Generation of quantum electrodynamic cascades by colliding laser pulses

Quantum electrodynamic cascades in intense electromagnetic fields arise when the proper electron acceleration , expressed in Compton units, can attain values greater than or on the order of unity. For times , where is the carrier frequency of the field, we have derived a general formula for of an initially resting electron in an arbitrary electromagnetic field. Using this formula, we have found an optimal configuration of colliding laser pulses, which provides a significant reduction in the threshold intensity of occurrence of cascades up to a level of .