Collapse and revival of electromagnetic cascades in focused intense laser pulses

Understand

We consider interaction of a high-energy electron beam with two counterpropagating femtosecond laser pulses.

• Nonlinear Compton scattering and electron-positron pair production by the emitted photons result in development of an electromagnetic "shower-type" cascade, which however collapses rather quickly due to energy losses by secondary particles.
• Nevertheless, the laser field accelerates the low-energy electrons and positrons trapped in the focal region, thus giving rise to development of electromagnetic cascade of another type ("avalanche-type").
• This effect of cascade collapse and revival can be observed at the electron beam energy of the order of several GeV and intensity of the colliding laser pulses of the level of $10^{24}$W/cm$^2$.