Re-creating the physics of astrophysical jets in laboratory experiments

本提案中概述的研究处于等离子体物理学和天体物理学之间的边界，并首次通过实验解决了坍缩星云如何能够发射高度准直的物质束这一突出问题。这个领域已经通过观察和数值模拟进行了多年的研究，但我们相信，特性良好的定量实验将在解决许多突出的科学问题方面发挥决定性作用。拟议的研究将有力地推动实验室天体物理学新研究领域的发展，该领域旨在通过规模实验室实验和计算机建模相结合，加强对控制天体物理对象行为的物理学的理解。本提案概述了这一迅速兴起的领域的深入研究计划，并着重于磁化超音速等离子体射流的研究。这些喷流将在帝国理工学院的MAGPIE等离子体设施中形成，并将使用各种诊断方法进行研究，包括使用强质子束成像，其中质子是使用靠近喷流的短脉冲激光产生的等离子体源形成的。使用质子束作为诊断手段将使我们第一次能够诊断出喷流内部的磁场结构。通过我们的大规模计算模型，对这些涉及高磁场的射流形成和演化的复杂等离子体过程的理解将转移到在各种天体物理情况下形成的等离子体射流上。事实上，在许多天体物理学背景下都观察到等离子体喷流，人们普遍认为磁场在它们的结构和进化中起着至关重要的作用。此外，最近有人提出，磁驱动喷流在伽马射线暴和超新星爆炸中起着重要作用。这一提议将使实验室天体物理学取得决定性的突破，通过结合目前存在的三个关键因素来实现：a)一种独特的实验方法，允许首次创建高马赫数（M bbb20）磁驱动等离子体射流，并具有与天体物理射流模型相关的磁场拓扑结构；B)激光技术和等离子体诊断的最新发展，为等离子体参数的准确诊断提供了手段；c)由实验室等离子体和天体物理学团体开发的三维MHD模拟代码，这些代码现在已经足够成熟，可以在实验、天体物理模型和观测之间提供强有力的联系。国际上对这一领域的兴趣日益增长，美国（罗切斯特、利弗莫尔、康奈尔、圣地亚哥、里诺）做出了重大努力，也突显了这一建议的及时性。该提案作者的专业知识和来自天体物理学界的国际合作者的参与将使我们能够为实验室天体物理学研究创造前所未有的能力，并为该计划提供广度和深度。

The research outlined in this proposal lies at the border between Plasma Physics and Astrophysics and for the first time addresses experimentally the outstanding issue of how collapsing nebulae are able to launch highly collimated beams of matter. This area has been studied through observations and by numerical simulations for many years but it is our belief that well characterised quantitative experiments will play a decisive role in resolving a number of outstanding scientific issues. The proposed research will strongly advance the development of the novel research area of Laboratory Astrophysics, which seeks to enhance the understanding of the physics governing the behaviour of astrophysical objects via scaled laboratory experiments, combined with computer modelling. This proposal outlines an in-depth programme of research in this rapidly emerging area and focuses on the study of magnetized supersonic plasma jets. These jets will be formed in our MAGPIE plasma facility at Imperial College and will be studied using a variety of diagnostics including the use of intense proton beam imaging where the protons are formed using a short-pulse laser-produced plasma source adjacent to the jet. The use of proton beams as a diagnostic will allow us, for the first time, to diagnose the magnetic field structure within the jets. The understanding of the complex plasma processes involved in the formation and evolution of these jets involving high magnetic fields will, through our large-scale computational models, be transferred to plasma jets which form in a variety of astrophysical situations. Indeed plasma jets are observed in many astrophysical contexts and it is widely believed that magnetic fields play a crucial part in their structure and evolution. Moreover, it was recently suggested that magnetically driven jets play important role in gamma ray bursts and supernova explosions. This proposal will enable a decisive breakthrough in Laboratory Astrophysics, achieved by combining the three key ingredients which are now in place: a) a unique experimental approach allowing for the first time the creation of high Mach number (M>20) magnetically driven plasma jets with magnetic field topology relevant to astrophysical jet models; b) recent developments in laser technology and in plasma diagnostics to provide means for accurate diagnosis of the plasma parameters; c) 3-D MHD simulation codes developed by the laboratory plasma and astrophysics communities that are now mature enough to provide a strong connection between experiment, astrophysical models and observations. The timeliness of this proposal is also underlined by the growing interest in this field internationally with major efforts in USA (Rochester, Livermore, Cornell, San Diego, Reno). The combined expertise of the authors of this proposal and the involvement of international collaborators from Astrophysics community will allow us to create an unprecedented capability for the Laboratory Astrophysics research and provide both breadth and depth to the programme.