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In this article, we perform a numerical investigation on the polarization of a terahertz wave transmitting through a dust acoustic wave. Assuming a triangular waveform of the particle number density in the dust acoustic wave, the transmission characteristics are calculated using the finite-difference time-domain method. It is shown that dust acoustic waves can function as a polarizer to control the polarization states of the terahertz wave, and the conversion efficiency depends on the parameters of the dust acoustic wave, such as the particle number density and the thickness of particle cloud. [ABSTRACT FROM AUTHOR]

Negative hydrogen ion sources (NHISs) based on surface production with cesium (Cs) seeded can fulfill the demanded parameters for neutral beam injection systems for ITER. In this study, the Global Model for Negative Hydrogen Ion Source based on volume-produced H − ions is developed to include surface-produced H − ions and is validated against experimental data obtained in a planar inductively coupled plasma discharge used for study of Cs effect on H − production. The H − density predicted by the model decreases three times with surface work function from 2.1 to 4.5 eV, achieving good agreement with the experimental results, as surface conversion yield of particles to H − ions shows exponential decline with surface work function. The model predicts the rise in neutral gas temperature remarkably enhances surface production but reduces volume production of H − ions, because of increase in surface conversion yield of H atoms to H − ions and in electron temperature, respectively. The dependences of H − production on surface work function and neutral gas temperature are analyzed by evaluating creation rates of the H − ions from different reaction pathways. The developed model can be applied for prediction of H − production in NHISs and ultimate parameter optimization of negative ion beams for fusion reactors. [ABSTRACT FROM AUTHOR]

The instability condition of a charged liquid dust particle (droplet) immersed in a plasma is considered theoretically. Both charging process and rotation effect are incorporated in the model. The dependence of the critical charge on the droplet radius is obtained for the regimes of fast and slow fragmentation. [ABSTRACT FROM AUTHOR]

Machine learning is applied to investigate the phase transition of two-dimensional complex plasmas. The Langevin dynamics simulation is employed to prepare particle suspensions in various thermodynamic states. Based on the resulted particle positions in two extreme conditions, bitmap images are synthesized and imported to a convolutional neural network (ConvNet) as a training sample. As a result, a phase diagram is obtained. This trained ConvNet model has been directly applied to the sequence of the recorded images using video microscopy in the experiments to study the melting. [ABSTRACT FROM AUTHOR]

This paper reports on the assembly of a compact, low-cost, pulsed-power facility used for plasma studies. The construction uses two modules placed on opposite sides of the test chamber to minimize the system impedance and improve access to test samples. The stored energy is 1 kJ with a peak current of 135 kA and a 1592 ns quarter-period time. Up until now, an imploding conical-wire array has been studied by using time-integrated (visible) imaging, and time-resolved laser imaging, providing a measure of the plasma jet speed in the range of 170 km/s. Our future plans will continue to investigate high-energy-density plasmas that are relevant to the space environment, fusion, and spectroscopy. [ABSTRACT FROM AUTHOR]

A two-dimensional super-cell phononic crystal semi-active isolator based on magnetorheological elastomers is designed, which can be used for vibration isolation of mechanical devices at medium and high frequencies. The plane wave expansion method of the super-cell is introduced to model the dynamic characteristics of the proposed phononic crystal isolator. The influence of the constituent materials, dimension parameter of the super-cell, and magnetic field intensity on the band structure is investigated by the plane wave expansion method. The results show that the change of material will affect the bandgap frequency of the super-cell and the dimension parameter of the super-cell will affect the bandgap formation mechanism. It is worth pointing out that the bandgap frequency and width of the isolator can be adjusted by controlling the applied current of the magnetorheological elastomer. Therefore, this method offers a broad range of possibilities for phononic crystal vibration isolation design. [ABSTRACT FROM AUTHOR]

In this paper, an intelligent shock isolation bearing based on the negative stiffness platform (SIBP) is designed, manufactured, and modeled. The addition of the negative stiffness platform to the SIBP can further reduce the natural frequency of the structure and enable the isolator to a broader range of isolation frequencies. It is noteworthy that the stiffness of the magnetorheological elastomer (MRE) limit layer can be adjusted to provide controllable seismic resistance and to achieve isolation and vibration reduction under various seismic conditions, such as small and large displacements. Through the theoretical analysis and magnetic field simulation of the SIBP's damping force, the structure of the SIBP is designed and established. Then, the MRE for the SIBP is prepared. The shear storage modulus and damping factor of MRE with different strains are tested and analyzed. A novel dynamics model is established to model the displacement–force hysteretic curve of the SIBP under small displacement and large displacement input. The experiment results show that the theoretical calculation results are in good agreement with the actual shock isolation bearing, and the proposed model can accurately describe the dynamic characteristics of the SIBP, which provides the design basis for the application of the SIBP in active control. [ABSTRACT FROM AUTHOR]

Agglomeration of highly charged microparticles was observed and studied in complex plasma experiments carried out in a capacitively coupled rf discharge. The agglomeration was caused by strong waves triggered in a particle cloud by decreasing neutral gas pressure. Using a high-speed camera during this unstable regime, it was possible to resolve the motion of individual microparticles and to show that the relative velocities of some particles were sufficiently high to overcome the mutual Coulomb repulsion and hence to result in agglomeration. After stabilizing the cloud again through the increase of the pressure, we were able to observe the aggregates directly with a long-distance microscope. We show that the agglomeration rate deduced from our experiments is in good agreement with theoretical estimates. In addition, we briefly discuss the mechanisms that can provide binding of highly charged microparticles in a plasma. [ABSTRACT FROM AUTHOR]

rf discharges are widely used in complex plasma experiments. In this paper, we theoretically investigate the dependence of the particle floating potential on the discharge frequency, assuming the model Margenau expression for the electron velocity distribution function. In doing so we use the orbital motion limited cross section to calculate the electron flux to the particle and collision enhanced collection approximation for the ion flux to the particle. The floating potential is then obtained from the flux balance condition. It is shown that for typical plasma conditions in laboratory rf discharges, normalized floating potential grows with increase of the discharge frequency in collisionless regime and decreases in weakly collisional regime. However, variations in the floating potential are usually small when plasma parameters do not depend on the rf frequency. [ABSTRACT FROM AUTHOR]

This letter reports a technique for increasing the carrier concentration and the conductivity of the p-type CuAlO2 through doping the material with nitrogen. The x-ray photoelectron spectroscopy and the optical band gap analyses suggested that the nitrogen atoms occupying the interstitial sites of the delafossite structure provided the p-type CuAlO2 with an impurity energy level in the energy gap. It was also found that the N-doped CuAlO2 film had its optimum conduction properties when the dopant level reached 1.1 at. %. Here, the carrier concentration was raised from 4.81×1016 in the undoped film to 2.13×1017 cm-3 in the doped film, and the corresponding film’s conductivity was increased from 3.8×10-2 to 5.4×10-2 (Ω cm)-1, as compared with the undoped CuAlO2 film. [ABSTRACT FROM AUTHOR]