Electron Acceleration in Multi-Kilojoule, Multi-Picosecond Laser Pulses

‘Super-ponderomotive’ electrons have been observed in experiments since the early days of energetic short-pulse laser-plasma interaction on NOVA-PW [Perry, RevSciInst1999], but they were largely ignored due to their relatively small number. Longer pulses, plasma density gradients and higher intensities favor the generation of an additional ‘super-ponderomotive’ electron population, at energies much larger than the ponderomotive potential. Recent 1D PIC simulations [Sorokovikova, Phys.Rev.Lett.2017], give twenty times larger MeV electron doses than in the NOVA-PW case. Such an enhancement would boost applications from proton acceleration (see talks by D.Mariscal and S.C.Wilks, this conference) to MeV x-ray generation and the creation of electron-positron plasmas. We discuss electron acceleration to super-ponderomotive energies in laser-solid interaction of multi-kilojoule, multi-picosecond pulses at the relativistic threshold, e.g. NIF-ARC, with 1D and quasi-2D Particle-in-Cell simulations.