Ball lightning project

Summary form only given. In the following up of our initial work on ball lightning, we have developed a special camera for photographing the initial stroke of a lightning discharge. The object is to obtain time resolved photographs of the closed current loops observed in sparkovers in the Holifield 25 MV, DC accelerator at the Oak Ridge National Laboratory. The apparatus comprises a commercial lightning photographic trigger that opens a camera shutter on reception of a light pulse from a lightning discharge. In the commercial configuration, the inherent time delay in the camera´s shutter mechanism causes the camera to miss the initial lightning stroke. However, in nature, lightning in general has several strokes, and so the camera captures the second and subsequent strokes. In our modification, the lightning image is focused on a semi-transparent disc coated with a phosphor having a time constant of about a second. This disc provides a temporary image storage mechanism while the camera shutter is being activated. Test photographs of pulsed light sources have been quite successful. We anticipate on having experimental lightning results at the forthcoming ICOPS meeting