Uncovering Relativistic Instabilities in Plasmas – UnRIP

Non-equilibrium plasmas generally exhibit phase space anisotropies, for instance in the case of particle beams traversing background plasmas or in interpenetrating plasma flows – common configurations in space and laboratory plasmas. This results in the spontaneous growth of micro- instabilities, that is, self-amplified electromagnetic and current fluctuations building up at kinetic scales, and leading to energy and momentum transfers between the plasma constituents.
In this project, we propose to exploit state-of-the-art laser and accelerator systems, combined with novel precision diagnostics, to study beam-plasma systems prone to relativistic streaming instabilities, similar to those arising in high-energy astrophysics. The required physical conditions will be achieved by means of (i) all-optical setups based on femtosecond relativistic laser-solid interactions probed by external wakefield-driven electron bunches, and (ii) high-density, GeV-level accelerator electron beams interacting with solid or gas targets. Supported by advanced numerical simulations, these highly resolved experiments will offer unprecedented insight into the dynamics and interplay of the competing instabilities, in a broad parameter range in terms of beam energy, fractional beam density and plasma collisionality. Notably, the experiments planned at the upgraded FACET-II facility at the SLAC National Accelerator Laboratory (USA) will allow plasma instabilities to be explored at beam energies and currents orders of magnitude increased over previous works. As a consequence, the instability-driven electromagnetic fields should be strong enough to induce intense synchrotron-type gamma-ray flashes, which we will intend to characterize for the first time.
These laboratory investigations will be complemented by prospective studies of even greater astrophysical relevance, involving ultrarelativistic electron-positron beams envisioned at next- generation multi-petawatt laser or accelerator facilities.