Radiation Cross Research Articles

A Broadband Metasurface Antenna Array With Ultrawideband RCS Reduction

In this communication, a metasurface-based antenna array with wideband radiation and broadband radar cross section (RCS) reduction is constructed. Without introducing additional radiators, the broadband radiation performance of the antenna array is achieved by inspiring the metasurface itself. In addition, the characteristic mode theory is introduced to analyze the radiation mechanism of the radiator elements and the proposed antenna array. Both simulations and measurements are carried out to verify the performance of the proposed antenna array. The results show that the impedance bandwidth and 3 dB gain bandwidth of the proposed antenna array are 5.1–9.0 and 5.1–8.0 GHz, respectively, with a peak gain of 12.1 dBi. Monostatic RCS reduction more than 10 dB is achieved within the frequency band of 6.0–26.2 GHz.

Progress in DMAPS developments and first tests of the Monopix2 chips in 150 nm LFoundry and 180 nm TowerJazz technology

Depleted Monolithic Active Pixel Sensors (DMAPS) are monolithic pixel detectors with high-resistivity substrates designed for use in high-rate and high-radiation environments. They are produced in commercial CMOS processes, resulting in relatively low production costs and short turnaround times, and offer a low material budget. LF-Monopix1 and TJ-Monopix1 are large DMAPS prototypes produced in 150 nm LFoundry and 180 nm TowerJazz technology, respectively, that follow two different design concepts regarding the charge collection electrode. Prototypes of both development lines have been extensively tested and characterized over the last years. The second-generation Monopix prototypes, Monopix2, were recently produced. They were designed to address the shortcomings of their predecessors, in particular related to radiation hardness and cross talk, and further improve upon their performance. The latest measurements with LF-Monopix1 and TJ-Monopix1 concerning hit efficiency, depletion, and radiation hardness as well as the initial test results of the new Monopix2 prototypes are presented.

Detailed spectral evaluation of rare earth co-doped glasses for photonic applications

We report herein the detailed evaluation of structural and radiative properties of a series of Sm3+ and Gd3+ co-doped lead phosphate glasses having the compositions (58.2-2x) PbO - 40 P2O5 - 1.8 Al2O3 - x Sm2O3 - x Gd2O3, where x = 0.4–1.4 mol%. The synthesized glass samples were investigated for their structural properties using XRD and FTIR spectroscopy. The oscillator strength of the glass samples was evaluated from UV–Vis absorption spectra. Method of least squares fit between experimental and calculated oscillator strengths had been utilized to obtain Judd-Ofelt intensity parameters W2, W4 and W6 for determining the local structure and nature of bonding around rare-earth ions. The radiative and lasing properties were evaluated from intensity parameters such as probability of radiative transition, branching ratio and radiative lifetime. The emission transitions from the excited level 4G5/2 of samarium to the lower manifolds 6H5/2 and 6H7/2 were observed to be most suitable for photonic applications due to their higher values of electric as well as magnetic dipole radiation transition probability, branching ratio, and cross section of stimulated emission. Glass sample PPASG4 had shown enhanced radiative properties as compared to some previously reported glass configurations with similar Sm2O3 content; which suggests it to be potential candidate for lasing applications.

Sorption of some rare earth elements from aqueous solutions using copolymer/activated carbon composite: Multivariate optimization approach

The present study investigated the sorption of Ce3+, Nd3+ and Gd3+ cations from aqueous solutions via the use of a synthesized poly (acrylamide-acrylic acid)/activated carbon ((P-AM-AA)/AC) prepared by ϒ Radiation-Induced Templatepolymerization technique. The effect of absorbed ϒ radiation dose rate (kGy/hr) and cross linker concentration on the sorption efficacy of the synthesized composite toward the concerned lanthanides was studied. The structure of the synthesized composite was confirmed by different characterization techniques. Batch sorption studies for Ce3+, Nd3+ and Gd3+ onto (P-AM-AA)/AC were investigated as a function of contact time, pH and cations concentration. The response surface methodology (RSM) was employed to optimize and simulate the sorption of the concerned cations from the solution onto the synthesized material. The studied factors include initial cation concentration, solution pH, contact time and temperature. From the desirability analysis it is found that, the optimal sorption efficacy of the cations onto the synthesized sorbent was determined as 50 mg/l, 3.9 pH, 7 min and 333 K for acquiring percentage sorption more than 98% with optimal desirability of 0.99.

Relativistic Abrasion–Ablation De-excitation Fragmentation (RAADFRG) model

Astronauts are exposed to ionizing radiation that may pose significant health risks from missions to low Earth orbit (LEO) and beyond. The National Aeronautics and Space Administration (NASA) uses the deterministic radiation transport code, High charge (Z) and Energy TRaNsport (HZETRN), to estimate particle fluxes inside shielded vehicles to evaluate risk of radiation exposure to crew members. Highly efficient radiation transport algorithms and cross section models are needed to perform calculations in realistic vehicles with complex geometrical configurations. The HZETRN code uses the NUClear FRaGmentation (NUCFRG) model to evaluate fragmentation cross section products from nucleus–nucleus collisions. Although highly efficient, the NUCFRG model has some limitations that are based on its unique implementation of the abrasion–ablation formalism. NUCFRG performs well in predicting fragmentation cross sections on the average when compared to experimental data; however, even–odd nuclear structure effects observed in laboratory measurements are absent. The aim of the present work is to formulate a self-consistent theory that produces accurate nuclear fragmentation cross sections while maintaining numerical efficiency. To that end, the Relativistic Abrasion–Ablation FRaGmentation (RAADFRG) model has been developed. The theoretical framework for nuclear interaction is multiple scattering theory (MST), where relativistic kinematics may be included in the momentum–space representation of the Lippmann–Schwinger equation. The nuclear abrasion model employs the Eikonal (Eik) approximation and is used to predict prefragment cross sections. A novel approach is utilized for the excitation energy of prefragment, where in addition to differences of binding energies between two nuclei, energy is transferred to the prefragment from subsequent multiple scattering of abraded nucleons with the spectator nucleon constituents of the prefragment. Next, the excited prefragment liberates particles through the nuclear ablation process, and a nuclear coalescence model that forms aggregate particles for each prefragment channel is included in the yield. The ElectroMagnetic Dissociation FRaGmentation (EMDFRG) model is also included for peripheral interactions that stimulates particle emission via nuclear-photon field interactions. When compared to NUCFRG3, uncertainty quantification analysis shows that RAADFRG is better able to predict experimental nuclear fragmentation cross sections. RAADFRG is also shown to produce the even–odd nuclear structure effects, which is achieved by modification of isospin pairing correction in the prefragment excitation energy model.

Monte Carlo simulations of chromium target under proton irradiation of 17.9, 22.3 MeV

Chromium material is commonly used for fusion plasma facing applications because of the low neutron activation property. The Monte Carlo method is one of the useful ways to investigate the ion-target interactions. In this study, Chromium target irradiated by protons was investigated using Monte Carlo based simulation tools. In this context, the calculations of radiation damage on Chromium material irradiated with protons at 17.9 and 22.3 MeV energies were carried out using GEANT4 and SRIM codes. Besides, the cross sections for proton interaction with Chromium target were calculated by the TALYS 1.9 code using CTM + FGM, BSFGM, and GSFM level densities. As a result, GEANT4, SRIM and TALYS 1.9 codes provide a suitable tool for the predictions of radiation damage and cross cross section with proton irradiation.

On heated surface transport of heat bearing thermal radiation and MHD Cross flow with effects of nonuniform heat sink/source and buoyancy opposing/assisting flow

AbstractHeat transport subject to nonlinear thermal radiation has multiple applications in physics, industry, engineering field, and space technology, such as aerodynamic rockets, solar power technology, large open water reservoirs, and gas‐cooled nuclear reactors. This effort studies the magnetohydrodynamic flow of cross fluid, which is a type of non‐Newtonian, along a heated surface. Furthermore, the transportation of heat in the fluid is induced by thermal radiation. Furthermore, the behavior of opposing/assisting flow and impact of nonuniform heat sink/source is scrutinized. The reserved suitable transformations are carried out to shift the ruling equations into nondimensional class. Through reserved transformations, two nonlinear partial differential equations are altered into corresponding nonlinear ordinary differential equations. Then a scheme of integration referred to as Runge–Kutta–Fehlberg is imposed to get a numerical solution of these. The impact of parameters are mentioned concisely on temperature and velocity profiles in the absence and presence of a magnetic parameter. It is proved that the presence of a magnetic field steps up the velocity and temperature as well.

Dual-Band Circularly Polarized Transmitarray With Single Linearly Polarized Feed

This communication proposes a novel method to design a dual-band circularly polarized (CP) transmitarray (TA) antenna with a linearly polarized (LP) feed. By using this method, a shared-aperture dual-band TA is developed, which forms independent beams with right-hand circular polarization (RHCP) or left-hand circular polarization (LHCP) in two frequency bands with a single LP feed antenna. Four different CP TA prototypes operating at 12 and 14.2 GHz with different senses of CP and different beam directions are designed, and two of the prototypes are fabricated to validate the design concepts. A good agreement is obtained between the radiation patterns, gain curves, polarizations, and cross polarization levels measured and computed in both frequency bands. The proposed single-source dual-band CP TA design has advantages of simple structure, lightweight, easy fabrication, low cost, and high performance, making it a good candidate for varied applications.

Gain-induced large optical torque in optical twist settings**Project supported by the National Natural Science Foundation of China (Grant Nos. 11674204 and 11704232) and the Fund from HK RGC, China (Grant Nos. AoE/P-02/12 and C6013-18GF).

Inducing a significant optical torque remains a challenging task, since the law of angular momentum conservation implies that one has to harvest a lot of light. Such a problem was partially resolved by using optical twist via strong internal multiple scattering to recycle the photons, and one can induce a large torque per unit of radiation cross section. By using the Maxwell stress tensor and the generalized Lorentz–Mie scattering theory for multi-spheres, we investigate the influence of gain materials in further amplifying optical torque in the optical twist settings. It is found that, when combined with a gain layer, the optical torque of lossy (both in PT - and non-PT-symmetric structures) or lossless (low dielectric materials) clusters at resonance could be one order of magnitude larger than those of a single layer and previous studied plasmonic double layer structures. Moreover, the gain-enhanced large opposite rotations (i.e., optical twist) of the two layers arise at resonances in these structures. In contrast, in the gain–gain double-layer cluster, optical torques on both layers have no significant increase and the two layers rotate in the same direction at resonances. This work provides an elaborate investigation on the gain media-induced optical twist, which offers more choices for optical micromanipulation.

Understanding the Impact of Quantization, Accuracy, and Radiation on the Reliability of Convolutional Neural Networks on FPGAs

Convolutional neural networks are quickly becoming viable solutions for self-driving vehicles, military, and aerospace applications. At the same time, due to their high level of design flexibility, reprogrammable capability, low power consumption, and relatively low cost, the field-programmable gate arrays (FPGAs) are very good candidates to implement the neural networks. Unfortunately, the radiation-induced errors are known to be an issue in static random-access memory (SRAM)-based FPGAs. More specifically, we have seen that particles can change the content of the FPGA's configuration memory, consequently corrupting the implemented circuit and generating the observable errors at the output. Through extensive fault injection, we determine the reliability impact of applying binary quantization to the convolutional layers of neural networks on FPGAs, by analyzing the relationships between model accuracy, resource utilization, performance, error criticality, and radiation cross section. We were able to find that a design with quantized convolutional layers can be 39% less sensitive to radiation, whereas the portion of errors that are considered critical (misclassifications) in the network is increased by 12%. Moreover, we also derive generic equations that consider both accuracy and radiation in order to model the overall failure rate of neural networks.

Design of a SIW Variable Phase Shifter for Beam Steering Antenna Systems

This paper proposes a new beam steering antenna system consisting of two variable reflection-type phase shifters, a 3 dB coupler, and a 90° phase transition. The entire structure is designed and fabricated on a single layer of substrate integrated waveguide (SIW), which makes it a low loss and low-profile antenna system. Surface mount tuning varactor diodes are chosen as electrical phase control elements. By changing the biasing voltage of the varactor diodes in the phase shifter circuits, the far-field radiation pattern of the antenna steers from −25° to 25°. The system has a reflection coefficient better than −10 dB for a 2 GHz bandwidth centered at 17 GHz, a directive radiation pattern with a maximum of 10.7 dB gain at the mid-band frequency, and cross polarization better than 20 dB. A prototype is fabricated and measured for design verification. The measured far-field radiation patterns, co and cross polarization, and the reflection coefficient of the antenna system agree with simulated results.

An Integrated Radiation and Scattering Performance Design Method of Low-RCS Patch Antenna Array With Different Antenna Elements

In this communication, a novel integrated radiation and scattering performance design method of patch antenna array is proposed that can realize good radiation and low radar cross section (RCS) characteristics simultaneously without any additional RCS reduction structures except for the antenna elements. Two different antenna elements, which have similar radiation performances and different reflection phases, are used to form the array. By using different feed and patch structures, both the desired radiation and scattering characteristics of the two antenna elements can be controlled separately. Thus, a similar radiation performance and a 180° reflection phase difference can be obtained simultaneously by adjusting the size of the patches and the length of the slots on the ground plane. The simulation results show that the proposed integrated design array has approximately the same radiation performances as the arrays with uniform elements. In addition, the monostatic RCS of the proposed array is significantly reduced from 4 to 8 GHz, with a maximum reduction value of 23 dB. To validate the simulation results, prototypes of the integrated design antenna array with $4\times 4$ elements are fabricated and measured. The measured results are in good agreement with the simulated results.

Calculation of the 6Li(n,n′γ)6Li and 7Li(n,n′γ)7Li cross sections up to 20 MeV neutron kinetic energy within a three-body approach

In this work we numerically calculate cross sections of the reactions 6Li(n,n′γ)6Li and 7Li(n,n′γ)7Li reactions in the region of neutron kinetic energy En=0.5−20 MeV. Neutron-nucleus interaction is defined in terms of the three-body problem wherein the target-nucleus is a bound two-body system. Dynamics in all two-body segments is described by the coupled Lippman-Schwinger equations with separable potentials. Free parameters of these potentials are chosen based on a fairly good description of elastic scattering phase shifts and radiation cross sections: tα→γ7Li, dα→γ6Li, nd→γt. The system of three-body strongly interacting particles is described by the Faddeev equations. Radiative relaxation of the excited nucleus is effectively taken into account by the electromagnetic vertex inserted in the three-body scattering amplitude. Total cross sections and also poorly measured double differential cross sections of 6Li(n,n′γ)6Li and 7Li(n,n′γ)7Li are obtained and briefly analyzed.

Active metasurface for broadband radiation and integrated low radar cross section

In this paper, a novel design method that integrates broadband agile radiation and controllable scattering performance in one surface is proposed for an active metasurface. Each unit cell of the metasurface is incorporated with tunable devices, such as an electronic or micro-electro-mechanical-system (MEMS) varactor, to obtain frequency or spatial electromagnetic (EM) wave modulation. Besides, a probe is also adopted in the metasurface element so that the element can function as an antenna once fed by a transmitter. In this way, integrated broadband radiation and low radar cross section (RCS) are achieved for this type of active metasurface antenna (AMSA). To illustrate this method, an AMSA with a simple patch structure and lumped varactors, as an example, is demonstrated both numerically and experimentally. The results show that scanning radiation beams are obtained across a broad frequency band. Meanwhile, broadband flexible scattering performance is also realized by tuning the embedded varactors. Thus, a broad working band, reconfigurable radiation pattern, and low RCS are attained simultaneously for the AMSA. Good agreements between simulations and measurements further prove the effectiveness of the proposed method, which may have potential applications in stealth devices. Moreover, this method and the design strategy can be easily extended to other frequency range.

Radiation Cross Calibration Based on GF-1 Side Swing Angle

Radiation Cross Calibration Based on GF-1 Side Swing Angle

Boron Trifluoride Anionic Side Groups in Polyphosphazene Based Polymer Electrolyte with Enhanced Interfacial Stability in Lithium Batteries.

A modified polyphosphazene was synthesized using a mixed substitution at phosphorus consisting of 2-(2-methoxyethoxy)ethoxy side groups and anionic trifluoroborate groups. The primary goal was to increase the low lithium ion conductivities of the conventional lithium salt containing poly[2-(2-methoxyethoxy)ethoxy-phosphazene] (MEEP) by the immobilized anionic groups. As in previous studies, the mechanical stability was stabilized by UV induced radiation cross linking. By variation of the molar ratio between different side groups, mechanical and electrochemical properties are controllable. The polymer demonstrated large electrochemical stability windows ranging between 0 and 4.5 V versus the Li/Li+ reference. Total and lithium conductivities of 3.6 × 10−4 S·cm−1 and 1.8 × 10−5 S·cm−1 at 60 °C were revealed for the modified MEEP. When observed in special visualization cells, dendrite formation onset time and short-circuit time were determined as 21 h and 90 h, respectively, under constant current polarization (16 h and 65 h for MEEP, both with 15 wt % LiBOB), which hints to a more stable Li/polymer interface compared to normal MEEP. The enhanced dendrite suppression ability can be explained by the formation of a more conductive solid electrolyte interphase (SEI) and the existence of F-contained SEI components (such as LiF). With the addition of ethylene carbonate–dimethyl carbonate (EC/DMC) to form MEE-co-OBF3P gel polymer, both total and lithium conductivity were enhanced remarkably, and the lithium transference numbers reached reasonable values (σtotal = 1.05 mS·cm−1, σLi+ = 0.22 mS·cm−1, = 0.18 at 60 °C).

A 60 GHz Horizontally Polarized Magnetoelectric Dipole Antenna Array With 2-D Multibeam Endfire Radiation

A novel substrate integrated waveguide (SIW) fed horizontally polarized endfire magnetoelectric (ME) dipole antenna composed of an open-ended SIW with broad walls vertical to substrates and a pair of electric dipoles realized by four metallic patches is proposed. Simple configuration and excellent performance including an impedance bandwidth of 46.5%, stable gain of around 6 dBi, and symmetrical cardioid radiation patterns with low backward radiation and low cross polarizations are achieved. An SIW 90° twist integrated in three-layered substrate is implemented in order to connect the ME-dipole antenna conveniently to the SIW beam-forming network with broad walls parallel to substrates. A $4 \times 4$ SIW Butler matrix with a three-layered zigzag topology is then designed, which enables a size reduction of 45% for the matrix compared with conventional single-layered configuration but not affecting its operating characteristics. By employing a $2 \times 4$ ME-dipole array with 90° twists, two-folded Butler matrices and four SIW 3 dB E-plane couplers, a multibeam endfire array that can radiate eight beams scanning in two dimensions is designed at the 60 GHz band. The fabricated prototype verifies that a wide impedance bandwidth of 22.1%, gain varying from 10 to 13 dBi and stable radiation beams can be obtained. Due to good performance and the compact structure with low fabrication costs, the proposed design would be attractive for future millimeter-wave wireless applications including 5G communications and the WiGig system.

Modified star‐star fractal (MSSF) super‐wideband antenna

ABSTRACTA microstrip line fed star‐star fractal antenna with notch loaded semi‐elliptical ground plane is presented for super wideband applications. An impedance bandwidth of 4.6–52 GHz, i.e., a bandwidth ratio of 11.31:1 is achieved for VSWR < 2. The antenna structure has advantages of compact dimensions and wider bandwidth over previously reported SWB structures. Radiation characteristics, i.e., co and cross polar radiation patterns, peak gain, and efficiency has been presented and discussed. The simulated and experimental results are found to be good agreement. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:624–630, 2017

Simplified Tightly-Coupled Cross-Dipole Arrangement for Base Station Applications

The electromagnetic fundamentals that govern the performance characteristics of dual-polarized tightly coupled cross-dipoles that are widely used in cellular base station applications are investigated. The mutual coupling effects and their impact on standard performance indices are stressed. A model is developed that considers this type of cross-dipole as an array. Links between the physical dimensions of the components of these model and key radiation characteristics, including directivity, half-power-beam width, and cross polarization discrimination levels, are established. The model guides the introduction and optimization of a simplified cross-dipole structure that exhibits excellent performance. A prototype was fabricated, assembled, and tested. The measured results are in good agreement with their simulated values, validating the model, and its governing principles.

人工股関節用クロスリンクUHMWPEの摩耗量に対する長期使用の影響

人工股関節用クロスリンクUHMWPEの摩耗量に対する長期使用の影響