We propose experiments on the collision of high intensity electromagnetic
pulses with electron bunches and on the collision of multiple electromagnetic
pulses for studying extreme field limits in the nonlinear interaction of
electromagnetic waves. The effects of nonlinear QED will be revealed in these
laser plasma experiments.Comment: 7 pages, 3 figures, 1 table; 15th Advanced Accelerator Concepts
Workshop (AAC 2012), Austin, Texas, 10-15 June, 201