Magnetically Collimated Relativistic Charge-Neutral Electron-Positron Beams From High-Power Lasers

We report the observation of charge-neutral MeV electron-positron beams from magnetically collimated laser-driven pair-production experiments. Relativistic pairs of electrons were generated from laser-solid interactions in an external 13-T mirror field. The pairs were subsequently confined, deflected, or collimated depending on the particle energy and field strength and measured by a magnetic particle spectrometer. Equal quantities of positrons and electrons were measured in the collimated beams with an energy around 13 MeV along the magnetic mirror axis.