  The extreme intensities obtainable with lasers such as Gemini allow
non-linear QED phenomena to be investigated according to our calculations.
Electron-positron pair production from a pure vacuum target, which has yet to
be observed experimentally, is possibly the most iconic process. Beyond
pair-production our campaign will allow the experimental investigation of
currently unexplored extreme radiation regimes, like the quantum radiation
dominated regime (where quantum and self-field effects become important) and
non-linear Compton scattering. This is the first experiment in a multi-part
campaign proposed by a major international collaboration to investigate
non-linear QED. This proposal is for the first experiment in a series of 3 to
achieve our most high-profile experimental goal of pair production in vacuum,
but each experiment is designed to have its own tangible high-profile outcome.
