Collective Ion Acceleration and Electron Beam Propagation in Dielectric Guides.
Final rept. 1 Feb 79-31 Jan 81,
SPIRE CORP BEDFORD MA
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The propagation of electron beam currents much greater than the space charge limit and collective ion acceleration in evacuated dielectric guides was investigated. Experiments at Spire and at the Gamble I facility of NRL show that the beam front propagation velocity is not affected by the dielectric guide downstream from the anode region of the accelerator. The propagated current, however, depends strongly on guide parameters, and is considerably diminished in a shortened guide configuration. Collectively accelerated ions were not observed using the 40 ns, 200 keV electron accelerator at Spire, although earlier experiments using longer, lower energy pulses showed considerable ion acceleration. Proton energies more than 14 times the electron beam energy were observed during the experiment on Gamble I. An estimated 2x10 to the 9th power protons at 12 MeV or greater along with 3x10 to the 11th power protons at 5 MeV or greater were observed in a single shot. The origin of the collectively accelerated protons was principally in the anode foil of the accelerator. Suggestions for increasing the energy and yield of collectively accelerated ions include improving the homogeneity of the downstream plasma and reducing the magnetic field of the propagating electron beam current. Author
- Particle Accelerators