Obervation of subrelativistic collisionless shocks generation and breakout dynamics

Relativistic collisionless shocks ¹ , which are ubiquitous in the cosmos, play a significant role in various astrophysical phenomena such as gamma-ray bursts ^2–4 , PeVatrons ^5–7 , and shock breakouts accompanying a supernova explosion ⁸ . To unravel these processes happening at enormous spatial and energy scales, the most convenient and feasible approach so far – laser – has been long sought to access such extreme conditions in an ultrafast and volume-efficient manner ^9–13 . Yet observing a relativistic collisionless shock in a laboratory has remained out of reach. Here, we demonstrate that sub-relativistic collisionless shocks with velocities ~ 0.03 c of astrophysical significance can be produced and characterized in a laboratory using a table-top femtosecond “laser engine”. We attribute the shock formation to a rapidly growing Weibel instability in a carefully adjusted low-density preplasma environment, which resembles the interstellar media near an astrophysical central engine. Owing to this Weibel instability, a magnetic field as high as ~ 5000 T is developed within 2.7 ps, leading to the formation of a collisionless shock and shock breakout is finally observed at the preplasma edge. Our results not only pave the way for further exploration of astrophysics related to relativistic collisionless shocks but also enable a new regime of ultrahigh magnetic field physics on a tabletop scheme ¹⁴ .