A Laboratory Analogue for Cosmic Ray Scattering and Acceleration in Laser-Driven Magnetized Plasmas

We present results from an experiment conducted at the GSI Helmholtz Centre for Heavy Ion Research, in which a monoenergetic beam of chromium ions (∼450 MeV) was propagated through a magnetized plasma interaction region formed by the collision of two counter-propagating, laser-ablated plasma flows. The plasma was diagnosed using laser interferometry and ion deflectometry, which showed no evidence for strong fluid-scale turbulence within the interaction region. This observation is consistent with magnetohydrodynamic (MHD) simulations performed using FLASH prior to the experiment [1].

Surprisingly, despite the absence of strong fluid-scale turbulence, time-of-flight measurements revealed both velocity-space diffusion and bulk acceleration of the ion beam. This scattering is consistent with a wave–particle interaction driven by short-wavelength, electrostatic, kinetic turbulence. These findings demonstrate that significant beam–plasma interactions can occur even in the absence of large-scale turbulent structures, with implications for cosmic ray injection and pre-acceleration in magnetized, collisionless shocks.

[1] K. Moczulski et al., Phys. Plasmas 31, 122105 (2024). https://doi.org/10.1063/5.0223496