Polarization of synchrotron emission from runaway electrons*

Runaway electrons (RE) can be produced during magnetic disruptions and, if not avoided or mitigated, they can damage the plasma facing components of fusion reactors. A key element to assess this damage is the accurate modeling of the RE spatial and phase-space distribution.  Synchrotron emission (SE) is a valuable experimental diagnostic commonly used to estimate the RE beam size, energy, and pitch angle.  Motivated by this, in Ref.[1] we developed a numerical SE synthetic diagnostic including full-orbit effects and taking into account the spectral and angular distribution of the SE, as well as optical and geometric properties of the camera. Based on this work, we present a new synthetic diagnostic that incorporates more efficient orbit integrator and Monte-Carlo sampling algorithms and, most importantly, SE polarization effects. Numerical simulations quantifying the dependence of the vertically and horizontally polarized radiation intensities on the pitch angle are discussed. The dependence of the radiation intensity and image shape on the wavelength and polarization direction are also studied for different energy and pitch angle distributions. 

[1] Carbajal and del-Castillo-Negrete, Plasma Phys. Control. Fusion 59, 124001 (2017).