Laser plasma based gamma-ray studies using micro-structured targets

The development of compact, efficient laser-driven radiation sources hinges critically on the interplay between laser parameters and target design. Here, we investigate the role of micro-structured targets in optimizing energy transfer from ultrashort high-intensity laser pulses to accelerate electrons and the subsequent generation of high-energy photons. Using two-dimensional particle-in-cell simulations, we propose a target configuration consisting of a conical target with embedded microwires. Simulations reveal that enhanced electron refluxing underpins the superior performance of this target configuration compared with a foil target. The self-generated magnetic field imposed by the conical shape further confines the electrons along the laser propagation axis. The proposed configuration exhibits improved conversion efficiencies for both electrons and photons relative to the foil target. In addition, the influence of an underdense hydrogen plasma layer placed in front of the overdense targets is examined. These results highlight the practical advantages of target engineering over modifications of laser infrastructure, providing a scalable pathway toward tailored gamma-ray sources with improved divergence and efficiency. These findings pave the way for advances in compact radiation sources relevant to applications in accelerator physics, medical imaging, and high-energy science.