Electromagnetic Moments Research Articles

Controlling the spontaneous emission of the telecom O-band centers in Silicon-on-Insulator with coherent dipole-quadrupole interactions on a silicon pillar lattice

The G-center in silicon-on-insulator (SOI) has emerged as a relevant single photon source due to the zero-phonon line at 1278 nm, matching the O-band of optical telecommunication wavelengths. Due to the weak emission of the G-center from planar SOI, it is necessary to enhance its emission, in terms of collection efficiency and fluorescence enhancement, to further study its optical properties for application in quantum technologies. Here we design a fabrication-ready SOI Mie-resonator made of a lattice of silicon nanopillars on silica to achieve the spontaneous emission enhancement of single G-centers. Using Si nanopillars lattice on silica with period and dimensions optimized, owing to the coherent superposition of the electric dipolar and magnetic quadrupolar electromagnetic Mie-scattering moments of the individual pillars to the periodic lattice, we show the G-center emission/decay rate enhancement averaged over it's possible dipole orientations is about 13 times compared to bulk. This corresponds to a fluorescence enhancement of about 125 times compared to bulk and about 5-6 times compared to an optimized single pillar with photon collection with a confocal objective. These results provide a fabrication pathway for out-of-plane single photon collection from the SOI G-center or other telecom O-band single-photon sources for their potential deployment in CMOS-compatible quantum optical technologies.

Observation of γγ→ττ in proton–proton collisions and limits on the anomalous electromagnetic moments of the τ lepton

The production of a pair of τ leptons via photon-photon fusion,γγ→ττ, is observed for the first time in proton-proton collisions, with a significance of 5.3 standard deviations. This observation is based on a data set recorded with the CMS detector at the LHC at a center-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 138 fb-1. Events with a pair of τ leptons produced via photon-photon fusion are selected by requiring them to be back-to-back in the azimuthal direction and to have a minimum number of charged hadrons associated with their production vertex. The τ leptons are reconstructed in their leptonic and hadronic decay modes. The measured fiducial cross section ofγγ→ττisσobsfid=12.4-3.1+3.8fb. Constraints are set on the contributions to the anomalous magnetic moment (aτ) and electric dipole moments (dτ) of the τ lepton originating from potential effects of new physics on theγττvertex:aτ=0.0009-0.0031+0.0032and|dτ|<2.9×10-17ecm(95% confidence level), consistent with the standard model.

All-dielectric meta-surface transmission-mode ultra-thin GaAs negative electron affinity photocathode

Transmission-mode (t-mode) GaAs negative electron affinity photocathodes (NEA-PCs) can be integrated with the optical focusing lenses and microchannel plates to produce high-quality electron beams and high-sensitive detectors. Quantum efficiency (QE) of ∼40% has been reported for the t-mode thick (&amp;gt;1000 nm) GaAs NEA-PCs. Nevertheless, practical applications of these devices have been seriously restricted by their long response time (tens of picoseconds). In this work, the all-dielectric meta-surfaces (ADMS) were designed as the light managers for the t-mode ultra-thin GaAs NEA-PCs. For the 500–850 nm waveband, high light absorption (&amp;gt;80%) can be obtained through coupling the electromagnetic dipole moments of ADMS into the leaky optical modes in 100 nm ultra-thin GaAs NEA-PC layer, which leads to enhanced QE higher than that of the thick ones, the response time less than 5 ps, and the mean transverse energy less than 60 meV, respectively. Given these properties, ADMS t-model ultra-thin NEA-PCs represent a promising photocathode to provide the high-brightness short-pulse spin-polarized electron beams and high-sensitive fast-response detectors for the electron accelerator and low-light-level photodetection applications, respectively.

High voltage determination and stabilization for collinear laser spectroscopy applications.

Fast beam collinear laser spectroscopy is the established method to investigate nuclear ground state properties such as the spin, the electromagnetic moments, and the charge radius of exotic nuclei. These are extracted with high precision from atomic observables, i.e., the hyperfine splitting and the isotope shift, which become possible due to a large reduction of the Doppler broadening by compressing the velocity width of the ion beam through electrostatic acceleration. With the advancement of experimental methods and applied devices, e.g., to measure and stabilize the laser frequency, the acceleration potential became the dominant systematic uncertainty contribution. To overcome this, we present a custom-built high-voltage divider, which was developed and tested at the German metrology institute, and a feedback loop that enabled collinear laser spectroscopy to be performed at a 100-kHz level. Furthermore, we describe the impact of field penetration into the laser-ion interaction region. This affects the determined isotope shifts and hyperfine splittings if Doppler tuning is applied, i.e., the ion beam energy is altered instead of scanning the laser frequency. Using different laser frequencies that were referenced to a frequency comb, the field penetration was extracted laser spectroscopically. This allowed us to define an effective scanning potential to still apply the faster and easier Doppler tuning without introducing systematic deviations.

Dynamic model of magnetic transmission

In the work, a non-contact electromechanical energy converter with permanent magnets, which is known as magnetic transmission, is studied. Magnetic transmissions have certain structural advantages compared to mechanical transmissions, namely: high reliability, efficiency, lower losses, non-contact transmission of mechanical power, no maintenance costs, and simplicity of construction. The use of magnetic transmissions for systems of conversion of low-potential mechanical energy into electrical energy is especially relevant: wind energy, water energy, energy of mechanical vibrations, etc. The use of magnetic gearboxes in autonomous wind power plants can be more promising from an economic and technical point of view compared to traditional mechanical transmissions. A numerical simulation mathematical model of magnetic transmission with permanent magnets has been developed. The use of magnetic transmission, for example, for autonomous wind power systems allows to increase the reliability of the operation of such installations, reduce operating costs and increase the efficiency of their operation. In emergency modes of operation, the use of magnetic transmission allows to avoid destruction or emergency shutdowns of electrical equipment. The developed simulation model of magnetic transmission takes into account the pulsations of the electromagnetic moment due to the discrete structure of the magnetic transmission and the change of the model parameters when the input moment changes: pulsations, losses in the magnetic core and permanent magnets, the change of the load angle and the transmitted electromagnetic moment. A feature of the developed model of the magnetic transmission system is that a change in the load of the electric power source leads to a change in the operating point on the mechanical characteristics of the rotor of the wind turbine. Conversely, when the wind parameters change, the output parameters of the source of electrical energy change: power, voltage, current and electromagnetic moment.

Analyzing the Nuclear Structure of 13O-13B and 13N-13C Mirror Nuclei

In the context of the shell model, electromagnetic transitions were used to analyze the nuclear structure of a mirror nucleus with the same mass number, A = 13. The shell model investigation was performed by calculating the root mean square (rms) for the proton, neutron, matter and charge radii, occupancies, the excitation energies, as well as electromagnetic moments, using the elements of a body density matrix of the PSDMOD two-body effective interactions carried out in the psdpn-shell model space. The present results adopted the harmonic oscillator's single particle eigen functions and Hartree-Fock approximation. In addition, the effect of core polarization was added using the effective charge and effective g factors to calculate electromagnetic moments. To acquire a fair analysis of the information, the core polarization has to be present. The outcomes were compared with experimental data

ПОРІВНЯЛЬНИЙ АНАЛІЗ МАЛОГАБАРИТНИХ ВИСОКОШВИДКІСНИХ СИНХРОННИХ МАГНІТОЕЛЕКТРИЧНИХ ДВИГУНІВ

Using the methods of mathematical modeling, a comparative analysis of the characteristics of three variants of small-sized high-speed synchronous magneto-electric motors (SMD) with permanent magnets on the rotor, which are intended for driving the propeller of quadcopter-type aircraft, was investigated and carried out. Namely: SMD with external grooved stator and internal rotor; SMD with internal grooved stator and external rotor; SMD with internal clear-pole stator and external rotor. On the example of an aircraft with a total mass of 4 kg, a comparative analysis of the amount of power developed by the specified engine variants under the same operating conditions: the same overall dimensions, rotor speed, current in the stator winding and volume of permanent magnets was carried out. An assessment of the magnitude of electromagnetic moment pul-sations is given. It was established that although an SMD with an internal clear-pole stator is the most technologically simple, but under the same other conditions, it is inferior in power to an SMD with an internal slotted stator and an external rotor. References 7, Figures 4.

Construction of the mathematical model of magnetic transmission for an autonomous wind power plant

The object of research is electromagnetic and mechanical processes in magnetic transmission for an autonomous wind power plant of small power. The use of magnetic transmission as part of an autonomous wind power plant makes it possible to improve the reliability and efficiency of such a system. In the current work, a study of magnetic transmission as part of an autonomous wind power plant was carried out to investigate the parameters and characteristics of magnetic transmission. This paper reports the construction of a numerical simulation mathematical model of a magnetic reducer operating as part of an autonomous wind power plant with a permanent magnet generator. The model takes into account discrete structure of internal and external rotors and modulator; changes in model parameters when input parameters change. It also takes into account losses, change of load angle and electromagnetic moment; the effect of changing the generator load. The built model of the magnetic reducer system differs in that the change in the generator load leads to a shift of the operating point on the mechanical characteristics of the rotor of the wind power plant (WPP). The model also works in the opposite direction: changes in wind parameters affect power, voltage, current, and electromagnetic moment. With the help of the model built, the parameters and characteristics of not only the magnetic reducer but also other components of the system were investigated. The efficiency at the output of the electric generator was determined, which is ≈75 % at a load of 2.0 kW. The magnetic transmission moment at a wind speed of 7.8 m/s for the high-speed rotor is 0.91 N∙m, and the low-speed rotor is 7.8 N∙m, which corresponds to a transmission ratio of 8.6. This expands opportunities for exploratory research

Nuclear moments: recent developments

The author has for many years kept a watching brief on the experimental study of nuclear electro-magnetic moments. Accurate values of nuclear magnetic dipole and electric quadrupole moments are a major product and the life blood of hyperfine interaction studies and their manifold applications. This paper outlines recent changes in the type of moment measurements being undertaken and the effect of modern complex electronic configuration computation on the extracted moment values.

Measuring the nuclear magnetic quadrupole moment of optically trapped ytterbium atoms in the metastable state

We propose a scheme to measure a nuclear magnetic quadrupole moment (MQM), a CP -violating electromagnetic moment that appears in the nuclear sector, using the long-lived 3P2 metastable state in neutral 173Yb atoms. Laser-cooling and trapping techniques enable us to prepare ultracold 173Yb atoms in the 3P2 state trapped in an optical lattice or an optical tweezer array, providing an ideal experimental platform with long spin coherence time. In addition, our relativistic configuration interaction calculation for the 3P2 electronic wavefunction reveals a large magnetic field gradient generated by the atomic electrons in this state, which amplifies the measurable effect of an MQM. Our scheme could lead to an improvement of more than one order of magnitude in MQM sensitivity compared to the best previous measurement (Murthy et al 1989 Phys. Rev. Lett. 63, 965).

Top quark anomalous couplings from top-pair tagged photoproduction at pe− colliders

We summarize the quantitative results of our analysis [1] of top-pair photoproduction in semileptonic mode in pe collisions at the LHeC and FCC-he. We define three photoproduction regions, based on the rapidity acceptance range of the electron tagger, that provide different degrees of sensitivity to top-quark effective couplings. We focus on the ttγ dipole couplings and the left-handed vector tbW coupling, for which we determine limits at both energies in the different photoproduction regions. Furthermore, we find that the LHeC and FCC-he will yield tight direct bounds on top dipole moments, greatly improving on current direct limits from hadron colliders, and direct limits on the tbW coupling as restrictive as those expected from the HL-LHC. We also consider indirect limits from b → sγ branching ratio and CP asymmetry, that are well known to be very sensitive probes of top electromagnetic dipole moments.

Measurements of binding energies and electromagnetic moments of silver isotopes – A complementary benchmark of density functional theory

We report on a set of high-precision measurements of nuclear binding and excitation energies, as well as nuclear spins, magnetic dipole and electric quadrupole moments of neutron-rich silver isotopes, 113−123Ag. The measurements were performed using the JYFLTRAP mass spectrometer and the collinear laser spectroscopy beamline at the Ion Guide Isotope Separator On-Line (IGISOL) facility. For the first time, we can firmly establish the ordering of the long-lived Iπ=1/2−,7/2+ states in these isotopes, and pin down the inversion of these two levels at either A=121(N=74) or A=123(N=76). We compare these findings to calculations performed with density functional theory (DFT), from which we establish the crucial role that the spin-orbit strength and time-odd mean fields play in the simultaneous description of electromagnetic moments and nuclear binding.

Electromagnetic moments of the antimony isotopes 112−133Sb

Nuclear moments of the antimony isotopes 113−133Sb are measured by collinear laser spectroscopy and used to benchmark phenomenological shell-model and ab initio calculations in the valence-space in-medium similarity renormalization group (VS-IMSRG). The shell-model calculations reproduce the electromagnetic moments over all Sb isotopes when suitable effective g-factors and charges are employed. Good agreement is achieved by VS-IMSRG for magnetic moments on the neutron-deficient side for both odd-even and odd-odd Sb isotopes while its results deviate from experiment on the neutron-rich side. When the same effective g-factors are used, VS-IMSRG agrees with experiment nearly as well as the shell model. Hence, the wave functions are very similar in both approaches and missing contributions to the M1 operator are identified as the cause of the discrepancy of VS-IMSRG with experiment. Electric quadrupole moments remain more challenging for VS-IMSRG.

Frequency analysis of stator currents of an induction motor controlled by direct torque control associated with a fuzzy flux estimator

Introduction. The best way to control the torque of an induction motor is conventional direct torque control (DTC); this control method is the most used approach in the industrial sector due to its many advantages. Its main advantages are its simplicity and its exclusive dependence on the stator resistance of the induction motor. However, the use of hysteresis comparators reduces its effectiveness, causing more torque ripple. Additionally, this results in variable operating frequency and limited frequency sampling, resulting in pseudo-random overshoot of the hysteresis band. Purpose. For these reasons, this article presents a new study aimed at confirming its shortcomings and improving the effectiveness of the control. Novelty. We propose to use fuzzy logic methods to estimate the two components of the stator flux. Methods. In traditional DTC the flux components are estimated from an equation relating the stator resistance to the stator voltage and current. In the proposed method, only stator currents and voltages are used for this evaluation, which eliminates the dependence of DTC on stator resistance. The aim of this proposal is to make DTC robust to parametric changes. Results. General harmonic distortions, rotational speed of the induction motor, electromagnetic moment, magnetic flux and stator currents are analyzed. Practical value. With this proposed technique, validated in Simulink/MATLAB, several improvements in motor behavior and control are endorsed: torque fluctuations are reduced, overshoot is completely eliminated, and total harmonic distortion is significantly reduced by 48.31 % for stator currents. This study also confirmed the robustness of DTC to changes in stator resistance.

Evaluation of magnetic gear parameters for autonomous wind installation with changing wind speed

Purpose. To evaluate the parameters and characteristics of the magnetic gearbox at constant and variable wind speed as part of an autonomous wind power plant. Methodology. Analysis of existing methods of mathematical modeling of magnetic gearboxes. Numerical methods of mathematical modeling based on finite elements. Numerical methods of processing the obtained results. Findings. A two-dimensional field mathematical model has been developed to estimate the parameters and characteristics of the magnetic gearbox at variable and constant wind speed. With the help of the developed model, the electromagnetic field, parameters and characteristics of the magnetic gearbox were analyzed both at a constant and at a variable speed of rotation. In particular, it was found that the magnetic system of the reducer does not reach saturation, while the average values of magnetic induction in the structural elements of the reducer remain within the permissible values for the used materials and grades of steel. The obtained data on the average values of the electromagnetic moments of the outer (high-speed) rotor and the inner rotor make it possible to understand the relationship between them and their influence on the operation of the system. A conclusion was made about the uneven distribution of induction along the middle line in the air gap, which is caused by the presence of a modulator in the design of the reducer. In addition, according to the obtained results, the change in wind speed affects the speed of rotation of the magnetic gearbox and the magnitude of the electromagnetic moments of the high-speed and low-speed rotors. Such information helps to understand the dynamics of system operation under different environmental conditions. The results obtained in the study are important for further improvement of the magnetic reducer design and ensuring more efficient operation of the low-power wind turbine. They can be used to optimize the structure and increase its productivity, which will contribute to the development of wind energy and the green energy industry in general. The average value of the electromagnetic moment of the outer (high-speed) rotor is about 7.4 N∙m, while for the inner rotor the value of the electromagnetic moment is about 66 N∙m. The ratio of the moments of the outer and inner rotors is 8.92, which correlates with the reduction factor of the gear under study. Originality. A two-dimensional field mathematical model has been developed, which takes into account the change in the parameters and characteristics of the magnetic gearbox when the wind speed changes and the random rotation speed of the wind generator rotor. Practical value. The results of the research of the magnetic reducer for a low-power wind turbine have an important contribution to the development of wind energy, contribute to increasing the efficiency and reliability of energy production, and contribute to the creation of a more sustainable and environmentally friendly energy complex.

Soft scattering evaporation of dark matter subhalos by inner galactic gases

The large gap between a galactic dark matter subhalo’s velocity and its own gravitational binding velocity creates the situation that small subhalos can be evaporated before dark matter thermalize with baryons due to the low binding velocity. In case dark matter acquires an electromagnetic dipole moment, the survival of low-mass subhalos requires stringent limits on the photon-mediated soft scattering. The current stringent direct detection limits indicate for a small dipole moment, which lets DM decouple early and allows small subhalos to form. We calculate the DM kinetic decoupling temperature in the Early Universe and evaluate the smallest protohalo mass. In the late Universe, low-mass subhalos can be evaporated via soft collision by ionized gas and accelerated cosmic rays. We calculate the subhalos evaporation rate and show that subhalos lighter than 10^{-5}M_{odot } in the gaseous inner galactic region are subject to evaporation via dark matter’s effective electric and magnetic dipole moments below current direct detection limits, which potentially affects the low-mass subhalos distribution in the galactic center.

ТРИСТУПЕНЕВА ЕЛЕКТРИЧНА МАШИНА З ВНУТРІШНІМ ТА ЗОВНІШНІМ РОТОРОМ: ПОРІВНЯЛЬНИЙ АНАЛІЗ ПОКАЗНИКІВ КЕРОВАНОСТІ

Two structures of electric machines with three degrees of freedom of the rotational movement of the rotor are considered - with an external and an internal rotor held on an internal cardan suspension. A three-plane symmetric magnetic system was chosen for the comparative analysis and such a choice was justified. Limitations are formulated that allow considering the rotor as a conservative mechanical system, as well as considering the magnetic field in the electric machine as magnetostatic. Mathematical models of the rotational motion of a body with a fixed center of mass, as well as the force interaction of the magnetic field of a permanent magnet located on the rotor and the control winding located on the stator, are given. The peculiarities of the distribution of electromagnetic forces in both structures are analyzed and the greater efficiency of the formation of these forces in the structure with an internal rotor is shown. Expressions for the components of the electromagnetic moment for use in the "COMSOL Multiphysics" interface are obtained. Forced precession movement for both structures was analyzed in the case of equal radii of the control windings and in the case of the same dimensions of the magnetic systems. It was determined that the structure with an external magnetic circuit is able to provide an order of magnitude smaller angular velocity of precessional movement and, at the same time, an equally smaller range of nutation. References 14, figures 10.

Isomeric Excitation Energy for ^{99}In^{m} from Mass Spectrometry Reveals Constant Trend Next to Doubly Magic ^{100}Sn.

The excitation energy of the 1/2^{-} isomer in ^{99}In at N=50 is measured to be 671(37)keV and the mass uncertainty of the 9/2^{+} ground state is significantly reduced using the ISOLTRAP mass spectrometer at ISOLDE/CERN. The measurements exploit a major improvement in the resolution of the multireflection time-of-flight mass spectrometer. The results reveal an intriguing constancy of the 1/2^{-} isomer excitation energies in neutron-deficient indium that persists down to the N=50 shell closure, even when all neutrons are removed from the valence shell. This trend is used to test large-scale shell model, abinitio, and density functional theory calculations. The models have difficulties describing both the isomer excitation energies and ground-state electromagnetic moments along the indium chain.

MTPA STRATEGY FOR THE ELECTRIC VEHICLE DRIVE

Abstract. When the vehicle is moving, the driving torque that the traction motor should develop can be very large. Therefore, to prevent over loading of the traction motor by current, it is necessary to limit the current in the stator winding to the nominal value. In this regard, it is necessary to develop a system of vector control of the stator current of an induction motor, in which, at the nominal value of the stator current, the induction motor will develop the largest possible electromagnetic moment. Today, the problem of obtaining the maximum electromagnetic moment per unit current stator decides the MTPA strategy. Therefore, the aim of the work is to develop a system for regulating the moment of induction motor using the MTPA strategy, which provides the maximum value of the electromagnetic moment per unit current in the stator winding, as well as conducting a comparative analysis of the traction properties of an asynchronous electric drive when applying the MTPA strategy and in its absence. It is also necessary to clarify the requirements that the MTPA strategy imposes on the technical parameters of the induction motor and the restrictions that the real parameters of the induction motor impose on the MTPA strategy. The study was conducted on the example of a traction asynchronous electric drive of a city bus. As a result of this work, it was found that with the same current value in the stator winding, the induction motor will develop the greatest electromagnetic moment if the angle between the stator current vector and the rotor flux vector is equal to 45 electric degrees. By limiting the current of the stator induction motor at the nominal level, the application of the MTPA strategy allows obtaining an electromagnetic moment 2.56 times greater than in the absence of an MTPA strategy. This is due to the fact that when applying the MTPA strategy, the rotor flux linkage should exceed 3.55 times the nominal flux coupling of induction motor. To get so big the flux coupling of the rotor must increase the value of the voltage on the stator winding by 3.57 times relative to the nominal voltage value. When applying the MTPA strategy, the flux linkage of the rotor will not exceed the nominal value only at stator current values 3.54 times less than the nominal value of the stator current. In this case, the maximum value of the electromagnetic moment that will develop induction motor will be 4.92 times less than the nominal value of the moment of induction motor. In developing the MTPA strategy, the saturation of the magnetic system AD was not taken into account. Keywords – induction motor, vehicle, electromagnetic moment, energy, MTPA strategy.

Double feed inductor generator mathematical model for studying generation modes with unbalance of electrical machine parameters

The analysis of systems using dual power generators revealed a variety of models, most of which are built in the α-β and d-q coordinate systems. Models and control systems are made taking into account the unbalance of the voltage of the electrical network. A model of a three-phase dual-supply generator with the possibility of introducing asymmetry of the electrical parameters of the stator and rotor has been synthesized. Modes with symmetric and asymmetric parameters of the machine windings were modeled. Unbalance is implemented by changing the inductance and resistance of one of the stators and/or rotor phases. In both cases, the required generation mode was obtained both in terms of voltage frequency and its effective value. In the case of unbalance parameters of the windings, asymmetry of the generated voltage and the occurrence of pulsations of the electromagnetic moment with a frequency of 100 Hz were noted. Using the approach to the analysis of the electric power caused by the voltage and current of positive, negative and zero sequences, according to the simulation results, it was noted that in the case of asymmetry, along with the appearance of the components of the negative sequence power, changes in the components of the positive sequence power occur. The indicated power components increase with increasing asymmetry of machine parameters