Electron Acceleration in Cavitated Channels Formed by a Petawatt Laser in Low-Density Plasma

Mangles, Stuart P. D. and Walton, B. and Tzoufras, M. and Najmudin, Zulfikar and Clarke, R. J. and Dangor, Aboobaker E. and Evans, R. G. and Fritzler, S. and Gopal, Abhijit and Hernandez-Gomez, C. and Mori, Warren B. and Rozmus, W. and Tatarakis, M. and Thomas, Alexander George Roy and Tsung, F. S. and Wei, M. S. and Krushelnick, Karl (2005) Electron Acceleration in Cavitated Channels Formed by a Petawatt Laser in Low-Density Plasma. Physical review letters, 94 (24). ISSN 1079-7114

Abstract

The spectra of energetic electrons produced by a laser interaction with underdense plasma have been measured at intensities > 3 × 10 20     W   cm − 2 . Electron energies in excess of 300 MeV have been observed. Measurements of the transmitted laser spectrum indicate that there is no correlation between the acceleration of electrons and plasma wave production. Particle-in-cell simulations show that the laser ponderomotive force produces an ion channel. The interaction of the laser field with the nonlinear focusing force of the channel leads to electron acceleration. The majority of the electrons never reach the betatron resonance but those which gain the highest energies do so. The acceleration process exhibits a strong sensitivity to initial conditions with particles that start within a fraction of a laser wavelength following completely different trajectories and gaining markedly different energies.