Growth and Saturation of Convective Modes of the Two-Plasmon Decay Instability in Inertial Confinement Fusion

Abstract

Particle-in-cell (PIC) and fluid simulations of two-plasmon decay (TPD) instability under conditions relevant to inertial confinement fusion show the importance of convective modes. Growing at the lower density region, the convective modes can cause pump depletion and are energetically dominant in the nonlinear stage. The PIC simulations show that TPD saturates due to ion density fluctuations, which can turn off TPD by raising the instability threshold through mode coupling.

Saturation of the Two-Plasmon Decay Instability in Long-Scale-Length Plasmas Relevant to Direct-Drive Inertial Confinement Fusion

“…The large fraction of laser energy converted into hot electrons and its observed saturation, is a direct consequence of the simultaneous high intensity and long-scale lengths produced in these experiments. ZAK [13] which solves the equations of the extended Zakharov model [14]. The saturating nonlinearities included in the model are density profile modification [29], Langmuir wave cavitation [30], and the generation of ion acoustic turbulence [13,15].…”

Current-Driven Filament Instabilities in Relativistic Plasmas. Final report

“…In the linear regime, the growth rates and thresholds predicted by the linear theories were examined in both PIC and fluid simulations. Pump depletion and convective modes' domination were observed in the well-above-threshold PIC simulations [9]. The PIC simulations showed that both the absolute and convective modes saturate due to ion density fluctuations, which can turn off TPD by raising the instability threshold through mode coupling and lead to intermittent growth [9].…”

“…Pump depletion and convective modes' domination were observed in the well-above-threshold PIC simulations [9]. The PIC simulations showed that both the absolute and convective modes saturate due to ion density fluctuations, which can turn off TPD by raising the instability threshold through mode coupling and lead to intermittent growth [9]. A series of PIC simulations were performed on the long-term (~10 ps) nonlinear behaviors of the TPD instability [18].…”

“…New modes with small phase velocities develop in the low-density region after saturation. These modes can couple to background thermal electrons and form the first stage for electron acceleration [9]. Rui Yan successfully passed his thesis defense exam in 11/2011.…”

“…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.…”