Large-scale Kinetic Simulations of Colliding Plasmas within a Hohlraum of Indirect Drive Inertial Confinement Fusions

The National Ignition Facility has recently achieved successful burning plasma and ignition using the inertial confinement fusion (ICF) approach. However, there are still many fundamental physics phenomena that are not well understood, including the kinetic processes in the hohlraum. Shan et al. [Phys. Rev. Lett, 120, 195001, 2018] utilized the energy spectra of neutrons to investigate the kinetic colliding plasma in a hohlraum of indirect drive ICF. However, due to the typical large spatial-temporal scales, this experiment could not be well simulated by using available codes at that time. Utilizing our advanced high-order implicit PIC code, LAPINS, we were able to successfully reproduce the experiment on a large scale of both spatial and temporal dimensions, in which the original computational scale was increased by approximately 7 to 8 orders of magnitude. When gold plasmas expand into deuterium plasmas, a kinetic shock is generated and propagates within deuterium plasmas. Simulations allow us to observe the entire progression of a strong shock wave, including its initial formation and steady propagation. Although both electrons and gold ions are collisional (on a small scale compared to the shock wave), deuterium ions seem to be collisionless. This is because a quasi-monoenergetic spectrum of deuterium ions can be generated by reflecting ions from the shock front, which then leads to the production of neutrons with unusual broadening due to beam-target nuclear reactions. This work displays an unprecedented kinetic analysis of an existing experiment, shedding light on the mechanisms behind shock wave formation. It also serves as a reference for benchmark simulations of upcoming new simulation codes and may be relevant for future research on mixtures and entropy increments at plasma interfaces

Target density effects on charge tansfer of laser-accelerated carbon ions in dense plasma

We report on charge state measurements of laser-accelerated carbon ions in the energy range of several MeV penetrating a dense partially ionized plasma. The plasma was generated by irradiation of a foam target with laser-induced hohlraum radiation in the soft X-ray regime. We used the tri-cellulose acetate (C$_{9}$H$_{16}$O$_{8}$) foam of 2 mg/cm$^{-3}$ density, and $1$-mm interaction length as target material. This kind of plasma is advantageous for high-precision measurements, due to good uniformity and long lifetime compared to the ion pulse length and the interaction duration. The plasma parameters were diagnosed to be T$_{e}$=17 eV and n$_{e}$=4 $\times$ 10$^{20}$ cm$^{-3}$. The average charge states passing through the plasma were observed to be higher than those predicted by the commonly-used semiempirical formula. Through solving the rate equations, we attribute the enhancement to the target density effects which will increase the ionization rates on one hand and reduce the electron capture rates on the other hand. In previsous measurement with partially ionized plasma from gas discharge and z-pinch to laser direct irradiation, no target density effects were ever demonstrated. For the first time, we were able to experimentally prove that target density effects start to play a significant role in plasma near the critical density of Nd-Glass laser radiation. The finding is important for heavy ion beam driven high energy density physics and fast ignitions.Comment: 7 pages, 4 figures, 35 conference

Analysis and Modeling of Novel Low-Temperature SOFC With a Co-Ionic Conducting Ceria-Based Composite Electrolyte

In recent years, ceria-based composites (CBCs) have been developed as electrolytes for low-temperature solid oxide fuel cells. These materials exhibit extremely high ionic conductivities at 400-600 degrees C. It has also been found that both oxide ion and proton can be conducted in the CBC electrolytes, which makes such co-ionic conducting fuel cell distinct from any other types of fuel cells. In this study, a model involving three charge carriers (oxide ion, proton, and electron) is developed to describe the fuel cell with CBC electrolytes. Various operating characteristics of the fuel cell with CBC electrolytes are investigated, compared to those of the fuel cell with doped ceria electrolytes. The results indicate that the CBC electrolyte behaves as a pure ionic conductor, the cell is more efficient, and a higher output is expected at low temperatures under the same pressure operation than that of the cell with doped ceria electrolytes. [DOI: 10.1115/1.2971173

A novel stable nanopositioner based on a single piezoelectric stack: PistolDrive

We describe a novel stable piezoelectric nanopositioner which just use one piezoelectric stack and one simple driving signal, in which the central shaft is clamped by one BeCu spring and four SiN balls that bonded to the inner wall of the cylindrical tube. The cylindrical tube is fixed on the free end of the piezoelectric stack. Applying one increasing voltage signal on the piezoelectric stack, according to the principle of piezoelectricity, the piezoelectric stack will extend smoothly. When canceling this voltage signal suddenly, the piezoelectric will recover to its original length while the central shaft will keep stationary for its inertance. So, the central shaft will be sliding a small distance relative to the piezoelectric stack. Normally, the heavier of the central shaft, the better moving stability, resulting in a high output force of the nanopositioner. Because of the simple structure, simple working principle and good mechanical stability, our novel nanopositioner can be easily used in Scanning Probe Microscopy system and Active Optical mirror adjustment system in large scale astronomical telescope

Low frequency acoustic energy harvester based on a planar Helmholtz resonator

A novel acoustic energy harvester (AEH) based on an acoustic Helmholtz resonator is proposed in this research to harvest low frequency acoustic energy. The height of the resonator is deep subwavelength of the interesting sound wave, meaning that the overall structure is compact. The neck component is designed as tapered form, specifically to reduce the influence of acoustic resistance. The proposed Helmholtz resonator was evaluated using numerical simulation and experimental tests. In the comparison experiment, the proposed acoustic resonator is compared with an acoustic resonator with uniform neck configuration, and the measured results show the proposed structure can amplify low frequency sound effectively and the resonance frequency corresponds well with the numerical simulation. A PZT-5H piezoelectric patch, bonded to the top side of the AEH, is used to convert mechanical strain energy into electrical power. Experimental results illustrate that under 100 dB SPL excitation, maximum 27.2 μW power can be harvested at 217 Hz and maximum 64.4 μW power can be harvested at 341 Hz. These results correspond to acoustic and mechanical resonance respectively

Nonlinear Ultrasonic Detection Method for Delamination Damage of Lined Anti-Corrosion Pipes Using PZT Transducers

Lined anti-corrosion pipes are widely used in oil and gas, petrochemical, pharmaceutical industries. However, defects, especially delamination, may occur in the production and service of pipes which result in safety accidents. Based on nonlinear ultrasonic theory, this paper studied the delamination detection method using the nonlinear harmonics for lined anti-corrosion pipes. The response characteristics of the anti-corrosion pipe were obtained through a sweep sine response experiment and the preferred excitation frequency was determined. The Wavelet Packet transform and Hilbert⁻Huang transform is applied for signal process and feature extraction. Then, a series of experiments were carried out and the results were analyzed and discussed. The results showed that a second-order and third-order nonlinear coefficient increased with the delamination damage. The amplitude of second-harmonic is much stronger than the third-order one. The mean squared error of the nonlinear coefficient, which was processed by Wavelet Packet transform and Hilbert⁻Huang transform, is smaller than wavelet packet transform and Discrete Fourier transform or processed only Hilbert⁻Huang transform. The higher harmonics can describe the change of delamination damage, which means that the nonlinear ultrasonic detection method could use for damage detection of anti-corrosion pipe. The nonlinear higher-harmonic is sensitive to delamination damage. The nonlinear ultrasonic method has the potential for damage detection for lined anti-corrosion pipes