Modification of Transport in Magnetized Burning Plasmas due to alpha-electron Collisions

Ignition in MIF requires alpha particles to transfer energy to the deuterium-tritium plasma via Coulomb collisions. For plasma temperatures < ~25 keV, the alphas transfer energy predominantly to the plasma electrons. The electron-electron collision time is much shorter than the alpha-electron collision time since the alpha number density is a small fraction of the electron number density. Therefore, it is usually assumed that the electron distribution function remains Maxwellian when alpha particles are present.

In this work it is shown that a net flux of alpha particles can perturb the electron distribution function from Maxwellian. The electron kinetic equation is solved in the presence of arbitrary populations of alpha particles and an external magnetic field to quantify this perturbation. This is used to derive a set of modified transport coefficients for magnetized burning plasmas. It is shown that a flux of alpha particles can increase the heat flow from hot regions of the plasma. Transport of the magnetic field is also affected by this process.