Quadrupole Electric Field Research Articles

Full-scale modeling and experimental study of a gas neutron tube with a Penning ion source

This paper studies full-scale gas neutron tube modeling, including the following processes: gas discharge combustion in a Penning ion source, particle motion in an ion optical system, and modeling the in-target processes, such as sputtering, diffusion, thermal desorption of hydrogen isotopes, and nuclear reactions. Plasma modeling in quadrupole electric and axial magnetic fields was based on the electrostatic particle-in-cell method with molecular kinetic processes. The TechX Vsim software package was used. The neutron tube element sputtering by ions was simulated using SRIM/TRIM software based on Monte–Carlo methods. The OpenFOAM, as an open integrated platform for numerical simulation in continuum mechanics, was used to calculate the hydrogen thermal desorption activated by ion irradiation. The time-dependent neutron yield modeling was performed using the Geant4 software based on Monte–Carlo methods with CHIPS-TPT VNIIA-developed library. In addition, an experimental study of a gas neutron tube with a Penning ion source was conducted here as well. Details are given on the experiment and measurement technique used in this study. The operating characteristics for the gas neutron tube, including amplitude-time characteristics of current flashes (discharge and extraction currents), were determined. The neutron flux dependencies on the discharge current at various accelerating voltages were also obtained. Finally, a comparison between the experimental and calculated results is presented.

Penning-trap eigenfrequency measurements with optical radiofrequency detectors

We use an electric-dipole laser-driven transition to precisely measure the cyclotron-frequency ratios of the pairs Ca+42−Ca+40, Ca+44−Ca+40, and Ca+48−Ca+40 in a 7-tesla Penning trap. A single laser-cooled (T≈1 mK) ion serves, together with photon-counting and photon-imaging units, as a radiofrequency detector covering a broadband frequency spectrum, in the present case from kHz to a few MHz. Such detectors (Ca+40,42,44,48) allow measuring extremely small forces increasing the sensitivity in Penning-trap mass spectrometry. The direct determination of the ions' amplitudes makes a cyclotron-frequency measurement process more robust against inhomogeneities of the magnetic field and/or deviations of the electric quadrupole field due to mechanical imperfections of the trap. Published by the American Physical Society 2024

Трехмерная ловушка с возбуждением колебаний ионов на границе устойчивости диаграммы Матье

Vibrations of charged particles in compositions of three-dimensional high-frequency quadrupole and static homogeneous electric fields in the stable region and in the vicinity of the stability boundary of the Mathieu diagram are investigated. Using a pseudopotential model of a rapidly oscillating field, it is shown that the motion of charged particles during linear scanning of a secular frequency is described by the Airy differential equation. Based on the properties of solutions of the Airy equation, a method of ion mass separation with resonant excitation of oscillations at the stability boundary of the Mathieu diagram has been developed. To implement the method, the ion-optical system of the three-dimensional trap is supplemented with corrective electrodes. Computer modeling has determined the optimal potentials of the correcting electrodes, at which the errors of the distributions of quadrupole and homogeneous fields do not exceed 10E-4 and 2·10E-3. Keywords: superposition of quadrupole and homogeneous fields, Airy differential equation, mode of resonant excitation of oscillations, three-dimensional ion trap with correcting electrodes.

Translation-deformation coupling effects on the Rayleigh instability of an electrodynamically levitated charged droplet.

The breakup pathway of the Rayleigh fission process observed in the past experiments carried out using high-speed imaging of a charged drop levitated in an AC quadrupole trap has shown to exhibit several cycles of shape and center-of-mass oscillations followed by asymmetric breakup by ejecting a jet in the upward direction (i.e., opposite to the direction of gravity). We recently attempted to explain this using boundary integral simulations in the Stokes flow limit, wherein the position of the droplet and the polarity of the end cap electrodes were assigned using physical arguments, and the center-of-mass motion was not estimated consistently invoking quasi-static conditions. In this work, we explain the experimental observation of upward breakup of charged droplets in a quadrupolar field, using numerical calculations based on the boundary element method considering inviscid droplets levitated electrodynamically using quadrupole electric fields. The center-of-mass motion and the end cap are consistently calculated in the numerical scheme. The simulations show that the gravity-induced downward shift in the equilibrium position of the drop in the trap causes significant, large-amplitude shape oscillations superimposed over the center-of-mass oscillations of the drop. An important observation here is that the shape oscillations due to the applied quadrupole fields result in sufficient deformations that act as triggers for the onset of the instability below the Rayleigh limit, thereby admitting a subcritical instability. The center-of-mass oscillations of the droplet within the trap, which follow the applied frequency, are out of phase with the applied AC signal. Thus the combined effect of shape deformations and dynamic position of the drop leads to an asymmetric breakup such that the Rayleigh fission occurs upward via the ejection of a jet at the north pole of the deformed drop.

Stability Conditions for a Penning Trap with Rotating Quadrupole or Dipole Electric Fields

Stability Conditions for a Penning Trap with Rotating Quadrupole or Dipole Electric Fields

Observation of second- and higher-order electric quadrupole interactions with an atomic ion

The response of matter to fields underlies the physical sciences, from particle physics to astrophysics, and from chemistry to biophysics. We observe an atom's response to an electric quadrupole field to second- and higher orders; this arises from the atom's electric quadrupole polarizability and hyperpolarizabilities. We probe a single atomic ion which is excited to Rydberg states and confined in the electric fields of a Paul trap. The quadrupolar trapping fields cause atomic energy level shifts and give rise to spectral sidebands. The observed effects are described well by theory calculations.

Mass-selective removal of ions from Paul traps using parametric excitation

We study a method for mass-selective removal of ions from a Paul trap by parametric excitation. This can be achieved by applying an oscillating electric quadrupole field at twice the secular frequency omega _{text {sec}} using pairs of opposing electrodes. While excitation near the resonance with the secular frequency omega _{text {sec}} only leads to a linear increase of the amplitude with excitation duration, parametric excitation near 2, omega _{text {sec}} results in an exponential increase of the amplitude. This enables efficient removal of ions from the trap with modest excitation voltages and narrow bandwidth, therefore, substantially reducing the disturbance of ions with other charge-to-mass ratios. We numerically study and compare the mass selectivity of the two methods. In addition, we experimentally show that the barium isotopes with 136 and 137 nucleons can be removed from small ion crystals and ejected out of the trap while keeping ^{138}text {Ba}^{+} ions Doppler cooled, corresponding to a mass selectivity of better than Delta m / m = 1/138. This method can be widely applied to ion trapping experiments without major modifications since it only requires modulating the potential of the ion trap.

Numerical simulation of the electric field induced in a contactless dielectrophoretic quadrupole cell separator

PurposeThis study aims to propose a contactless and continuous dielectrophoretic cell-separation device using quadrupole electric field. To examine the separation performance, numerical simulations of the electric field in the cross-section of the glass capillary installed in the center of the quadrupole electrode were conducted.Design/methodology/approachTo estimate the magnitude of the dielectrophoretic force induced on cells, electrostatic analysis was performed by using a boundary-fitted coordinate system.Distribution of the electric field and gradient of the electric field square in the cross-section of the glass capillary were simulated for various ratios of radii of the glass capillary to the electrode rod.FindingsThe distribution of the electric field was found to have a cone-like profile about the center axis of the glass capillary with maximum at the internal surface of the glass capillary. The magnitude of the gradient of electric field square had similar distribution as that of the electric field, but had steeper slope near the internal surface of the glass capillary. The optimal values of the ratio of radii and the applied voltage were also estimated to achieve the local electric field strength suitable for cell separation.Originality/valueOne major advantage of the proposed device is simple and low fabrication cost, in addition to its contactless structure free from cell damage. Derived knowledge is instructive in achieving high-throughput cell separation without the use of devices of complex structure.

The steady states of dielectric particles with Quincke rotation under ion traps

The dynamics of dielectric particles with Quincke rotation under nonuniform electric fields generated by ion traps are researched. Based on a recently proposed model, I make a further discussion about a quadrupole electric field with numerical simulation. According to the results, the steady state of a single particle under different field strength can be classified into several stages. Some more complicated electric fields are considered too. But the dynamics of particle under other multipole fields can’t be simulated well with the model, which indicates that the model still needs to be improved. A more complicated 3D electric fields are considered too, the evolution of steady states under this 3D electric field is similar to the quadrupole field.

Liquid-Phase Ion Trap for Ion Trapping, Transfer, and Sequential Ejection in Solutions

In this study, a new method/mechanism to manipulate ions in solution was developed, based on which liquid-phase ion trap was built. In this liquid-phase ion trap, ion manipulations conventionally performed in a quadrupole ion trap or in a trapped ion mobility spectrometer placed in a vacuum were achieved in solutions. Through theoretical derivation and numerical simulation, it is found that ions have different motional characteristics than those in vacuum. Instead of a radio frequency quadrupole electric field, tunable DC electric fields together with a constant liquid flow were applied to control ion motions in solution. Different ions could be trapped and focused in a potential well, and ion densities could be increased by over 100-fold. By adjusting the DC electric field of the potential well, trapped ions could be transferred into another trapping region or sequentially released for detection. Ions released from the liquid-phase ion trap were then detected by a mass spectrometer interfaced with an electrospray ionization source. Since the ion manipulation mechanism in solution is different and complementary to that in vacuum, the use of a liquid-phase ion trap could also boost detection sensitivity and the mixture analysis capability of a mass spectrometer.

Free and Forced Oscillations of Charged Particles in the Presence of Inertially Nonstationary Fast Oscillating Quadrupole Electric Fields

Free and forced oscillations of charged particles in the presence of inertially nonstationary quadrupole HF electric fields are studied. Polyharmonic oscillations of charged particles in the presence of fast oscillating fields with slowly varying parameters are represented using a model of a nonstationary harmonic oscillator with the aid of linear relationships of the coefficients of series that serve as solutions to the Mathieu differential equation. The Green function is used to derive expressions for resonance oscillations of charged particles in the presence of nonstationary HF fields with superimposed uniform excitation fields. A particular case of a polyharmonic oscillator with a linearly varying natural oscillation frequency is considered, and expressions for parameters of the excitation function are derived. Analytical expressions are proven by the results of computer simulation.

Nonreciprocal Directional Dichroism Induced by the Quantum Metric Dipole.

We identify the quantum metric dipole as the geometric origin of the nonreciprocal directional dichroism which describes the change in the refractive index upon reversing the light propagation direction. Specifically, we find that the static limit of the nonreciprocal directional dichroism corresponds to a quadrupolar transport current from the quantum metric dipole, in response to a quadrupolar electric field. Moreover, at a finite frequency, we demonstrate that the steepest slope of the averaged quantum metric dipole gives rise to a peak in the differential refractive index between counterpropagating lights. Finally, we illustrate both features in a low-energy model.

Proposed Scheme to Generate Bright Entangled Photon Pairs by Application of a Quadrupole Field to a Single Quantum Dot.

Entangled photon sources are crucial for quantum optics, quantum sensing, and quantum communication. Semiconductor quantum dots generate on-demand entangled photon pairs via the biexciton-exciton cascade. However, the pair of photons are emitted isotropically in all directions, thus limiting the collection efficiency to a fraction of a percent. Moreover, strain and structural asymmetry in quantum dots lift the degeneracy of the intermediate exciton states in the cascade, thus degrading the measured entanglement fidelity. Here, we propose an approach for generating a pair of entangled photons from a semiconductor quantum dot by application of a quadrupole electrostatic potential. We show that the quadrupole electric field corrects for the spatial asymmetry of the excitonic wave function for any quantum dot dipole orientation and fully erases the fine-structure splitting without compromising the spatial overlap between electrons and holes. Our approach is compatible with nanophotonic structures such as microcavities and nanowires, thus paving the way towards a deterministic source of entangled photons with high fidelity and collection efficiency.

A 3D boundary integral method for the electrohydrodynamics of surfactant-covered drops

We present a highly accurate numerical method based on a boundary integral formulation and the leaky dielectric model to study the dynamics of surfactant-covered drops in the presence of an applied electric field. The method can simulate interacting 3D drops (no axisymmetric simplification) in close proximity, can consider different viscosities, is adaptive in time and able to handle substantial drop deformation. For each drop global representations of the variables based on spherical harmonics expansions are used and the spectral accuracy is achieved by designing specific numerical tools: a specialized quadrature method for the singular and nearly singular integrals that appear in the formulation, a general preconditioner for the implicit treatment of the surfactant diffusion and a reparametrization procedure able to ensure a high-quality representation of the drops also under deformation. Our numerical method is validated against theoretical, numerical and experimental results available in the literature, as well as a new second-order theory developed for a surfactant-laden drop placed in a quadrupole electric field.

An appreciation of the scientific researches of Dr Peter H. Dawson.

Upon the death of Peter H. Dawson in 2015, mass spectrometry lost a major figure. Within the area of radiofrequency quadrupole electric fields applied to mass spectrometry, Dawson stands alongside its pioneers Wolfgang Paul, Nobelist and inventor of the technology, and Wilson Brubaker, who identified and overcame the deleterious effects of fringing electric fields on quadrupole mass filter performance. Seventy-one of Dawson's 97 scientific publications are concerned with quadrupole mass analysers, ion traps and monopole mass spectrometers. Of especial note are his book and review articles in which he disseminated information on the theoretical fundamentals and practicalities of these systems to a wider audience, thereby having a major impact on the development of this important field of endeavour. The scientific researches of Dr Dawson, and his advice and counsel, influenced to a major degree, and to the better, the research careers, teachings and the lives of the authors of this piece. Their combined researches on quadrupole devices led to the commercialization of the ion trap as a mass spectrometer by which mass spectral information became available at greatly reduced cost. Thus, the advent of commercial ion trapping instruments permitted a greater use of mass spectrometry in both technically advanced countries and those less well advanced. The greatest impact in health services was mass spectrometric analysis of environmental problems, well and stream water, food free of pesticides, etc., and forensic sciences. Our combined indebtedness to Dr Dawson is manifested by this appreciation of his scientific work, the highlighting of his main contributions, and creation of a substantive reference source to his work that can be used by other scientists. A comprehensive list of Dr Dawson's publications, including abstracts or summaries, has been arranged in chronological order of date of submission.

Hybrid ring design in the storage-ring proton electric dipole moment experiment

A new, hybrid design is proposed to eliminate the main systematic errors in the frozen spin, storage ring measurement of the proton electric dipole moment. In this design, electric bending plates steer the particles, and magnetic focusing replaces electric. The magnetic focusing should permit simultaneous clock-wise and counter-clock-wise storage to cancel systematic errors related to the out-of-plane dipole electric field. Errors related to the quadrupole electric fields can be eliminated by successive runs of magnetic focusing with different strengths.

Design of Helical Resonator for the Detection of Signal in Penning Ion Trap

Penning Ion trap is an instrument where charged particles can be stored by means of quadrupolar electric field and high magnetic field. Motion of charged particle within the trap electrodes induces weak image signal which is detected by LC resonant circuit followed by a Low noise amplifier. To get a large voltage signal, the quality factor of the resonator should be very high. So, a high Q helical resonator is commonly used in ion trapping devices, as it offers considerably high Q (∼ 1000) in a small geometry. Resonating frequency of the resonator is selected based on the trap geometry and mass of trapped particle. For ion trapping system we have designed a 20 MHz helical resonator and studied its parameters through simulations.

Shape deformation of a vesicle under an axisymmetric non-uniform alternating electric field

We suggest that non-uniform electric fields that are commonly used to study vesicle dielectrophoresis can be employed in hitherto relatively unexplored areas of vesicle deformation (for electromechanical characterization) and electroporation. Conventionally, the tension generated in vesicles is commonly modeled to be entropic or enthalpic in origin. A comparison of the configuration of a vesicle in the enthalpic and entropic regimes as well as the cross over between the two regimes during vesicle deformation has eluded understanding. A lucid demonstration of this concept is provided by the study of vesicle deformation under axisymmetric quadrupole electric field and the shapes of the vesicles obtained using the entropic and the enthalpic approaches, show significant differences. A strong dependence of the final vesicle shapes on the ratio of electrical conductivities of the fluids inside and outside the vesicle as well as on the frequency of the applied quadrupole electric field is observed. A comparison with experimental data from the literature is also made. Moreover, an excess area dependent transition between the entropic and enthalpic regimes is observed. The method could be used to estimate electromechanical properties of the vesicle.

Surface oscillations of a sub-Rayleigh charged drop levitated in a quadrupole trap

A conducting charged drop, when subjected to a small amplitude perturbation, becomes unstable when the surface charge exceeds its Rayleigh limit. On the other hand, a drop with a charge in the sub-Rayleigh limit exhibits capillary oscillations whose amplitude and frequency depend upon the amount of the charge. In experiments, such systems are studied by levitating them in a quadrupole potential. The oscillations of a sub-Rayleigh charged drop in such setups now also depend upon the strength of the quadrupole potential. We conduct the first of its kind of experiments which indicate that a highly charged drop (but in the sub-Rayleigh limit) undergoes several cycles of prolate and oblate shape deformations. The surface oscillations of the levitated charged drop are observed to follow the frequency of the applied alternate current electric field, and the magnitude of prolate deformations is higher than the oblate deformation. To explain this, we provide a theory in the viscous potential flow limit that assumes axisymmetric shape oscillations of a perfectly conducting charged drop levitated in a quadrupole electric field. The analysis indicates that the experimental results can be explained only if a positional shift of the drop in the quadrupole field is assumed, thereby demonstrating the role of the local electric field.A conducting charged drop, when subjected to a small amplitude perturbation, becomes unstable when the surface charge exceeds its Rayleigh limit. On the other hand, a drop with a charge in the sub-Rayleigh limit exhibits capillary oscillations whose amplitude and frequency depend upon the amount of the charge. In experiments, such systems are studied by levitating them in a quadrupole potential. The oscillations of a sub-Rayleigh charged drop in such setups now also depend upon the strength of the quadrupole potential. We conduct the first of its kind of experiments which indicate that a highly charged drop (but in the sub-Rayleigh limit) undergoes several cycles of prolate and oblate shape deformations. The surface oscillations of the levitated charged drop are observed to follow the frequency of the applied alternate current electric field, and the magnitude of prolate deformations is higher than the oblate deformation. To explain this, we provide a theory in the viscous potential flow limit that assume...

Structure and Performance of Polygonal Electrode Linear Ion Trap

Abstract The polygonal electrode linear ion trap (PeLIT) can produce quadrupolar electric field plus some higher order field, which balances the relationship between mass resolution and electrode manufacturing difficulties. The electrodes of PeLIT are relatively simple, but have a good mass resolving power. This study investigated the relationship between the electric field distribution and the ion trap structures, and the performances of PeLIT through theoretical simulation and experimental study. Research results of simulation showed that the polygonal electrode linear ion traps with different structures had different electric field distributions and mass analysis performances. The negative decapole field distorted the performances significantly. The experimental results showed that the mass resolution of reserpine ions (m/z 609) was more than 2500 using a polygonal electrode ion trap. At the same time, mass selective excitation and tandem mass spectrometry experiments were also carried.