The European Physical Journal D最新文献

Atmospheric pressure plasma jets (APPJs) are versatile devices with numerous applications. This work focuses on APPJs generated at the tip of long, flexible tubes using the jet transfer technique. The plasma source consists of a primary discharge and a secondary discharge forming the plasma jet. Discharge power measurements were carried out in a way that it was possible to separate the contribution of the primary discharge from the total power dissipated by the plasma source. Both power and effective current were analyzed under different operating conditions. The results show that the variation in the primary discharge power is much lower than the power dissipated by the plasma jet. Additionally, the electrical characteristics of the plasma device were analyzed. Notable differences were observed between the negative and positive phases of the discharge, with a more resistive load in the negative one, which suggests that the electrical equivalent circuit model changes according to the voltage polarity.

The primary discharge spectra are not affected by differences in electrical characteristics of the discharges with the plasma jet on and off

Electron motion in an atom driven by an intense linearly polarized laser field can exhibit a laser-dressed stable state, referred to as the Kramers–Henneberger (KH) state or KH atom. Up to now, the existence conditions of this state rely on the presence of a double well in the KH potential, obtained by averaging the motion over one period of the laser. However, the approximation involved in the averaging is largely invalid in the region of the double well structure; therefore, this raises the question of its relevance for identifying signatures of these exotic states. Here, we present a method to establish conditions for the existence of the KH atom based on a nonperturbative approach. We show that the KH atom is structured by an asymmetric periodic orbit with the same period as the laser field in a wide range of laser parameters. Its imprint is clearly visible on the wavefunction in quantum simulations. We identify the range of parameters for which this KH state is effective, corresponding to an elliptic periodic orbit.

Korteweg–de Vries (KdV) equation with the influence of Landau damping of electrons is developed to explore the weakly nonlinear and weakly dispersive ion-acoustic waves in a non-collisional unmagnetized plasma system whose constituents are adiabatic warm ions, negative-charged immobile dust grains and combined Kappa–Cairns distributed electrons. It is found that the nonlinear coefficient of the KdV equation vanishes along different parametric curves in the parametric space. In this situation, a modified KdV equation with the Landau damping effect is obtained to demonstrate the nonlinear propagation of the ion-acoustic waves. By employing multiple time scale method, the solitary wave solutions of these equations are derived. The solitary wave’s amplitudes have been noticed to decay gradually over time.

In a two-photon Jaynes–Cummings model which consists of an atom interacting with a cavity mode with a two-photon interaction, we find the photon blockade effect can be largely improved by inducing a interference pathway. The interference pathway can be either a two-photon transition or an atom transition. The purity of the single photon can be improved by (10 sim 100) times, and we find the high purity of single photon is induced by combination of conventional and unconventional photon blockade. The method provides a way to improve the purity of single photon.

In a system consisting of a cavity coupled to a two-level atom via a two-photon interaction, the two photon state can be reduced by destructive interference between different transition pathways.

Prerequisites for the goal of studying long-lived, magnetically confined, electron–positron pair plasmas in the laboratory include the injection of both species into the trap, long trapping times, and suitable diagnostic methods. Here we report recent progress on these tasks achieved in a simple dipole trap based on a supported permanent magnet. For the injection of electrons, both an (textbf{E}times B) drift technique (of a (sim )2–(upmu )A, 6-eV beam) and “edge injection” (from a filament emitting a few mA and biased to some tens of volts) have been demonstrated; the former is suitable for low-density beams with smaller spatial and velocity spreads, while the latter employs fluctuations arising from collective behavior. To diagnose the edge-injected electrons, image potentials and currents induced on a wall probe, the magnet case, and wall electrodes were measured. Confinement of drift-injected positrons, measured experimentally, exhibited at least two well-separated timescales. Simulations reproduced this qualitatively, using a simple model of elastic collisions with residual background gas, and point to small adjustments for increasing trapping times. In a major upgrade to diagnostic capabilities, 25 bismuth germanate detectors, placed in three reentrant ports, are able to localize annihilation gammas, which will be used in future experiments to distinguish between different loss channels.

The electron capture by heavy charged particles is of interest in a wide range of physical applications. In radiation biophysics, electron capture cross sections (ECCS) is a key information for the implementation of Monte Carlo simulation codes. In this work, the time-dependent density functional theory (TD-DFT) has been used for the determination of ECCS for protons impacting on atoms with presence in organic compounds, in the 1–200 keV energy range. Later, these atomic cross sections were combined through the pixel counting method for determining corresponding cross section of small and large organic molecules and water, which is of primordial importance in radiation biophysics. The large organic molecules include DNA bases and a whole DNA base pair. Excellent results were obtained for the small molecules along the whole energy range. For DNA components, good results were found at high energies (100–200 keV). At lower energies, larger discrepancies were obtained when compared with other theoretical and experimental work. The possible causes for these discrepancies are deeply discussed. This work should support later works for developing a charge equalization method for classical molecular dynamics to describe fast proton collisions with organic materials.

We propose theoretically a non-magnetic optical nonreciprocity (ONR) scheme with high efficiency by employing the four-wave mixing (FWM) effect in an asymmetric semiconductor three-coupled-quantum-well (TCQW) nanostructure. Nonreciprocal transmission and nonreciprocal phase shift in this TCQW, both with high transmission rates, can be achieved using suitable parameters. Considering an orbital-angular-momentum (OAM) probe beam, the perfect nonreciprocity can be obtained based on the highly efficient FWM. Furthermore, the integration of this TCQW nanostructure into a Mach–Zehnder interferometer enables the fabrication of highly efficient optical isolators and optical circulators by selecting appropriate parameters. The optical isolator exhibits an isolation ratio of 97.76 dB and an insertion loss of 0.25 dB, while the optical circulator demonstrates a fidelity of 0.9993 and a photon survival probability of 0.9517. Our approach based on semiconductor media has the advantages of easy fabrication and good integration with adjustable parameters. In conjunction with the distinctive characteristics of the OAM beam, our protocol offers a theoretical framework for the development of highly integrated and multi-dimensional nonreciprocity and nonreciprocal photonic devices.