Increasing the yield and energy of high-intensity laser-produced positrons by adding microstructures

Creating positrons in a small laboratory setting has attracted great interest from researchers. It helps understand the physics underlying various astrophysical phenomena, such as black holes and gamma ray bursts, and paves the way for creating a dense electron-positron plasma in the laboratory. Making enough electron-positron antimatter for laboratory astrophysics applications, however, is usually considered beyond the capability of state-of-the-art lasers.

Jiang et al. provide clear experimental and simulation results demonstrating a substantial increase in the yield and energy of positrons, produced by high-intensity lasers, by using large-scale, front-surface target structures.

By simply adding microstructures to the target and without having to upgrade the laser, the researchers’ microwire array target yielded a near 100% increase in the laser-to-positron conversion efficiency and a 10 MeV increase in positron energy.

“These results are important to the grand quest of establishing a laboratory relativistic electron-positron pair plasma for astrophysics relevant studies,” said author Sheng Jiang.

The work presents the first experiment to improve pair production using a target structure design that is optimized by particle-in-cell simulations. In the experiment, intense laser-plasma interactions produced very high energy electrons, whose energy, when interacting with the gold target, could generate electron-positron pairs.

The next step will be to probe a broader parameter space to further optimize the microstructures for the highest positron yield. The structure could be designed to accommodate different laser conditions for different applications, such as improving the number of X-rays or positrons produced during the laser-plasma interaction.

Source: “Enhancing positron production using front surface target structures,” by S. Jiang, A. Link, D. Canning, J. A. Fooks, P. A. Kempler, S. Kerr, J. Kim, M. Krieger, N. S. Lewis, R. Wallace, G. J. Williams, S. Yalamanchili, and Hui Chen, Applied Physics Letters (2021). The article can be accessed at https://doi.org/10.1063/5.0038222 .