Title :
Observation of strong self-focusing of an intense relativistic electron beam impinging on a SiO2 target
Author :
Vermare, C. ; Donohue, John T. ; Labrouche, J. ; Le Taillandier de Gabory, P. ; Villate, D.
Author_Institution :
CEA/Centre d´´Etudes Sci. et Tech. d´´Aquitaine, Le Barp, France
fDate :
10/1/1999 12:00:00 AM
Abstract :
A substantial reduction in the spot size of an electron beam striking a SiO2 target has been observed during a 60 ns pulse. We attribute this to the emission of positive ions, most probably protons, from the target. These are then accelerated upstream and focused along the axis by the electron beam, where they partially neutralize the space-charge of the beam, and produce a sharp pinch. A simulation of the effect with a particle-in-cell code provides an adequate quantitative description, and a simple model, based on space-charge-limited emission of protons by the target confirms qualitatively the results of the simulation. The presence of an aluminum foil on the upstream side of the target is shown to suppress the effect, probably by stopping the protons
Keywords :
digital simulation; electron beam focusing; electron-surface impact; relativistic electron beams; secondary ion emission; self-focusing; silicon compounds; space charge; 60 ns; LELIA injector; SiO2; SiO2 target; aluminum foil; beam space-charge; electron beam; induction machine; intense relativistic electron beam; ion acceleration; ion focusing; partial neutralization; particle beam measurement; particle-in-cell code; positive ions; proton stopping; protons; secondary ion emission; sharp pinch; simulation; space-charge-limited emission; spot size; strong self-focusing; suppression; upstream acceleration; Acceleration; Aluminum; Electron beams; Heating; Induction machines; Ion emission; Particle beam optics; Particle beams; Protons; Silicon compounds;
Journal_Title :
Plasma Science, IEEE Transactions on
