Fig. 1

Experimental evidence for late-time plasma stagnation when colliding two fast plasmas in an ambient magnetic field as a signature of magnetic field compression. a Schematic of the experimental set-up. Two lasers irradiate two solid targets, accelerating two quasi-neutral, fast flows (electrons and ions, which are mostly protons) from the rear surface, which expand into each other in the imposed 20 T magnetic field. The axis of the Thomson Parabola (TP) is shown and the interferometry diagnostic axis is into the page. b–e Electron density in the plasma, integrated along the line of sight (and hence in units of cm⁻²), as measured by the interferometer, at different times from the laser interaction. The frame (b), corresponding to 5 ps, uses a colorscale that represents 3 times more density than that of the other frames in order to better highlight the plasma profile at this time