Laser Channeling in Millimeter-Scale Underdense Plasmas of Fast-Ignition Targets

Abstract

Two dimensional particle-in-cell simulations show that laser channeling in millimeter-scale underdense plasmas is a highly nonlinear and dynamic process involving longitudinal plasma buildup, laser hosing, channel bifurcation and self-correction, and electron heating to relativistic temperatures. The channeling speed is much less than the linear group velocity of the laser. The simulations find that low-intensity channeling pulses are preferred to minimize the required laser energy but with an estimated lower bound on the intensity of I approximately 5x10(18) W/cm(2) if the channel is to be established within 100 ps. The channel is also shown to significantly increase the transmission of an ignition pulse.

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.…”

Current-Driven Filament Instabilities in Relativistic Plasmas. Final report

“…This thesis studied laser channeling under parameters relevant to fast ignition with twodimensional (2D) [5] and three-dimensional (3D) [15] particle-in-cell (PIC) simulations. Laser channeling was found to be a highly nonlinear and dynamic process.…”

“…It has also partially supported 4 PhD thesis projects in ICF, plasma astrophysics, and high performance computing. So far it has generated 20 publications [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20], including 4 Physical Review Letters [1,5,9, 18]. The results have also been disseminated in a number of contributed and invited talks in international conferences (a list of selected invited talks is attached at the end of this report.…”

Upper-limit power for self-guided propagation of intense lasers in underdense plasma

“…[11][12][13][14][15], and the well-known critical laser power P c = 17(n c /n e ) GW required for self-focusing was found [13,14] , where n e is the plasma electron density, n c = mω 2 /4π e 2 is the critical density, and ω is the laser frequency. Since then, there have been a lot of studies on this topic when the laser power is around P c , e.g., laser channeling in underdense plasmas [16][17][18] , laser guiding in plasma channels [19,20] , and propagation of multi-laser beams in plasmas [21][22][23][24] .…”

“…Usually, these applications require that intense laser pulses can stably propagate over a large distance in plasma. On this issue, many theoretical and experimental studies have been performed in the last 30 years [11][12][13][14][15][16][17][18][19][20][21][22][23][24] . Selffocusing of an ultrashort intense laser pulse in a tenuous plasma was investigated theoretically in Refs.…”