Dynamics of an Intense Relativistic Electron Beam Injected into Full Density Air.
Abstract
We have injected an intense relativistic electron beam (about 1 Mev, 16 kA, 25 ns) into the atmosphere and observed the beam in visible light caused by direct beam excitation of air molecules. The emitted visible light was primarily emission in the 2nd positive system of N2 which was delayed with respect to the beam current by about 6 ns but had the same duration (FWHM) as the beam current. Streak photographs of the beam in this visible light were taken with an Imacon 790 camera at various axial positions with a camera time resolution of about 1 ns. These photographs show that the beam remained a single current filament which oscillated about its initial direction as it propagated through the atmosphere, and that while the 'body' of the beam was pinched to a radius of < or = 5 cm the 'nose' was expanded to give the characteristic trumpet-like shape. Beam and net current monitors were used to determine the beam current and the plasma return current whose peak value was > or = 60% of the peak beam current. Comparison of the measured net current to that predicted from the calculated air conductivity and a simple circuit model to represent the beam propagating in the atmosphere showed good agreement provided a transmission line model including the capacitance of the beam in the ionized atmosphere was used. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 21, 1981
- Accession Number
- ADA104743
Entities
People
- E. W. Fordham
- John D. Sethian
- Joseph R. Greig
- R. B. Fiorito
- R. E. Pechacek
Organizations
- United States Naval Research Laboratory