The generation of collimated <italic>γ</italic>-ray pulse from the interaction between 10 PW laser and a narrow tube target.

A scheme to radiate a highly collimated <italic>γ</italic>-ray pulse is proposed through the interaction between an ultra-intense laser pulse and a narrow tube target. The <italic>γ</italic>-ray pulse, with high conversion efficiency, can be generated as a result of electron acceleration in a longitudinal electric field. In a Particle-in-Cell simulation with a 10-PW laser, 18% of the laser energy is transferred into the forward <italic>γ</italic>-rays in a divergence angle less than 3 °. It is also found that such a highly collimated <italic>γ</italic>-ray pulse can be produced with a large range of tube diameters and laser intensities. This scheme could be realized in experiment with the coming 10-PW class lasers in the near future. [ABSTRACT FROM AUTHOR]