Numerical study of effect of magnetic field on laser-driven Rayleigh-Taylor instability

Abstract

Rayleigh-Taylor instability (RTI) is a fundamental physical phenomenon in fluids and plasmas and plays a significant role in astrophysics, space physics, and engineering. Especially in inertial confinement fusion (ICF) research, numerous experimental and simulation results have identified RTI as one of the most significant barriers to achieving fusion. Understanding the origin and development of RTI will allow for formulating mitigation measures to curb the growth of instability, thereby improving the odds of ICF success. Although there have been many theoretical and experimental studies on RTI under high energy density, there are few experiments to systematically explore the influence of magnetic fields on the evolution of magnetized RTI. Here, a new experimental scheme is proposed based on the Shenguang-II laser facility which uses nanosecond laser beams to drive modulation targets of polystyrene (CH) and low-density foam layers. A shock wave is generated after the laser's CH modulation layer is ablated, propagates through CH to low-density foam, and causes Richtmyer-Meshkov instability when the shock wave accelerates the target. When the laser pulse ends, the shock wave evolves into a blast wave, causing the system to decelerate, resulting in RTI in the reference system of the interface. This paper uses the open-source radiation MHD simulation code (FLASH) to simulate the RTI generated by a laser-driven modulation target. The evolution of RTI without magnetic field, Biermann self-generated magnetic field, and different applied magnetic fields are systematically investigated and compared. The simulation results show that the Biermann self-generated magnetic field and the applied magnetic field in parallel flow direction do not change the interface dynamics in the evolution process of RTI. Nevertheless, the applied magnetic field in the vertical flow direction can stabilize RTI and the Kelvin-Helmholtz vortex at the tail of the RTI spike. Magnetic pressure plays a decisive role. The results provide a reference for the follow-up study of target physics related to ICF and deepen the understanding of the fluid mixing process.

Numerical study of the effect of magnetic field on laser-driven Rayleigh–Taylor instability under multi-mode disturbance

“…The multimode sinusoidal disturbance is introduced between the ch and foam layers. The simulation in this paper includes four cases, as shown in Table 1 Based on our previous work 4,7 , the results show that the Biermann self-generated magnetic field does not change the interface dynamics of RTI, and all simulation cases involved in this paper ignore the Biermann self-generated magnetic field effect.…”

“…When the direction of the pressure gradient is opposite to the direction of the density gradient, the interface disturbance gradually loses stability and leads to violent, turbulent mixing. Its typical characteristics are bubble and spike structure 3,4 . RTI is a fundamental physical process in fluid and plasma.…”

“…Rigon et al 9 carried out RTI calibration simulation experiments in type Ia supernovae on the LULI2000 laser facility and studied the evolution of RTI on the scale of young supernova remnants. Sun et al 4 investigated and compared the effects of Biermann's self-generated magnetic field and external magnetic field on the evolution of RTI under single-mode perturbation. Although there have been many theoretical and experimental research progress on RTI under high energy density, they have not systematically studied the magnetization RTI induced by multi-mode disturbance.…”