Pair Creation in QED-Strong Pulsed Laser Fields Interacting with Electron Beams

QED effects are known to occur in a strong laser pulse interaction with a counterpropagating electron beam, among these effects being electron-positron pair creation. We discuss the range of laser pulse intensities of $J\ge 5\times {10}^{22}\mathrm{W}/{\mathrm{cm}}^2$ combined with electron beam energies of tens of GeV. In this regime multiple pairs may be generated from a single beam electron, some of the newborn particles being capable of further pair production. Radiation backreaction prevents avalanche development and limits pair creation. The system of integro-differential kinetic equations for electrons, positrons and $\gamma$ photons is derived and solved numerically.

Figure 1

Distribution functions of electrons and positrons, $f_{e,p}(\chi )$, and a spectrum of emission, ${\chi }_{\gamma }{f}_{\gamma }(\chi )/{\chi }_0$, after the interaction of 46.6 GeV electrons with one cycle (top) and five cycles (bottom) of a laser pulse of intensity $J\approx 5\times {10}^{22}\mathrm{W}/{\mathrm{cm}}^2$ [so that $\chi \approx 2\mathcal{E}[\mathrm{GeV}]$—see Eq. (2)]. Here $f_e-f_p$ is the distribution of the beam electrons and $\int (f_e-f_p)d\chi =1$.

Figure 2

Pair production for longer pulse durations, measured in cycles. Other parameters are the same as in Fig. 1.