Using XFELs to Probe Extreme Magnetic Fields in Relativistic High Power Laser Matter Interactions

The relativistic laser matter interaction is a complex interplay of ionization, extreme current densities, rapidly
evolving strong fields and acceleration processes. Understanding the interaction physics is a challenging but
highly rewarding endeavor. The recently commissioned X-Ray free electron lasers (XFELs) with unprecedented
brightness and polarization purity open a new window for discovering the interior of solid-density plasmas
created by relativistic laser interactions with matter, resolving the relevant femtosecond and nanometer scales
experimentally. Here, we focus on discussing the feasibility of probing the Kilotesla to Megatesla-level magnetic
fields by X-Ray polarimetry via Faraday rotation using XFELs. The synthetic simulations show that XFELs are
capable to detect the extreme magnetic fields from relativistic laser interactions with solid and near-critical
density targets[1, 2].

[1] L. G. Huang, H. P. Schlenvoigt, H. Takabe, and T. E. Cowan,
Physics of Plasmas 24, 103115 (2017).
[2] T. Wang, T. Toncian, M. S. Wei, and A. V. Arefiev, Physics of
Plasmas 26, 013105 (2019).