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，它在带负电荷(电子)和带正电荷(正电子)的成分之间呈现出精确的对称性。尽管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，它被认为是黑洞、类星体和脉冲星等巨大天体大气的主要组成部分。天体物理界的普遍共识是，EPPS很可能是这些天体释放出的一些最强大物质的主要成分，这些物质以准直喷流的形式存在，最终与超亮和短暂的伽马射线爆发的发射有关。这些天体是测试极限物理的特殊自然实验室，由于它们离地球很远(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EPPS在广泛的基本物理场景中扮演着令人着迷的角色，但由于在实验室中生成它们极其困难，人们对EPPS知之甚少。我们对物质这种特殊状态的所有知识完全依赖于天体物理观测及其理论解释。然而，天体物理测量在本质上是有限的，而且由于它们离地球很远，几乎不可能获得这些天体的微物理信息。实验室实验将极大地提高我们对这种物质状态的了解，直到最近，首席研究员和他的合作者才在实验室成功地产生了中性电子-正电子等离子体。在这里，我们建议通过使用由美国密歇根大学超快光学科学中心(CUOS)主持的大力神激光进行一系列实验，来继续这一令人兴奋的实验研究。特别是，我们计划通过最小化它们的发散来提高激光产生的EPP的质量，从而显著延长它们在受控背景电子-离子等离子体中的传播距离。准直中性电子对撞机的成功产生将首次允许在与星系间介质中天体物理喷流传播相关的条件下研究背景电子-离子等离子体中的电子对撞机动力学。这项初步工作不仅本身将是有意义的，而且还将成为在这一新发展的实验研究领域获得更多延长赠款资金的基础。

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.