High Energy, Relativistic Intensity Laser Channeling and Direct Laser Acceleration of Electrons from an Underdense Plasma*

The channeling of a high-intensity laser pulse through an underdense plasma and simultaneous direct laser acceleration of electrons to superponderomotive energies are dynamic and complex processes. For all laser-plasma interactions, the transfer of the laser energy to the electrons is the fundamental step and also has applications in producing secondary radiation like bright, directional X-ray beams. A wide variety of parameter scans were performed using the OMEGA EP facility to explore the effect of experimental conditions, i.e.\ laser pulse duration, focusing geometry, plasma density, on the channel evolution and relativistic electron acceleration. Proton deflectometry observed the channel evolution, instabilities and filament formation. Corresponding particle-in-cell simulations illustrate the laser modulation, channel electromagnetic fields development and electron movement in interaction with laser pulse, giving insight into the energy transfer mechanism. Using simulations, we study double pulse interactions to separate the channel and quasi-static field formation by a leading pulse, to enable a trailing laser pulse to be better guided in the preformed channel and therefore more effectively couple energy to the electrons. We would like to acknowledge the OSIRIS Consortium.