Synthetic optical diagnostics for "MAgnetic Reconnection on Z" (MARZ) experiments*

Using numerical ray-tracing techniques to create synthetic diagnostic images, we test the performance of laser probing diagnostics for radiatively-cooled reconnection experiments on Sandia’s Z Machine, as part of the “MAgnetic Reconnection on Z” (MARZ) collaboration.

The electron density and magnetic field of the plasma determine its refractive index.  Shadowgraphy and schlieren imaging measure the probe beam’s deflection from density gradients; interferometry measures electron density from phase shifts; Faraday rotation imaging measures magnetic field from probe polarization rotations.

We use GORGON, a resistive MHD code, to simulate the electron density and magnetic field in 2D and 3D for MARZ’s dual exploding aluminium wire arrays.  We then use a Monte Carlo ray-tracing code to transport the rays through plasma, tracking the position, angle, phase, and polarization.  After exiting the plasma, the rays propagate through a realistic optical configuration; ray-transfer matrix analysis includes finite aperture effects.

Our results show that, before the radiative collapse of the layer, the density gradients are small enough for the beam to transmit through without being refracted out of the collection optics; this allows us to measure properties of the reconnection layer.