The new intensity frontier: exploring quantum electrodynamic plasmas

激光技术的进步使光聚焦到极端强度，能够创造出奇特的物质状态，典型的特征是高温等离子体——物质的第四种状态，其中电子和离子物质成分以高速移动。新的超高强度激光器将在未来几年内在国际研究机构上线，它将把光聚焦到比目前高10倍的强度。这将足以创造一个全新的等离子体状态，其中量子电动力学（QED）过程起着重要作用。这种新状态就是所谓的qed等离子体。这种物质状态在很大程度上尚未在实验室中被探索，但将在使用下一代高功率激光器进行的许多实验中发挥关键作用。虽然QED理论已经很好地建立了单个粒子的相互作用，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，大量的粒子为标准QED理论提供了太多的可能性。虽然半经典模型已经被开发出来，其中包括了预期中最重要的量子效应，但这些还有待实验检验。我们将开展一项工作计划，利用现有的粒子加速器和高功率激光器，首次在强电磁场中测试我们的QED相互作用模型。然后，我们将使用该模型设计实验，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进行实验。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电子-正电子等离子体填充磁层。qed等离子体态的实验证明和研究将使我们第一次有机会在实验室中探索这一物理现象。

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.