Using MeV photon sources generated by UHI lasers, a new experimental set-up is proposed to study the two-photon Breit-Wheeler process. The possibility to study this process in the laboratory would allow to test new concepts of pair plasma production and to explore this pair creation process in the ultra high field regime with important potential applications in astrophysics. Moreover, the obtained optimized gamma sources could also have promising applications as radiography sources.
Direct production of electron-positron pairs in photon collisions is one of the basic processes in the Universe. The linear Breit-Wheeler (BW) pair creation process (γ+γ to e++e-), is the lowest threshold process in photon-photon interaction, controlling the energy release in Gamma Ray Bursts and Active Galactic Nuclei . It is also responsible for the TeV cutoff in the photon energy spectrum of extra-galactic sources. The linear BW process has never been clearly observed in laboratory with important probability of matter creation . Using MeV photon sources a new experimental set-up based on numerical simulations with QED effects is proposed. This scheme offers a possibility of conducting a multi-shot experiment with reliable statistics on laser systems with pulse energies on the level of a few joules to tens of joules. This scheme relies on a collision of relatively low energy (few MeV), intense photon beams that can be created by intense laser pulses interacting with thin plastic targets or dense gas jets. By colliding two of them, one would be able to produce a significant number of electron-positron pairs in a controllable way.
We provide details of the experimental setup, analytical estimates and an optimization study using numerical simulations with QED effects of the expected yield of reactions for different possible ways of creation of the MeV photon source. Using MeV photon sources  obtained in numerical simulations at ultra high intensities in the synchrotron-like radiation dominated regime more than $10^4$ BW pairs per shot can be achieved . A comparison of these results with Bremsstrahlung sources obtained with numerical simulations will be presented. Results from photon collision simulations using a recently developed innovative algorithm will also be given to propose a robust experimental design. Moreover, the noise level due to other pair creation processes is estimated.
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