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In power transformers, the degradation of the insulating oil due to aging, overheating, and electric discharge leads to the production of characteristic gases including H2, CH4, $\text{C}_{{2}}\text{H}_{{2}}$ , $\text{C}_{{2}}\text{H}_{{4}}$ , $\text{C}_{{2}}\text{H}_{{6}}$ , CO, and CO2. The composition and concentration of these gases provide valuable insights into the operational condition of the transformer. Dissolved gas analysis (DGA) is a vital diagnostic and predictive technique for transformer faults, which is closely associated with the transportation of gases in the oil through convection and diffusion. This study employs a combination of molecular dynamics simulation and experimental measurement to determine the diffusion coefficients ${D}$ of the seven characteristic gases in a naphthenic mineral oil across a range of temperature ( ${T}$ = 20 °–90 °C) and dc electric field strength ( ${E}$ = 0–3 kV/mm). The calculated and measured results of the diffusion coefficients exhibit a strong agreement, demonstrating a positive correlation with temperature following ${D}\propto \text{e}^{-\text {a}/\text {T}}$ , in which the influence from a weak dc electric field ranging from 0 to 3 kV/mm could be negligible.

The modular augmented staged electromagnetic launcher can save electric current through the armature and increase projectile acceleration, helping to miniaturize the system. First, to predict the launcher performance, an improved simulation method considering the rail and coil structure as well as the coupling magnetic field action is proposed. The proposed method is then used to compare the equal-length and equal-time segment ways of the two-stage launcher. It is demonstrated that the former holds a higher muzzle velocity and a segment-by-segment rise in efficiency. Specifically, it can realize a muzzle velocity of 1.8 km/s at a peak current of 65.5 kA in the main circuit. Finally, an optimization of the structure is carried out to analyze the main parameters that influence the muzzle velocity. This study serves as a guide for the design of the launcher’s structure and the selection of the pulsed power system of a modular augmented staged electromagnetic launcher.

The Type-I edge-localized mode (ELM) is one of the transient events threatening the first wall, with the heat flux $\sim $ GW $\cdot ~\text{m}^{-2}$ , duration 0.5–1.0 ms, and the frequency 1–10 Hz expected in international thermonuclear experimental reactor (ITER)-like Tokamak. First, a millisecond pulsed repetitive plasma generator based on capillary discharge is designed to produce high heat flux plasma for simulating ELM heat load. Then, experimental study is carried out on the plasma discharge characteristics, jet morphology, and plasma parameters under different capillary diameters and materials, which shows that the central heat flux is 0.8–1.31 GW $\cdot ~\text{m}^{-2}$ , with the plasma temperature 1.16–1.25 eV and electron density 5.19– $9.12\times 10^{22}\,\,\text{m}^{-3}$ . It also shows that the discharge characteristics and plasma parameters of polycarbonate (PC) are less affected by the capillary diameter than polyethylene (PE), which is mainly due to the higher average ionization energy for PC, indicating that PC capillaries are more appropriate for repetitive pulsed discharge. The research can provide basic parameters and material selection guidance for repetitive capillary plasma generator to produce transient high heat load.

Rod pinch diode (RPD) is an intense text X-ray point source with a millimeter spot diameter, tens of nanosecond pulsewidth, and tens of keV to MeV photon energy, resulting in extraordinary flash radiography performance. Classical RPD is featured with a high-impedance vacuum gap between the annular cathode and the central anode rod, which limits the electron current and electrical power density, therefore is not conducive to the improvement of brightness. Plasma prefilling can effectively reduce the RPD impedance, thereby increasing the electron current and realizing an impedance match of RPD with low-impedance, high-power-density drivers. In this article, an experimental study on text plasma-prefilled RPD is carried out based on a fast linear transformer driver (FLTD) with relatively low charging voltage; the RPD anode and cathode are initially connected by metal wires, which are transformed into plasma shortly after the onset of discharge current. A quasi-spherical X-ray spot is obtained with $\sim $ 0.45 mm diameter, $\sim $ 30 ns pulsewidth, 0.6 rad@1 m (LiF) dose, and 55–60 keV equivalent mono-energy photon energy. The radiography performance is further characterized by a tungsten text rolled-edge and slit plate. The preliminary results proved the feasibility of text low-impedance RPD as a flash radiography source within the relatively low photon energy range.

Magnetic field measurement in Z-pinch plasma has drawn considerable interest because it is a key problem in the research of dynamic behaviors and the coupling of magnetic field and plasma. In this study, the measurement sensitivity of the rotation angle in Z-pinch plasma was improved by considering the second polarization effect caused by optical elements. The magnetic field distribution of preconditioned single-wire Z-pinch plasma was determined by this method. The Faraday rotation of the 1064-nm probe laser was measured by the beam-splitting polarization method when the plasma acted as a Faraday medium. A second polarization effect on the rotation angle was realized by taking the different transmittances and reflectivities of the $p$ and $s$ components of the beam splitters into account. This configuration doubled the sensitivity of the Faraday rotation measurement. The diagnostic errors produced by the techniques and data processing were quantified. The early stage of the preconditioned imploding plasma was monitored, and the distributions of areal electron density, Faraday rotation, and magnetic field were measured. The experimental results demonstrated that the current distribution can be divided into three parts by two dense shells. The majority of the current was distributed outside the dense shell which existed inside the coronal plasma. In addition, only a small amount of current was distributed in the wire core.

The combination of energetic material (EM) and electrical wire explosion (EWE) is an efficient and economical method to generate strong shock waves (SWs). The idea resembles the exploding bridge-wire (EBW) detonator, but in this case, the EWE operates with much higher electrical energy storage, and the EMs of much lower sensitivity can be directly ignited, which provides a practical compromise among limited energy storage, strong SWs, and safe usage of explosives. The hybrid load based on EWE ignited EMs has been successfully applied for reservoir stimulation in exploitation of both conventional and unconventional oil/gas resources. In this brief review, we summarize the EWE characteristics, SW characteristics, ignition mechanism, and engineering applications of this hybrid load, and give suggestions for future research directions.