Hannover 2020 – scientific programme

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P: Fachverband Plasmaphysik

P 19: Helmholtz Graduate School 4 and Magnetic confinement 4

P 19.4: Talk

Thursday, March 12, 2020, 12:15–12:40, b305

Radiation cooling in strongly anisotropic electron-positron plasmas — •Daniel Kennedy and Per Helander — Max-Planck-Institut für plasmaphysik

Electron-positron plasmas have been found to possess ``remarkable stability properties'' [Helander, 2014] due to the mass symmetry of the two species. As such, it is thought that electron-positron plasmas confined in the magnetic field generated by a circular current- carrying coil ought to enjoy excellent confinement. In previous studies, it has been assumed that the equilibrium distribution function of such a plasma, ought to be an isotropic Maxwellian.

However, we have recently found that electron-positron plasmas under expected laboratory conditions are optically thin to cyclotron radiation. This radiative cooling is an extremely efficient way for the plasma to dissipate perpendicular energy on timescales which are typically much faster than the collision time. The presence of cyclotron cooling results in a strongly anisotropic equilibrium distribution function due to the different distributions of perpendicular and parallel velocities.

In this talk, I discuss these findings and show how cyclotron cooling can be incorporated into kinetic models for electron-positron plasmas. In particular I discuss how the presence of radiation cooling can impact the energy of the plasma and the ramifications this might have in terms of plasma stability.