Effect Of Ion Motion Research Articles

Effect of Ion Motion on Generation and Lifetime of Magnetic Fields in a Cluster Plasma Irradiated with Intense Circularly Polarized Laser Pulses

Effect of Ion Motion on Generation and Lifetime of Magnetic Fields in a Cluster Plasma Irradiated with Intense Circularly Polarized Laser Pulses

Effect of ion motion on breaking of longitudinal relativistically strong plasma waves: Khachatryan mode revisited

The effect of ion motion on the spatiotemporal evolution of a relativistically strong space charge wave is studied using a 1D fluid simulation code. In our simulation, these waves are excited in the wake of a rigid electron beam propagating through a cold homogeneous plasma with a speed close to the speed of light. It is observed that the excited wave is a mode as described by Khachatryan [Phys. Rev. E 58, 7799–7804 (1998)] whose profile gradually sharpens and the wave eventually breaks after several plasma periods exhibiting explosive behavior. It is found that breaking occurs at amplitudes, which is far below the breaking limit analytically derived by Khachatryan [Phys. Rev. E 58, 7799–7804 (1998)]. This phenomenon of wave breaking, at amplitudes well below the breaking limit, is understood in terms of phase mixing of the excited wave. It is further found that the phase mixing time (wave breaking time) inversely scales with the energy density of the wave.

Adiabatic matching of particle bunches in a plasma-based accelerator in the presence of ion motion

Witness beam stability and preservation of its ultra-low emittance have been identified as critical challenges toward realizing a TeV-class, plasma-based linear collider. In fact, the witness bunch parameters required by a future TeV-class collider have been expected to trigger hosing instability and background ion motion, leading to emittance degradation and, potentially, to bunch loss. Recently, it has been shown that ion motion suppresses the hosing instability, and proper longitudinal bunch shaping can eliminate the ion-motion-induced emittance growth. In this paper, we propose and analyze a plasma-based method to generate the shaped bunches that enable emittance preservation in the presence of ion motion. The method is based on an adiabatic matching procedure, where a bunch with an initially untapered profile is injected in the plasma accelerator stage with an energy low enough that ion motion effects are initially small. As the bunch accelerates, it is adiabatically compressed, ion motion is gradually triggered, and the bunch slowly but continuously readjusts itself in the ion motion-perturbed wakefield acquiring the desired taper. The production of tapered witness bunch profiles that minimize energy spread and preserve emittance for collider-relevant parameters could enable the use of plasma-based accelerators for high-energy physics applications.

Device Model for Methylammonium Lead Iodide Perovskite With Experimentally Validated Ion Dynamics

AbstractBeing based on mixed ionic‐electronic semiconductors, the operation of perovskite solar cells depends on many parameters. To develop an experimentally validated numerical device model, it is therefore necessary to isolate individual physical phenomena. To this end, the dynamics of ion motion in lead halide perovskites is investigated by measuring impedance spectra and the electric displacement as a function of frequency in dark. The displacement response is fully reproduced by a numerical device model that combines electronic and ionic conduction. For a quantitative description of the displacement, it is critical to consider the frequency‐dependent apparent dielectric constant, the ion concentration and the ion diffusion coefficient. The numerical simulations enable to quantify the effect of ion motion and voltage scan speed on the electric field distribution in MAPbI3 based devices, laying the foundations for an experimentally validated perovskite device model.

Compound atom-ion Josephson junction: Effects of finite temperature and ion motion

We consider a degenerate Bose gas confined in a double-well potential in interaction with a trapped ion in one dimension and investigate the impact of two relevant sources of imperfections in experiments on the system dynamics: ion motion and thermal excitations of the bosonic ensemble. Particularly, their influence on the entanglement generation between the spin state of the moving ion and the atomic ensemble is analyzed. We find that the detrimental effects of the ion motion on the entanglement protocol can be mitigated by properly choosing the double-well parameters as well as timings of the protocol. Furthermore, thermal excitations of the bosons affect significantly the system's tunneling and self-trapping dynamics at moderate temperatures; i.e., thermal occupation of a few double-well quanta reduces the protocol performance by about 10%. Hence, we conclude that finite temperature is the main source of decoherence in such junctions and we demonstrate the possibility to entangle the condensate motion with the ion vibrational state.

Plasma high-order-harmonic generation from ultraintense laser pulses.

Plasma high-order-harmonic generation from an extremely intense short-pulse laser is explored by including the effects of ion motion, electron-ion collisions, and radiation reaction force in the plasma dynamics. The laser radiation pressure induces plasma ion motion through the hole-boring effect, resulting in frequency shifting and widening of the harmonic spectra. The classical radiation reaction force slightly mitigates the frequency broadening caused by the ion motion. Based on the results and physical considerations, parameter maps highlighting the optimum regions for generating a single intense attosecond pulse and coherent XUV radiation are presented.

Effects of ion motion on linear Landau damping

The effects of ion motion on Landau damping has been studied by the use of one-dimensional Vlasov-Poisson simulation. It is shown that the ion motion may significantly change the development of the linear Landau damping. When the ion mass is multiple of proton mass, its motion will halt the linear Landau damping at some time due to the excitation of ion acoustic waves. The latter will dominate the system evolution at the later stage and hold a considerable fraction of the total energy in the system. With very small ion mass, such as in electron-positron plasma, the ion motion can suppress the linear Landau damping very quickly. When the initial field amplitude is relatively high such as with the density perturbation amplitude δn/n0 > 0.1, the effect of ion motion on Landau damping is found to be weak or even ignorable.

Effect of ion motion on plasma oscillation phase mixing and breaking

The evolution of a given sinusoidal density perturbation in cold quasi-neutral unmagnetized plasma is investigated using a fluid model by taking into account the ion response. Plasma oscillations at roughly the harmonics of the initial perturbation are generated until wave breaking appears. It is found that the ion response can enhance the plasma oscillations, leading to earlier occurrence of wave breaking (as compared with the ions-at-rest case). The dependence of wave breaking time on the amplitude of the initial perturbation is also discussed.

The Effect of Ion Motion on Laser-Driven Plasma Wake in Capillary**supported by National Natural Science Foundation of China (No. 11247016), the Natural Science Foundation of Jiangxi Province, China (Nos. 2014ZBAB202001 and 20151BAB212010), and the Science Foundation for Youths of the Jiangxi Education Committee of China (No. GJJ14224)

The effect of ion motion in capillary-guided laser-driven plasma wake is investigated through rebuilding a two-dimensional analytical model. It is shown that laser pulse with the same power can excite more intense wakefield in the capillary of a smaller radius. When laser intensity exceeds a critical value, the effect of ion motion reducing the wakefield rises, which becomes significant with a decrease of capillary radius. This phenomenon can be attributed to plasma ions in smaller capillary obtaining more energy from the plasma wake. The dependence of the difference value between maximal scalar potential of wake for two cases of ion rest and ion motion on the radius of the capillary is discussed.

Solitary waves in asymmetric electron–positron–ion plasmas

By solving the coupled equations of the electromagnetic field and electrostatic potential, we investigate solitary waves in an asymmetric electron–positron plasma and/or electron–positron–ion plasmas with delicate features. It is found that the solutions of the coupled equations can capture multipeak structures of solitary waves in the case of cold plasma, which are left out by using the long-wavelength approximation. By considering the effect of ion motion with respect to non-relativistic and ultra-relativistic temperature plasmas, we find that the ions’ mobility can lead to larger-amplitude solitary waves; especially, this becomes more obvious for a high-temperature plasma. The effects of asymmetric temperature between electrons and positrons and the ion fraction on the solitary waves are also studied and presented. It is shown that the amplitudes of solitary waves decrease with positron temperature in asymmetric temperature electron–positron plasmas and decrease also with ion concentration.

Time dependent Doppler shifts in high-order harmonic generation in intense laser interactions with solid density plasma and frequency chirped pulses

High order harmonic generation from solid targets is a compelling route to generating intense attosecond or even zeptosecond pulses. However, the effects of ion motion on the generation of harmonics have only recently started to be considered. Here, we study the effects of ion motion in harmonics production at ultrahigh laser intensities interacting with solid density plasma. Using particle-in-cell simulations, we find that there is an optimum density for harmonic production that depends on laser intensity, which scales linearly with a0 with no ion motion but with a reduced scaling if ion motion is included. We derive a scaling for this optimum density with ion motion and also find that the background ion motion induces Doppler red-shifts in the harmonic structures of the reflected pulse. The temporal structure of the Doppler shifts is correlated to the envelope of the incident laser pulse. We demonstrate that by introducing a frequency chirp in the incident pulse we are able to eliminate these Doppler shifts almost completely.

A Theoretical Method for Characterizing Nonlinear Effects in Paul Traps with Added Octopole Field.

In comparison with numerical methods, theoretical characterizations of ion motion in the nonlinear Paul traps always suffer from low accuracy and little applicability. To overcome the difficulties, the theoretical harmonic balance (HB) method was developed, and was validated by the numerical fourth-order Runge-Kutta (4th RK) method. Using the HB method, analytical ion trajectory and ion motion frequency in the superimposed octopole field, ε, were obtained by solving the nonlinear Mathieu equation (NME). The obtained accuracy of the HB method was comparable with that of the 4th RK method at the Mathieu parameter, q = 0.6, and the applicable q values could be extended to the entire first stability region with satisfactory accuracy. Two sorts of nonlinear effects of ion motion were studied, including ion frequency shift, Δβ, and ion amplitude variation, Δ(C(2n)/C0) (n ≠ 0). New phenomena regarding Δβ were observed, although extensive studies have been performed based on the pseudo-potential well (PW) model. For instance, the |Δβ| at ε = 0.1 and ε = -0.1 were found to be different, but they were the same in the PW model. This is the first time the nonlinear effects regarding Δ(C(2n)/C0) (n ≠ 0) are studied, and the associated study has been a challenge for both theoretical and numerical methods. The nonlinear effects of Δ(C(2n)/C0) (n ≠ 0) and Δβ were found to share some similarities at q < 0.6: both of them were proportional to ε, and the square of the initial ion displacement, z(0)(2).

Nonlinear effects in Paul traps operated in the second stability region: analytical analysis and numerical verification.

Paul trap working in the second stability region has long been recognized as a possible approach for achieving high-resolution mass spectrometry (MS), which however is still far away from the experimental implementations because of the narrow working area and inefficient ion trapping. Full understanding of the ion motional behavior is helpful for solving the problem. In this article, the ion motion in a superimposed octopole field, which was characterized by the nonlinear Mathieu equation, was solved analytically using Poincare-Lighthill-Kuo (PLK) method. This method equivalently described the nonlinear disturbance by an effective quadrupole field with perturbed Mathieu parameters, a(u) and q(u), which would bring huge convenience in the studies of nonlinear ion dynamics and was, therefore, used for rapid evaluation of the nonlinear effects of ion motion. Fourth-order Runge-Kutta method (4th R-K) indicated the error of PLK for characterizing the frequency shift of ion motion was within 15%.

Influence of Microfield Directionality on Line Shapes

In the framework of the Spectral Line Shapes in Plasmas Code Comparison Workshop (SLSP), large discrepancies appeared between the different approaches to account for ion motion effects in spectral line shape calculations. For a better understanding of these effects, in the second edition of the SLSP in August, 2013, two cases were dedicated to the study of the ionic field directionality on line shapes. In this paper, the effects of the direction and magnitude fluctuations are separately analyzed. The effects of two variants of electric field models, (i) a pure rotating field with constant magnitude and (ii) a time-dependent magnitude field in a given direction, together with the effects of the time-dependent ionic field on shapes of the He II Lyman-α and -β lines for different densities and temperatures, are discussed.

Ion motion effects on the generation of short-cycle relativistic laser pulses during radiation pressure acceleration

AbstractThe effects of ion motion on the generation of short-cycle relativistic laser pulses during radiation pressure acceleration are investigated by analytical modeling and particle-in-cell simulations. Studies show that the rear part of the transmitted pulse modulated by ion motion is sharper compared with the case of the electron shutter only. In this study, the ions further modulate the short-cycle pulses transmitted. A 3.9 fs laser pulse with an intensity of $1.33\times 10^{21}\ {\rm W}\ {\rm cm}^{-2}$ is generated by properly controlling the motions of the electron and ion in the simulations. The short-cycle laser pulse source proposed can be applied in the generation of single attosecond pulses and electron acceleration in a small bubble regime.

Effects of the Ion Motion on Rotating Magnetic Field Current Drive in a Cylindrical Model

The effects of ion motion on the rotating magnetic field current drive are studied in the infinitely cylindrical configuration. The approximate relationships are obtained by using the motion equations of ions and electrons, also the viscosity effect generated from shear motion is included. It is shown that owing to the collision of the ion–electron, the ions will be spin up and its rotate speed can reach around 30 % of that of electrons. The viscous term will inhabit the motion of ion and decrease the ion rotating speed. The improved theoretic model is also adapted to the axial pressure balance.

Hysteresis effects on I–V relations in a single crystal of the Cu–In–Te system with two mobile ions

Three slices of the same In-rich chalcopyrite single crystal ingot of the Cu–In–Te system with different compositions and stoichiometric deviations are studied by means of electrical measurements. The slices are mixed electronic and ionic conductors, and under a constant applied voltage and under dark conditions, variations of the current intensity with time are observed due to ionic motion. The measuring time was 25, or 300 s, in measurements carried out subsequently two months later. Symmetric electrodes formed by graphite paint are used on both sides of the samples. The electrode/semiconductor/electrode solid-state device does not block the electrons, while it blocks the ions at the semiconductor/electrode interface. Nonlinear I–V relations and different hysteresis effects are obtained, relating the different ionic mobilities to the measuring time. To understand the different I–V relations and hysteresis cycles, a two-mobile-ion framework is applied. The effect of ion motion in the electronic current and the voltage drop at the semiconductor/electrode interface, due to ionic accumulation, are studied. The different results in each sample can only be explained by taking into account the motion of two different ions, and the different compositions and stoichiometric deviations of the slices. The understanding and, above all, the control of the ionic motion in In-rich chalcopyrites could be the key to improve the reproducibility of solar cell efficiency.

Ion Motion in Self-Modulated Plasma Wakefield Accelerators

The effects of plasma ion motion in self-modulated plasma-based accelerators are examined. An analytical model describing ion motion in the narrow beam limit is developed and confirmed through multidimensional particle-in-cell simulations. It is shown that the ion motion can lead to the early saturation of the self-modulation instability and to the suppression of the accelerating gradients. This can reduce the total energy that can be transformed into kinetic energy of accelerated particles. For the parameters of future proton-driven plasma accelerator experiments, the ion dynamics can have a strong impact. Possible methods to mitigate the effects of the ion motion in future experiments are demonstrated.

Study on the effects of ion motion on laser-induced plasma wakes

A 2D analytical model is presented for the generation of plasma wakes (or bubbles) with an ultra-intense laser pulse by taking into account the response of plasma ions. It is shown that the effect of ion motion becomes significant at the laser intensity exceeding 1021 W/cm2 and plasma background density below 1019 cm−3. In this regime, ion motion tends to suppress the electrostatic field induced by charge separation and makes the electron acceleration less effective. As a result, the assumption of immobile ions overestimates the efficiency of laser wake-field acceleration of electrons. Based on the analytical model, the dynamics of plasma ions in laser-induced wake field is investigated. It is found that only one bubble appears as the plasmas background density exceeds the resonant density and the deposited laser energy is concentrated into the bubble, resulting in the generation of an ion bunch with extremely high energy density.

Kinetic theory for charge-exchange spectroscopy: Effects of magnetic and electric fields on the distribution function after charge-exchange

In plasmas equipped with neutral beam injection, excitation of atomic spectral lines via charge-exchange with neutral atoms is the basis of one of the standard plasma diagnostic techniques for ion density, temperature, and velocity. In order to properly interpret the spectroscopic results, one must consider the effects of the energy dependence of the charge-exchange cross-section as well as the motion of the ion after charge-exchange during the period when it is still in the excited state. This motion is affected by the electric and magnetic fields in the plasma. The present paper gives results for the velocity distribution function of the excited state ions and considers in detail the cross-section and ion motion effects on the post charge-exchange velocity. The expression for this velocity in terms of the charge-exchange cross-section and the pre charge-exchange velocity allows that latter velocity to be determined. The present paper is the first to consider the effect of the electric as well as the magnetic field and demonstrates that electric field and diamagnetic terms appear in the expression for the inferred velocity. The present formulation also leads to a novel technique for assessing the effect of the energy dependence of the charge-exchange cross-section on the inferred ion temperature.