Trap Configuration Research Articles

Evaluating methods for controlling feral cats that minimise non‐target impacts at Taunton National Park (Scientific)

SummaryFeral Cat (Felis catus) (cat) is a predator of the Bridled Nail‐Tailed Wallaby (BNTW) (Onychogalea frenata) living at Taunton National Park (Scientific) (Taunton). The aim of this study was to determine if traps and poison baits could be used to control feral cats without impacting non‐target species at Taunton. The techniques trialled included poison fresh meat baits and several types of traps presented in different ways and with various lures. Thirty‐one percent of fresh meat baits was taken during bait uptake trials; corvids removed 40% of these and dogs removed 16%. Cats were not detected, on camera traps, taking a bait. The elevated soft‐jaw traps (81 trap nights/cat) and single‐entry cage traps (98 trap nights/cat) were found to be the most successful of all the trap types trialled and had low amounts of by‐catch. Other trap types trialled took more than 166 trap nights to catch a cat. The elevated soft‐jaw trap configurations had the lowest amount of by‐catch (avg. 0.33%), and the log trap had the highest amount of by‐catch (1%). Ground‐set traps successfully trapped cats (305 trap nights/cat) but caught more by‐catch (0.9%) compared to the elevated soft‐jaw trap types and most wallabies caught in these traps had to be euthanised.

Optimization of power matching and transfer in the helicon plasma discharge

Helicon plasma source is being developed at the Budker Institute of Nuclear Physics SB RAS, Novosibirsk. The parameters are studied of the plasma confined in a mirror trap configuration of the magnetic field at an operating frequency of 13.56 MHz. For matching the antenna impedance and generator load, the Π-type matching box was designed and successfully tested at powers of 20–25 kW. The low reflected power (1–2%) was obtained, as compared to that for the L-type matching network used previously (the reflected power was more than 15% at the generator output power of 18 kW). The triple Langmuir probe is used to determine the plasma density. The plasma resistive characteristics were determined using the Rogowski coil measuring the RF antenna current. In the experiments, the plasma with a density of ∽5⋅1012 cm-3 and an electron temperature on axis of 10 eV was obtained, and the RF power transfer efficiency was ∽85% at the RF power of 25 kW.

Infrared rainbow trapping via optical Tamm modes in an one-dimensional dielectric chirped photonic crystals.

The phenomenon of trapping a broad spectrum of light is known as "rainbow trapping" and is achieved by using all-dielectric, hybrid metallo-dielectric, or all-metallic configurations. The latter architectures allow strong confinement but exhibit very high ohmic losses. This results in practical lifetimes of trapped modes to less than 1 ps. Therefore, novel strategies are required to be devised for trapping and, subsequently, releasing broadband electromagnetic field with lifetime >1ps. We present a rainbow trapping configuration using the excitation of multiple optical Tamm (OT) modes in an one-dimensional chirped photonic crystal (CPC) designed for adiabatically coupling counterpropagating modes. In the geometry, the backscattered phase undergoes multiple discontinuities (=π), which enables excitation of many OT modes in the presence of a thin plasmon-active metal, which is placed adjacent to the terminating layer of CPC. All the OT modes are spatially separated in the CPC, and the strong modal confinement manifests into group velocities as low as 0.17c. The time-domain simulations depict mode-localization in the dielectric sections of CPC, which manifest into lifetimes ∼3ps.

Numerical simulations of storage and thermometry of small biomolecular ions in a 16-pole ion trap and a 16-wire ion trap

This work focuses on numerical simulations of ion dynamics of small biomolecular ions (m/z ∼ 200) under the influence of elastic collisions with a buffer gas in a 16-pole ion trap and a 16-wire ion trap. A comparison between effective potentials in these trap configurations is provided. Particular emphasis is placed on studying storage efficiency and ion temperature in both traps. The dependence of ion temperature on various trapping parameters is discussed. It is found that the optimum operating range in terms of storage efficiency in a wire trap is limited compared to that in a pole trap and exhibits higher sensitivity to various parameters at low temperatures. However, with a proper choice of the operating parameters, the wire trap can serve as a practical alternative to the conventional design of a multipole ion trap while providing the lateral optical access, which will open a new window for spectroscopic studies with such traps.

Kosyu–Rogov Composite Tectono-Sedimentary Element, Northwestern Russia

Abstract The Kosyu–Rogov Composite Tectono-Sedimentary Element (CTSE) is one of the last exploration frontiers left in the European part of Russia. A sedimentary section up to 15 km thick comprises several working petroleum systems. Multiphase structural development created various trapping configurations and numerous reservoir–seal pairs. There are several mature source rocks including the world-class Domanik bituminous shale in the area. The past exploration efforts fell short of delivering the expected volumes of oil and gas reserves. This was mainly due to an underestimation of the technical difficulties related to exploration in the complex tectonic settings and an inadequate understanding of the petroleum system development. They were in unfavourable conditions for the presence of a reservoir and hydrocarbon retention. A revision of the tectonostratigraphic framework of the Kosyu–Rogov CTSE shows new high-impact exploration opportunities. The large petroleum potential of the area was confirmed by the discovery of the Nertseta oilfield, the largest oil find in Russia, in 2016.

Dual-plane multiple-trapping by tightly focused petal-like circular Airy beam in an aqueous medium

Superposition of two circular Airy vortex beams (CAVB), with opposite sign topological charges (l), produces a new type of petal beam called petal-like circular Airy beam (PCAB) with a transverse field distribution in the form of azimuthally modulated concentric rings that follow Airy function over the radial distance on a transverse plane. In this paper, tight focusing of a truncated PCAB and its application in optical trapping is numerically investigated. It is shown that by adjusting the topological charge, l, and the aperture radius of the focusing objective lens, R, four different trapping configurations can be achieved: a single transverse trap at a single axial position, a multi-trap geometry at a single axial position, two single transverse traps at two positions along the axial direction, and two multi-trap geometries at two different axial positions. It is also shown that the number of trapped particles in the multi-trap configurations is 2l per focal plane, while the number of axial trap positions is determined by the truncation aperture size, R. Moreover, trap stiffnesses and corresponding potential energies for the trapping configurations are presented and discussed. Finally, for a special case of large R and l, it is shown that the focused beam may both guide and traps the particles.

Total-Ionizing-Dose Response of Highly Scaled Gate-All-Around Si Nanowire CMOS Transistors

Gate-all-around (GAA) silicon nanowire (NW) CMOS transistors demonstrate outstanding total-ionizing-dose (TID) tolerance due to the ultrascaled gate dielectric thickness, enhanced electrostatic gate control, and suppression of parasitic leakage current paths. nFETs and pFETs show similar TID responses, making the GAA NW technology an excellent candidate for CMOS IC applications in high-radiation environments. The slight degradation of the threshold voltage suggests limited charge buildup in the gate dielectrics. However, low-frequency noise and random telegraph noise measurements show the importance of change in trap configurations in both the near-interfacial SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> dielectric layers to the radiation response and reliability of GAA NW devices. These traps are most likely due to oxygen vacancies and/or hydrogen complexes.

Fully-structured counter-propagating optical trap sculpted by spherical aberration

Aberrations of light are commonly known as undesired effects in different applications, including optical trapping. However, here we demonstrate how to take advantage of controlled spherical aberration in order to shape extended optical trapping landscapes, fully-structured in three-dimensional (3D) space and embedding transverse as well as longitudinal electric field contributions. We numerically analyze the light field customization by the simple means of including glass plates in a counter-propagating trapping configuration, presenting sculpted intensity as well as 3D polarization ellipse structures. Experimentally, we prove the realized counter-propagating optical structure by particle velocimetry as well as the analysis of scattered light of optically guided micro-particles. Finally, we demonstrate the potential of our approach by creating extended 3D particle assemblies.

Grid-Assisted Co-Sputtering Method: Background, Advancement, and Prospect

In this paper, the incorporation of auxiliary grids/electrodes into the design of the sputtering method is scrutinized by studying the impact of factors such as grid size, grid position, grid bias voltage, electrode sheath design, substrate bias voltage, reactive gas partial pressure, and magnetic trap configuration on the discharge condition and thin-film growth. In this regard, utilizing the updated Berg model for reactive sputtering, the authors obtained a formulation for the reactive grid-assisted sputtering. By the newly-developed formulation, the sputtering rate and the reactive gas partial pressure were simulated as a function of the reactive gas flow rate for various grid-to-target distances, argon partial pressures (0.67, 1.6, and 3.6 Pa), and discharge current densities (0.01, 0.015, and 0.02 A/cm2). According to the computation results, with a grid being utilized, the width of the hysteresis loops can be modified in a broader range by changing either the grid-to-target distance, the argon partial pressure, or the discharge current, resulting in better control over the deposition process. Moreover, the novel configuration of anode-spot-assisted sputtering was proposed to significantly ionize sputtered/neutral atoms near the substrate and to simultaneously deposit sputtered species and products produced as the direct result of introducing dust into the dense plasma. Finally, diverse configurations of the grid-assisted co-sputtering method were introduced for two prime purposes: deposition of composite films in any desired ratios of constituents without significantly changing the other co-sputtering parameters, and favorable alternation of a hysteresis loop for one of the guns at shared gas flow rates.

Dynamic multiple nanoparticle trapping using metamaterial plasmonic tweezers

Optical manipulation has attracted remarkable interest owing to its versatile and noninvasive nature. However, conventional optical trapping remains inefficient in the nanoscopic world. The emergence of plasmonics in recent years has brought a revolutionary change in overcoming limitations due to diffraction and the requirements for high trapping laser powers. Among the near-field optical trapping cavity-based systems, Fano-resonant optical tweezers have a robust trapping capability. In this work, we experimentally demonstrate sequential trapping of 20 nm particles through the use of metamaterial plasmonic optical tweezers. We investigate the multiple trapping via trap stiffness measurements for various trapping configurations at low and high incident laser intensities. Our plasmonic configuration could be used as a light-driven nanoscale sorting device under low laser excitation. Our results provide an alternative approach to trap multiple nanoparticles at distinct hotspots, enabling ways to control mass transport on the nanoscale.

Research Spotlights

The first of our two Research Spotlights articles in this issue gives a general framework and corresponding algorithm for computing accurate approximations to the spectral measures of self-adjoint operators, the key to which is the resolvent of the operator. As authors Matthew Colbrook, Andrew Horning, and Alex Townsend detail, the spectral measure is necessary in their applications of interest to give a more complete description of the operator and associated dynamics. Their article, “Computing Spectral Measures of Self-Adjoint Operators," begins with the formal mathematical description of the spectral measure and associated assumptions. Several applications that rely on the computation of spectral measure are highlighted throughout the article: for example, applications in particle and condensed matter physics are discussed in the context of a survey of previous work in estimation of spectral measure. The crux of the proposed approach, first formulated in section 4 and generalized to higher order kernels for improved accuracy in section 5, is to evaluate a smoothed approximation (i.e., defined through convolution with appropriate kernel) to the spectral measure by evaluating the resolvent, with the latter calculation akin to solving shifted systems of linear equations. The authors detail carefully and demonstrate graphically the challenges associated with designing a tractable and robust scheme. The discussion of algorithmic issues in section 6, including the ability of their approach to dynamically adjust to reach desired accuracy, also features use cases of their associated publicly available MATLAB code. Within the body of the article, the versatility of their proposed framework is well illustrated on differential, integral, and lattice operators. Readers may be interested in the suggestions in section 8 on possible further use cases for the new framework, such as in “understanding the behavior of large real-world networks and new random graph models." Our second article, “Optimization of the Mean First Passage Time in Near-Disk and Elliptical Domains in 2-D with Small Absorbing Traps," is coauthored by Sarafa A. Iyaniwura, Tony Wong, Colin B. Macdonald, and Michael J. Ward. Narrow escape or capture problems are those portrayed in the introduction as first passage time problems that describe the expected time for a Brownian particle to reach some absorbing set with small measure. Two of the applications in which such problems arise include the time it takes for a diffusing surface-bound molecule (the “particle” in this case) to reach a localized signaling region on the cell membrane and the time it takes for a predator to locate its prey. The authors define the “average MFPT" for a diffusion process to be the expected time for capture given a uniform distribution of starting points for the random walk. The optimal trap configurations for the average MFPT in geometries other than the disk had been unsolved and provided the impetus for the authors to investigate the question in the context of near-disk and elliptical domains. Through a combination of asymptotic analysis and numerical techniques (e.g., use of numerical quadrature and numerical time stepping for solving equations (3.4) and (4.3)), the authors design “hybrid asymptotic numerical" approaches to predicting optimal configurations of small stationary circular absorbing traps that minimize the average MFPT in these new domains. Though much of the paper is devoted to detailed derivations that will take some time for the reader to absorb, one can get some immediate appreciation for the results from the graphical illustrations in which the new results are compared against numerical PDE generated solutions. Extensions of the approach and remaining open problems are included in the last section for consideration by the reader.

Breakup of rotating asymmetric quartic-quadratic trapped condensates

The threshold conditions for a rotating pancake-like asymmetric quartic-quadratic confined condensate to break in two localized fragments, as well as to produce giant vortex at the center within the vortex-pattern distributions, are investigated within the Thomas-Fermi (TF) approximation and exact numerical solution of the corresponding Gross-Pitaevskii (GP) formalism. By comparing the TF predictions with exact GP solutions, in our investigation with two different quartic-quadratic trap geometries, of particular relevance is to observe that the TF approach is not only very useful to display the averaged density distribution, but also quite realistic in establishing the critical rotational conditions for the breakup occurrence and possible giant-vortex formation. It provides almost exact results to define the contour of the condensate distribution, even for high rotating system, after the system split in two (still confined) clouds. The applicability of the Feynman rule to the vortex distribution (full-numerical GP solutions) is also being confirmed for these non-homogeneous asymmetric trap configurations. This study is expected to be relevant for manipulating the rotation and trap parameters in addition to Feshbach resonance techniques. It can also be helpful to define initial conditions for any further studies on dynamical evolution of vortex pattern distributions.

The Neuquén Super Basin

With more than 6000 m of sedimentary thickness and several superimposed petroleum systems, the Neuquen Basin of Argentina has all the elements to be considered a super basin. The basin developed during the Triassic–Early Jurassic in a rift environment that generated a localized petroleum system. Continued subsidence during the Early Jurassic resulted in the first marine ingression (Los Molles Formation, total organic carbon [TOC] 1%–7%). This unit matured 120 to 55 m.y.a., before the formation of major structures, with the exception of the Huincul high. A fast marine flooding in a retroarc setting occurred during the latest Jurassic–Early Cretaceous. At its base lies the Vaca Muerta Formation, a 50- to 1000-m-thick world-class source rock, composed by calcareous shales and marls (TOC 2%–9%). This unit reached maturity at 95 Ma, when the only traps available were structures along the Huincul high or stratigraphic. A new marine ingression occurred during the Early Cretaceous, depositing bituminous shales and marls (Agrio Formation, TOC 2%–5%) that matured during the Paleogene. These superimposed petroleum systems, combined with different structural settings, gave rise to numerous plays and trapping configurations that resulted in the discovery of 14 billion BOE. In addition, the unconventional potential of the Vaca Muerta is now being developed, with estimated resources of 91.5 TCF and 14.3 billion bbl of oil. The Neuquen Basin has gone through three main phases of development: conventional, tight, and unconventional. After a century of production, the basin still shows a wide variety of opportunities for both conventional and world-class unconventional plays.

Monolithic bowtie cavity traps for ultracold gases

We report on trapping and cooling 6 L i atoms in a monolithic ring bowtie cavity. To make the cavity insensitive to magnetic fields used to tune atomic interactions, we constructed it entirely from fused silica and Zerodur. The components were assembled using hydroxide bonding, which we show can be compatible with ultra-high vacuum. Backscattering in high-finesse ring cavities readily causes trap intensity fluctuations and heating, but with phase-controlled bi-directional pumping, the trap lifetime can be made long enough for quantum gas experiments in both the crossed-beam trap (unidirectional pump) and 2D lattice trap (bidirectional pump) configurations.

Benchmarking and validation of a combined CFD-optics solver for micro-scale problems

In this work, we present a new approach for coupled CFD-optics problems that consists of a combination of a finite element method (FEM) based flow solver with a ray tracing based tool for optic forces that are induced by a laser. We combined the open-source computational fluid dynamics (CFD) package FEATFLOW with the ray tracing software of the LAT-RUB to simulate optical trap configurations. We benchmark and analyze the solver first based on a configuration with a single spherical particle that is subjected to the laser forces of an optical trap. The setup is based on an experiment that is then compared to the results of our combined CFD-optics solver. As an extension of the standard procedure, we present a method with a time-stepping scheme that contains a macro step approach. The results show that this macro time-stepping scheme provides a significant acceleration while still maintaining good accuracy. A second configuration is analyzed that involves non-spherical geometries such as micro rotors. We proceed to compare simulation results of the final angular velocity of the micro rotor with experimental measurements.

Electromagnetic surface waves supported by a resistive metasurface-covered metamaterial structure

This study examines the analytical and numerical solution of electromagnetic surface waves supported by a resistive metasurface-covered grounded metamaterial structure. To simulate the metamaterial, the Kramers–Kronig relation based on the causality principle is used, while the modeling of the resistive metasurface has been done by implementing the impedance boundary conditions. The analytical expressions for the field phasors of surface waves are developed for the transverse magnetic (TM) polarized mode and transverse electric (TE) polarized mode. The characteristic equations are computed for both modes, and the unknown propagation constant is evaluated numerically in the kernel. After computation, the dispersion curves, electric field profiles, effective mode index (N_{eff}), and phase speeds (v_{p}) are presented for both the TM and TE polarized modes. To study the tunability of surface waves, the influence of the thickness of the metamaterial slab (d), effective permittivity of the metamaterial (varepsilon_{1}), thickness of the resistive metasurface (t), and effective permittivity of the metasurface (varepsilon_{r}) on all the numerical results has been studied. However, the geometrical parameters are found to be more sensitive to the effective mode index (N_{eff}) and phase speed (v_{p}) of the surface waves. The results are consistent with the published results, which reflects the accuracy of the work. It is concluded that the appropriate choice of parameters can be used to achieve surface waves with the desired characteristics in the GHz range. The present work may have potential applications in surface waveguide design, surface wave speed controllers, surface communication devices, and light trapping configurations.

Dynamics and management of siltation in a macro-tidal marina: The case of La rochelle marina, France

La Rochelle marina, in the south-west of France, is one of the largest recreational port in Europe. As many ports around the world, La Rochelle marina is not spared by siltation and has to face serious dredging operations over a period of 8 months per year. Consequently, there is a big interest in determining sediment fluxes in the area and implementing measures to minimise siltation and/or to optimise dredging operations. In the present study, a three-dimensional hydro-sedimentary model (TELEMAC-3D) was calibrated with field measurements from 2014 to 2019. Analysis of the in situ measurements (turbidity, bathymetric surveys, seabed elevation) showed that the macro-tidal influence and local wind-wave regime significantly contributed to the siltation in the marina. In order to minimise the cost and time associated with maintenance dredging, multiple scenarios have been tested numerically and subsequently analysed. Numerous sediment trap configurations were defined to focus the deposition of sediment in dredged traps and constructional measures were also assessed in terms of siltation reduction (e.g. entrance closure, narrowing entrances, Current-Deflecting-Wall). Numerical simulations showed that the best solution is to create a sediment trap at the downstream corner of the marina, along the main navigation channel, to intercept sediment particles arriving from the ocean. The constructional measures as well as the use of sediment traps inside the marina are not efficient in reducing siltation. These results highlight the importance of using operational numerical model to define a more sustainable strategy to fight against siltation in a more efficient and less costly way.

Thermometry in a Multipole Ion Trap

We present a characterization of the ions’ translational energy distribution in a multipole ion trap. A linear mapping between the energy distribution of the trapped ions onto the ions’ time-of-flight (TOF) to a detector is demonstrated. For low ion temperatures, a deviation from linearity is observed and can be attributed to the emergence of multiple potential minima. The potential landscape of the trapped ions is modeled via the finite element method, also accounting for subtleties such as surface-charge accumulation. We demonstrate the validity of our thermometry method by simulating the energy distribution of the ion ensemble thermalized with buffer gas using a Molecular Dynamics (MD) simulation. A comparison between the energy distribution of trapped ions in different multipole trap configurations—i.e., with hyperbolic rods, cylindrical rods, and cylindrical wires—is provided. With these findings, one can map the temperature of the trapped ions down to the Kelvin regime using their TOF distributions. This enables future studies on sympathetic cooling and chemical reactions involving ions in multipole traps.

Tune-Out and Magic Wavelengths for Ground-State ^{23}Na^{40}K Molecules.

We demonstrate a versatile, state-dependent trapping scheme for the ground and first excited rotational states of ^{23}Na^{40}K molecules. Close to the rotational manifold of a narrow electronic transition, we determine tune-out frequencies where the polarizability of one state vanishes while the other remains finite, and a magic frequency where both states experience equal polarizability. The proximity of these frequencies of only 10GHz allows for dynamic switching between different trap configurations in a single experiment, while still maintaining sufficiently low scattering rates.

Anisotropic expansions of a strongly interacting Fermi superfluid containing a vortex

We present a study of static and expansion properties of strongly interacting Fermi superfluids containing a vortex initially trapped by cylindrically symmetric potentials. Based on the order-parameter equation in the framework of the Gross–Pitaevskii equation, a unified expression for the energy of a vortex line in the crossover from a Bardeen–Cooper–Schrieffer superfluid to a molecular Bose–Einstein condensate is analytically presented. Numerical simulations show that the combined effects of interactions and trap configurations lead to an interesting property that the free expansion rate of the vortex core radius is smaller than that of the radius of the superfluid in the radial direction, when the strongly interacting Fermi superfluid containing a vortex is released from a cigar-shaped trap. The effects of the trap anisotropy and vortex on the Efimovian expansions of a unitary Fermi superfluid in real experimental setups are also predicted.