pair production

A long laser interacting with an under-dense plasma can form a plasma channel. When an intense laser propagates through such a channel, under certain conditions it directly accelerates electrons to higher energies than allowed in vacuum interaction [1]. One of the mechanisms at play is the parametric resonance, that can lead to an increase of the maximum energy compared to vacuum [2].  At very high laser intensities, the radiation reaction changes the onset of the parametric resonance.  
Due to the energy loss of the electrons, the local resonance is achieved under different global conditions. Nevertheless, using near-future lasers (10 PW, 150 fs), we can obtain multi-GeV electrons in a single-stage acceleration within a 0.5 mm-long channel. The electrons can then be used as a seed for a γ-ray source in a collision with another laser. One can choose a setup where the first laser is not significantly depleted during the acceleration stage. As the accelerated electrons are naturally superimposed with the first laser, they can be used for seeding of e^-e⁺ pair production within a two-pulse standing wave. We show that ~10¹² positrons can be obtained using 30 PW of power.

[1] A. P. L. Robinson et al, PRL (2013), A. Arefiev et al., POP (2016);
[2] V. Khudik et al., POP (2014)