Channel optimization of high-intensity laser beams in millimeter-scale plasmas

Abstract

Channeling experiments were performed at the OMEGA EP facility using relativistic intensity (>10^{18}W/cm^{2}) kilojoule laser pulses through large density scale length (∼390-570 μm) laser-produced plasmas, demonstrating the effects of the pulse's focal location and intensity as well as the plasma's temperature on the resulting channel formation. The results show deeper channeling when focused into hot plasmas and at lower densities, as expected. However, contrary to previous large-scale particle-in-cell studies, the results also indicate deeper penetration by short (10 ps), intense pulses compared to their longer-duration equivalents. This new observation has many implications for future laser-plasma research in the relativistic regime.

Preparations for a European R&D roadmap for an inertial fusion demo reactor

“…In this special issue, Spiers et al [38] present results of an experimental campaign on the ORION laser of the Atomic Weapons Establishment [51] that confirm the feasibility of propagating electron beams into the central hot spot of a fusion implosion. These results reinforce the conclusions of recently reported experiments conducted on the OMEGA EP laser facility at the Laboratory for Laser Energetics at the University of Rochester, NY [36]. They demonstrate that it is possible to use high-power short pulse lasers to carve a long-lasting, low-density channel through large-scale length, fusion-relevant plasmas in the direction of the density gradient via relativistically enhanced channelling: the Habara-Kodama-Tanaka (HKT) 'super-penetration' mechanism [37,52].…”

“…The European consortium has also undertaken studies of stable channel formation in fusion relevant plasmas [36–38], electromagnetic pulse generation and mitigation [39], UV fast electron generation and energy transport [40], magnetic fields [41], reactor materials under hostile radiation environments [23], among others, including the role of magnetic fields in guiding fast electrons.…”

Energy absorption in the laser-QED regime

“…At this frontier of high-energy density physics it will be possible to conduct experimental investigations into a range of topics including non-linear quantum electrodynamic (QED) processes that spawn electron-positron pair production 3 and laser wakefield acceleration of electron bunches up to multi-GeV energies 4 . There will also be the opportunity to make advances in several other fields within laser-plasma interactions such as coherent harmonic generation and focusing [5][6][7] , attosecond science 8 ion beam characterisation and acceleration [9][10][11][12][13] , electron beam generation via laser-channeling and hole-boring [14][15][16] , and laboratory astrophysics 17 .…”

Direct observation of imploded core heating via fast electrons with super-penetration scheme

“…These findings uncover the importance of applying an additional channeling pulse in this super-penetration scheme, because the plasma channel preformed by the channeling pulse not only helps to suppress the filamentation of the second heating pulse but also provides a short density scalelength plasma at the channel front. As demonstrated experimentally, by optimizing the experimental configuration, a plasma channel up to critical density surface can be created 29,40 . Besides, a magnetic field could be produced by the channeling pulse, collimating the fast electrons generated by the second pulse 41 .…”