Conical Aperture Research Articles

Experimental Assessments on a Pressure Swirl Oil Atomizer for Positive Displacement Vane Compressors

The current work presents an experimental characterization of a pressure swirl nozzle that is used to spray the lubricant in positive displacement vane compressors such that the overall convective heat transfer between oil droplets and air is able to lower the specific energy consumption of the machine, bringing the closed volume compression phase towards an isothermal transformation. An experimental test bench was designed and built to reproduce the compressor operating conditions. Tests at different injection pressures and temperatures allowed to estimate some macroscopic features of the spray, namely break-up length and cone spray angle. In particular, measurements showed that while break-up length decreased at high pressure and temperature up to 3.1mm at 65°C and 10 barg, the cone aperture tended to diverge from the nominal value of 80° up to 106°. Furthermore, measurements with a laser diffractometric particle size analyzer allowed to retrieve the droplet size distribution and to estimate a key parameter for the heat transfer capabilities of the spray, namely the Sauter Mean Diameter (SMD). At 55°C and 9 barg the droplet size distribution fitted a Rosin Rammler function with shape parameter of 1.87 and scale parameter of 228μm while the spray SMD was 122μm. In these operating conditions, a series of nozzles equally distributed along the closed volume compression phase of a mid-size industrial vane compressor would lead to specific power savings up to 0.3kW/(m3/min), that corresponds to 20-25% of the saving potential achievable considering an isothermal compression. This methodology will allow to calibrate a simulation platform of the sprayed injection technique such that further refinements of the energy saving strategy will be addressed.

Optimization of n_TOF-EAR2 using FLUKA

In 2014 a new vertical flight path was installed at the neutron time-of-flight facility, n_TOF, at CERN. The beam line optimization of this second experimental area (EAR2) was performed by FLUKA simulations with a detailed model of the facility, including the spallation target, neutron beam line, magnet, collimators and beam dump. The beam profile as well as neutron and gamma fluxes were calculated at the measurement position, 150 cm from the exit of the second collimator. The design of the collimator system was optimized taking into account the shape of the beam, the neutron flux and the background. The effect of the background of each studied configuration was evaluated from the response of a C6D6 detector at the measurement position. The design of the beam dump was modified according to each configuration to reduce the backscattered radiation. Among the studied configurations, a final collimator with a conical closing aperture was found to be the best compromise between a high flux and low background at the experimental station. By scoring the neutron flux at the measurement position and taking the air and windows at the nominal sample position into account, the neutron beam has a radius of 2.5 cm and the outside background is three orders of magnitude lower than the maximum flux. The ratio between background and maximum flux is similar to that in the first experimental area (EAR1), but the maximum flux in EAR2 is 30 to 50 times higher than in EAR1 for neutron energies between 100 eV and 30 keV, respectively.

Protection of extreme ultraviolet lithography masks. II. Showerhead flow mitigation of nanoscale particulate contamination

An analysis is presented of a method to protect the reticle (mask) in an extreme ultraviolet (EUV) mask inspection tool using a showerhead plenum to provide a continuous flow of clean gas over the surface of a reticle. The reticle is suspended in an inverted fashion (face down) within a stage/holder that moves back and forth over the showerhead plenum as the reticle is inspected. It is essential that no particles of 10-nm diameter or larger be deposited on the reticle during inspection. Particles can originate from multiple sources in the system, and mask protection from each source is explicitly analyzed. The showerhead plate has an internal plenum with a solid conical wall isolating the aperture. The upper and lower surfaces of the plate are thin flat sheets of porous-metal material. These porous sheets form the top and bottom showerheads that supply the region between the showerhead plate and the reticle and the region between the conical aperture and the Optics Zone box with continuous flows of clean gas. The model studies show that the top showerhead provides robust reticle protection from particles of 10-nm diameter or larger originating from the Reticle Zone and from plenum surfaces contaminated by exposure to the Reticle Zone. Protection is achieved with negligible effect on EUV transmission. The bottom showerhead efficiently protects the reticle from nanoscale particles originating from the Optics Zone. With similar mass flow rates from the two showerheads, this system provides efficient protection even when a significant overpressure exists between the Optics Zone and the Reticle Zone. Performance is insensitive to the fraction of incident particles that sticks to walls, the accommodation coefficient, the aperture geometry, and the gas pressure. The showerheads also protect the aperture (and therefore the Optics Zone) during mask loading and unloading. Commercially available porous-metal media have properties suitable for these showerheads at the required flow rates. The benefits of the approach compared to a conceptual EUV pellicle are described.

Cylindrically polarized Bessel–Gauss beams

We present a study of radially and azimuthally polarized Bessel–Gauss (BG) beams in both the paraxial and nonparaxial regime. We discuss the validity of the paraxial approximation and the form of the nonparaxial corrections for BG beams. We show that independently on the ratio between the Bessel aperture cone angle and the Gaussian beam divergence , the nonparaxial corrections are alway very small and therefore negligible. The explicit expressions for the nonparaxial vector electric field components are also reported.

Ion optics of probe-forming systems on the base of magnetic quadrupole lenses with conical aperture

This paper describes the performance of probe-forming systems based on a new type of magnetic quadrupole lens with a conical aperture (MQL CA). The main difference in the MQL CA from the conventional quadrupole lens with a cylindrical aperture is that the poles in it are not parallel to the lens axis and positioned at a certain angle. The basic advantage of such a lens is that the conical angle of the aperture allows the profile of the longitudinal distribution of the main components of the quadrupole field to be changed. It provides for the changing of the focal length value, displacement of the principal plane relative to the centre of the lens and aberration variations depending on the conical angle. A theoretical study of the ion optics of the probe-forming systems consisting of a triplet MQLs CA was carried out. A comparison of the systems with MQLs CA and conventional systems based on the magnetic quadrupole lens (MQL) with a cylindrical aperture shows the possibility of increasing the acceptance of the first due to using the new type of lens.

Locally resolved stress and strain analysis of sinter-joined micro valves using synchrotron X-ray diffraction and conical slit apertures

For assessing the quality of the joining area as well as researching the influence of joining parameters in combination with different materials, the principal stress components of sinter-joined micro valves were analysed. Transmission experiments have been conducted at the high-energy material science (HEMS) beamline P07 at PETRA III, DESY. Due to the dimensions of the samples, a high spatial resolution of the measurements was required. Of special interest was the distribution of residual stress in the joining area of the valves, which demanded a depth resolved measurement using a conical slit. Strains were deduced from the obtained Debye---Scherrer rings of the {200}, {211}, and {220}-planes of the ?/??-phase involving reference measurements on non-sintered powder of the specimen materials. The grain statistics have been improved by integrating over slices of the diffraction rings and by calculating a mean lattice parameter taking into account all lattice planes. From the strain data, the hydrostatic and the deviatoric stress were calculated for the three dimensional stress state.

Magnetic Neumann Laplacian on a sharp cone

This paper is devoted to the spectral analysis of the Laplacian with constant magnetic field on a cone of aperture $$\alpha $$ and Neumann boundary condition. We analyze the influence of the orientation of the magnetic field. In particular, for any orientation of the magnetic field, we prove the existence of discrete spectrum below the essential spectrum in the limit $$\alpha \rightarrow 0$$ and establish a full asymptotic expansion for the $$n$$ -th eigenvalue and the $$n$$ -th eigenfunction.

Mechanisms and shape predictions of nematic disclination branching under conical confinement

Liquid crystals (LCs) are self-organizing anisotropic viscoelastic soft materials that flow like viscous liquids and display anisotropies like crystals. When a nematic liquid crystal is confined to a capillary tube with strong anchoring conditions, disclination defects of higher (+1) and lower (+1/2) topological charges can coexist, connected through a defect branch point. The shape of the +1/2 disclination lines emanating from the branch point are functions of confinement and bulk elasticity. Previous work shows that nematic liquid crystals under cylindrical confinement display a radial (one +1 line)-to-planar polar (two +1/2 lines) defect texture transition through the nucleation and uniform motion of a disclination branch point. Here we present analysis, scaling and modeling based on a non-linear non-local nematic elastic equation that shows that a branch point also can be generated from disclinations in a liquid crystal confined to different conical geometries with homeotropic anchoring conditions. The cone aperture increases the bending stiffness but decreases the curvature of the disclination. These competing effects lead to a decrease in the total disclination curvature, increase in elastic energy and volume of the branching region. The results are summarized into power laws and integrated into a shape/energy diagram that reveals the effects of confinement and its gradient (cone angle) on disclination shape selection. These new findings are useful to assess the Frank elasticity of new nematic liquid crystals and to predict novel defect structures in complex confinement, including biological microfluidics and mesophase fiber spinning.

The active area shadow-shielding effect on detection efficiency of collimated broad energy germanium detectors

The ISOCS calibration, when utilized for a BEGe detector with a small angled collimator, produces inaccuracies of about 19% for gamma rays with energies greater than 0.4MeV. Such a discrepancy is caused by the collimator algorithms currently utilized in the ISOCS software which, originally developed for HPGe detectors, are less suited for BEGe detectors. ISOCS's errors are due to the different crystal configurations of broad energy detectors compared to coaxial detectors, i.e. to a different importance of the active area portion obscured by the collimator. This work proposes some solutions for the problem, either using the ISOCS software or implementing a stochastic calibration procedure. In particular, the present work considers a virtual collimator that, maintaining its angular aperture, is capable of continuously enlarging its bottom collimator's aperture cone radius, to expose growing active area portions. In such a way two goals may be achieved: the mathematical characterization of ISOCS’ errors and the minimization of observed errors by means of the stochastic calibration procedure.Different reference set-ups are considered in order to test source geometry effects, source materials and different detectors. In particular, a 220L drum, a 2m3 box filled with uniformly contaminated cellulose or PVC, and small BE3825 and large BE5030 Canberra detectors are considered. Detection efficiencies calculated by ISOCS software are compared against a completely stochastic MCNPX simulation procedure, that is unaffected by any algorithmic correction. MCNPX simulations demonstrate, when widening collimators’ cone but maintaining the angular aperture unchanged, that ISOCS and MCNPX difference percentage between efficiency data points reduces, depending on energy, by more than 50%. This happens as far as the shadow-shielded portion of detector's active area reduces.

Peak power in the 3D magnetic Schrödinger equation

This paper is devoted to the spectral analysis of the magnetic Neumann Laplacian on an infinite cone of aperture α. When the magnetic field is constant and parallel to the revolution axis and when the aperture goes to zero, we prove that the first n eigenvalues exist and admit asymptotic expansions in powers of α2.

Conical Horn: Gain and Amplitude Patterns

The conical horn radiation characteristics (gain, aperture phase distributions, loss factors, and amplitude patterns) are revisited based on the spherical and quadratic aperture phase distributions. Calculations of the conical horn gain, using over the aperture either the dominant -mode of a circular waveguide or the modal variations of a conical waveguide, are calculated using the aperture phase distribution represented by spherical and quadratic wavefronts. The gains are compared with the classical data by Gray and Schelkunoff, in an attempt to confirm their validity and accuracy and to determine whether they were derived based on spherical or quadratic phase distribution. In addition, more accurate loss factors, to account for amplitude and phase tapering over the conical horn aperture, are derived which improve the conical horn gain. New formulas for the design of optimum gain conical horns, based on the more accurate spherical aperture phase distribution, are derived and reported, and guidelines are provided for their utility. This paper also introduces a method to calculate accurately the far-zone amplitude patterns in the E and H planes, including those in the far side and back lobe regions, of a conical horn by utilizing geometrical optics and diffraction theory.

Matrix Assisted Ionization Vacuum (MAIV), a New Ionization Method for Biological Materials Analysis Using Mass Spectrometry

The introduction of electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) for the mass spectrometric analysis of peptides and proteins had a dramatic impact on biological science. We now report that a wide variety of compounds, including peptides, proteins, and protein complexes, are transported directly from a solid-state small molecule matrix to gas-phase ions when placed into the vacuum of a mass spectrometer without the use of high voltage, a laser, or added heat. This ionization process produces ions having charge states similar to ESI, making the method applicable for high performance mass spectrometers designed for atmospheric pressure ionization. We demonstrate highly sensitive ionization using intermediate pressure MALDI and modified ESI sources. This matrix and vacuum assisted soft ionization method is suitable for the direct surface analysis of biological materials, including tissue, via mass spectrometry.

Dipole Decay Rates Engineering via Silver Nanocones

A full control of the interaction between confined plasmons and point sources of radiation is a central issue in molecular plasmonics. In this paper, a theoretical contribution towards a physical understanding on the localized surface plasmons excited into metallic nanocones by a point dipole is given. A numerical approach based on the discrete dipole approximation is applied to determine the modifications of the dipole decay rates for varying geometrical parameters of the dipole-metal nanoparticle system. Results declare the centrality of the cone aperture to control the plasmon resonances and to handle the effects it induces on the lifetime of a point emitter. A full spectral tuning of the resonances in the decay rates can be achieved by operating on a unique spatial degree of freedom: by tailoring the aperture alone, total decay rates 105 times higher than the free-space value can be obtained at short distances from the metal in a large region of the spectral range. Quite unexpectedly, size dependence of the antenna is found to have a marginal role if only a lifetime manipulation is desired. It becomes, instead, a crucial aspect of the problem when large quantum yields are required. Results presented in this work shed light on spontaneous emission modification due to interaction with plasmonic nanocones of different shapes and are relevant for a number of applications in the fields of nanoplasmonics and fluorescence microscopy.

Optimization of Microphone Array Wall Mountings in Closed-Section Wind Tunnels

The objective of the present paper is to improve the implementation of microphone arrays on the wall of closed-section wind tunnels. A test campaign has been conducted in the ONERA F2 1.4 m × 1.8 m wind tunnel to investigate the performance of thin and smooth metallic clothes to protect the microphones from the hydrodynamic fluctuations in the turbulent boundary-layer flow and, still, to preserve the transmitted acoustic signal. Three microphone mountings have been considered : individually recessed microphones in (i) cylindrical and (ii) conical apertures and (iii) a recessed, screened, large-scale microphone mounting plate (microphones flush with the plate). It was found that by covering the top of the cylindrical and conical microphone apertures with a wire-mesh, the strong self-noise due to the interaction of the boundary-layer flow with the cavities can be suppressed. The most significant noise reduction is obtained when the large-scale microphone mounting plate is recessed behind the metallic wire-mesh. A reduction by up to 20 dB is then obtained with respect to a flush-mounted, unscreened, microphone. This microphone mounting out-performs the cone-nose-protected and Kevlar-protected microphone mountings, two conventional low-noise devices. Thanks to an original calibration technique, the acoustic response of the tested microphone mountings could be evaluated in presence of flow (� 80 m/s). The recessed, screened, microphone mounting plate has an oscillating acoustic response (in function of the frequency) by less than 5 dB deviation. This attenuation can be post-corrected by using a very simple acoustic model.

An opposed-anvil-type apparatus with an optical window and a wide-angle aperture for neutron diffraction

We designed new anvil assemblies for acquiring high-quality neutron diffraction data and ruby fluorescence spectra inside a sample chamber. The conical aperture of Ni-binded WC anvils was expanded by a factor of two. A hybrid gasket made of TiZr- and Al-alloy was developed to prevent outward extrusion. A small and optically transparent window of moissanite was introduced to allow for the determination of pressure and hydrostaticity by measurement of ruby fluorescence spectra. High pressure-generation tests that make use of Bi electrical conductivity and ruby pressure markers revealed that pressure could be determined over 10 GPa. In situ synchrotron X-ray diffraction experiments were also carried out using NaCl as the pressure calibrants. The maximum pressure achieved was approximately 13 GPa. The neutron diffraction intensity from the newly generated anvil assemblies was 2.5–3.0 times greater than that using the standard toroidal anvil assemblies used previously.

Geometrically induced electric polarization in conical topological insulators

Topological magnetoelectric and gravitation-like Aharonov-Bohm effects yield electric polarization of conical topological insulators that depends only on the cone aperture angle, δ. Concretely, under the same external conditions, wider (δ > 30°) and narrower (δ < 30°) cones appear to polarize in opposite directions. Observation of such a phenomenon could be faced as a microscopic physical realization of (2 + 1)-dimensional Einstein gravity.

Strong Uniqueness Theorems and the Phragmèn–Lindelöf Principle in Nonhomogeneous Elastostatics

We find sharp uniqueness classes for the contact problem of nonhomogeneous linear elastostatics in exterior domains. Moreover, we prove that a solution of the displacement problem in a cone of aperture φ enjoys the asymptotic properties expressed by the classical Phragmen–Lindelof principle; in particular, uniqueness holds in the class of all functions that are bounded at large distance by r1/cφ for some positive c. Then, by means of a counter–example we observe that the same properties are no longer satisfied by the solutions of the contact problem.

Epsilon-hypercyclic operators on a Hilbert space

For every fixed , we construct a bounded linear operator on the separable Hilbert space having an orbit which intersects every cone of aperture , but such that every orbit avoids a certain ball of positive radius (which depends on the orbit) and a fixed centre.

Increased light gathering capacity of sub-wavelength conical metallic apertures

We study light transmission through individual and arrays of sub-wavelength metallic apertures of conical shape as a function of their taper angle. With a fixed aperture size at the substrate, there is a dramatic increase in light throughput with increasing taper angle. Similar behaviors hold when considering the intensity enhancement inside the aperture near the substrate interface, where more than four-fold increase can be obtained. When arranged in regular arrays, apertures can interact via surface waves, creating distinct minima and maxima in light transmission and intensity enhancement. The effect of aperture taper is also to dramatically increase light transmission and intra-aperture intensity, but with a red shift in the maxima and negligible shift in the minima. The use of conical apertures should improve the efficiency of nonlinear optical processes as well as applications of light harvesting, such as biomolecule detection.

GLRT Versus MFLRT for Adaptive CFAR Radar Detection With Conic Uncertainty

In this paper, we consider the problem of detecting an unknown signal, belonging to a conic region, in the presence of complex Gaussian disturbance. We assume that the cone aperture parameter, which ranges in a pre-assigned interval, is unknown. Hence, we devise two decision rules which are respectively based on the Generalized Likelihood Ratio Test (GLRT) and on the Multifamily Likelihood Ratio Test (MFLRT). Both the receivers ensure the Constant False Alarm Rate (CFAR). At the analysis stage, we compare the performance of the two decision strategies in correspondence of different parameters for the useful signal component.