Miniature Atomizer Research Articles

Rapid and Portable Detection of Hg and Cd in Grain Samples Based on Novel Catalytic Pyrolysis Composite Trap Coupled with Miniature Atomic Absorption Spectrometry.

As toxic metals, Hg and Cd are a concern for food safety and human health; their rapid and portable analysis is still a challenge. A portable and rapid Hg-Cd analyzer constructed from a metal-ceramic heater (MCH)-based electrothermal vaporizer (ETV), an on-line catalytic pyrolysis furnace (CPF), a composite Pt/Ni trap, and a homemade miniature atomic absorption spectrometer (AAS) was proposed for grain analysis in this work. To enhance sensitivity, a new folded light path was designed for simultaneous Hg and Cd analysis using charge coupled device (CCD) in AAS. To eliminate the grain matrix interference, a catalytic pyrolysis furnace with aluminum oxide fillers was utilized to couple with a composite Pt/Ni trap. The method limits of detection (LODs) were 1.1 μg/kg and 0.3 μg/kg for Hg and Cd using a 20 mg grain sample, fulfilling the real sample analysis to monitor the grain contamination quickly; linearity R2 > 0.995 was reached only using standard solution calibration, indicating the sample was free of grain matrix interference. The favorable analytical accuracy and precision were validated by analyzing real and certified reference material (CRM) grains with recoveries of 97-103% and 96-111% for Hg and Cd, respectively. The total analysis time was less than 5 min without sample digestion or use of any chemicals, and the instrumental size and power consumption were <14 kg and 270 W, respectively. Compared with other rapid methods, this newly designed Hg-Cd analyzer is proven to be simple, portable, and robust and is, thus, suitable to quickly monitor Hg and Cd contamination in the field to protect grain and food safety.

Design of Uniform Magnetic Field Coil by Quasi-Elliptic Function Fitting Method With Multiple Optimizations in Miniature Atomic Sensors

This article presents a design method of cylindrical uniform field coil based on quasi-elliptic function fitting (EFF) method with multiple optimizations. The EFF method is a type of discrete wire techniques aiming at simplifying the coil structure. Combing with particle swarm optimization (PSO) algorithm, the optimized parameters of EFF coil are obtained for highly uniform magnetic field. To further improve the uniformity of magnetic field in the central space, a new regional points selection optimization method is proposed. The calculation results show that after PSO optimization, the absolute maximum relative error in the target region is optimized to 0.098% by EFF coil comparing with modified single saddle coil (3.08%), nest coil (2.4%), and target field method (TFM) coil (0.11%). After regional points selection optimization, the volume proportion of absolute magnetic field relative error less than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$1\times 10^{-4}$</tex-math></inline-formula> increases from 35.24% to 54.38% by EFF coil comparing with TFM coil. In addition, the simple EFF coil structure is verified to be easy to process and keep high performance through experiments. As the EFF coil’s high uniformity and simple structure, the new method has important significance for the miniaturization of atomic sensors.

Design of Self-Shielded Uniform Magnetic Field Coil via Modified Pigeon-Inspired Optimization in Miniature Atomic Sensors

This article presents a modified pigeon-inspired optimization method for designing self-shielded uniform magnetic field coils that offers an innovation in miniature atomic sensors. The proposed coil system consists of circular coil pairs distributed on two coaxial cylinder surfaces, which can provide a highly uniform magnetic field at the coil center and rapidly attenuate the external field. This design is transformed into a nonlinear objective optimization problem with constraints, so that the coil geometric parameters can be obtained by the proposed algorithm, instead of solving closed-form equations by pure numerical method. Parallel competition and hierarchical search strategy are firstly introduced to accelerate the convergence speed and avoid falling into the local optimal value. Comparative experiments of several algorithms demonstrate the accuracy, effectiveness, convergence stability of the proposed method. Compared with traditional design methods, this method can automatically find the optimal parameters of the coil according to any constraints. Theoretical contrast shows that compared with the Lee-Whiting coil, the uniformity of proposed coil is improved by about 2 to 3 orders of magnitude and has a significant self-shielded effect. This work is beneficial to the miniaturization of atomic sensors.

Self-Shielded Uniform Magnetic Field Coil Design for Miniature Atomic Sensors Using a Particle Swarm Optimization Algorithm

In this paper, an optimization method that uses the derivatives and the target field information of the magnetic field simultaneously is proposed to suppress the coupling between the coil and the magnetic shielding in miniature atomic sensors. The coupling between the coil and the magnetic shielding varies with the material magnetic permeability, which causes the magnetic field to fluctuate with the temperature as the material permeability. The magnetic field fluctuations will cause the measurement errors and drifts of the sensors. The proposed method can effectively suppress the magnetization of the magnetic shielding caused by the coil magnetic field. A shielded coil outside the main coil is used to efficiently attenuate the magnetic field outside the main coil to suppress the coupling between the coil and the magnetic shielding. A coil system consisting of pairs of circular coils distributed on two coaxial cylinder surfaces is proposed in this paper. The Taylor expansion is used to ensure the uniformity of the internal magnetic field, while the target field information is used to ensure the attenuation of the external magnetic field. A particle swarm optimization (PSO) algorithm is used to optimize the parameters of the main and shielded coils. The theoretical calculations and the finite element analysis prove that the proposed approach is an effective design method for the self-shielded coils.

Cascaded collimator for atomic beams traveling in planar silicon devices

Micro- and increasingly, nano-fabrication have enabled the miniaturization of atomic devices, from vapor cells to atom chips for Bose-Einstein condensation. Here we present microfabricated planar devices for thermal atomic beams. Etched microchannels were used to create highly collimated, continuous rubidium atom beams traveling parallel to a silicon wafer surface. Precise, lithographic definition of the guiding channels allowed for shaping and tailoring the velocity distributions in ways not possible using conventional machining. Multiple miniature beams with individually prescribed geometries were created, including collimated, focusing and diverging outputs. A “cascaded” collimator was realized with 40 times greater purity than conventional collimators. These localized, miniature atom beam sources can be a valuable resource for a number of quantum technologies, including atom interferometers, clocks, Rydberg atoms, and hybrid atom-nanophotonic systems, as well as enabling controlled studies of atom-surface interactions at the nanometer scale.

Uniform Field Coil Design Based on the Target-Field Method in Miniature Atomic Sensors

This paper presents the design of a uniform field coil based on the target-field method that offers an innovation in miniature atomic sensors. A selected uniform field cubical target region is located inside a cylinder with the surface comprised of coil windings. First, the current density was defined with unknown coefficients, and then a straightforward approach was used to obtain these coefficients via solving a matrix constructed by selecting field points in the target region. Subsequently, using the stream-function, the winding patterns of the coils are generated. Compared to the traditional coil design method, this method effectively solves the inconsistency between the uniform field areas and the sensor structures, by predefining the size of the coil surface before calculating the current distribution. It also avoids the cumbersome calculation process caused by the multi-order Taylor expansion based on the traditional method. Furthermore, a current density formula was expanded by trigonometric series that is particularly suitable for a cylindrical coil system with a uniform internal field. The theoretical accuracy can be greatly improved by choosing an optimal order of the trigonometric series. To prove its performance, a contrast with a Lee-Whiting coil is proposed. In addition, the utilized coil was manufactured by flexible printed circuit technology and magnetic field uniformities were verified by an actual test using a fluxgate magnetometer.

An Improved Target-Field Method for the Design of Uniform Magnetic Field Coils in Miniature Atomic Sensors

An improved target field method is proposed for the cylindrical coil design to meet the constraint of limited coil volume. It realizes the design of uniform magnetic field coil by predetermining the coil configuration and optimizing the coordinate positions of the target field points. Compared with conventional methods, this current density distribution is divided into two symmetric subregions to solve the problem of reserving a gap in the coil center for setting the light-passing holes. Therefore, this method is more applicable in the miniature atomic devices with optical paths. Moreover, the overall coil performance can be significantly improved using the optimized configuration of coil design parameters. The numerical evaluation shows that the coil designed by this method has remarkable advantages over the nested saddle coil, whose uniformity performance can be improved by about one order of magnitude. The measurements show that the relative magnetic field uniformities of the proposed coils reach $4\times 10^{-4}$ and $3\times 10^{-4}$ along the z-axis in the range of $\pm 0.24~R$ . The measurement results match well with the theoretical simulation.

Operation Study of Miniature Air-blast Atomizer under Very Low Liquid Pressures

Abstract Miniature air blast atomizers are intended for use in small jet engines. The typical miniature atomizer with rotating air outside the pressure swirl nozzle was investigated by theoretically and experimentally. The equations which describe the flow of rotating hollow liquid jet in a gaseous environment, where there is difference between outer and inner pressures of the liquid film were developed. The effects of surface tension, gravity forces, and inner-outer pressure difference on liquid film modes and its disintegration were considered. A set of the relevant equations was solved numerically. The initial conditions for the equations: pressure distribution inside and outside of the ‘onion’ as function of outer rotating air and liquid parameters, were obtained experimentally. The numerical results were verified by the experimental study. It was shown that exists two shapes of liquid film nearby nozzle exit – ‘onion’ and open film. Shape of the liquid film for the given nozzle pressure drop depends mainly on air pressure difference outside and inside the film. Two resulting spray modes are distinguished in droplet characteristics drastically. The results can be applied for estimation of the operational parameters of air-blast atomizers that operate with very low liquid pressure drop.

Thermal Characterization of an LTCC Module for Miniature Atomic Clock Packaging

This paper presents the design and thermal characterization of a 15 × 22 mm2 LTCC module dedicated to the packaging of the elements of a miniature atomic clock. This module acts as a carrier for the components of the clock as well as temperature controller; this is particularly attractive since each component of the atomic clock requires precise and well defined working temperatures. For the thermal characterization of the designed module, various thermal simulations have been performed, by finite-element modelling using the software ANSYS; in each simulation a different experimental heating configuration was hypothesized, in order to determine the power required for achieving the desired temperature in the ideal case (module in perfect vacuum with no losses rather than conduction towards the external “cold” zone, through two small bridges) , and also for estimating the thermal losses that convection introduces into the system. The simulations were then experimentally validated by realizing and characterizing the different configurations, yielding results that were consistent with the simulations. The best experimental configuration was found, in which the heating performance was fairly close to the ideal one. The results show that LTCC is a very attractive technology for atomic clock packaging also in terms of dissipated power, provided the system is efficiently insulated.

Atom interferometry on a chip

Atom-waves interferometers are becoming ever more compact. A new way of coherently splitting atom waves, based on radiofrequency fields, could extend the capabilities of these miniature atom traps.

New on-source miniature atomic FAB and alkali ion SIMS sources

Miniature atom and ion sources have been developed which mount directly onto the mass spectrometer ion source, within the vacuum chamber. The new sources are inexpensive to construct and require no external mounting flange. The use of an ion versus atom beam has been found to be unimportant, although the particle mass and impact energy have important effects on the intensity of quasimolecular ions, apparently due to the deposited momentum. A model of ionization of samples suspended in a liquid matrix and bombarded by energetic particles is proposed, in which ionization occurs in the “gas phase” by a charge-cascade mechanism similar to chemical ionization.