Several regions, including the base Zry-4 tube and P-ODS layer, were considered as indentation points. As a result, the mechanical properties of the P-ODS Zry-4 tube at the local scale were effectively obtained from the IIT. Considerable strength enhancement of the P-ODS layer was observed by comparing with the base Zry-4 tube. Furthermore, the strength enhancement was studied using microstructure-based strengthening models such as Orowan and Hall-Petch to predict the amount of strengthening theoretically. From the suggested strengthening models, the strengthening of the P-ODS layer was effectively investigated, and the results can be useful for both fabricating and simulating the P-ODS Zry-4 tube.

Single Sensor to Estimate DOA With Programmable Metasurface

With the small sampling length, a novel Direction-of-Arrival (DOA) estimation method based on a single programmable metasurface sensor is proposed in this article. Serving as a physical random sampling receiver, a dynamic metasurface generates series of random radiation patterns to sense the incident signals, which is subsequently processed by the compressive sensing (CS) orthogonal matching pursuit (OMP) algorithm to recover the DOA information. A mathematical model of DOA estimation is first built for theoretical analyses. Furthermore, numerical simulations are investigated with extensive performance analyses. In comparison with the metasuface-based beam-scanning method, metasurface-based CS for DOA estimation has superior performance with a smaller sampling length. Finally, a proof-of-concept experiment is made to verify the feasibility of the programmable metasurface for DOA estimation. Compared to other traditional estimation techniques that require multiple channels, the programmable metasurface can achieve estimation with only a single channel and small sampling length.

High performance thin-film transistors fabricated on a single crystal Si strip by micro-chevron laser beam scanning method

High performance and uniform thin-film transistors were fabricated on a grain-boundary (GB) free single crystal Si strip for the first time. Here sputter-SiO2 gate insulator was used. Electron mobility μ was 548 cm2 V−1 s−1, subthreshold swing ss was 0.279 V dec−1, and on/off ratio was 2.4 × 107. Variability of ss was only 9.4% but that of μ was 34.2%. Carrier scattering was known to be dominated by GB in conventional polycrystalline Si, but it was dominated by phonon scattering in the GB-free Si strip irrespective of μ value. The μ deviation was shown to be due to crystal orientation variation along channel direction.

Investigation of an interlaced laser beam scanning method for ultrashort pulse laser micromachining applications

Abstract This article investigates picosecond and sub-picosecond laser micromachining of Borofloat®33 glass and provides clear evidence that a simple modification of the laser beam scanning strategy can lead to significant improvement of machining efficiency and hence process throughput. Besides studying the impact of the fundamental laser machining parameters, such as laser fluence, pulse overlap, pulse repetition frequency (PRF), pulse duration and laser spot diameter, on the machined depth, surface roughness and material removal rate (MRR), it also compares the machining results for two different laser beam scanning strategies, called here sequential” method (SM) and “interlaced” method (IM). By changing the scanning strategy from SM to IM, the MRR can be significantly increased because IM allows high-quality machining of the glass at higher PRF values. The experimental results show that this simple, cost-free modification allows the MRR value to be increased by more than 4 times, i.e. from 0.12 mm3/s to 0.53 mm3/s. Moreover, by using a Phantom V2512 high-speed camera, the picosecond laser micromachining process using both SM and IM was filmed. The videos show that SM leads to the accumulation of glass particles within the laser-machined area, whereas in IM the glass material is removed layer by layer which leads to the generation of “cleaner” and deeper areas. The mechanisms associated with these machining improvements are discussed.

Low Sideband Radiation Beam Scanning at Carrier Frequency for Time-Modulated Array by Non-Uniform Period Modulation

A novel beam scanning method utilizing the carrier frequency component for time-modulated array (TMA) is proposed and a significant algorithm based on the non-uniform period modulation is implemented to suppress the maximum sideband radiation (SR) level. The signal in each channel is modulated by a pair of high-speed radio-frequency (RF) switches and totally three or four delay lines with different phases. In each modulation period, three selected delay lines are connected successively with proper pulse durations to keep the switches in ON states constantly and ensure the maximum efficiency in the feeding network. Additionally, in order to suppress the relatively higher SR generated by both switches and delay lines, each channel of the TMA system has a different modulation period, which will separate the harmonic components of different elements on the frequency axis. A desired relatively low maximum SR level without complicated optimization is obtained compared with uniform period modulation and optimization algorithms. Several numeric simulations are brought out to examine the performance of the proposed methods, and the results for comparison to existing methods are also provided. A group of experiments have been done to verify its effectiveness.

Technical commissioning of the spot scanning system in Shanghai Proton Therapy Facility

In the field of particle therapy, the method of pencil beam scanning is of great potential for clinical application, now and in the future. The authors made strong effort to develop a spot scanning system for Shanghai Proton Therapy Facility. Design parameters and basic layout of the system are introduced. Functionalities and specifications of crucial devices are described in detail. Most of the devices in the system were designed in house by the authors themselves, including scanning nozzle, scanning magnets and their power supplies, beam monitors, irradiation control modules and safety interlock modules. During the technical commissioning stage in the fix beam room, the spot scanning system was tested and verified. Under conditions of the maximum dose rate and minimum dose rate, a) repeatability of the single spot dose is less than ± 0.1%; b) nonlinearity of the single spot dose is less than ± 0.1%; c) FWHM for spot size in air at isocenter varies from 8mm to 12mm for full energy, consistent with the design values; d) lateral dose distribution achieves a flatness of less than 2% for multiple proton energies. According to the results of technical commissioning, the spot scanning system is capable of producing a prescribed 3D dose distribution for target tumor successfully.

Dynamic beam current control for improved dose accuracy in PBS proton therapy

The step-and-shoot method of pencil beam scanning delivers the dose on a 3D grid in the target volume, with one dimension defined by the proton energy. While the dose per pencil beam may vary substantially within an iso-energy layer, the beam current typically remains constant. In this static operation mode, the inherent latency of the beam switch-off mechanism results in a lower limit for the deliverable spot dose, which may prevent the application of some of the low-weighted spots prescribed by the treatment planning system. To overcome this limitation, we introduced dynamic beam current control at the PSI Gantry 2, an innovative new approach successfully commissioned and in clinical operation since fall 2017. The control system was enhanced with a direct link to the vertical deflector located at the centre of the cyclotron. This connection allows much faster beam current changes (~0.1 ms) and hence opens up the possibility of dynamically reducing the current for individual low-dose spots. We demonstrate that with this new dynamic operation mode, all spots are delivered as planned without compromising treatment time. We show by two independent and complementary methods that the delivered dose distribution is improved.