Unveiling the Physics of High-Density Relativistic Pair Plasma Jets in the Laboratory

伽马射线暴(GRB)是宇宙中能量最高的事件之一。它们发生在距离宇宙很远的地方，是大质量恒星或合并的中子星坍塌的结果，伴随着电子-正电子对的相对论火球的发射。从天体物理观测中，已经收集了大量关于导致如此强烈的辐射发射的机制的信息，主要的模型预测这是由于光束爆炸通过周围的等离子体时造成的破坏。这会产生激波和磁流体湍流，产生同步辐射，有可能加速到超高能量的质子，而这些质子在地球上被观察到是宇宙射线。然而，没有直接证据表明伽玛暴产生了磁场或宇宙射线。估计通常基于原油能量均分的论点或理想化的数值模拟，难以捕捉到极端的等离子体条件。我们建议通过在欧洲核子研究中心进行实验室实验来模拟射流在其周围等离子体中的传播来解决这一漏洞。这样的实验将能够实现对等离子体性质的现场测量，并提供其他地方无法实现的精细细节。这些实验还通过提供延伸到非线性区域的长测量时间来补充数值模拟，在非线性区域，数值模拟今天是不可能的。拟议中的实验将研究基本的物理过程，揭示伽玛暴的微观物理，并解决下列尚未回答的关键问题：1)什么机制驱动高能光束不稳定及其长期演化？2)湍流在粒子加速到最高能量过程中起什么作用？3)磁场和粒子之间的相互作用是什么，这对观测到的电磁发射有什么影响？我们将利用新的地面实验室实验为高能天体物理提供一个新的窗口。

Gamma-ray bursts (GRBs) are among the most energetic events in the Universe. They occur at cosmological distances and are the result of the collapse of massive stars or neutron stars mergers, with emission of relativistic 'fireballs' of electron-positron pairs. From astrophysical observations, a wealth of information has been gleaned about the mechanism that leads to such strong emission of radiation, with leading models predicting that this is due to the disruption of the beam as it blasts through the surrounding plasma. This produces shocks and hydromagnetic turbulence that generate synchrotron emission, potentially accelerating to ultra-high energies the protons which are observedon Earth as cosmic rays. However, there is no direct evidence of the generation of either magnetic fields or cosmic rays by GRBs. Estimates are often based on crude energy equipartition arguments or idealized numerical simulations that struggle to capture the extreme plasma conditions. We propose to address this lacuna by conducting laboratory experiments at CERN to mimic the jet propagation through its surrounding plasma. Such experiments will enable in situ measurement of the plasma properties, with exquisite details that cannot be achieved elsewhere. The experiments also complement numerical simulations by providing long measurement times extending into the non-linear regime where numerical simulations are not possible today. The proposed experiments will study fundamental physics processes, unveil the microphysics of GRBs, and address the following, yet answered, key questions:1) What mechanisms drive the energetic beams unstable and their long-term evolution?2) What is the role of turbulence in the acceleration of particles to the highest energies?3) What is the interplay between magnetic fields and particles and how does this affect the observedelectromagnetic emission?We will provide a new window in high energy astrophysics using novel Earth-based laboratory experiments.