Spectral emissions of the Experimental Test Accelerator beam in 500-Torr synthetic air have been measured in the wavelength range 250–700 nm for beam currents of 4.5 and 8 kA. Intense emissions are identified as radiation from nitrogen. Relative intensities agree well with Franck–Condon factors. Wet air results in a dramatic decrease (by a factor of 2–3) in intensity over the scanned range. This effect is presently attributed to increased hose motion. Near 700 nm, emissions that are not observed in dry air, are identified as emanating from water vapor, nitric oxide, and oxygen. The pressure dependence of emitted intensities at 337.1 and 391.4 nm were measured from 80 μ to 500 Torr of nitrogen as well as dry synthetic air. Results obtained for an 8-kA beam are not explained by a time-dependent Boltzmann air chemistry code which predicted very well previous measurements for a 1–kA beam.
This report presents results from the RINGBEARER II linearized monopole/ dipole particle simulation for an intense relativistic electron beam propa gating in a gas near three types of channels: 1) pre-existing conductivity, 2) density, and 3) density with pre-existing conductivity. Comparisons are made with earlier analytic results for the initial conditions for the pre existing conductivity channel. DISCLAIMER
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The utility of optical emissions for diagnostic purposes in the ionfocused regime is explored. Two possible uses of the emissions are examined: (1) The time delay of 337.1-nm emissions relative to 391.4-nm emissions is observed to scale with the beam-neutralization time; (2) Emissions at 391.4 nra may delerjnijis beam-current density at the front of the beam.
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