Towards the optimisation of direct laser acceleration
Amina Hussein, Alexey Arefiev, Thomas Batson, H Chen, R. S. Craxton, Andrew Davies, D. H. Froula, Zheng Gong, D. Haberberger, Y. Ma, P. M. Nilson, W. Theobald, T. Wang, Kathleen Weichman, G. J. Williams, L. Willingale
Abstract
Abstract Experimental measurements using the OMEGA EP laser facility demonstrated direct laser acceleration (DLA) of electron beams to (505 ± 75) MeV with (140 ± 30) nC of charge from a low-density plasma target using a 400 J, picosecond duration pulse. Similar trends of electron energy with target density are also observed in self-consistent two-dimensional particle-in-cell simulations. The intensity of the laser pulse is sufficiently large that the electrons are rapidly expelled along the laser pulse propagation axis to form a channel. The dominant acceleration mechanism is confirmed to be DLA and the effect of quasi-static channel fields on energetic electron dynamics is examined. A strong channel magnetic field, self-generated by the accelerated electrons, is found to play a comparable role to the transverse electric channel field in defining the boundary of electron motion.