Short-Pulse Electron-Beam Propagation Experiments in a Controlled-Environment Chamber.

摘要

Propagation of a 500-keV, 6-kA, 3-ns electron beam in air has been studied in a 3.4 m diam controlled-environment chamber at pressures of 75-1600 Pa (0.56-12 Torr). Open-shutter photography, Faraday cup, and magnetic-field probe measurements were performed, and results were compared with those obtained for beam propagation in a 7.6 cm diam glass tube. Over a propagation window of 270-800 Pa, rectilinear propagation to within < or approx. 5 mrad was observed despite the lack of guide tube walls. Propagation at the low end of the window was limited by rapid nose-erosion rates of up to 10 cm/ns. At optimal propagation pressures (400-550 Pa), magnetic probe data were used to estimate induced electric fields and nose erosion caused by ohmic energy loss. Results were consistent with Faraday cup and calorimeter data. At higher pressures, propagation was erratic, and appeared to be terminated by the lack of a stable pinch formation. For those shots where propagation was observed at pressures above 550 Pa, Faraday cup traces show a loss of the beam tail. (Author)