Measurements of Diamagnetic Cavity Formation and Collapse using Proton Radiography in HED Plasmas

The interaction of laser-produced high-energy-density (HED) plasma with a magnetic field plays a key role in magnetized fusion schemes and laboratory astrophysics experiments such as magnetic reconnection and magnetized collisionless shocks.

Here we present recent experiments focused on the study of cross-field transport in magnetized HED plasmas at the OMEGA laser facility using an in-situ proton radiography platform, which allows precise measurements of non-uniform magnetic fields in plasma [1]. The plasma was generated by expanding a laser-produced plasma into a background magnetic field powered by MIFEDS, while the corresponding local electron temperature and density of the plasma were measured with 2ω Thomson scattering. The measured 2D magnetic field topology showed the clear formation of a diamagnetic cavity, its expansion in time, and subsequent collapse. The results are compared to magnetic field dynamics in GORGON 3D MHD simulations with initial non-uniform magnetic fields.

[1] C. Johnson et al, paper in preparation to RSI (2021)