Trapped Field Research Articles

Effects of electric field on pool boiling heat transfer over composite microstructured surfaces with microcavities on micro-pin-fins

In this study, we proposed to achieve synergistically enhanced pool boiling performance by combining the effects of an electric field and composite microstructures. To test the proposed strategy, the pool boiling heat transfer performances of four kinds of microstructured surfaces, including a micro-pin-fined surface (PF-30–60) and three kinds of composite microstructured surfaces with different numbers of microcavities at the top of each micro-pin-fin, were investigated in HFE-7100 under an electric field. The experimental results show that the bubbles on the composite microstructured surfaces are preferential to generate at the top of the micro-pin-fins, which not only effectively reduces the wall superheats at the onset of nucleate boiling on the composite microstructured surfaces, but also prevents a large number of bubbles from generating at the roots of the micro-pin-fins, and thus effectively alleviates the deterioration of boiling heat transfer caused by the field trap effect. Such a trend becomes more obvious with the increase in the number of microcavities. The CHF of the composite microstructured surface can be improved by 50%∼100% by the electric field, but it can only be enhanced by 26%∼78% on PF-30–60. Compared with that of the smooth surface, the CHF of PF-30–60 is increased by 36%∼52%, while the CHF of the composite microstructured surface is increased by 75%∼91% under the electric field.

Numerical modelling of soldered superconducting REBCO stacks of tapes suggests strong reduction in cross-field demagnetization

Stacks of superconducting REBCO tapes (or “stacks”) can trap high magnetic fields, above 17 T. However, relatively low oscillating transverse magnetic fields can fully demagnetize the stacks. This is an issue if the stacks act as poles in the rotor of a superconducting motor, for instance. Here, we study the drastic suppression of cross-field demagnetization in stacks by soldering the tapes at the ends using a normal conductor. In particular, we analyzed by numerical modeling a stack of five REBCO thin films connected at the ends by resistances. The computed trapped field of a stack with zero solder resistance decays very fast at the beginning but then tends to stabilize to relatively high values, while the trapped field of an isolated stack (infinite resistance at the ends) decays further (it decays to zero if the transverse field is above the parallel penetration field). For intermediate solder resistances, the stable value of the trapped magnetic field is in between those of the isolated and zero-resistance configurations. Since the stable trapped field in soldered stacks increases with the number of tapes, stacks of sufficiently high number of soldered tapes could be immune to cross-field demagnetization. This opens the gate for a new kind of superconductors that mostly behave as bulks, especially if the stacks are made of delaminated tapes or it is possible to solder the tapes by very low resistance.

Modelling and mitigating flux jumps in bulk high-temperature superconductors during quasi-static, high-field magnetisation

(RE)-Ba2Cu3O bulk superconductors acting as permanent trapped field magnet analogues have been shown to trap fields in excess of 17 T. However, the occurrence of thermomagnetic instabilities during their magnetisation process can limit their performance. In 2019, Naito et al trapped 15.1 T in a (Y)-BaCuO bulk pair under applied fields of up to 22 T (2019 J. Appl. Phys. 126 243901), whilst also documenting the mechanical failure of the bulks due to a flux jump. Here, we accurately numerically model this experiment and the observed flux jump, providing insight into the experimental results, such as the role of heating, the presence of thermal gradients, and a possible reason for the location of the bulk-pair fracturing. Extending the study with an investigation into the role of enhanced cooling of the bulk-pair, the influence of cooling power on the calculated trapped field and flux jump is explored. Finally, we propose and numerically investigate a new composite bulk configuration, consisting of stacks of (Y)-BaCuO bulk and interspaced metallic discs, to enhance the thermal stability of the bulk pair, to ultimately improve the trapped field performance.

Magnetization mechanism of a hybrid high temperature superconducting trapped field magnet

This paper studies the magnetization mechanism of a hybrid high temperature superconducting (HTS) trapped field magnet. To address the size limitation of traditional HTS bulk materials, hybridization between HTS-stacked ring magnets and HTS bulks is proposed here. A jointless HTS-stacked ring magnet is used to increase the trapped field area for HTS bulks. A hybrid HTS magnet with 90 mm in length and 60 mm in width was tested to provide a trapped field of 7.35 T in a field cooling magnetization. The paper focuses mainly on understanding the novel magnetization mechanism of this hybrid HTS trapped field magnet. A numerical model based on homogenized H formulation was used to compare with experimental results, and a good match was found. Our experimental and numerical study of the electromagnetic interaction between the HTS-stacked ring magnet and the HTS bulks reveals that there are two magnetization stages, and the magnetization speed differs in these two stages by a sing criterion: whether the HTS-stacked ring magnet is fully penetrated or not. This study confirms that hybridization helps to build large HTS trapped field magnets.

Developing efficient small molecule-based organic photo-couplers by optimizing the cathode interfacial layer in the photodetector

Thorough electrical and optical characterizations are carried out herein to investigate the phenomena of thermionic field emission, trap density, and exciton quenching, which justifies the superior performance of the proposed organic photo-coupler.

Spatial and temporal distribution of hydrocarbon production on the UK continental shelf

AbstractHydrocarbon production from oil and gas fields is controlled by a variety of interconnected factors with a hierarchy of significance that is, for the most part, difficult to untangle. This article documents and investigates the spatial and temporal distribution of key hydrocarbon field parameters on the UK Continental Shelf. Data have been compiled from publicly available sources for 424 fields. Variables are considered as “descriptive parameters,” “control parameters” and “outcomes”. Descriptive parameters are metadata such as field name, location, etc. Control Parameters include depositional environment, present depth of burial, porosity, permeability, reservoir formation pressure, reservoir temperature, average net‐to‐gross, number of fault populations, hydrocarbon API, field area, bulk rock volume, well density, number of wells (production and injection), well spacing, gas oil ratio, reservoir thickness, fluid saturation, compartmentalization (quantitated by number of observable non‐communicating fault compartments), structural complexity (scaled from 0 to 5), field production strategy, trap type and stratigraphic heterogeneity. Outcomes are used to assess field performance and include final recovery factor (estimated), maximum production rate, and cumulative monthly production. Analysis of the database illustrates a number of empirical observations regarding hydrocarbon production on the UKCS. The Jurassic plays have been the most successful in the region in terms of total volumes produced while the Permian reservoirs of the SNS account for the majority of the gas. Most of the UKCS reservoirs record top depths between 2000 and 4500 m with good reservoir quality. The best reservoir quality is observed in reservoirs that were deposited within deep marine systems. The largest hydrocarbon reserves are found in the Northern North Sea basin in these deep marine (as well as paralic and shallow marine) reservoirs. Using the data from this article and affiliated data, potential exists for extracting insight beyond spatio‐temporal distributions.

Vaccinating badgers in a post‐cull landscape; insights from the field

Abstract In 2010 the BadgerBCG vaccine was licenced for use in badgers in the United Kingdom to reduce the severity of Mycobacterium bovis infection, and hence the risks of onward transmission to cattle. To date badger vaccination in the United Kingdom has been deployed at a relatively limited spatial scale (compared to the large‐scale badger culls) and almost exclusively in high‐density badger populations which have not been recently culled. UK Government policy direction has moved towards the wider rollout of badger vaccination as an exit strategy following culling. Field resources required to carry out vaccination in undisturbed badger populations are well documented, but levels of effort are unlikely to be directly transferable to previously culled populations where badger density and social behaviour may be markedly different. We present an evidence‐based assessment of the likely effort required to vaccinate badger populations that have recently been culled, drawing on data from past culling operations, vaccination operations in a previously culled area and the practical field experiences of expert badger trappers. Trapping efficiency declined over successive years of industry‐led culling, however, this effect was not consistently noted in the government‐run randomized badger culling trial (RBCT). Fewer badgers were removed using cage trapping (compared to ‘controlled shooting’) in the latter years of intensive industry‐led culls. When trapping badgers for vaccination in areas that had previously been culled, highly experienced government field staff adapted their practices in response to the lower density and likely more mobile residual population. A longer and more variable pre‐baiting period was expected and there was a greater reliance on higher levels of skill and experience in interpreting field signs and trapping effectively in such populations.

The effect of pre-sintering and high-temperature infiltration on the properties of single-domain YBCO bulk superconductors by the Y + 011 top-seeded infiltration growth process

The top-seeded infiltration growth process (TSIG) is one of the most important methods for the fabrication of single-domain rare-earth barium copper oxide (REBCO) bulk superconductors. The performance of samples is in the main closely related to the quality of the solid phase pellets (SPPs). In this paper, we report a new method for optimizing the SPPs and properties of single-domain REBCO bulks, including sintering of the SPPs (Y2O3 + BaCuO2), infiltration of the Ba–Cu–O liquid phase and the melting growth process. A group of single-domain YBCO bulk superconductors with a diameter of 20 mm have been fabricated by the modified RE + 011 TSIG method. Both the levitation force and the trapped field of the samples increase at first and then decrease with increase in the sintering time. The largest levitation force of 42.8 N and trapped field of 0.41 T (77 K, 0.5 T) are obtained in the sample sintered at 1000 °C for 4.5 h; this is mainly related to the optimal microstructure of the pre-sintered SPPs and the YBCO bulk. These results indicate that pre-sintering and high-temperature infiltration is a very important method for controlling the microstructure and improving the physical properties of single-domain YBCO bulk superconductors.

Mechanisms of instability retention for ferroelectric field effect transistors with HfZrO2 gate stack scaling down

Instability threshold voltage (VT) with retention loss of read-after-write is a critical issue with fundamental physics for ferroelectric field effect transistors (FeFETs) scaling down under high-speed operation. The mechanisms including charge trapping and depolarization field (Edep) are discovered and related to surface potential and coercive field (EC). The trapped charge can be effectively detrapped by opposite polarity stimulation and validated by technology computer-aided design modeling. In addition, the Edep is revealed to be serious with ferroelectric HfZrO2 (FE-HZO) thin-down due to the unstable low-VT state at a gate voltage (VG) of 0 V. The tunable base voltage (Vbase) compensates the Edep-based polarization degradation. A stable low-VT read-after-write for a 5-nm-thick HZO FeFET is experimentally demonstrated by the opposite polarity detrapping scheme hybrid with a Vbase optimization simultaneously for a wide range of delay times from 10−7 to 102 s. This result provides the feasibility for scaling down FeFETs for nonvolatile memory applications in the future.

Tunable energy-level inversion in spin-orbit-coupled Bose-Einstein condensates

A method to realize controllable inversion of energy levels in a one-dimensional spin-orbit (SO)-coupled two-component Bose-Einstein condensate under the action of a gradient magnetic field and harmonic-oscillator (HO) trapping potential is proposed. The linear version of the system is solved exactly. By adjusting the SO coupling strength and magnetic-field gradient, the energy-level inversion makes it possible to transform any excited state into the ground state. The full nonlinear system is solved numerically, and it is found that the results are consistent with the linear prediction in the case of the repulsive intercomponent interaction. On the other hand, the intercomponent attraction gives rise to states of superposition and edge types. Similar results are also reported for the system with the HO trap replaced by the box potential. These results suggest a possibility to realize any excited state and observe it in the experiment.

Fiber-integrated catenary ring-array metasurfaces for beam shaping.

Catenary is referred to as "the real mathematical and mechanical form" in the architectural field. Because of the unique phase control characteristic of the catenary, it has excellent ability in optical manipulation. Here, we propose an optical waveform conversion device based on optical fiber-integrated catenary ring-array metasurfaces. The device consists of a cascade structure of a single-mode fiber (SMF) and a graded-index fiber (GIF). At the GIF end, two kinds of catenary ring-array metasurfaces are introduced to realize beam shaping from Gaussian beam (GB) to Bessel beam. The device can selectively generate a focused or non-diffracting Bessel beam by changing the circular polarization state of the incident light. It is worth noting that under some parameters of the device, the output Bessel beam can break through the diffraction limit, which has potential applications in the fields of optical imaging, optical communication, and optical trapping.

Quantitative assessment and suppression of anharmonic potential of quadrupole linear radiofrequency ion traps with round electrodes

Precision manipulation of the quantum coherence of radiofrequency (RF) ion trap systems is one of the most important prerequisites for the development of high-performance ion frequency standards, high-fidelity ion trap quantum computing, and ion precision spectroscopy. The anharmonic potential of the ion trap exacerbates the non-ideal kinetic properties of the trapped ions and the simple harmonic motions of the heated ions, which in turn constrain the coherence time of the trapped ion systems. In this study, we developed a precision assessment and optimization method for the potential field of a quadrupole linear RF ion trap with round electrodes based on the joint weight suppression of the multi-order anharmonic potential, which is applicable for ion ensembles of cloud, liquid, and crystalline forms, and for different ion numbers. By quantifying the potential of each radial order of the decoupled transient RF potential, we established the quantitative loss relationship between the structure parameter of the linear RF ion trap with round electrodes and the trapping potential and outlined the influence of the structure parameter of the trap on the weight of the anharmonic potential. We determined the optimal structure parameter k (the ratio of pole radius re to radius r0 of the maximum trapping field) of the quadrupole linear ion trap with round electrodes as 1.1451447, which minimizes the overall anharmonic potential and achieves the highest reported accuracy (Reuben et al., 1996) [1]. This result provides a basis for the solution of problems in physics such as obtaining long-time trapping under low heating rate, precision manipulation of coherence, motion effect suppression, and efficient cooling of 3D ion systems, which are conducive to quantum coherence with time delays, spectral measurement approaching the theoretical accuracy limit, and high-performance frequency standards of 3D ion systems.

Tunable light trapping in the graphene metasurface.

Graphene metasurfaces based on surface plasmon resonance can greatly enhance the interaction between light and matter at the nanoscale. At present, the resonance of graphene metasurfaces is widely used to enhance the absorption of atomic layer graphene, but little work has focused on the light field trapping capabilities it brings. In this paper, we numerically study the light trapping and manipulation of an asymmetric graphene metasurface. The designed device supports two resonant modes, and the multipole decomposition confirms that the electric dipole response dominates them. The calculated average electric field enhancement factor (EF) can reach 1206 and 1779, respectively. The near-field distribution indicates that the electric field is mainly localized in the graphene nanodisks. When the Fermi energy changes, the intensity and peak position of EF can be effectively regulated. In addition, when the polarization of the incident light is adjusted, the light field capture of the two modes is independently regulated. These results reveal that the graphene metasurface has significant light field capture and regulation ability, which provides a new idea for the realization of active regulation of high-performance low-dimensional optical devices.

No Evidence of Responding Individuals Constraining the Evolution of the Pheromone Signal in the Pine Engraver Ips avulsus

Chemical signals are important mediators of interactions within forest ecosystems. In insects, pheromone signals mediate intraspecific interactions such as mate location and acceptance. The evolution of pheromones in insects has been mostly studied from a theoretical perspective in the Lepidoptera. With this study, we aimed to broaden our understanding of pheromone communication in bark beetles. We first demonstrated that the enantiomeric ratios of ipsdienol produced by male I. avulsus, showed little variation. Subsequently, with field trapping trials we characterized the influence of the enantiomeric ratio of ipsdienol (pheromone component of I. avulsus) on I. avulsus captures and observed a great amount of variation in the receiver preference function. Most importantly, we demonstrated that responding individuals responded indiscriminately to all the enantiomeric ratios produced by the emitting individuals. These observations are consistent with the asymmetric tracking model which postulates that if the limiting sex is the emitting sex, responding individuals should not discriminate between emitted ratios. Consequently, responding individuals do not constrain the evolution of the signal. Our data suggest that, in I. avulsus, the composition of the aggregation pheromone signal might be more responsive to external selection forces, such as predation and metabolic constraints, as suggested by the asymmetric tracking model.

Asian corn borer (Ostrinia furnacalis Gn., Lepidoptera: Crambidae): Attraction to a bisexual lure and comparison of performance with synthetic sex pheromone

AbstractHost plant-derived semiochemicals are becoming the most promising attractants to lure corn borers to traps in the field. Following success with the European corn borer (Ostrinia nubilalis), a two-component blend bisexual lure (phenylacetaldehyde and 2-(4-methoxyphenyl)ethanol) of the host plant odor was tested in wind tunnel and field trapping experiments on the Asian corn borer (Ostrinia furnacalis) (ACB). To be able to compare the lure's performance with synthetic pheromone, a new route for the sex pheromone components (Z)-12-tetradecenyl acetate and (E)-12-tetradecenyl acetate was also developed, and the biological activity of the products was confirmed. The bisexual lure attracted both males and females of ACB in laboratory wind tunnel, and also in the field. Field trapping results indicated that traps with the bisexual lure attracted somewhat more ACB (both sexes) than pheromone baited traps, but this indication needs further confirmation. Traps baited with the bisexual lure may offer a new tool for monitoring ACB for practical purposes.

Constructing spin-structured focal fields for chiral-sensitive trapping with dielectric metalens

Engineering the chiral field is crucial for the flexible manipulation of chiral particles. Some complex optical setups for constructing spin-structured fields have been well developed to sort particles with opposite chiralities toward opposite transversal directions. In this work, we demonstrate the robust construction of a class of focal fields that possess laterally variant optical spin angular momentum by using the monolayer dielectric metalens. By utilizing the simultaneous modulation capacity of the phase and polarization of the dielectric metalens, we can establish a line focus with laterally tailored gradient optical helicity. The focusing property of this metalens and the polarization structure of the focal field are theoretically analyzed using a hybrid vector-focusing model and experimentally demonstrated by NA = 0.2 and 0.5 samples. We illustrate that this type of gradient helicity offers opportunities to induce a chirality-sensitive lateral force for chiral particles.

Autofocusing field constructed by ring-arrayed Pearcey Gaussian chirp beams.

In this work, we propose and demonstrate the ring-arrayed Pearcey Gaussian chirp beams (RAPGCBs) synthesized by multiple two-dimensional Pearcey beams. The general analytical formula for the propagation of RAPGCBs is presented. We find that, depending on synthesized number n, the profiles of the beams present different polygonal shapes, and the autofocusing properties can be controlled by chirp factor β. Furthermore, we study the properties of the RAPGCBs carrying optical vortices (OVs). It shows that a single OV or two positive OVs form an autofocusing hollow field, and opposite OVs will annihilate, which results in greatly increased autofocusing ability. Our experimental results agree with the simulations. Such beams have potential applications in particle trapping and biology medical fields.

Understanding the porosity and its effects on the superconducting properties of YBCO single grains

The influence of porosity on the trapped field achievable in 22 YBCO bulk superconductors of different sizes has been investigated and evaluated using Spearman's correlation coefficient in order to explore the significance of these critical features in a statistically significant way. The diameter of the single grain YBCO bulk sample correlates strongly with trapped field, and significantly more so than the effect of porosity. Therefore, the direct effect of porosity on the average Jc was investigated as the main aim of this investigation. A correlation was found between the average Jc calculated from trapped field measured at the top and bottom of the single grain and the porosity of the sample. This observation suggests that any method of reducing the porosity may significantly improve Jc and trapped field.

Identification and Field Evaluation of Sex Pheromone Components and Its Antagonist Produced by a Major Tea Pest, Archips strojny (Lepidoptera: Tortricidae).

Pesticide application is the only known control method for the tea tortrix Archips strojny (Lepidoptera: Tortricidae), which is a major pest of spring tea in China. To develop sex pheromone-based, environmentally safe control strategies, here we identified the sex pheromone components of this species. The male moths' antennae responded electrophysiologically to two compounds in female pheromone gland extracts. Gas chromatography-mass spectrometry analysis indicated that the two bioactive compounds were (Z)-11-tetradecenyl acetate (Z11-14:Ac) and (Z)-11-tetradecenyl alcohol (Z11-14:OH). Field trapping assays showed that lures baited with only the major component Z11-14:Ac were the most attractive to male moths, and the attractiveness decreased significantly when the lure was impregnated with increased relative ratios of the minor component Z11-14:OH. Our study demonstrated that Z11-14:Ac was the major attractant in the A. strojny sex pheromone, and the minor component Z11-14:OH seemed to serve as an antagonist. The results indicate that lures baited with 1 mg of Z11-14:Ac could be used as a monitoring or mass trapping tool for A. strojny management in Chinese tea plantations. Furthermore, Z11-14:Ac was identified as a common sex pheromone attractant of nine Archips species; these results lay the foundation for developing mating disruption techniques that target multiple leafroller pests.

An integrated instrument of a tandem quadrupole mass spectrometer for cluster reaction and soft-landing deposition.

We have developed an integrated instrument system of a multiple-ion laminar flow tube (MIFT) reactor combined with a tandem quadrupole mass spectrometer (TQMS) and soft-landing deposition (SD) apparatus. A customized water-cooling magnetron sputtering (MagS) source is designed, by which we are able to attain a highly efficient preparation of metal clusters of 1-30 atoms with tunable size distributions. Following the MagS source, a laminar flow tube reactor is designed, allowing for sufficient gas-collision reactions of the as-prepared metal clusters, which is advantageous for probing magic clusters and minimizing wall effects when probing the reaction dynamics of such clusters. The customized TQMS analyzer involves a conical octupole, two linear octupoles, a quadruple ion deflector, and a 19mm quadruple mass analyzer, allowing to decrease the pressure stepwise (from ∼5 to ∼10-9 Torr), thus ensuring high sensitivity and high resolution of the mass spectrometry analysis. In addition, we have designed a dual SDapparatus for the mass-selected deposition of clusters and their reaction products. For the whole system, abbreviated as MagS-MIFT-TQMS-SD, we have performed a detailed ions-fly simulation and quantitatively estimated the ions transfer efficiency under vacuum conditions determined by real experiments. Taking these advantages, well-resolved Pbn +, Agn +, and Nbn + clusters have been produced, allowing for meticulous studies of cluster reactions under sufficient gas-phase collisions free of electric field trapping. Also, we have tested the efficiency of the dual SD.