Early-time behavior of spectral emissions from the interaction of intense relativistic electron beams with initially neutral gases

Visible‐UV spectral emissions from electron beam (700 kV, 12 kA, 50 ns) generated neon plasmas have been investigated over a wide pressure range (0.1–100 Torr) with and without axial magnetic guide field. The Ne I–III line emissions were viewed perpendicular to the beam propagation; attention was focused on a time delay of the onset of the emission with respect to the beam front arrival in the field of view, and on correlations of the subsequent intensity evolution with that of the beam and net (beam plus plasma) currents. The observations are interpreted as direct confirmation of the major processes for gas ionization and excitation that occur depending on the gas pressure and magnetic guide field.