Experimental investigation of pre-magnetization effects on laser-plasma dynamo processes.

It has recently been demonstrated experimentally on the OMEGA Laser Facility that a turbulent plasma created by the collision of two destabilized (but initially unmagnetized) plasma jets is capable of generating strong stochastic magnetic fields via the small-scale turbulent dynamo mechanism, provided the plasma's magnetic Reynolds number is sufficiently high (Tzeferacos et. al., Nat. Comm., vol. 9, 2018, 591). In this talk, we compare such a plasma with one arising from two pre-magnetized plasma jets, whose creation is identical save for the presence of a 10 T external magnetic field imposed by a pulsed magnetic field generator. We investigate differences between the two turbulent systems using Thomson scattering diagnostics, self-emitted X-ray imaging and proton radiography. While the Thomson scattering spectra are broadly similar between the magnetized and unmagnetized interactions, the proton radiographs are qualitatively different. In addition, the self-emitted X-rays in the magnetized interaction show a greater variation in relative magnitude between adjacent structures, a possible indication that the external field is capable of significantly altering the dynamics of the turbulent plasma despite only possessing a finite fraction of the initial plasma-jet kinetic energy.