In recent years, with the development of short pulse laser technology, the intensity of laser can exceed the relativistic level (>10¹⁸ W/cm²), making the use of this ultra-strong laser to generate positron beams a widely studied direction^1-9. However, currently, the peak energy of positron beams generated by ultra-intense lasers does not exceed 30MeV, which is still far from the energy required to achieve high-energy particle collisions. We propose a positron acceleration scheme in which a laser-driven positron beam is injected into a solid target hit by a laser beam and accelerated in the sheath field on the target back side. The positron beam injection and acceleration in the target have been investigated with numerical simulation. The feasibility of such an acceleration scheme was proved according to the simulation results which show that a 10 MeV positron beam can be accelerated up to 30 MeV. The dependency of the positron beam properties on the positron injection location, injection time, and target thickness was studied. Related acceleration details were obtained and analyzed. The acceleration scheme provides a method in positron energy controlling and its related applications.

positron acceleration, laser, sheath field