The new intensity frontier: exploring quantum electrodynamic plasmas

Advances in laser technology have enabled the focussing of light to extreme intensities, capable of creating exotic states of matter, typically characterised as high temperature plasma - the forth state of matter, in which the electrons and ion matter constituents are moving around with high velocity. New ultrahigh intensity lasers, due to come online in the next few years at international research facilities, will focus light to ten times higher intensity that is achievable at present. This will be sufficient to create an entirely new state of plasma in which quantum electrodynamics (QED) processes play an important role. This new state is the so-called QED-plasma. This state of matter is largely unexplored in the laboratory and yet will play a crucial role in many of the experiments to be performed using next generation high power lasers. While QED theory is well established for the interaction of single particles, but QED-plasmas are complex systems of very many particles. This creates a challenge as in quantum theory all possible interactions must be considered and in QED-plasmas the large number of particles gives far too many possibilities for standard QED theory to be used. While semi-classical models have been developed which include what are expected to be the most important quantum effects, these have yet to be tested experimentally. We will conduct a programme of work to test our models of QED interactions in strong electromagnetic fields for the first time using existing particle accelerators and high power lasers. We will then use this model to design experiments to generate and explore the first QED-plasma in the laboratory, which we will subsequently perform on new next generation high-intensity laser facilities. QED-plasmas are postulated to play a key role in extreme astrophysical environments such as in the extremely strong magnetic fields around pulsars, for example populating the magnetosphere with an electron-positron plasma in a cascade of antimatter production. The demonstration and investigation of the QED-plasma state in experiments will give us the opportunity to probe this physics in the laboratory for the first time.