"Kinetic Modeling of Magnetized Inertial Fusion Plasmas"

 

 

 

Much of inertial fusion plasma modeling is performed using hydrodynamic models that not only ignore the effects of self-generated magnetic fields, but also kinetic effects that arise in these environments due to steep gradients in density and temperature. A kinetic code with full electromagnetic capabilities circumvents these assumptions and helps illustrate the effect of magnetic fields and non-Maxwellian distributions. Since inertial fusion plasmas are collisional, the Vlasov-Fokker-Planck-Maxwell (VFPM) formalism is used to model these plasmas using a code known as IMPACTA.

 

From the VFPM simulations, we show that self-generated magnetic fields inside hohlraums affect thermal energy dynamics due to non-uniformities created by plasma magnetization and cross-field heat transport. The intense heating at the inner surface of the hohlraum results in steep temperature gradients that cause strong heat flows exhibiting non-local behavior.

 

In the presence of an externally applied magnetic field, the non-local heat flow contributes towards a magnetic field transport mechanism called the Nernst effect. The non-local augmentation of the Nernst effect results in magnetic field transport towards the hohlraum axis on a time-scale much faster than that predicted through “frozen-in-flow” alone.

 

The self-generated magnetic fields can be driven towards one another enabling a magnetic reconnection geometry. In such geometries, the magnetic field is primarily transported by the Nernst effect into the reconnection region. Very analogous to Hall reconnection in collisionless plasmas, this novel magnetic reconnection mechanism in a high β plasma recovers the fast magnetic reconnection rate but results in thermal energy outflows rather than accelerated particles.

A. S. Joglekar 1,2, A.G.R. Thomas 2,3, C. P. Ridgers 4, R. J. Kingham 5, W. Fox 6, A. Bhattacharjee 6, W. B. Mori 2