Study of electron-beam-produced plasmas by fast photography and emission spectroscopy

Abstract

The luminous events produced by a drifting relativistic electron beam (REB) (1–2 MeV, 100 kA, 40 nsec) have been photographed with an image converter of 5-nsec gate time. Coupled with a transmission spectrograph, time-gated snapshots (1 μsec) of the spectra have been recorded. For air pressure between 0.1 and 0.3 Torr, the beam is self-focused and it yields a spark spectrum containing mainly N+, with some O+ and N++ lines. In 0.8–1 Torr of air, the beam is unfocused and it yields the N2 (B←C) but not the (A←B) bands. In the presence of a target, the unfocused beam may again produce an air breakdown. A slitless spectrum then yields a two-dimensional image of the event, which may be related to the spatial distribution of the beam. The results are discussed in connection with REB and ion acceleration research. In addition, Lichtenberg-type discharge tracks in a Plexiglas disk irradiated by 2-MeV beams are photographed and compared with the fluorescence lifetime of the N2 (B←C) bands.

Advanced Electron Beam Diagnostics.

“…In some studies of surface breakdown the entrance slit of the TRW transmission spectrograph was removed. 12 The slitless arrangement allows twodimensional mapping as well as spectral dispersion of the event. In the photograph shown in figure 30, multiple images of the breakdown region The spectral image shows a somewhat hollow pattern instead of the centerpeaked damage pattern.…”

Argon ion excitation by relativistic electrons: II. Chemical kinetics

“…Plasmas produced by relativistic electron beams (REB) often emit large amounts of light (Wei et al 1977). This property has allowed them to be successfully used as pump sources for gas lasers, particularly those utilizing atomic transitions in rare gases.…”