Identifying Signature of the QED Plasma Regime

该奖项将使对光、物质和反物质之间相互作用的研究成为可能。一种由电子和正电子组成的物质-反物质等离子体被认为存在于脉冲星和其他奇特天体物理环境的大气中。当电子遇到正电子时，电子-正电子对相互湮灭，释放出大量的光；相反，高强度光源可以产生电子和正电子对。到目前为止，只有少量的电子-正电子对在实验室中被制造出来。然而，产生许多电子-正电子对来观察物质-反物质等离子体中的集体相互作用将是非常有趣的。这种状态被称为量子电动力学（QED）等离子体状态，包括一个电子-正电子等离子体，具有强场量子和集体等离子体效应。存在QED等离子体状态的理论模型，但在实验室中得到证明之前，我们不能确定不会有意外。这项工作的目标是展示如何用现有技术在实验室中演示QED等离子体状态。产生足够数量的电子-正电子对以观察集体效应，将需要大型设施来相互碰撞超强激光束，与强粒子束或与固体目标碰撞。但是，即使粒子对大量产生，集体效应也很难观察到，原因如下：等离子体很小；它是短暂的；它以相对论的速度运动；而且，由于高速，集体等离子体效应由于相对论性质量增强而减弱。但是，通过确定集体效应的非常明显的特征，可以大大放宽对设施的要求。对于反向传播到强激光的相对论电子束，当激光穿过发展中的电子-正电子等离子体时，会产生频率偏移。这些特征为等离子体集体效应提供了重要信息，为利用现有技术观察QED等离子体体系提供了一种联合生产-观测解决方案。本项目将对该联合解进行优化，从理论上和数值上确定辐射反应如何降低对能量，从而增强集体效应。该项目还将研究空间和时间结构的激光脉冲如何增加对等离子体密度，降低对能量，从而增强集体效应的特征。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This award will enable a study of interactions between light, matter, and antimatter. A matter-antimatter plasma, comprising electrons and positrons, is thought to be found in the atmosphere of pulsars and other exotic astrophysical settings. When electrons encounter positrons, there is mutual annihilation of the electron-positron pair, releasing a large amount of light; conversely, pairs of electrons and positrons may be produced by sources of very high intensity light. To date, only small amounts of electron-positron pairs have been produced in the laboratory. However, it would be of great interest to produce many electron-positron pairs to observe the collective interactions in a matter-antimatter plasma. This regime is called the Quantum ElectroDynamics (QED) plasma regime, comprising an electron-positron plasma and featuring both strong field quantum and collective plasma effects. There exists a theoretical model of the QED plasma regime, but until it is demonstrated in the laboratory we cannot be sure there will be no surprises. The goal of this effort is to show how the QED plasma regime may be demonstrated in the laboratory with existing technology.Producing electron-positron pairs in sufficient numbers to observe collective effects will require large facilities to collide ultra-intense laser beams with each other, with intense beams of particles, or with a solid target. But even if the pairs are created in large numbers, collective effects are notoriously hard to observe for several reasons: the plasma is small; it is ephemeral; it is moving at relativistic speeds; and, because of the high speeds, collective plasma effects are diminished due to the relativistic mass enhancement. However, the requirements on the facilities might be considerably relaxed by identifying very distinct signatures of the collective effects. For a relativistic electron beam counter-propagating to an intense laser, there are induced frequency shifts in the laser light as it traverses through the developing electron-positron plasma. Those signatures inform importantly on plasma collective effects, suggesting a joint production-observation solution to observing the QED plasma regime with existing technology. Optimizing this joint solution, this project will identify theoretically and evaluate numerically how the radiation reaction reduces the pair energy, thereby enhancing the collective effects. This project will also investigate how spatially and temporally structured laser pulses might increase the pair plasma density, reduce the pair energy, and thereby enhance signatures of the collective effects.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.