Effect of the laser pulse temporal shape on the hole boring efficiency

Abstract

Laser hole boring is a process of ion expulsion from the path of an intense laser beam under the effect of the ponderomotive force. It is considered as a method for more efficient electron energy deposition in fast ignition of inertial fusion reactions. Analysis of the electron dynamics on the laser-plasma interface shows that the hole boring efficiency can be significantly enhanced by an appropriate temporal shaping of the laser pulse. The pulse shape optimization is carried out with a newly developed fast quasi-neutral particle-in-cell (PIC) code and verified with the full PIC simulations.

Kinetic and finite ion mass effects on the transition to relativistic self-induced transparency in laser-driven ion acceleration

“…By our choice of normalization of the incident laser pulse vector potential, equation (5), the laser wave amplitude a 0 relates to the wave intensity as l ḿ -- I a 1. 38 10 W cm m ) can propagate in a nominally overdense plasma. However, when one considers a laser pulse incident on a bounded plasma, the situation is much more complicated.…”

“…Ions are accelerated in the electrostatic field induced by charge separation and a double layer structure known as a laser piston is formed, figure 1(c). For non-relativistic ions, the resulting ion energy scales as  µ a n HB 0 2 0 , where n 0 is the normalized electron plasma density, and thus there has been considerable interest in operating HB as close to the threshold density for RSIT as possible [15,24,37,38].…”

Vlasov modelling of laser-driven collisionless shock acceleration of protons

“…Pulse splitting Previous numerical results indicate that using a train of short laser pulses may produce more efficient ion-acceleration than one Gaussian pulse with the same energy [25][26][27] . Furthermore, experimental results in Ref.…”

Analytical model for fast-shock ignition

“…[1][2][3][4] Recently, the original idea of Tabak (1994) 1 for pushing the corona by pondermotive force of a high power laser pulse and forming a channel in the corona up to the outer surface of the assembled fuel is vigorously pursued. [23][24][25][26][27][28][29][30][31][32][33][34][35][36] The results of numerical simulations [25][26][27][28][29] are promising and some interesting methods have been proposed to overcome the difficulty of the beam divergence of the laser produced electron beam by magnetic field generated by another laser beam with proper timing with respect to the main beam and self-generated resistive magnetic fields in a multilayered target. [31][32][33] Other problems with laser bored channel are laser self-focusing, bifurcation and deflection of geometrical axis of the channel respect to the direction of the laser beam propagation, so called hosing and channel bending, 26 that may be overcome by using laser pulse(s) with proper time behavior to obtain a good quality channel for propagation of ignitor laser driver with a minimum loss and high beam transmission.…”

“…[31][32][33] Other problems with laser bored channel are laser self-focusing, bifurcation and deflection of geometrical axis of the channel respect to the direction of the laser beam propagation, so called hosing and channel bending, 26 that may be overcome by using laser pulse(s) with proper time behavior to obtain a good quality channel for propagation of ignitor laser driver with a minimum loss and high beam transmission. 35,36 In addition, laser hole boring for guiding the ignitor laser beam has several advantages over the hollow metallic cone; it has no preferential orientation for alignment and causing the least undesirable mechanical distortion and is fully compatible with shock ignition approach. Therefore, hole-boring approach is the main candidate for realization of FSI concept.…”