Speaker
Description
Intense relativistic electron beams such as those produced by the DARHT accelerators, consist of large total currents of 1.6-2 kA at modest energies in the range of 16-20 MeV. Beam envelope codes are generally used to predict the evolution of the first moment of the radial distribution (i.e. beam 2-RMS radius) assuming a constant emittance. Upon passing through a thin metal foil, such as may be used in a vacuum window, the beam experiences multiple Coulomb scattering and foil focusing effects which modify downstream transport. We measure the 4-RMS emittance of the beam with and without a material scattering foil using the solenoid sweep method with a downstream magnet. A 50 μm Ti foil is found to increase the emittance from about 0.09 cm-rad to 2.9 cm-rad after 1.5 m of transport. We also make measurements with aluminum scattering foils 1.5 m upstream and 3 cm upstream of the imaging foil to examine the beam dynamics after scattering. We find envelope codes are able to describe the 2-RMS radius of the beam after foil interaction taking into account appropriate weights on the scattering angle after 1.5 m of transport.
| Region represented | North America |
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