Quantum phenomena in high-intensity laser-matter interactions

高强度激光实验的新时代已经开始。英国最近的超相对论电子束与强激光脉冲碰撞的实验表明，不仅可以使用强激光探测基础物理，还可以产生具有独特性质的辐射源，这些辐射源在科学中得到了应用。这样的实验极具挑战性，尽管最近取得了成功，但在观察到量子效应的程度上仍存在分歧。实验结果和理论预测之间的差异被归因于用于模拟和分析实验的粒子在单元(PIC)代码中使用的量子效应的数值模型。一系列新的实验将于今年开始，这些实验将能够探索在强电磁场中从经典物理到量子物理的转变。因此，提高我们对理论模型及其实现的理解是至关重要的，以确保理论预测和分析跟上实验的进展。为了满足这一迫切的实验需求，我们建议从两个方面发展现有的理论。在一个方面，我们将以一种系统的方式扩展现有的模型，以包括目前被忽视的过程(如吸收和三叉戟的产生)，从而可以立即被模拟器使用。在第二方面，我们将分析一些现有的数值模型无法捕获的量子效应(但在未来设施的重叠场几何形状或密集电子束中变得相关)，评估它们对实验活动的重要性，并开发一种超越当前模型的数值实现方法。要做到这一点，需要一组不仅是强激光物理中量子效应理论的专家，而且还具有理解数值实施和实验分析所需的经验的研究人员团队。这不是对现有代码进行基准测试的情况，文献中已经对此进行了很好的介绍。现在需要的是一种“自上而下”的方法，这种方法可以验证和改进代码中使用的量子效应模型。普利茅斯拥有一个在激光与物质强烈相互作用领域处于世界领先地位的老牌研究小组。工作人员积极从事研究，在社区中作为强激光物理中量子效应理论的专家而广为人知。此外，参与该项目的研究人员积极参与实验工作，例如，最近在英国中央激光设施的一项实验中展示了激光与物质碰撞中的辐射反应的团队的成员。因此，研究人员恰恰拥有合适的技能来承担这一及时的项目，并向广泛的物理学家社区提供新的重要成果。这将有助于保持英国在激光-物质相互作用活跃研究领域的世界领先能力。

A new era of high-intensity laser experiments has begun.Recent UK experiments, in which beams of ultra-relativistic electrons were collided with intense laser pulses, have shown that it is possible not only to use intense lasers to probe fundamental physics, but also to generate radiation sources with unique properties, which find applications across the sciences. Such experiments are extremely challenging, and despite recent successes there is disagreement over to what extent quantum effects have been observed. Discrepancies between experimental results and theoretical predictions have been attributed to the numerical models of quantum effects employed in Particle-In-Cell (PIC) codes used to simulate and analyse experiments.A host of new experiments will begin this year, and will be able to probe the transition from classical to quantum physics in intense electromagnetic fields. It is therefore critical that we improve our understanding of theoretical models, and their implementations, in order to ensure that theoretical predictions and analyses keep up with experimental progress.To meet this urgent experimental demand we propose developing existing theory on two fronts.On one front, we will extend existing models to include currently neglected processes (such as absorption and trident pair production) in a systematic way that can be immediately employed by simulators. On the second front, we will analyse a number of quantum effects which cannot be captured by existing numerical models (but which become relevant in e.g. the overlapping field geometries of future facilities, or in dense electron bunches), assess their importance to experimental campaigns, and develop a methodology to implement them numerically, going beyond current models.Doing so requires a team of researchers who are not only experts in the theory of quantum effects in intense laser physics, but who also have the experience required to understand numerical implementation and experimental analyses. This is not a case of benchmarking existing codes, already well-covered in the literature. What is needed, rather, is a "top down", approach which can verify, and improve upon, the models of quantum effects which are used in the codes.Plymouth hosts an established, world-leading research group in the area of intense laser-matter interactions. Staff members are research-active and well-known in the community as experts in the theory of quantum effects in intense laser physics. Furthermore, the Investigators attached to this project are actively involved in experimental efforts, being for example part of the team which recently demonstrated radiation reaction in laser-matter collisions in an experiment at the UK's Central Laser Facility.As such the Investigators have precisely the right skillset to undertake this timely project and deliver new results of import to a wide community of physicists. This will help maintain the UK's world-leading capabilities in the active research area of intense laser-matter interactions.