Mu Haibao

Study on the Property Evolution of Atmospheric Pressure Plasma Jets in Helium

Nowadays atmospheric pressure plasma jets (APPJs) are being widely applied to many fields and have received growing interests from cold plasma community. A helium APPJ with co-axial double ring electrode configuration is driven by an AC high voltage power with an adjustable frequency of 1–60 kHz. Experiments are conducted for acquiring the electrical and optical properties of APPJ, including the discharge mode, current peaks phase and APPJs length, etc. Moreover, the actions of Penning effect on APPJ are discussed by adding impurity nitrogen into highly pure helium. The results may contribute to further research and applications of APPJs.

Calibration Algorithm of Surface Charge Density on Insulating Materials Measured by Pockels Technique

Surface charges greatly affect the discharge/flashover development process across an insulator. The relationship between surface charge distribution on insulating materials and measurement data based on Pockels technique is discussed, and an improved algorithm is built to calculate the real surface charge density from original data. In this algorithm, two-dimensional Fourier transform technique and Wiener filter are employed to reduce the amount of numerical calculation and improve the stability of computation. Moreover, this algorithm considers not only the influence of samples thickness and permittivity, but also the impact of charges at different positions. The achievement of this calibration algorithm is demonstrated in details. Compared with traditional algorithms, the improved one supplies a better solution in the calibration of surface charge distribution on different samples with different thickness.

The comparison of the residual charge distribution of surface leader discharge under positive and negative impulse voltage application

Summary form only given. Flashover on insulator surface in the air at atmospheric pressure occurs as a sequence of several processes and leads to the formation of a plasma channel which bridges the electrode gap. The streamer-to-leader transition is a very critical stage of such a breakdown since the leader can propagate a long distance with a low increment of application voltage. The transition and the propagation process of a leader bas become the object of intensive experimental and theoretical studies.

Influence of Surface Carburization of Machinable Ceramics on Its Pulsed Flashover Characteristics in Vacuum

For pulsed power devices, surface flashover phenomena across solid insulators greatly restrict their overall performance. In recent decades, much attention has been paid on enhancing the surface electric withstanding strength of insulators, and it is found that surface treatment of material is useful to improve the surface flashover voltage. The carburization treatment is employed to modify the surface components of newly-developed machinable ceramics (MC) materials. A series of MC samples with different glucose solution concentration (0%, 10%, 20%, 30% and 40%) are prepared by chemical reactions for surface carburization modification, and their surface flashover characteristics are investigated under pulsed voltage in vacuum. It is found that the surface carburization treatment greatly modifies the surface resistivity of MCs and hence the flashover behaviors. Based on the reduction of surface resistivity and the secondary electron emission avalanche (SEEA) theory, the adjustment of flashover withstanding ability can be reasonably explained.