This paper suggests that such a setup can generate a non-trivial amount of electron-positron pairs: "Matching experimental parameters to current-generation faci

This paper suggests that such a setup can generate a non-trivial amount of electron-positron pairs: "Matching experimental parameters to current-generation facilities, Monte Carlo simulations suggest that this scheme is capable of producing of the order of 10^5 Breit–Wheeler pairs in a single shot." [1] https://www.nature.com/articles/nphoton.2014.95 https://www.nature.com/articles/nphoton.2014.95