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Секция 3. Модификация свойств материалов = Section 3. Modification of Material Properties The polymeric materials could degrade due to the electron irradiation, photo-irradiation and heat effect following with the surface flashover in vacuum. On the other hand, the surface insulating performance could be improved by electron irradiation. In order to study the effect of electron irradiation on the insulating materials, the surface parameters were measured and the flashover experiment was performed in vacuum after electron beam irradiation. First, several typical polymeric samples, such as polytetrafluoroethylene (PTFE), polymethylmethacrylate (PMMA) and polyamide (PA6), were exposed by different energy electron beam from 10 keV to 30 keV and in different radiation times. Then the surface parameters, such as surface topography, chemical group and surface roughness, were measured for insulating samples in different processing conditions. Since the surface trap distribution is closely related to the microscopic structure and defects, the trap parameters of PA6 samples were deduced based on the surface potential data. In this measurement, the polymeric surface was charged by needle-to-plane corona discharge, and then the surface potential was measured by Kelvin electrostatic probe. The surface flashover experiment in vacuum was performed using finger-type plane-electrodes, and the relationship between electron beam energy, irradiation time, and flashover voltage was analyzed. The experiment results indicate that the surface trap energy level is deeper and the trap density is greater after electron irradiation, and the surface flashover voltages for several materials are also improved to different degrees. Combined the macroscopic dielectric parameters with the microscopic one, the effect of electron irradiation on surface insulating property was analyzed.

The mechanism of audible noise caused by corona discharge of UHV transmission lines is not well resolved. The sound characteristic produced by discharge is the foundation to analyze the intrinsic relation of audible noise and corona discharge. The experiment of sing point corona discharge under DC voltage was developed and the sound pressure produced by corona discharge was measured. The sound pressure in time domain was measured by capacitor microphone. The research results indicate the corona discharges in DC voltage are composed of a series of single discharge pulses. The rising edge and pulse width of single discharge pulse have relation to discharge voltage and electrode polarity. The corona discharge produces the sound pressure with a microsecond pulse lagging behind the single discharge pulse in their waveforms. The time delay between current pulse and sound pulse is mainly caused by sound propagation time from discharge spot to measurement spot. The nanosecond pulsed discharge platform was set up to study the relation of discharge parameter and sound characteristic. The sound pressure waveforms in different discharge parameters were obtained. Experiment results showed that pulsed discharge produce the similar sound pressure with corona discharge. The pulsed discharge platform could be used to study the mechanism of audible noise caused by corona discharge.