Elliptical Cavity Research Articles

650 MHz elliptical superconducting RF cavities for CiADS Project

650 MHz multicell superconducting radio frequency (SRF) elliptical cavities are proposed for effective acceleration of proton beam in the Chinese initiative Accelerator Driven Subcritical System (CiADS). Two families of such cavities will be used in the driver superconducting linac to accelerate the H+ beam from 175 MeV to 500 MeV, with the possibility to upgrade the energy to 1 GeV and higher. Detail designs of a six-cell βopt = 0.62 elliptical cavity and a five-cell βopt = 0.82 elliptical cavity will be presented in this paper, including the multi-parameter electromagnetic design and optimization, high order modes analyses, multipacting simulations, mechanical and engineering analyses. Sub-systems of the cavity such as the fundamental power coupler antenna tip design and mechanical design of cavity-helium vessel-tuner system will also be discussed in detail. Three single cell prototype cavities were fabricated and vertical tested to verify the electromagnetic properties, the fabrication and post-processing technologies. Four multi-cell prototype cavities are under manufacturing and expected to be ready in 2021.

Coaxial multimode cavities for fundamental superconducting rf research in an unprecedented parameter space

Recent developments in superconducting radio-frequency (SRF) research have focused primarily on high frequency elliptical cavities for electron accelerators. Advances have been made in both reducing RF surface resistance and pushing the readily achievable accelerating gradient by using novel SRF cavity treatments including surface processing, custom heat treatments, and flux expulsion. Despite the global demand for SRF based hadron accelerators, the advancement of TEM mode cavities has lagged behind. To address this, two purpose-built research cavities, one quarter-wave and one half-wave resonator, have been designed and built to allow characterization of TEM-mode cavities with standard and novel surface treatments. The cavities are intended as the TEM mode equivalent to the 1.3GHz single cell cavity, which is the essential tool for high frequency cavity research. Given their coaxial structure, the cavities allow testing at the fundamental mode and higher harmonics, giving unique insight into the role of RF frequency on fundamental loss mechanisms from intrinsic and extrinsic sources. In this paper, the cavities and testing infrastructure are described and the first performance measurements of both cavities are presented.

Design of Fundamental Power Coupler of 5 Cell Elliptical SRF Cavity Using CST Microwave Studio

A 5 cell elliptical cavity prototype has been build to accelerate the 100 MeV high beam of protons [1]. For cavity = 0.61 β g at 650 MHz in which the cavity structure is optimized by using the code from SUPERFISH [2]. The Q value of the cavity measured is 0.61x109 for 4.2 K. In the frequency range 2 – 5 GHz with CST MICROWAVE STUDIO [3]. It has been designed taking into account the advantages of both the waveguide type and coaxial type coupler This paper explains the current design of the cavity with a different angle of aperture and wall which have better mechanical stability and flatness, consisting of facilities for surface processing and less loss of beam. In this paper, the fundamental power coupler of a 5-cell 650MHz elliptical SRF cavity has been designed using CST MICROWAVE STUDIO. Here we have considered the ceramic window matching and co-axial to rectangular waveguide matching for the power coupler.

Optimization of hybrid nanoparticles with mixture fluid flow in an octagonal porous medium by effect of radiation and magnetic field

Investigation of fluid behavior in a cavity enclosure has been a significant issue from the past in the field of fluid mechanics. In the present study, hydrothermal evaluation of hybrid nanofluid with a water–ethylene glycol (50–50%) as the base fluid which contains MoS2–TiO2 hybrid nanoparticles, in an octagon with an elliptical cavity in the middle of it, has been performed. In this problem, the effects of the radiation parameter, porosity, and the magnetic parameter have been analyzed on temperature distribution and fluid flow streamlines and also, on the local and average Nusselt numbers. The governing equations have been solved by the finite element method (FEM). As a novelty, the Taguchi method has been utilized for test design. Further, the response surface method (RSM) has been applied to achieving the optimum value of the involved parameters. The obtained results illustrate that with an augment in the Rayleigh number from 10 to 100, the average Nusselt number will improve by about 61.82%. Additionally, regarding the correlation, it is indeed transparent that the Rayleigh number has the most colossal contribution comparing other factors on the achieved equation, by about 61.88%.

Development of a superconducting radio frequency double spoke cavity for CSNS

China Spallation Neutron Source (CSNS) has been in operation for about 2 years, and an upgrade is proposed to compensate the space charge effect. A superconducting radio frequency (SRF) linac with double spoke cavities and medium-beta elliptical cavities has been designed to increase the injection energy from 80MeV to 300MeV, and institute of high energy physics (IHEP) has developed a prototype double spoke cavity at β0 0.5. The cavity shape was optimized to minimize Ep/Eacc while keeping Bp/Eacc reasonably low. Meanwhile, mechanical design was applied to check stress, Lorentz force detuning and microphonic effects, and to minimize pressure sensitivity. A new input power coupling scheme was proposed to avoid electrons hitting directly on ceramic window. After fabrication and post processing of cavity, the cavity was vertical tested for several times, and mechanical polishing was applied to improve the performance. The cavity finally reached Bp of 140mT at Eacc = 16.1MV/m and Q0=1.42×1010 under vertical test at 2K.

A Reconfigurable Dual-Band Dual-Circularly Polarized Antenna for Vehicle Global Navigation Satellite System Application

A simple and novel reconfigurable dual-band dual-circularly polarized (CP) cavity backed high-gain antenna for vehicle global navigation satellite system (GNSS) is first reported in this paper. This design consists of a simple planar printed monopole with four branches, four pin-diodes and a modified cavity. Four pin-diodes are used to control the length of these four branches. By asymmetrically changing the states of these four diodes, this antenna can resonate both right-hand circular polarization (RHCP) wave and left-hand circular polarization (LHCP) wave at two bands. An elliptical cavity with a metal step is adopted to realize unidirectional radiation. To verify the concept, one prototype is fabricated and measured. The measured impedance bandwidths (|S11| < −10 dB) are 22.69% (1.055-1.325 GHz) and 5.68% (1.54-1.63 GHz), and the 3-dB axial ratio (AR) bandwidths are 7.4% (1.211-1.304 GHz) and 3.91% (1.554-1.616 GHz) with only 1.261 center frequency-ratio (CFR). The proposed antenna has advantages of simple structure, reconfigurability, higher gain, and smaller CFR.

A novel three-dimensional tetranuclear CoII coordination polymer with water hexamers based on the V-shaped tetracarboxylate ligand 4-(2,4-dicarboxylatophenoxy)phthalate.

A new coordination polymer (CP), namely, poly[[diaquatris[μ2-1,4-bis(1H-imidazol-1-yl)benzene]bis[μ6-4-(2,4-dicarboxylatophenoxy)phthalato]tetracobalt(II)] hexahydrate], {[Co4(C16H6O9)2(C12H10N4)3(H2O)2]·6H2O}n, has been synthesized by solvothermal reaction. The CP was fully characterized by IR spectroscopy, elemental analysis, thermogravimetric analysis, and powder and single-crystal X-ray diffraction. It presents a three-dimensional (3D) structure based on tetranuclear CoII secondary building units (SBUs) with a tfz-d net and point symbol (43)2(46·618·84). The 4-(2,4-dicarboxyphenoxy)phthalic acid (H4dcppa) ligands are completely deprotonated and link {Co4(COO)4}4- SBUs into two-dimensional (2D) layers. Furthermore, adjacent layers are connected by 1,4-bis(1H-imidazol-1-yl)benzene (bib) ligands, giving rise to a 3D supramolecular architecture. Interestingly, there are numerous elliptical cavities in the CP where isolated unique discrete hexameric water clusters have been observed. The results of thermogravimetric and magnetic analyses are described in detail.

Sensing Features of the Fano Resonance in an MIM Waveguide Coupled with an Elliptical Ring Resonant Cavity

In this article, a novel refractive index sensor composed of a metal–insulator–metal (MIM) waveguide with two rectangular stubs coupled with an elliptical ring resonator is proposed, the geometric parameters of which are controlled at a few hundreds of nanometer size. The transmission feature of the structure was studied by the finite element method based on electronic design automation (EDA) software COMSOL Multiphysics 5.4 (Stockholm, Sweden). The rectangular stub resonator can be thought of as a Fabry–Perot (FP) cavity, which can facilitate the Fano resonance. The simulation results reveal that the structure has a symmetric Lorentzian resonance, as well as an ultrasharp and asymmetrical Fano resonance. By adjusting the geometrical parameters, the sensitivity and figure of merit (FOM) of the structure can be optimized flexibly. After adjustments and optimization, the maximum sensitivity can reach up to 1550 nm/RIU (nanometer/Refractive Index Unit) and its FOM is 43.05. This structure presented in this article also has a promising application in highly integrated medical optical sensors to detect the concentration of hemoglobin and monitor body health.

Four-Poles Parameter of an Elliptical Cavity Having the Outlet on the Body

This paper deals with the computation of the four-poles parameter of a thin elliptic cylinder in which the output is fitted to the side that is perpendicular to the input side. The four-poles parameter is based on the sound pressure calculated by solving the wave equations, with the assumption that the loss can be ignored. The four-poles parameter is widely used to estimate the noise characteristic for the acoustic system which are composed of several elements of various cross-sectional areas, various shape connected in series.

Four-Poles Parameter of an Elliptical Cavity Having the Outlet on the Body

This paper deals with the computation of the four-poles parameter of a thin elliptic cylinder in which the output is fitted to the side that is perpendicular to the input side. The four-poles parameter is based on the sound pressure calculated by solving the wave equations, with the assumption that the loss can be ignored. The four-poles parameter is widely used to estimate the noise characteristic for the acoustic system which are composed of several elements of various cross-sectional areas, various shape connected in series.

High Temperature Solar Linear Receiver Enclosed in a Reflecting Elliptic Cavity

Abstract A linear receiver able to achieve temperatures up to 800 °C is presented. The high-temperature resistance is achieved by avoiding critical aspects (vacuum, glass-metal joints, surface films) that limit the temperature in usual receivers; the thermal insulation is obtained by enclosing the receiver tube in an elliptic reflecting cavity. The tube is placed near a focus of the cavity, and the primary collector concentrates the radiation on the other focus, where the cavity has a small opening: the ellipse reflects the radiation toward the tube and largely contains the reflected radiation and thermal emission, thus acting both as a secondary reflector and as a cavity receiver. Optical and thermal simulations show that temperatures up to 800 °C can be achieved, with optical efficiency above 70% and thermal efficiency in the range 45–85% for temperatures in the range 500–800 °C; the local overall efficiency ranges from about 40% to 66%, depending on the receiver tube emissivity and fluid temperature. In this way, the field of applicability of the linear collector technology can be significantly extended to include a vast amount of processes such as thermochemical cycles for hydrogen production, and solar fuel production processes, which require temperatures above 700 °C.

Natural convection and entropy production in hybrid nanofluid filled-annular elliptical cavity with internal heat generation or absorption

This study is an attempt to understand the characteristics of heat transfer by natural convection, flow, and entropy generation of Cu-Al2O3/H2O based hybrid nanoliquid filled-annulus delimited by two elliptic cylinders considering internal heat generation or absorption (IHG/A) phenomenon. The buoyancy-driven flow is induced by a thermal gradient between isothermal and differentially heated inner and outer cylinders. A numerical solution of the governing equations in the dimensionless and non-primitive form is performed using the technique of finite volume discretization. Impacts of diverse parameters of the study such as copper-alumina nanoparticles volumic concentration, Rayleigh number, and dimensionless internal heat generation or absorption parameter on the thermohydrodynamic characteristic and entropy generation are examined. An analysis of the results showed that the combined effects of internal heat generation/absorption and hybrid nanoliquid significantly alter the hydrothermal characteristics, heat transfer rate, and entropy generation within the annulus.

Optical properties of MIM plasmonic waveguide with an elliptical cavity resonator

Metal–insulator–metal waveguide structure, which has a fascinating feature to confine the signal far beyond the diffraction light is numerically investigated by the finite difference time domain and the finite element methods. In this study, the MIM waveguide is both coupled with a half-elliptical groove (HEG) and an elliptical cavity resonator (ECR), and it can support the propagation of light in the nanoscale regime at the visible and near-infrared ranges. The interaction between these last elements gives rise to Fano resonance modes. Thanks to its interesting characteristics, a high sensitivity value, a factor of merit and interesting value of the group index are obtained for the proposed structure. We show that the transmission of the Fano system and the group index can reach 90% and a value of 63, respectively. We also report an investigation of the influence of the both geometrical HEG and ECR’s parameters on optical properties. Hence, the proposed structure could find a potential for applications in the integrated optical circuits such as optical storage, ultrafast plasmonic switchers, high performance filters and slow light devices.

Acoustic performance of an elliptical cavity on the application for soundproof ventilation units installed in dwelling walls

A new type of soundproof ventilation unit installed in the walls of residential units is proposed in this work. The ventilation unit consists of a solid, thin, elliptic cylinder with the output mounted on the side perpendicular to the input side. In this study, the theoretical calculations of the sound pressure inside an elliptic cylinder are carried out by solving the wave equation. Next, the resonance frequencies of the higher-order mode wave component are calculated. Some comparisons between the experimental results and the estimated ones by the proposed method are discussed. The cavity in which the unit will attach inside the wall can be fabricated in a rectangular cuboid or elliptical cylinder form. The comparison of resonance frequencies of the higher-order mode wave between the rectangular cuboid and elliptic cylinder is also discussed leading to the conclusion that the use of the elliptic cylinder in the unit will be more soundproofing-efficient.

γ-Glutamylcysteine- and Cysteinylglycine-Directed Growth of Chiral Gold Nanoparticles and their Crystallographic Analysis.

Chiral optical metamaterials with delicate structures are in high demand in various fields because of their strong light-matter interactions. Recently, a scalable strategy for the synthesis of chiral plasmonic nanoparticles (NPs) using amino acids and peptides has been reported. Reported herein, 3D chiral gold NPs were synthesized using dipeptide γ-Glu-Cys and Cys-Gly and analyzed crystallographically. The γ-Glu-Cys-directed NPs present a cube-like outline with a protruding chiral wing. In comparison, the NPs synthesized with Cys-Gly exhibited a rhombic dodecahedron-like outline with curved edges and elliptical cavities on each face. Morphology analysis of intermediates indicated that γ-Glu-Cys generated an intermediate concave hexoctahedron morphology, while Cys-Gly formed a concave rhombic dodecahedron. NPs synthesized with Cys-Gly are named 432 helicoid V because of their unique morphology and growth pathway.

γ‐Glutamylcysteine‐ and Cysteinylglycine‐Directed Growth of Chiral Gold Nanoparticles and their Crystallographic Analysis

AbstractChiral optical metamaterials with delicate structures are in high demand in various fields because of their strong light–matter interactions. Recently, a scalable strategy for the synthesis of chiral plasmonic nanoparticles (NPs) using amino acids and peptides has been reported. Reported herein, 3D chiral gold NPs were synthesized using dipeptide γ‐Glu‐Cys and Cys‐Gly and analyzed crystallographically. The γ‐Glu‐Cys‐directed NPs present a cube‐like outline with a protruding chiral wing. In comparison, the NPs synthesized with Cys‐Gly exhibited a rhombic dodecahedron‐like outline with curved edges and elliptical cavities on each face. Morphology analysis of intermediates indicated that γ‐Glu‐Cys generated an intermediate concave hexoctahedron morphology, while Cys‐Gly formed a concave rhombic dodecahedron. NPs synthesized with Cys‐Gly are named 432 helicoid V because of their unique morphology and growth pathway.

Enhanced absorption of monolayer graphene using a metal–dielectric elliptical cavity array

In this paper, a strong coupling system consisting of a metal–dielectric elliptical cavity array and graphene nanoribbons is demonstrated, which can effectively enhance the light absorption of monolayer graphene in the mid-infrared spectral region. The elliptical cavity excites a strong localized field, which facilitates strong coupling between a cavity mode and a graphene surface plasmon (GSP) mode, leading to ultrabroad Rabi splitting. The classical LC circuit model is used to reveal the resonance relationship of the cavity mode. The coupled harmonic oscillator model is used to confirm the strong coupling phenomenon. The numerical simulation results demonstrate that fluctuations can be effectively tuned by adjusting the filling factor of the graphene nanoribbons. In addition, the broadband absorption of monolayer graphene can be further enhanced by changing the mobility of the graphene. A bandwidth of 6 μm with an average broadband absorption rate of 78.8% is obtained for the monolayer graphene. Such a substantial enhancement in the broadband absorption of graphene can lead to high-performance graphene optoelectronic components in the mid-infrared spectral region.

Multi-metallic conduction cooled superconducting radio-frequency cavity with high thermal stability

Superconducting radio-frequency cavities are commonly used in modern particle accelerators for applied and fundamental research. Such cavities are typically made of high-purity, bulk Nb and with cooling by a liquid helium bath at a temperature of ∼2 K. The size, cost and complexity of operating a particle accelerator with a liquid helium refrigerator make the current cavity technology not favorable for use in industrial-type accelerators. We have developed a multi-metallic 1.495 GHz elliptical cavity conductively cooled by a cryocooler. The cavity has a ∼2 µm thick layer of Nb3Sn on the inner surface, exposed to the rf field, deposited on a ∼3 mm thick bulk Nb shell and a bulk Cu shell, of thickness mm deposited on the outer surface by electroplating. A bolt-on Cu plate 1.27 cm thick was used to thermally connect the cavity equator to the second stage of a Gifford-McMahon cryocooler with a nominal capacity of 2 W at 4.2 K. The cavity was tested initially in liquid helium at 4.3 K and reached a peak surface magnetic field of ∼36 mT with a quality factor of 2 × 109. The cavity cooled by the cryocooler achieved a peak surface magnetic field of ∼29 mT, equivalent to an accelerating gradient of 6.5 MV m–1. The conduction-cooled cavity could be operated in continuous-wave with as high as 5 W dissipation in the cavity for 1 h without any thermal breakdown, because of the Cu outer layer with high thermal conductivity. This result represents a paradigm shift in the technology of superconducting accelerator cavities.

Resonance scattering of plane waves by a soft elliptic cavity with a variably placed longitudinal slit.

Using previous results [Vinogradova, J. Acoust. Soc. Am. 144(3), 1146-1153 (2018)] on the spectrum of complex eigenvalues for an open elliptic cavity with variably placed longitudinal slits, the author investigates the resonance excitation of such a cavity by obliquely incident plane waves. The complete investigation of the resonance response is based on accurate calculation of the monostatic and bi-static sonar cross-sections, as well as calculation of the jump in normal velocity at the cavity surface. High-accuracy calculations are obtained by employing the rigorous Method of Analytical Regularization. Furthermore, studies of semi-elliptic cavities with high eccentricities, modelling the extremely deep acoustical cavities, are also performed.

Elliptic cavity filled with hybrid nanomaterial under consideration of magnetic field

CVFEM usage for modeling of nanomaterial flow style in a permeable elliptical tank including Lorentz effect was scrutinized in the current research. Hybrid material with use of homogeneous model was applied and radiation term has been involved in governing equations. Outputs have been depicted in contours and plots. In addition, a new formula for Nu was reported. Augment of Nu by considering greater permeability can be explained by stronger temperature gradient in cases with higher Da. Nanomaterial flow becomes suppressed with augment of Ha which results in lower Nu. As Ha was augmented from 0 to 20, 18% reduction was reported in Nu. Permeability has favorable influence on nanomaterial flow and the impact of Ha is the opposite of permeability.