Hybrid Dipole Research Articles

Highly-efficient tunable dipole-driven Yagi–Uda antenna with end-fire radiation for terahertz application

This paper presents a highly efficient tunable dipole antenna with omnidirectional radiation. The main radiator of the hybrid dipole is designed using a perfect electric conductor, whereas tunability has been achieved using graphene strips in the antenna’s proximity. The dipole antenna resonates at 1.3785 THz and provides a bandwidth (BW) of 8.58% for the graphene’s chemical potential (μc) equal to 0.6 eV. The peak gain and total efficiency (ηTotal) are 1.46 dBi and 83.13%, respectively. The proposed dipole provides tunability from 1.32 to 1.411 THz by varying μc from 0.4 to 0.7 eV. Further, a compact dipole-driven tunable Yagi–Uda antenna has been designed with end-fire radiation. The proposed Yagi–Uda antenna has a size of only 90 μm × 60 μm, i.e., 0.61λg×0.38λg, where λg is the guided wavelength calculated at 1.3631 THz and provides tunability from 1.328 to 1.5 THz. The peak gain, front-to-back ratio (FBR) and ηTotal at 1.3631 THz for the μc = 0.6 eV are found to be 4.93 dBi, 17.3 dB, and 63.36%, respectively. A practical parallel plate DC biasing configuration with a common ground plane has also been proposed to independently tune the μc of each element in the passive Yagi–Uda array. The proposed Yagi antenna provides reasonable gain and FBR to cater for high propagation loss in the terahertz regime.

Battery-Free Wireless Torque Sensor Powered by RF Energy

Conventional dynamic torque measurement usually requires wires and slip rings for supply and data transmission, which shows many drawbacks in terms of device installation, maintenance, durability, and reliability. We here present a wireless torque measurement sensor without a battery, which can achieve a long-term and real-time torque monitoring on either static or dynamic rotation systems. The proposed battery-free wireless torque sensor (BWTS) is non-destructive and low-cost. The BWTS is equipped with a Koch-Meander hybrid dipole antenna to receive the radiofrequency (RF) energy emitted from a customized reader. The BWTS can be activated at an input power of -15 dBm (32 lW), and the maximum operational distance in the open air is 3 meters. We also study the sampling rate of the BWTS on a dynamic shaft and demonstrate it on the road, which to our best knowledge, is the first successful demonstration of fully self-powered and wireless torque monitoring in a real running car. This work indicates the feasibility of wirelessly powering torque sensors using far-field RF energy, introducing a new power solution to wireless and batteryless automotive sensors.

Nb3Sn CIC for Outsert Windings of Hybrid Dipoles

A Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn Cable-in-Conduit (CIC) conductor is being developed for use in the outsert winding of a hybrid dipole for a future hadron collider. The CIC provides several significant benefits for use in a hybrid dipole: Lorentz stress is managed at the cable level, flared ends can be formed with small bend radius with no degradation to the wires within, and supercritical helium cooling flows through the perforated center tube to provide enhanced wire stability. The Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn outsert is heat-treated as an autonomous assembly, then assembled onto a REBCO insert and preloaded within the dipole yoke structure. The cable and coil technologies of the Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn CIC are described, and its incorporation in the 18.5 T hybrid dipole is presented.

Conceptual Design of a 20 T Hybrid Cos-Theta Dipole Superconducting Magnet for Future High-Energy Particle Accelerators

High energy physics research will need more and more powerful circular accelerators in the next decades. It is therefore desirable to have dipole magnets able to produce the largest possible magnetic field, in order to keep the machine diameter within a reasonable size. A 20 T dipole is considered a desired achievement since it would allow the construction of an 80 km machine, able to circulate 100 TeV proton beams. In order to reach 20 T, a hybrid Low-Temperature Superconductor (LTS) - High-Temperature Superconductor (HTS) magnet is needed, since LTS technology is presently limited to ∼16 T for accelerator magnet applications. In this paper, we present the design of a 6 layers 20 T hybrid dipole magnet using Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn (LTS) and Bi2212 (HTS). We show that it is possible to achieve this magnetic field with accelerator field quality, with sufficient margin on a realistic conductor, keeping the stresses within safe limit, avoiding conductor degradation.

Strategies for conformal REBCO windings

A high-field winding can be fabricated from a cable of non-insulated REBCO tapes stacked face-to-face without twisting. If the cable is oriented within each turn of a winding so that the tape face is closely parallel to the magnetic field at its location, the supercurrent capacity of that cable is enhanced ∼3x greater than in a transverse or twisting orientation. This concept for a conformal winding was presented in a previous paper pertinent to the body winding of a REBCO based high-field dipole. Strategies are presented and simulated for how the same orientation can be sustained in the flared ends of a high-field hybrid dipole.

Electromagnetic Design and Fabrication of LPF2: A 12-T Hybrid Common-Coil Dipole Magnet With Inserted IBS Coil

High field dipole magnets with common-coil configuration are under development at IHEP (the Institute of High Energy Physics, Chinese Academy of Sciences) for key technology pre-study of high energy colliders. A model magnet named LPF1 has been fabricated and tested in 2018, which was made up of four flat racetrack NbTi coils and two flat racetrack Nb3Sn coils, and a main dipole field of 10.2 T has been reached in the two apertures at 4.2 K. A new model magnet LPF2 is being designed and fabricated in 2019, with four new Nb 3 Sn coils included comparing with LPF1, and the magnet is expected to reach a much higher field. To reduce the field enhancement at the coil ends, the newly fabricated Nb 3 Sn coils are designed with different straight lengths and bending radii. This hybrid dipole magnet is designed to provide a 12-T main field in the two apertures with an operating current of 5300 A, corresponding to a load line ratio of 78% at 4.2 K. A single-pancake racetrack IBS (Iron-based superconducting) coil wound with a 100-m IBS tape would be inserted into the middle of the magnet (between the inner-most two Nb 3 Sn coils). This magnet is also used to test the IBS coil performance under high field and high stress. The main design parameters, fabrication process of the magnet will be presented.

Equivalent Electromagnetic Hybrid Dipole Based on Cascade-Forward Neural Network to Predict Near-Field Magnitude of Complex Environmental Radiation

This article proposes a new method to predict the radiation field in a complex environment. The magnetic field probe is used to scan the magnitude of the radiation field, and a cascade-forward neural network (CFNN) is introduced to establish the nonlinear relationship between Green's function and the magnitude of the radiation field. The trained CFNN can replace the real radiation source in a complex environment and produce the same radiation field, which is helpful to analyze electromagnetic interference problems. The innovation of this article is to establish an equivalent source based on only scanning the magnitude of the radiation field. At the same time, the electric current source and the magnetic current source of the radiator are equivalent to electric dipoles and magnetic dipoles, respectively. After CFNN training, we can predict the radiation field beyond the scanning plane. Simulation and measurement examples are used to verify the effectiveness of the proposed method.

An All-New Ultradeep Detection Method Based on Hybrid Dipole Antennas in Electromagnetic Logging While Drilling

We have developed an all-new ultradeep boundary detection method for reservoir mapping using borehole electromagnetic (EM) logging while drilling (LWD) measurements. The new method is based on hybrid dipole antennas, which combine the magnetic dipole (MD) transmitter with an electric dipole (ED) receiver. This takes advantage of the strong signal strength of the crosscoupling electric component and its slow attenuation property. Thus, the detection capability improves significantly. Moreover, the induced signal at the ED antenna usually enlarges with decreasing transmitter-to-receiver (T–R) spacing, which has balanced the tradeoff between the depth of detection (DoD) and the tool size. A practical geosteering tool configuration is then proposed by introducing a new open-loop half-circle antenna. Numerical results demonstrate that the new method is feasible for ultradeep boundary detection. By using the coaxial opened half-circle antenna and a coaxial MD transmitter, the DoD can be extended to tens of meters, up to 16 times larger than the T–R spacing under favorable conditions. The new method is a breakthrough in geosteering techniques and it will benefit the wellbore placement optimizations and reservoir evaluation.

A Differentially Fed Hybrid Dipole, Slot, and Patch Antenna With Unidirectional Radiation Patterns

A differentially fed hybrid dipole, slot, and patch antenna with unidirectional radiation patterns is designed in this article. The antenna consists of a metal strip, a patch loaded with a slot, and a simple wideband 180° out-of-phase power splitter (OPS). The OPS can generate two signals with the same amplitude but accurate phase difference of 180° to achieve one-port differential feeding. The hybrid modes of different types of antennas, i.e., dipole, patch, and slot, are excited to obtain five bands. Additionally, the TM01, TM21, and TM03 modes of the patch antenna are excited. By loading the slot and the metal strip, the radiation pattern of TM21 mode is converted from conical to broadside, and the ground walls further concentrate the radiation pattern. The ground walls also enhance the antenna gain, with the increments of 1 dB at 3.5 GHz, 3.4 dB at 4.65 GHz, 4.1 dB at 5.5 GHz, and 1.4 dB at 6.3 GHz. Finally, the antenna is fabricated and measured. The measured results show that the antenna covers five impedance bandwidths (IMBWs) of 1.85–1.91 GHz (3.2%), 3.13–3.66 GHz (15.6%), 4.62–4.98 GHz (7.5%), 5.10–5.82 GHz (13.2%), and 6.10–6.57 GHz (7.4%) for $\vert \,\,{S} _{11}\vert dB. The radiation patterns at each band are toward the broadside, with peak gains of 5.1 dBi at 1.85 GHz, 8.8 dBi at 3.45 GHz, 8.8 dBi at 4.7 GHz, 12.2 dBi at 5.5 GHz, and 9.7 dBi at 6.3 GHz.

Electromagnetic Design, Fabrication, and Test of LPF1: A 10.2-T Common-Coil Dipole Magnet With Graded Coil Configuration

R&D of high-field accelerator magnets is ongoing at the Institute of High Energy Physics for the prestudy of high-energy accelerators in the future. As the first step, a 12-T subscale common-coil dipole magnet named Let the Proton Fly (LPF1) with two 7-mm apertures and graded coil configuration was designed, fabricated, and tested. With 4 NbTi double-pancake racetrack coils outside and 2 Nb3Sn double-pancake racetrack coils inside, this hybrid dipole magnet was designed to provide a 12-T main field in two apertures operating at 6100 A. The load line ratio is 83% @ 4.2 K for the designed current and field. To reduce the field enhancement at the ends of the coils, the coils were designed with different lengths. All of the six coils were wound with superconducting Rutherford cables and impregnated with epoxy CTD-101k. Bladders and keys technology was used to prestress coils during the assembly of LPF1. A 0.1 Ω dump resistor and a voltage-dependent varistor were used for the quench protection during the test of LPF1. LPF1 was tested at 4.2 K under the self-field and a field plateau was shown around 10.2 T after the 13th quench. The parameters of the design, process of the fabrication, and the test performance of LPF1 are presented in this paper.

Design, Construction, and Test of HTS/LTS Hybrid Dipole

This paper presents the design, construction, and test results of a hybrid dipole magnet. The inner coils were of second generation (2G) high-temperature superconductor (HTS) ReBCO tape and the outer coils were of low-temperature superconductor (LTS) Nb3Sn Rutherford cable. The HTS and LTS coils were independently powered and protected using different power supplies. The HTS coils were quenched many times with no degradation in performance observed. The hybrid field reached ∼8.6 T, which is believed to be a record for a hybrid dipole. The maximum field was limited by the stable operation of the leads in the LTS coil at 8000 A. The HTS coils were independently ramped to 800 A, and the LTS coils to 10 000 A. With improved leads and instrumentation, this hybrid dipole is expected to produce over 13 T when the ReBCO tape in the HTS coil is aligned nearly parallel to the field. One major purpose of this program was to perform magnetization studies in the coils made with the HTS tape. Magnetization-induced field errors are expected to be small when the field is nearly parallel to the wide face of the tape. The magnetization measurements were performed at 77 K with the two racetrack coils in two orientations, with field predominantly either parallel or perpendicular to the wide face of the HTS tape. In addition, measurements were also performed at 4 K in different background fields provided by the outer Nb3Sn coils. This paper will summarize the magnetization measurements and present the quenching experience of the HTS coils in this hybrid magnet system.

A rigid, stand-off hybrid dipole, and birdcage coil array for 7 T body imaging.

To design a robust and patient friendly radiofrequency coil array (8-channel transmit and 16-channel receive) for cross-sectional body imaging at 7 T, and to improve our understanding of the combination of dipole and loop like elements for ultra high field strengths. The hybrid coil array was optimized in eletromagnetic simulations. Considered array candidates were the dipole, loop and birdcage array. The winning design was constructed and the signal-to-noise (SNR) was compared to a close fitting array at 3 T. Transmit and receive properties for different body sizes were assessed, and multi-parametric maps were acquired with the Plug-and-Play MRF method. The winning design consists of a dipole array for transceive combined with a birdcage array for receive only. The central SNR improved by a factor of 3 as compared to a 3 T system with a local receive array. A transmit efficiency between 2.4 and 3.9 μT/kW, a specific absorption rate efficiency of 0.25 to 0.53 μT/W/kg, and a high SNR was achieved in the center for the targeted patient population. The constructed coil array is easy to handle, safe, and patient friendly, allowing further development of abdominal imaging at 7 T. Quantitative MRI in the abdomen is possible with Plug-and-Play MRF using the designed coil array. Magn Reson Med 80:822-832, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Few-Electron Ultrastrong Light-Matter Coupling at 300 GHz with Nanogap Hybrid LC Microcavities.

Ultrastrong light-matter coupling allows the exploration of new states of matter through the interaction of strong vacuum fields with huge electronic dipoles. By using hybrid dipole antenna-split ring resonator-based cavities with extremely small effective mode volumes Veff/λ03 ≃ 6 × 10-10 and surfaces Seff/λ02 ≃ 3.5 × 10-7, we probe the ultrastrong light-matter coupling at 300 GHz to less than 100 electrons located in the last occupied Landau level of a high mobility two-dimensional electron gas, measuring a normalized coupling ratio of ΩR/ωc = 0.36. Effects of the extremely reduced cavity dimensions are observed as the light-matter coupled system is better described by an effective mass heavier than the uncoupled one. These results open the way to ultrastrong coupling at the single-electron level in two-dimensional electron systems.

Exchangeless magnetoelectric magnons: A new class of mixed hybrid dipole waves

A layer of an easy-axis antiferromagnet with antisymmetry center is considered. It is shown that the combination of magneto- and electric-dipole mechanisms of the indirect spin–spin interactions gives rise to the previously unknown class of hybrid dipole waves such as exchangeless magnetoelectric magnons and to the spin–spin and spin–dipole resonances accompanying them. The conditions for the formation of these waves are determined.

Strong-Field-Enhanced Spectroscopy in Silicon Nanoparticle Electric and Magnetic Dipole Resonance near a Metal Surface

Strong-field-enhanced spectroscopy in a hybrid dipole resonance system composed of a low-loss semiconductor nanoparticle and metal film is proposed and demonstrated. This hybrid Si nanoparticle on silver system is featuring extraordinary near-field enhancement and large field confinement. Extensive numerical calculations are carried out to investigate the influence of the gap size, particle diameter, and metal substrate on the near-field enhancement response in the Si particle–metal gap in order to properly model their hybridization. Our analysis reveals that this near-field enhancement originates from the strong gap magnetic resonance response by the Si nanoparticle dipole interaction with metal mirror image and metal film surface plasmon effects. We further demonstrate the strong enhanced Raman spectroscopy of a single silicon nanoparticle over Ag film with a precisely sized molecular spacer layer between them. These results illustrate the capacity and tunability of the low-loss silicon particle on the ...

Bi-2212 Canted-Cosine-Theta Coils for High-Field Accelerator Magnets

report on wind-and-react (W&R) Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Sr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> CaCu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8+x</sub> (Bi-2212) insert coils that were fabricated using a Canted-Cosine-Theta (CCT) coil technology. In the CCT technology, a conductor is wound into canted helical channels that are machined into cylindrical coil winding mandrels, thereby creating a cosine-theta current distribution and providing stress support at the conductor level. The prevention of stress accumulations by the internal structure of winding mandrels is considered an enabling technology for high field Bi-2212 insert coils that target the 20 T magnetic field range. We report on the fabrication and reaction of coils for two proof-of-principle Bi-2212 inserts, BIN1 and BIN2, each consisting of two CCT coils. The BIN1 coils use insulated 0.8 mm diameter wires and INCONEL 600 coil winding mandrels with a stainless steel 316 shell, an overall diameter of 50.0 mm and a clear bore of 35.3 mm. The BIN2 coils use insulated 6-around-1 cables from 0.8-mm diameter wires, and aluminum-bronze mandrels with an aluminum alloy 6061 shell, an overall outer diameter of 68.6 mm, and a clear bore of 38.8 mm. The coils are designed to study the fabrication, reaction, and impregnation in Bi-2212 CCT technology, and provide a baseline for a Rutherford cable-wound coil set (BIN3). These latter coils target an insert-coil set with optimized current density in the windings, to enable the construction of an 18 T Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn-Bi-2212 hybrid dipole magnet.

Nonradiative resonance energy transfer directed from colloidal CdSe/ZnS quantum dots to epitaxial InGaN/GaN quantum wells for solar cells

AbstractWe report on Förster‐type nonradiative resonance energy transfer (NRET) directed from colloidal quantum dots (QDs) to epitaxial quantum wells (QWs) with an efficiency of 69.6% at a rate of 1.527 ns–1 for potential application in III‐nitride based photovoltaics. This hybrid exciton generation–collection system consists of chemically‐synthesized cyan CdSe/ZnS core/shell QDs (λPL = 490 nm) intimately integrated on epitaxially‐grown green InGaN/GaN QWs (λPL = 512 nm). To demonstrate directional NRET from donor QDs to acceptor QWs, we simultaneously show the decreased photoluminescence decay lifetime of dots and increased lifetime of wells in the hybrid dipole–dipole coupled system. (© 2010 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Single-pass BBU instability in a solenoidal field within a 4D hypercomplex space

Transverse instability of a multi-bunch beam in the presence of a longitudinal magnetostatic field and hybrid dipole modes is considered analytically within a single-section model. It incorporates resonant interaction with beam harmonics and eigenmodes, degenerated waves of different polarizations, and the Lorentz’ RF force contribution. The analysis is performed in a very compact form using a bi-complex i,j-space including four-component collective frequency ν ˜ of the instability. Rotating polarization of the collective field is determined by Im i Im j ν ˜ , which is in agreement with experimental data. The other three components represent detuning of the collective frequency Re i Re j v ˜ , the “left-hand”, and “right-hand” increments Im i Re j v ˜ ± Im i Re j v ˜ of the gyro-magnetic BBU effect. The approach can be applied for characterization of complex transverse dynamics and spin transport. The phenomenon mechanism studied here can be used in non-reciprocal, non-ferrite, high-power microwave devices.

Stimulated regenerative BBU instability of a bunch train in a single linac section

Stimulated multi-bunch transverse instability caused by hybrid dipole mode is studied using single cavity model. An accurate solution for the transverse displacement is found for sequence of bunches at presence and in absence of the input of signal. Threshold currents are calculated for resonant and non-resonant instability build-up including interaction with backward wave and Lorentz’ force contribution into the transverse wakefield. Linear amplification gain below the threshold was analyzed analytically. Transition from the cavity model to the waveguide model and validity of single-mode approximation is considered. It is shown, that for resonantly stimulated BBU the increment can be higher and threshold current lower than that for spontaneous instability.

The cohesive energy of tetrathiafulvalenium 7,7,8,8-tetracyanoquinodimethanide (TTF TCNQ) as a function of charge transfer

The Madelung, polarization, charge–dipole, and dispersion contributions to the theoretical lattice energy of tetrathiafulvalenium 7,7,8,8-tetracyanoquinodimethanide (TTF TCNQ) were computed for the uniform lattice as a function of charge transfer ρ and for the ρ = 1/2 Wigner lattice. The atom-in-molecule charges, local hybrid dipole moments, and polarizabilities used in this study were obtained from a finite-electric-field perturbation MINDO/3 calculation. Some improvements were obtained over the Madelung- only case, but the charge–dipole term tends to cancel the polarization energy term (or the Madelung energy term). The dispersion energies calculated with atom-in-molecule polarizabilities and molecular and ionic ionization energies are smaller than the dispersion energies obtained by using parametrized van der Waals coefficients for neutral hydrocarbons. The lattice energy terms at intermediate charge transfer were obtained by linear interpolation of the charges, local moments, and polarizabilities between their ρ = 0.0 values and their ρ = 1.0 values. The McConnell, Hoffman, and Metzger criterion for ionicity used along with all of the cohesive energy terms included here fails to yield the desired cohesive energy minimum at fractional charge transfer. Using the Soos estimate of the cost of ionization does provide a minimum at intermediate charge transfer, but not significantly far from the minimum obtained from using the Madelung energy alone.