Instability growth for magnetized liner inertial fusion seeded by electro-thermal, electro-choric, and material strength effects

Abstract

A critical limitation of magnetically imploded systems such as magnetized liner inertial fusion (MagLIF) [Slutz et al., Phys. Plasmas 17, 056303 (2010)] is the magneto-Rayleigh-Taylor (MRT) instability which primarily disrupts the outer surface of the liner. MagLIF-relevant experiments have showed large amplitude multi-mode MRT instability growth growing from surface roughness [McBride et al., Phys. Rev. Lett. 109, 135004 (2012)], which is only reproduced by 3D simulations using our MHD code Gorgon when an artificially azimuthally correlated initialisation is added. We have shown that the missing azimuthal correlation could be provided by a combination of the electro-thermal instability (ETI) and an "electro-choric" instability (ECI); describing, respectively, the tendency of current to correlate azimuthally early in time due to temperature dependent Ohmic heating; and an amplification of the ETI driven by density dependent resistivity around vapourisation. We developed and implemented a material strength model in Gorgon to improve simulation of the solid phase of liner implosions which, when applied to simulations exhibiting the ETI and ECI, gave a significant increase in wavelength and amplitude. Full circumference simulations of the MRT instability provided a significant improvement on previous randomly initialised results and approached agreement with experiment. V C 2015 AIP Publishing LLC.

Experimental observation of the stratified electrothermal instability on aluminum with thickness greater than a skin depth

“…2a, and within 40 ± 20 µm in Fig. 2d, interestingly consistent with [26] despite the difference in metallic composition. Inter-strata axial distances and intrastrata axial full width at half maxima grow with increasing load current.…”

“…While the complete, tamped, hydrodynamic case has not been addressed by theory, it is useful to estimate the ETI growth rate via thick-rod MHD simulations. For example, 2D [27] and 3D [26] MHD calculations suggest the temperature growth rate of the ETI in uncoated thick aluminum rods carrying ! ≈ 2 MA mm !…”

The influence of the solid to plasma phase transition on the generation of plasma instabilities

“…These uncertainties have been the trigger of dedicated investigation of the processes related to the initial target physical conditions 10,17,18 . Until now all these studies were limited to the coupling of properties of the solid, among others the resistivity, the heat conduction, the magnetic diffusion, the viscous damping and the stress tensors, into the system of the MHD equations.…”

The effects of magnetic field topology on secondary neutron spectra in Magnetized Liner Inertial Fusion

“…However, MHD simulations show that current and, consequently, azimuthal field can penetrate into the fuel region. [20] The presence of an azimuthal B field in the fuel can result in tritons flowing preferentially in one axial direction due to the phenomenon of singular orbits. [21,22] These are illustrated in 2 dimensions in fig.…”

“…We now use the Gorgon code [20] to carry out 1D MHD simulations which result in a time-varying stagnation phase. These simulations show that the current can penetrate through the liner resulting in an azimuthal B field in the fuel that affects the secondary spectra.…”