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Directionality properties of the nGEM detector of the CNESM diagnostic system for SPIDER
摘要： The ITER project requires additional heating by two neutral beam injectors, each accelerating up to 1 MV a 40 A beam of negative deuterium ions for one hour. Such requirements have never been reached, so it was decided to build in Padova a facility (PRIMA) that hosts two experimental devices: SPIDER, a 100 kV negative H/D RF beam source, and MITICA, a full-scale injector for the ITER NBI. SPIDER has begun operation in 2018, while MITICA is expected to start after 2020. In both devices the accelerated deuterium beam impinges on an actively cooled beam dump used to stop the deuterons. Detection of fusion neutrons produced between beam–deuterons and dump-embedded deuterons will be used as a means to resolve the horizontal beam intensity profile. A neutron detection system called Close-contact Neutron Emission Surface Mapping (CNESM) is installed right behind the SPIDER beam dump, with the aim to provide the neutron emission map of the beam dump surface. The core of this diagnostic system is an nGEM (neutron-Gas Electron Multiplier) detector which will be able to reconstruct the fast neutron beam profile with an efficiency of about 10?4. A crucial point in order to correctly reconstruct the profile of the deposited D? power is the directionality discrimination capability of the detector. This paper reports on the results of the characterization of the nGEM directionality capabilities, performed at the Frascati Neutron Generator (FNG) using 2.5 MeV neutrons, before installation of the detector inside the SPIDER vacuum vessel.
关键词： Neutral beam injector,Directionality,Neutron imaging,GEM detectors,Deuterium map
更新于2025-09-23 15:22:29
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[IEEE 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - Singapore, Singapore (2019.8.28-2019.8.30)] 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - A Milimeter Scale Long Waveguide Grating Antanna with High Directionality for Optical Phased Array
摘要： We propose a highly directional millimeter-scale waveguide grating antenna (WGA). The directionality is close to 90% while the length of the WGA is longer than 4 mm. And the large critical dimension of this structure moderates the fabrication process.
关键词： optical phased array,high directionality,WGA
更新于2025-09-16 10:30:52
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Engineering Directionality in Quantum Dot Shell Lasing Using Plasmonic Lattices
摘要： We report how the direction of quantum dot (QD) lasing can be engineered by exploiting high-symmetry points in plasmonic nanoparticle (NP) lattices. The nanolaser architecture consists of CdSe?CdS core?shell QD layers conformally coated on two-dimensional square arrays of Ag NPs. Using waveguide-surface lattice resonances (W-SLRs) near the Δ point in the Brillouin zone as optical feedback, we achieved lasing from the gain in CdS shells at off-normal emission angles. Changing the periodicity of the plasmonic lattices enables other high-symmetry points (Γ or M) of the lattice to overlap with the QD shell emission, which facilitates tuning of the lasing direction. We also increased the thickness of the QD layer to introduce higher-order W-SLR modes with additional avoided crossings in the band structure, which expands the selection of cavity modes for any desired lasing emission angle.
关键词： band structure engineering,laser directionality,surface lattice resonances,colloidal quantum dots,lattice plasmons,waveguide
更新于2025-09-16 10:30:52
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[IEEE 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - Singapore, Singapore (2019.8.28-2019.8.30)] 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - A Milimeter Scale Long Waveguide Grating Antanna with High Directionality for Optical Phased Array
摘要： We propose a highly directional millimeter-scale waveguide grating antenna (WGA). The directionality is close to 90% while the length of the WGA is longer than 4 mm. And the large critical dimension of this structure moderates the fabrication process.
关键词： WGA,optical phased array,high directionality
更新于2025-09-12 10:27:22
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Proceedings [EAGE Publications BV 76th EAGE Conference and Exhibition 2014 - Amsterdam, Netherlands (2014.06.16-2014.06.19)] Proceedings 76th EAGE Conference and Exhibition 2014 - Fundamentals of Vibration Sensing with Distributed Fibre Optic Sensors through Downscaled Experiments
摘要： In the past few years the Distributed Vibration Sensing of fibre optic sensors (also called Distributed Acoustic Sensing) has gained great interest in geophysics, despite the fundamentals of the measurement being poorly understood. The technology offers immense improvement in terms of efficiency when compared with current geophysical methods and also could be preferred for applications such as permanent reservoir monitoring. We present a method for downscaled experimentation that enabled us to define the fundamentals of the optical fibre measurement. We show seismic data that were recorded simultaneously by both the fibre optical interferometer and conventional geophones, thus enabling the comparison of sensor performance. We present results focused on wave-polarity sensitivity and the directionality of fibre measurements. The current interrogation method of optical fibre cables cannot distinguish between wavefields coming from opposite azimuthal directions, which can be an issue in certain applications where the identification of up-going and down-going wavefields is essential. Observations are also presented that describe the relationship between the velocity signal that is measured using a geophone array and the phase difference measurement from the fibre optic sensing system.
关键词： directionality,Distributed Vibration Sensing,Distributed Acoustic Sensing,optical fibre measurement,geophones,wave-polarity sensitivity,seismic data,fibre optic sensors,geophysics
更新于2025-09-11 14:15:04
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DESIGN OF 2D METAL PHOTONIC CRYSTAL ARRAY OF DIRECTIONAL RADIATION IN MICROWAVE BAND
摘要： A 2D metal photonic crystal structure with a rectangular lattice is designed for directed wave propagation in the microwave frequency band. The dispersion curve of EPC is computed for designing the directed period array. In order to favor the computing, the rectangular period array is studied, which is di?erent from the reference that is designed in optical range and uses the dielectric rods and hexagonal structure to compose the period array. The computed dispersion curves are combined with the theory of ?nite thick period array for obtaining the directed wave propagation structure. The in?uence of the number of metal rods on the antenna directionality is investigated, and the simulation results are compared and analyzed. It is found that when the number of transverse metal rods increases, the directionality of the antenna is enhanced, and the radiant power of the sidelobe radiation can be reduced. Based on the simulation results, the actual 2D metal photonic crystal array is constructed for the measurement validation. According to measurement results, the antenna located in the center of the array can get good directionality at 3.1 GHz.
关键词： 2D metal photonic crystal,antenna directionality,microwave band,directional radiation,dispersion curve
更新于2025-09-10 09:29:36
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[IEEE 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Espoo, Finland (2018.8.27-2018.9.1)] 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Eccentric metallo-dielectric core-shell nanoparticles for switching and guiding purposes
摘要： Metallo-dielectric or dielectric-dielectric core-shell nanoparticles have been proposed during last years for enhancing the near Zero-Forward and Zero-Backward conditions because they support tunable electric and magnetic resonances. By changing the relative size of the core respect to the particle size, electric and magnetic resonances are shifted. As a consequence, they can be used to control the direction of the scattered radiation. Here, we demonstrate the possibility of using isolated eccentric metallo-dielectric core-shell nanoparticles for redirecting the incident radiation into some specific directions eventually different from the forward and backward ones. In particular, we show their utility for building operational switching devices, whose on/off state only depends on the polarization of the incident radiation. Chains of these scattering units have shown good radiation guiding effects at the nanoscale level.
关键词： metallo-dielectric,core-shell nanoparticles,scattering directionality,radiation guiding,switching devices
更新于2025-09-10 09:29:36
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Application of Fiber Bragg Grating Acoustic Emission Sensors in Thin Polymer-Bonded Explosives
摘要： Fiber Bragg grating (FBG) acoustic emission (AE) sensors have been used in many applications. In this paper, based on an FBG AE sensor, the sensing principle of the interaction between the AE wave and the sensor is introduced. Then, the directionality of the FBG AE sensor on the surface of a thin polymer-bonded explosive (PBX) material is studied. Finally, the time coefficient location method is proposed to correct the AE time detected by the FBG AE sensor, thereby improving the accuracy of location experiments.
关键词： directionality,polymer-bonded explosives,time coefficient location method,fiber Bragg grating acoustic emission sensor
更新于2025-09-10 09:29:36
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From Geometric-Optical Remote Sensing Modeling to Quantitative Remote Sensing Science—In Memory of Academician Xiaowen Li
摘要： The academician Xiaowen Li devoted much of his life to pursuing fundamental research in remote sensing. A pioneer in the geometric-optical modeling of vegetation canopies, his work is held in high regard by the international remote sensing community. He codeveloped the Li–Strahler geometric-optic model, and this paper was selected by a member of the International Society for Optical Engineering (SPIE) milestone series. As a chief scientist, Xiaowen Li led a scienti?c team that made outstanding advances in bidirectional re?ectance distribution modeling, directional thermal emission modeling, comprehensive experiments, and the understanding of spatial and temporal scale effects in remote sensing information, and of quantitative inversions utilizing remote sensing data. In addition to his broad research activities, he was noted for his humility and his dedication in making science more accessible for the general public. Here, the life and academic contributions of Xiaowen Li to the ?eld of quantitative remote sensing science are brie?y reviewed.
关键词： geometric-optical model,scale effects,quantitative remote sensing inversion,thermal radiation directionality,comprehensive ?eld experiment
更新于2025-09-10 09:29:36