中文摘要：

为了研究大气压氦气的介质阻挡放电机理，利用像增强高速相机（ICCD），以20ns曝光时间，拍摄了多组时序发展的时空分辨放电图像，揭示了放电形式由汤森放电向辉光放电的演化。所测阴极位降区厚度0．4mm，应属亚辉光放电类型，而底面拍摄的图像则揭示了放电径向发展的过程。将放电图像转化为可视性更强的三维图像后，发现放电由覆盖整个电极的微弱汤森放电起始，在场强略高的中心处率先发展，并迅速向外扩散。

英文摘要：

Dielectric barrier discharge in helium at atmospheric pressure was studied by taking fast images of the discharge during one current pulse using a fast-gated intensified charge coupled device（ICCD）camera. It was observed that there appeared a weak luminous layer close to the anode at the very beginning of the discharge, and then the luminous area gradually expanded into the entire gap as the anode layer moves towards to the cathode, finally a strong luminous layer formed close to the cathode at the time around the maximum of the current pulse. The evolution of the discharge pattern indicates a transition from Townsend discharge to glow discharge. The measured thickness of cathode fall is 0.4mm, which indicates the discharge being a subnormal glow discharge. The radial evolution of dielectric barrier discharge in helium at atmospheric pressure was also studied by taking end-view photographs of the discharge during one current pulse using the ICCD. The photographs were transformed into three-dimensional ima- ges that make the radial evolution of the discharge more visualized. It was found that the discharge began with a weak Townsend discharge covering the entire electrode surface, developed much more rapidly in the central part where the electric field is higher, and spread rapidly outwards.