The new intensity frontier: exploring quantum electrodynamic plasmas

激光技术的进步使光能够聚焦到极高的强度，能够产生奇异的物质状态，通常被描述为高温等离子体--物质的第四种状态，在这种状态下，电子和离子物质成分高速移动。新的超高强度激光将在未来几年内在国际研究设施上线，它将使光聚焦到目前可以实现的十倍强度。这将足以创造一种全新的等离子体状态，量子电动力学(QED)过程在其中发挥重要作用。这种新的状态就是所谓的QED等离子体。这种物质状态在很大程度上还没有在实验室中得到探索，但它将在使用下一代高功率激光进行的许多实验中发挥关键作用。虽然QED理论是为单粒子相互作用而建立的，但QED-等离子体是由非常多的粒子组成的复杂系统。这带来了一个挑战，因为在量子理论中，必须考虑所有可能的相互作用，而在QED等离子体中，大量的粒子给标准QED理论提供了太多的可能性。虽然已经开发出了半经典模型，其中包括了预计最重要的量子效应，但这些模型还有待于实验测试。我们将实施一项工作计划，首次使用现有的粒子加速器和高功率激光来测试我们的QED相互作用模型。然后，我们将使用这个模型来设计实验，在实验室中产生和探索第一个QED等离子体，随后我们将在新的下一代高强度激光设备上执行这些实验。QED等离子体被认为在极端的天体物理环境中发挥着关键作用，例如在脉冲星周围的极强磁场中，例如在反物质产生的级联中用正电子等离子体填充磁层。QED等离子体态的实验演示和研究将使我们有机会首次在实验室中探索这一物理过程。

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.