Multi-messenger probing of ultra-intense/relativistic light-matter interactions

Laser-matter interactions at relativistic intensities are at the forefront of plasma physics research nowadays. This is in part driven by the fast progress in laser technology, which enabled the design, construction, and operation of multi-PW laser facilities. This progress opened new avenues of research and a plethora of new phenomena to study, which require new tools to characterize and explore. We propose to study the interaction of a multi-10 PW laser pulse with a near critical density plasma by employing two plasma targets each irradiated by a multi-10 PW laser pulse. The first laser target interaction would produce copious amounts of high energy electrons, ions, and photons, which will be used to probe extreme electromagnetic fields and density waves generated by the second laser target interaction. These multiple messengers will arrive at the second target at various delays, due to their varying time of flight, providing multiple screenshots of the laser matter interaction. Thus, it would be the first multi-messenger study of relativistic light matter interaction, which will deliver a comprehensive suite of data describing from start to end the entire history of the interaction at unprecedented laser intensities.