Development of high speed and high sensitive digital video camera for lightning to theorize the reliable shielding method against lightning

为研究雷电击地的最终跳跃过程，研制了一种高速、高灵敏度的雷电数码摄像机。该数字摄像机由一个多阳极光电倍增管、直流至50MHz带宽前置放大器、一个静止相机和一个多通道数字记录器组成。该相机具有100倍的感光度、4倍的时间分辨率、2倍的空间分辨率、16倍的动态范围等性能。使用该相机的四次闪电测量活动分别于夏季在岐阜大学和冬季在Uchinada进行。我们得到了一个很好的数据，闪电击中了一个风车。从这些数据中我们发现：(1)新摄像机的波形与旧摄像机的波形非常相似。这两个数据都是可靠的。(2)在闪电起始阶段，新相机的波形中有一些信号，而旧相机的波形中没有信号。这意味着新的比旧的更敏感。(3)新相机的脉冲上升时间比旧相机短。(4)在开始向上先导冲程之前，风车顶端有一些排出物。

To make clear the final jump process of lightning ground stroke, we developed a high speed and high sensitive digital video camera for lightning. This digital video camera consists of a multi-anode photomultiplier, DC to 50MHz bandwidth pre-amplifiers, a still camera and a multi-channel digital recorder. This camera has some performance with one hundred times sensitivity, four times time resolution, two times space resolution and sixteen times dynamic range compared with old one.Four lightning measurement campaigns using this camera have done at Gifu University in summer and at Uchinada in winter. We got a good data of lightning ground stroke to a windmill. From this data we found in the followings,(1) The waveform of the new video camera is very similar with that of the old video camera. Both data are to be reliable.(2) There are some signals in the waveform of the new camera in an initiation stage of lightning when the signal is nothing in the waveform of the old camera. It means the new one is more sensitive than old one.(3) The pulse rising time of the new camera is shorter than that of the old one.(4) There are some discharge from tip of the windmill before starting of an upward leader stroke.