Collimated and neutral electron-positron plasmas in the laboratory

电子-正电子对等离子体（EPP）是一种独特的物质状态，在其带负电（电子）和带正电（正电子）的成分之间呈现精确对称。尽管它在地球上几乎不存在，但它被认为是宇宙中相当常见的现象，并且被认为是巨大天体（如黑洞，类星体和类星体）大气层的主要组成部分。天体物理学界普遍认为，EPP很可能是这些天体以准直喷流形式发射的一些最强大物质的主要成分，这些喷流最终与超亮和短寿命伽马射线爆发的发射有关。这些天体是测试物理极限的特殊天然实验室，由于它们与地球的巨大距离（有些超过10亿光年），它们为我们宇宙的原始阶段提供了一个独特的窗口。尽管它们在广泛的基本物理场景中发挥着迷人的作用，但由于在实验室中产生它们的极端困难，人们对EPP的了解甚少。我们对这种特殊物质状态的所有知识完全依赖于天体物理学的观测及其理论解释。然而，天体物理学测量本身是有限的，由于这些天体与地球的距离很远，几乎不可能获得这些天体的微观物理学。实验室实验将极大地推进我们对这种物质状态的认识，直到最近，首席研究员和他的合作者才成功地在实验室中产生了中性电子-正电子等离子体。我们在这里建议继续这一令人兴奋的实验研究，使用美国密歇根大学超快光学科学中心（CUOS）主持的HERCULES激光器进行一系列实验。特别是，我们计划通过最小化它们的发散度来提高激光产生的EPP的质量，从而显着延长它们在受控背景电子离子等离子体中的传播距离。准直和中性EPP的成功产生将允许，第一次，在背景电子离子等离子体中的EPP动力学的研究在星系际介质中的天体物理射流的传播相关的条件。这项初步工作不仅本身具有重要意义，而且还将作为在这一新发展的实验研究领域获得更多资助的基础。

An electron-positron pair plasma (EPP) is a unique state of matter that presents an exact symmetry between its negatively charged (electrons) and positively charged (positrons) constituents. Despite being virtually absent on Earth, it is believed to be a rather common occurrence in the Universe and it is thought to represent the main constituent of the atmosphere of immense astrophysical objects such as black holes, quasars, and pulsars. There is general consensus in the astrophysical community that EPPs are likely candidates for being the main ingredient of some of the most powerful emissions of matter from these objects, in the form of collimated jets, which are ultimately associated with the emission of ultra-bright and short-lived gamma-ray bursts. These astrophysical objects are exceptional natural laboratories to test physics at its limits and, due to their immense distance from Earth (some exceeding a billion light years), they provide a unique window on the primordial stages of our Universe. Despite their fascinating role in a wide range of fundamental physical scenarios, EPPs are poorly understood due to the extreme difficulty in generating them in the laboratory. All our knowledge of this peculiar state of matter relies exclusively on astrophysical observations and their theoretical interpretation. However, astrophysical measurements are intrinsically limited and it is virtually impossible to access the microphysics of these objects due to their immense distance from Earth. Laboratory experiments would greatly advance our knowledge of this state of matter and only recently the Principal Investigator and his collaborators have succeeded in producing a neutral electron-positron plasma in the laboratory.We propose here to continue this line of exciting experimental research by performing a series of experiments using the HERCULES laser hosted by the Centre for Ultrafast Optical Sciences (CUOS) at the University of Michigan, US. In particular, we plan to improve the quality of laser-generated EPPs by minimising their divergence and therefore significantly extend their propagation distance in controlled background electron-ion plasmas. The successful generation of a collimated and neutral EPP will allow, for the first time, for the study of EPP dynamics in background electron-ion plasmas in conditions of relevance to the propagation of astrophysical jets in the intergalactic medium. This preliminary work will not only be of interest in its own right but it will also serve as the basis for obtaining more extended grant funding on this newly developing area of experimental research.