Arrowsmith C D, Simon P, Bilbao P J, Bott A F A, Burger S, Chen H, Cruz F D, Davenne T, Efthymiopoulos I, Froula D H, Goillot A, Gudmundsson J T, Haberberger D, Halliday J W D, Hodge T, Huffman B T, Iaquinta S, Miniati F, Reville B, Sarkar S, Schekochihin A A, Silva L O, Simpson R, Stergiou V, Trines R M G M, Vieu T, Charitonidis N, Bingham R, Gregori G
Department of Physics, University of Oxford, Parks Road, Oxford, OX1 3PU, UK.
European Organization for Nuclear Research (CERN), CH-1211, Geneva 23, Switzerland.
Nat Commun. 2024 Jun 12;15(1):5029. doi: 10.1038/s41467-024-49346-2.
Relativistic electron-positron plasmas are ubiquitous in extreme astrophysical environments such as black-hole and neutron-star magnetospheres, where accretion-powered jets and pulsar winds are expected to be enriched with electron-positron pairs. Their role in the dynamics of such environments is in many cases believed to be fundamental, but their behavior differs significantly from typical electron-ion plasmas due to the matter-antimatter symmetry of the charged components. So far, our experimental inability to produce large yields of positrons in quasi-neutral beams has restricted the understanding of electron-positron pair plasmas to simple numerical and analytical studies, which are rather limited. We present the first experimental results confirming the generation of high-density, quasi-neutral, relativistic electron-positron pair beams using the 440 GeV/c beam at CERN's Super Proton Synchrotron (SPS) accelerator. Monte Carlo simulations agree well with the experimental data and show that the characteristic scales necessary for collective plasma behavior, such as the Debye length and the collisionless skin depth, are exceeded by the measured size of the produced pair beams. Our work opens up the possibility of directly probing the microphysics of pair plasmas beyond quasi-linear evolution into regimes that are challenging to simulate or measure via astronomical observations.
相对论性电子 - 正电子等离子体在诸如黑洞和中子星磁层等极端天体物理环境中普遍存在，在这些环境中，吸积驱动的喷流和脉冲星风预计富含电子 - 正电子对。在许多情况下，它们在这种环境动力学中的作用被认为是至关重要的，但由于带电成分的物质 - 反物质对称性，它们的行为与典型的电子 - 离子等离子体有显著不同。到目前为止，我们在实验上无法在准中性束中产生大量正电子，这使得对电子 - 正电子对等离子体的理解仅限于简单的数值和分析研究，而这些研究相当有限。我们展示了首个实验结果，证实了利用欧洲核子研究组织（CERN）超级质子同步加速器（SPS）的440 GeV/c束流产生了高密度、准中性、相对论性电子 - 正电子对束。蒙特卡罗模拟与实验数据吻合良好，并表明所产生的对束的测量尺寸超过了集体等离子体行为所需的特征尺度，如德拜长度和无碰撞趋肤深度。我们的工作开启了直接探究对等离子体微观物理的可能性，超越了准线性演化，进入到通过天文观测进行模拟或测量具有挑战性的 regime。 （注：原文最后一词“regime”未准确翻译，可根据上下文灵活处理，此处保留英文以便理解）
