Comparison of three hohlraum configurations with six laser entrance holes for indirect-drive inertial confinement fusion

Abstract

The radiation drive asymmetry and laser-plasma instabilities (LPIs) inside the conventional cylindrical hohlraum configuration are two daunting issues in indirect-drive inertial confinement fusion. Recently, an octahedral spherical hohlraum (SH) (Lan et al 2014 Phys. Plasmas 21 010704), a novel three-axis cylindrical hohlraum (TACH) (Kuang et al 2016 Sci. Rep. 6 34636), and an advanced three-axis elliptical hohlraum (TAEH) (Jing et al 2017 arXiv:1703.01579) with six laser entrance holes (LEHs) were proposed to mitigate these issues. In this paper, the performance of these three new hohlraum configurations is compared. Preliminary simulations indicate that the TAEH (with a case-to-capsule ratio, CCR = 2.8) could provide excellent radiation symmetry, comparable to those inside the SH (CCR = 5.1) and TACH (CCR = 2.2). The filling time of plasma affecting the LPIs is between those of the SH and TACH, and about 1.5 times the one in the ignition hohlraum Rev5-CH (300 eV) of the National Ignition Campaign (Haan et al 2011 Phys. Plasmas 18 051001). The energy coupling efficiency of the TAEH is about 29% and 17% greater than those inside the SH and TACH, respectively. Moreover, all three configurations have robust symmetry with respect to laser beam pointing errors and capsule offset, with the SH being the most insensitive.

An improved view-factor method including plasma filling for angular distribution of radiation temperature from a laser-driven hohlraum

“…where r S t , ( ) is the flux emitted by the surface element r at time t, a r t , ( ) is the albedo that is defined as the ratio of the re-emitted flux to the incident flux onto the surface element [20], ¢ r r V , ( ) is the view factor [5,[20][21][22][23][24][25][26][27][28][29][30][31] between the surface element r and surface element ¢ r , representing the fraction of energy from surface ¢ r to surface r, and r S t , 0 ( ) is the source term (only existing in laser-spots region).…”

“…With the model and parameters stated above, the equivalent radiation temperature from the LEHs at different angles can be calculated by the improved view-factor code IRAD3D [19,[29][30][31], as shown in figure 5. The view fields are illustrated in the inset.…”

“…An effective practical method for calculating radiative energy redistribution inside the hohlraum, particularly suitable for the angular distribution of radiation temperature from the LEHs of a hohlraum [19], is based on a view-factor approach [5,[20][21][22][23][24][25][26][27][28][29][30][31]. A major drawback of the original system of the view factor code is associated with poor accuracy in describing radiation temperature from the LEH at smaller angles [32,33], where the plasma filling from the wall ablated by the laser is neglected.…”

“…However, the influence of the filling plasma (Au bubble) motion and temporal angular distribution of radiation temperature is unable to be simultaneously predicted by these models. Therefore, an equivalent radiative volume (ERV) model is firstly advanced to approximately characterize the contribution of the blow-off bubble in the new view-factor method integrated in the viewfactor code IRAD3D [19,[29][30][31].…”

Spectral Failsafe System of High-Power Laser Using Dual Fiber Bragg Gratings

“…High-power lasers are excellent tools for investigating high-density physics, highintensity interactions between light and matter, and plasma physics [1][2][3]. One far-reaching potential application of high-power lasers is inertial confinement fusion (ICF), where nuclear fusion reactions are initiated by heating and compressing a deuterium-tritium (DT) target with high-power nanosecond lasers [4,5].…”