Near‐ultraviolet emission spectrum from an intense relativistic electron‐beam discharge

Time‐integrated emission spectra from the pulsed discharge of a 3.5‐MeV electron beam, with 90‐kA peak current of about 30‐nsec duration, and guided by a glass rod protruding from the cathode in a field‐emitting diode, have been studied with a quartz‐prism spectrograph. With anodes of graphite or polyethylene, the spectrum in the near‐uv to visible range is found to consist mainly of emission lines from C, C+, C++, and C+3, and similar ones from silicon. The spatial dependence of emission intensity indicates that a hot spot is present during the discharge near the anode surface. The temperature and the electron density in the plasma are estimated through a theoretical analysis of the composition of carbon in the gas phase.