Control over the space-time structure of electron beams by high-intensity femtosecond laser radiation
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Control over the Space–Time Structure of Electron Beams by HighIntensity Femtosecond Laser Radiation S. A. Aseev, V. G. Minogin, B. N. Mironov, and S. V. Chekalin Institute of Spectroscopy, Russian Academy of Sciences, Troitsk, Moscow oblast, 142190 Russia email: [email protected]; [email protected] Received January 11, 2010
Abstract—The space–velocity distribution of electrons propagating in vacuum can be deformed by the pon deromotive potential produced by highintensity femtosecond laser pulses, which makes it possible to subse quently separate such electrons from the initial beam. It is shown that optical modification of electron beams with kinetic energies on the order of 100 eV by femtosecond laser radiation with an intensity from 1014 to 1018 W/cm2 makes it possible to form electron beams with a duration on the order of 50–100 fs. Examples of optical control over the shape of electron beams, based on deflection, reflection, focusing, and splitting of electron beams, are considered. DOI: 10.1134/S1063776110110014
1. INTRODUCTION Obtaining femtosecond electron beams with a required space–time structure is of considerable inter est due to their possible application in diagnostics of rapidly occurring physicochemical processes, includ ing those initiated by highfrequency electromagnetic fields generated over extremely short time intervals. In contemporary studies, two approaches are mainly used for forming ultrashort electron beams with a duration of a few picoseconds and shorter. In the first approach, ultrashort electron beams are produced by exposing a solid photocathode, an atomic or molecu lar gas, or a dielectric with a highintensity evanescent (surface) field formed on its surface to highintensity femtosecond laser radiation. Under special condi tions, this approach makes it possible to obtain elec tron beams of femtosecond and even attosecond dura tion. This vast field of investigations in contemporary global research work has been described in the litera ture in detail [1–7]. In the second approach, the object of pulsed irradi ation is the electron beam itself, which propagates in vacuum. In this case, highintensity ultrashort laser pulses produce ponderomotive potentials that modify the electron velocity distribution and ensure condi tions for spatial separation of ultrashort electron beams from the initial electron beam. In contrast to the former approach, this method is not subjected to the basic constraint associated with the laser radiation intensity that must be lower that the photocathode or dielectric breakdown threshold. To deform the initial space–velocity distribution, pulsed optical gradient forces are used, which are basically delayless over the time scale of action of femtosecond laser radiation. The second approach also creates broader opportuni
ties for controlling the electron beam parameters because the ponderomotive potential produced by a femtosecond laser field in vacuum may have a diversi fied space–time structure [8–10]. Another ad
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