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The Kirkpatrick–Baez (KB) microscope is an effective instrument for x-ray imaging of hot spot. However, the non-uniform distribution of response efficiency in the field of view is a drawback of the KB microscope. A more accurate hot spot image requires the correction of the measured image by combining the hot spot position and the response efficiency distribution. Here, we describe a method to locate the position of the hot spot in the field of view during hot spot imaging with a KB microscope. The position of the hot spot in the field of view can be obtained by measuring the grazing incidence angle change during hot spot imaging. In the experiment of hot spot self-emission imaging with a four-channel KB microscope, the location of the hot spot with an accuracy of 15 μm was realized, and the intensity corrected hot spot image was obtained. This will solve the problem of the non-uniform distribution of the response efficiency of the KB microscope and enable quantitative measurement of hot spot radiation intensity. [ABSTRACT FROM AUTHOR]

We demonstrate similarity-based scaling networks for capacitive radio frequency (RF) plasmas, which extensively correlate discharge characteristics under varied conditions, incorporating the transition from original to similarity states. Based on fully kinetic particle-in-cell simulations, similar RF discharges in argon are demonstrated with three external control parameters (gas pressure, gap distance, and driving frequency) simultaneously tuned. A complete set of scaling pathways regarding fundamental discharge parameters is obtained, from which each plasma state finds its neighboring node with only one control parameter tuned. The results from this study provide a promising strategy for plasma multi-parameter mapping, enabling effective cross-comparisons, prediction, and manipulation of RF discharge plasmas. [ABSTRACT FROM AUTHOR]

To investigate the decomposition law of SF6 under negative direct current partial discharge (PD) at different energies, a SF6 PD hybrid numerical model based on fluid dynamics and plasma chemical reaction models, in which 14 particle species and 24 chemical reactions are considered, is proposed. The effectiveness of the proposed model is validated with the current pulse waveform and the V–I discharge curve obtained by experiment. The influence of discharge energy on SF6 PD characteristic quantities and SF6 decomposition products is investigated with simulation and experiment. The results show that most of the discharge area of SF6 is neutral, and the cation clouds only exist in the ionosphere (4.79–5 mm). With the increase in applied voltage, the electric field intensity of the needle plate gap does not increase completely and even decreases in some areas. Moreover, different from the traditional opinion, the generation of SO2F2 under PD is mainly generated by the hydrolysis reaction of SOF4, which is formed by [SF5], [SF4], and [OH], [O]. The reaction path of [SF2] with O2 is not important. Thus, c(SO2F2)/c(SOF2 + SO2) can be used as the energy characteristic component ratio because of its ability to represent the low-fluorine sulfide ratio n([SF5])/n([SF4]). [ABSTRACT FROM AUTHOR]

The plasma arc caused by lightning overvoltage can significantly degrade the power grid reliability. Thus, it is essential to design an efficient arc extinguishing system. The modeling and analysis of the plasma arc in an arc extinguishing system can provide an essential theoretical basis for improving and optimizing its structure. However, the precision of the governing equation and boundary value of the plasma arc model chosen in previous studies can be entirely different from the corresponding practical values. This study develops an arc extinguishing system named "convective shock wave complex system." In order to further optimize its structure and achieve a better arc extinguishing effect, an appropriate model is established to analyze the plasma's operation characteristics inside the arc extinguishing device while stroking by lightning. Based on the magnetohydrodynamics theory, the COMSOL software is utilized to analyze the temperature of the plasma arc, the flow rate of gas in the cavity, and the conductivity and current density of some monitoring points to comprehensively analyze the plasma's physical characteristics in the system. Finally, a virtual lightning experiment is utilized to evaluate the simulation results. [ABSTRACT FROM AUTHOR]

The x-ray emissivity of gadolinium (Gd) and gold (Au) has been studied using the FLYCHK code. The results show that the Gd M-band is lower than 2 keV and that Gd has a higher x-ray emissivity at low temperature. Thus, we proposed a Gd + Au + Gd sandwich design to improve the x-ray conversion efficiency (CE). Under a laser intensity of 1 × 1015 W/cm2, a 11%–17% enhancement of the CE and an optimized x-ray spectrum were achieved in one-dimensional simulation. The enhancement of the CE is mainly due to an enhancement of the soft x-ray flux (0 keV–2 keV). In addition, the high energy x-ray flux (2 keV–5 keV) is lower than that of Au. Particularly at an early stage, the laser ablates the Gd layer, and the temperature of the Au layer is insufficient for producing an M-band emission. Thus, the high energy x-ray flux is rather low. A sandwich design not only takes advantage of the higher x-ray emissivity of Gd under specific conditions in an efficient manner but also simplifies the target fabrication, which is important. In addition, Gd can also be used to optimize the future design of depleted uranium Hohlraum. [ABSTRACT FROM AUTHOR]

In order to study the laser plasma instabilities (LPIs) in the context of some novel six-side laser-driven indirect designs like the six-cylinder-port hohlraum and the three-axis cylindrical hohlraum, where the laser beams inject in hohlraum with a large angle. LPI experiments in cylindrical hohlraum with only outer beams were designed and performed based on the current laser arrangement condition of SGIII laser facility for the first time. Stimulated Brillouin backscatter (SBS) was found to be the dominant instability with high instantaneous reflectivity in experiments. A typical feature was obtained in the time-resolved spectra of SBS, which maintained similar for different laser intensities of the interaction beam. The experimental data are analyzed by the hydrodynamic simulations combined with HLIP code, which is based on the ray-tracing model. By analysis of experimental data, it is argued that the mixture of gas and Au in the region of their interface is important to SBS, which indicates the need for the mixture model between the filled gas and the high Z plasma from hohlraum wall in the hydrodynamic simulations. Nonlinear saturation of SBS as well as the smoothed beam are also discussed here. Our effective considerations of the ions pervasion effect and the smoothed beam provide utilitarian ways for improvement of the current ray-tracing method. [ABSTRACT FROM AUTHOR]