Investigations on the P2 drive asymmetry and its effect on the shell asymmetry in a symmetry tuning experiment at the 100 kJ laser facility

Abstract

Understanding and controlling time-dependent implosion asymmetry are essential requirements to achieve ignition. In a recent symmetry tuning experiment at the 100 kJ laser facility, an effective time-dependent symmetry control was demonstrated by modifying the ratio of the inner beam power to the outer beam power. The hohlraum radiation and the P2 drive asymmetry of a shot used to measure backlit shell asymmetry have been analyzed, and the sensitivity of the P2 shell asymmetry to the drive asymmetry has been illustrated by using the two-dimensional code LARED. The variation in the shell P2 distortion, resulting from the variation in the P2 drive asymmetry due to the three-dimensional perturbing effects introduced to the hohlraum by the diagnostic windows (DWs) and the eight removed beams, has been assessed quantitatively using a three-dimensional postprocessor. It is found that the DWs and the four removed inner beams do not vary the P2 drive asymmetry, while the four removed outer beams cause a ∼−1% variation in the P2 drive asymmetry, resulting in a more prolate implosion.

A 2D dynamic model for the impact of time-dependent low-mode drive asymmetries on the shell asymmetries during acceleration phases of ICF implosions

“…In this section, we apply the dynamic model to the acceleration phases of typical gas-fill capsule and layered DT capsule implosions with P 2 or P 4 drive asymmetries, and compare the P n mode amplitudes of v s and R s derived from the model, the 2D capsule-only radiation hydrodynamic simulations and available backlit shell distortion measurements. The angleaveraged ρR s (t), v s (t), and R s (t) in equations ( 13), ( 14), (18), and (19) were obtained from 1D multi-group radiation transfer (MGRT) code RDMG [31]. The 2D capsule-only simulations were performed using the 2D MGRT code LARED [32][33][34].…”

“…The term t − t 2 in equation (19) indicates that the R s asymmetry gradually accumulates with time. Meanwhile, the Green's function W R (t, t 2 ) for the R s asymmetry of degree n is given through equation (18) as…”

“…Finally, the P n mode amplitudes of v s and R s during acceleration can be extracted from equations ( 13), ( 14), (18), and (19), in which v s , R s , and ρR s are obtained from 1D implosion simulations and defined as…”

“…Over the past few decades, the ICF community has performed a lot of experiments to measure implosion asymmetries and explore the impact of low-mode drive asymmetries on the implosion performances [11][12][13][14][15][16][17][18][19]. Meanwhile, significant efforts have been dedicated to theoretical investigations on the sensitivity of the implosion performances to low-mode drive asymmetries.…”

Spin Transport Hydrodynamics of Polarized Deuterium-Tritium Fusion Plasma

“…The capsule is ablated by radiations with peak temperature of 250 eV and reaches maximum fusion rate after 12.85 ns (bang time) [23]. The polar mode-2 (P 2 ) perturbation which forms from low-mode radiation drive asymmetries [25,26] is added to the implosion velocity of STHD simulation. The asymmetry amplitude of shell radius measured at bang time is P 2 /P 0 = 0.21.…”