Observable Features of QED Cascades in Collisions of GeV Electrons with Intense Laser Pulses

We consider interaction of multi-GeV electron beam with electromagnetic field formed by intense focused laser pulses. At intensity ∼ 10²⁴ ÷ 10²⁵ W/cm² such a scheme can be used to produce both S(Shower)-type and A(Avalanche)-type (or "self-sustained") QED cascades. The proposed experimental design provides a solution to the problem of injection of seed particles into the strong field region. Here we are focusing on discussion of some peculiarities of cascade dynamics and evaluation of such quantities as final angular and spectral particle distributions, that could be observed in a realistic experiment. It turns out that one can unambiguously attribute some features of such distributions to either an S- or A-type cascade. We also discuss the possibility to initiate A-type cascades by collision of GeV electrons with a single tightly focused laser pulse. As a byproduct, it would be possible to produce in this way bright collimated γ-ray beams of GeV energies. (paper)