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<jats:p>A new heating method is proposed to increase the cell temperature of the 6–8 type multi-anvil apparatus without reducing the volume of the sample chamber. The double-layer heater assembly (DHA) has two layers of heaters connected in parallel. The temperature of the cell was able to reach 2500 °C by using 0.025 mm rhenium foils, and the temperature limit was increased by 25% compared with that of the traditional single-layer assembly. The power–temperature relationships for these two assemblies with different sizes were calibrated by using W/Re thermocouple at 20 GPa. When the volume of samples was the same, the DHA not only attained higher temperature, but also kept the holding time longer, compared to the traditional assembly. The results of more than ten experiments showed that the new 10/4 DHA with a relatively large sample size (2 mm in diameter and 4 mm in height) can work stably with the center temperature of the sample cavity exceeding 2300 °C under the pressure of 20 GPa.</jats:p>

<jats:p>The behaviors of helium clusters and self-interstitial tungsten atoms at different temperatures are investigated with the molecular dynamics method. The self-interstitial tungsten atoms prefer to form crowdions which can tightly bind the helium cluster at low temperature. The crowdion can change its position around the helium cluster by rotating and slipping at medium temperatures, which leads to formation of combined crowdions or dislocation loop locating at one side of a helium cluster. The combined crowdions or dislocation loop even separates from the helium cluster at high temperature. It is found that a big helium cluster is more stable and its interaction with crowdions or dislocation loop is stronger.</jats:p>

<jats:p>The ionization processes of NH<jats:sub>3</jats:sub> molecule are studied by photoelectron velocity map imaging technique in a linearly polarized 400-nm femtosecond laser field. The two-dimensional photoelectron images from ammonia molecules under different laser intensities are obtained. In the slow electron region, the values of kinetic energy of photoelectrons corresponding to peaks 1, 2, 3, and 4 are 0.27, 0.86, 1.16, and 1.6 eV, respectively. With both the kinetic energy and angular distribution of photoelectrons from NH<jats:sub>3</jats:sub> molecules, we can confirm that the two-photon excited intermediate Rydberg state is A<jats:sup>∼1</jats:sup> <jats:inline-formula> <jats:tex-math><?CDATA ${{\rm{A}}}_{2}^{\prime\prime}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi mathvariant="normal">A</mml:mi> <mml:mn>2</mml:mn> <mml:mrow> <mml:mo>′</mml:mo> <mml:mo>′</mml:mo> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_29_9_093201_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> (<jats:inline-formula> <jats:tex-math><?CDATA ${v}_{2}^{^{\prime} }=3$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>v</mml:mi> <mml:mn>2</mml:mn> <mml:mo>′</mml:mo> </mml:msubsup> <mml:mo>=</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_29_9_093201_ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>) state for photoelectron peaks 2, 3, 4, and the three peaks are marked as 1<jats:sup>2</jats:sup>2<jats:sup>3</jats:sup> (2 + 2), 1<jats:sup>1</jats:sup>2<jats:sup>3</jats:sup> (2 + 2), and 1<jats:sup>0</jats:sup>2<jats:sup>3</jats:sup> (2 + 2) multi-photon processes, respectively. Then, peak 1 is found by adding a hexapole between the source chamber and the detection chamber to realize the rotational state selection and beam focusing. Peak 1 is labeled as the 1<jats:sup>3</jats:sup>2<jats:sup>3</jats:sup> (3 + 1) multi-photon process through the intermediate Rydberg state <jats:inline-formula> <jats:tex-math><?CDATA ${{\rm{E}}}^{\sim 1}{A}_{1}^{^{\prime} }$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msup> <mml:mi mathvariant="normal">E</mml:mi> <mml:mrow> <mml:mo>∼</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> <mml:msubsup> <mml:mi>A</mml:mi> <mml:mn>1</mml:mn> <mml:mo>′</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_29_9_093201_ieqn3.gif" xlink:type="simple" /> </jats:inline-formula>. The phenomena of channel switching are found in the slow electron kinetic energy distributions. Our calculations and experimental results indicate that the stretching vibrational mode of ammonia molecules varies with channels, while the umbrella vibration does not. In addition, we consider and discuss the ac-Stark effect in a strong laser field. Peaks 5 and 6 are marked as (2 + 2 + 1) and (2 + 2 + 2) above threshold ionization processes in the fast electron region.</jats:p>

<jats:p>With the semiclassical ensemble model, we explore the relative phase-dependent nonsequential double ionization (NSDI) of Mg by counter-rotating two-color circularly polarized (TCCP) laser pulses. The yield of Mg<jats:sup>2+</jats:sup> sensitively depends on the relative phase Δ<jats:italic>φ</jats:italic> and the intensity of TCCP laser fields. At Δ<jats:italic>φ</jats:italic> = 1.5<jats:italic>π</jats:italic>, the yield of Mg<jats:sup>2+</jats:sup> exhibits a pronounced peak in the 0.05 PW/cm<jats:sup>2</jats:sup> laser field. This behavior results from the increase of the initial transverse velocity compensating for the drift velocity with the decreasing angle by analyzing the angular distributions of the electron pairs in four relative phases. By changing the relative phases, we find that the recollision excitation with subsequent ionization and the recollision-impact ionization mechanisms can be controlled with TCCP laser fields.</jats:p>

<jats:p>Resonance enhanced two-photon ionization process of hydrogen atom via the resonant laser pulse is studied by Bohmian mechanics (BM) method. By analyzing the trajectories and energies of Bohmian particles (BPs), we find that under the action of high frequency and low intensity multi-circle resonant laser pulses, the ionized BPs first absorb one photon completing the excitation, and then absorb another photon, completing the ionization after staying in the first excited state for a period of time. The analysis of work done by the forces shows that the electric field force and quantum force play a major role in the whole ionization process. At the excitation moment and in the excitation-ionization process, the effect of the quantum force is greater than that of the electric field force. Finally, we discuss the principle of work and energy for BPs, and find that the electric field force and quantum force are non-conservative forces whose work is equal to the increment of mechanical energy of the system. In addition, it is proved that the quantum potential energy actually comes from the kinetic energy of the system and the increment of kinetic energy is equal to that of the kinetic energy of the system.</jats:p>

<jats:p>The effects of temperature and pressure on laser-induced fluorescence (LIF) of OH are numerically studied under the excitation of A–X (1,0) transition at high pressures. A detailed theoretical analysis is carried out to reveal the physical processes of LIF. It is shown that high pressure LIF measurements get greatly complicated by the variations of pressure- and temperature-dependent parameters, such as Boltzmann fraction, absorption lineshape broadening, central-frequency shifting, and collisional quenching. Operations at high pressures require a careful choice of an excitation line, and the <jats:italic>Q</jats:italic> <jats:sub>1</jats:sub>(8) line in the A–X (1,0) band of OH is selected due to its minimum temperature dependence through the calculation of Boltzmann fraction. The absorption spectra of OH become much broader as pressure increases, leading to a smaller overlap integral and thus smaller excitation efficiency. The central-frequency shifting cannot be omitted at high pressures, and should be taken into account when setting the excitation frequency. The fluorescence yield is estimated based on the LASKIN calculation. Finally, OH-LIF measurements were conducted on flat stoichiometric CH<jats:sub>4</jats:sub>/air flames at high pressures. And both the numerical and experimental results illustrate that the pressure dependence of fluorescence yield is dominated, and the fluorescence yield is approximately inversely proportional to pressure. These results illustrate the physical processes of OH-LIF and provide useful guidelines for high-pressure application of OH-LIF.</jats:p>

<jats:p>A novel leaky-wave antenna (LWA) utilizing spoof surface plasmon polaritons (SSPPs) excitation is proposed with continuous scanning range from endfire to forward. The designed transmission line unit supports two SSPPS modes, of which the 2nd order mode is applied in the design. A novel strategy has been devised to excite the spatial radiation of the –1st order harmonics by arranging periodic counter changed sinusoidal structures on both sides of the SSPPs transmission line. Both full-wave simulation and measurement results show that the proposed LWA presents wide scanning angle from endfire to forward. In the frequency range from 4 GHz to 10 GHz, LWAs achieve scanning from 90° to +20°, covering the entire backward quadrant continuously.</jats:p>

<jats:p>Based on the coupled acoustic scattering of two neighboring fluid-filled thin elastic shells suspending in an unbounded viscous liquid, an analytical method is developed to calculate the acoustic radiation force (ARF) of the shells. Two physical effects are taken into account: elastic radiation scattering and the multiple interactions of shells. Numerical results reveal that the magnitude of ARF can be enhanced by the sound radiation from the elastic shell undergoing forced vibrations and two resonant peaks can be observed on the ARF function curves. The feature of the lower peak is determined by the interactions and acoustic response of the back shell. The attractive forces can be obtained in the low <jats:italic>kR</jats:italic> <jats:sub>1</jats:sub> band for the case of radius ratio <jats:italic>R</jats:italic> <jats:sub>2</jats:sub>/<jats:italic>R</jats:italic> <jats:sub>1</jats:sub> &gt; 1, while the magnitude of ARF at the lower peak may be influenced to some extent by acoustic shielding phenomenon for the case of radius ratio <jats:italic>R</jats:italic> <jats:sub>2</jats:sub>/<jats:italic>R</jats:italic> <jats:sub>1</jats:sub> &lt; 1. Accordingly, the interactions of particles cannot be ignored. The results may provide a theoretical basis for precisive manipulation of multiple particle systems.</jats:p>

<jats:p>This work presents the Gaussian process tomography (GPT) based on Bayesian data analysis and its applications in soft x-ray (SXR) and absolute extreme ultraviolet spectroscopy (AXUV) diagnostics on experimental advanced superconducting tokamak (EAST). This is the first application of the GPT method in the AXUV diagnostic system in fusion devices. It is found that even if only horizontal detector arrays are used to reconstruct the two-dimensional (2D) distribution of SXR and AXUV emissivity fields, the GPT method performs robustly and extremely fast, which enables the GPT method to provide real-time feedback on impurity transport and fast magnetohydrodynamics (MHD) events. By reconstructing SXR emissivity in the poloidal cross section on EAST, an <jats:italic>m</jats:italic>/<jats:italic>n</jats:italic> = 1/1 internal kink mode has been observed, and the plasma redistribution due to the kink mode is clearly visible in the reconstructions, where <jats:italic>m</jats:italic> is the poloidal mode number and <jats:italic>n</jats:italic> is the toroidal mode number. Sawtooth-like internal disruptions extended throughout the entire plasma core and mainly driven by the <jats:italic>m</jats:italic>/<jats:italic>n</jats:italic> = 2/1 mode have been acquired. During the sawtooth-like internal disruption crash phase, the conversion from an <jats:italic>m</jats:italic> = 2 mode to an <jats:italic>m</jats:italic> = 1 mode is observed. Using the reconstructed AXUV emissivity field we were able to observe the process of impurity accumulated in the plasma core and the mitigation of core impurity due to neon injection in the plasma edge. The data from all other diagnostics involved in the analysis shows that the reconstructions from AXUV measurements are reliable.</jats:p>

<jats:p>In supersonic flowing plasmas, the auto-resonant behavior of ion acoustic waves driven by stimulated Brillouin backscattering is self-consistently investigated. A nature of absolute instability appears in the evolution of the stimulated Brillouin backscattering. By adopting certain form of incident lights combined by two perpendicular linear polarization lasers or polarization rotation lasers, the absolute instability is suppressed significantly. The suppression of auto-resonant stimulated Brillouin scattering is verified with the fully kinetic Vlasov code.</jats:p>