High-energy photon generation from self-organized plasma cavities in field-enhanced laser-preplasma interactions

The interaction of an ultraintense Nd:glass laser pulse with a near-critical plasma self-organizes into a highly efficient γ-ray source. Three-dimensional particle-in-cell simulations demonstrate that relativistic self-focusing, aided by a self-generated electron cavity, enhances the laser intensity by more than an order of magnitude, driving the system into the radiation-reaction-dominated regime, i.e., one where the electrons lose a substantial amount of their energy as hard radiation. Peak photon emission occurs near 0.5 times the relativistic critical density, with a γ-photon yield exceeding 20% of the laser energy. Compared to Ti:Sa lasers of the same power, the longer duration of Nd:glass laser pulses leads to an order of magnitude increase in γ-photon number in the extreme conversion efficiency regime, making them particularly well suited for photonuclear physics applications. These findings point to a robust and scalable mechanism for compact, ultrabright γ-ray generation in the multipetawatt regime.