IRFP: High energy ion interactions in warm dense matter

1064468陈国际研究奖学金计划使美国科学家和工程师能够在国外进行9至24个月的研究。该项目的奖项提供了联合研究的机会，并提供了使用国外独特或互补的设施、专业知识和实验条件的机会。该奖项将资助苏菲亚·N·陈博士与法国帕莱索理工学院的Julien Fuchs Lee博士合作的为期24个月的研究奖学金。目前的高强度短脉冲激光使研究热致密物质(WDM)的性质成为可能。这是一个出了名的难研究领域，因为它位于凝聚态物质、高密度等离子体和核物理的交界处，核物理涵盖了广泛的研究课题，包括高压物理、应用材料研究、天体物理、地球物理、惯性聚变以及许多工业应用。在这种状态下，等离子体的密度从固体密度到10倍以上，温度从0.1到100 eV不等。对这种暂态特性的实验室研究具有双重挑战性：第一，产生存在足够长的时间可以在皮秒时间尺度上探测的WDM的均匀样本是非常困难的；第二，在理论和模型方面，这种物质是部分关联和简并的，这使得数值模拟成为一个巨大的挑战。因此，这自然表明需要实验数据来对当前代码进行基准测试。现在，随着这些利用短脉冲高功率激光来产生WDM的新技术的出现，它开辟了许多现在可以研究的课题。该项目通过实验和建模，将回答一些基本问题。首先，由于目前的停止模型依赖于弹丸的有效电荷状态Z*，Z*的修正如何取决于它所通过的等离子体的特性？当前的哪个理论模型能够准确地预测这种相互作用，以及在哪些条件下？其次，需要开发什么基础平台来研究等离子体中的离子阻止能力，以便将冷停止数据与热等离子体停止数据联系起来？该计划正在与法国的两个实验室进行，分别是LULI(波尔多理工学院L激光强度利用实验室)和CELIA(波尔多大学中心激光强度与应用实验室)。Luli在那里拥有独特的实验能力，即灵活的高功率、多光束激光用户设备。有了这个系统，多束激光将允许物质在固体密度(即WDM等离子体)下被加热到几个eV温度，产生高达数十MeV的宽带离子束，并提供短持续时间的探测束用于诊断。现场诊断分为两类：一类是测量离子束的特性，另一类是提供离子束通过的等离子体条件的信息。随着CELIA所开发的用于模拟短脉冲激光与等离子体相互作用的PIC和QMD代码的出现，实验工作将从理论上得到保障。最重要的是，在更广泛的范围内，这种方法将有助于验证和验证目前在美国和欧洲都在开发的模拟。此外，这项研究将补充和开发在X-FEL、加速器和HiPER(欧洲激光聚变项目)研究WDM的平台，所有这些最终都将在国家点火设施(NIF)准备实验。

1064468 Chen The International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad. This award will support a twenty-four-month research fellowship by Dr. Sophia N. Chen to work with Dr. Julien Fuchs Lee at Ecole Polytechnique in Palaiseau, France. Current high intensity short pulse lasers have now made possible investigations into the properties of warm dense matter (WDM) regime. This is a notoriously difficult area to study since it lies at the junction between condensed matter, dense plasma and nuclear physics, which covers a wide panel of research topics including, high-pressure physics, applied material studies, astrophysics, geophysics, inertial fusion as well as many industrial applications. Plasmas in this state have density ranging from the solid density up to 10 times greater and temperature that vary from 0.1 to 100 eV. Laboratory studies of the properties of this transient state are doubly challenging: first, there is tremendous difficulty in producing homogeneous samples of WDM which exist long enough to be probed over picosecond time-scales, and second, in regards to theory and model, such matter is partially correlated and degenerate which renders numerical modeling a tremendous challenge. This therefore naturally points to the need for experimental data to benchmark current codes. Now, with these new techniques of employing short-pulse high-power lasers to create WDM, it opens up numerous topics which can now be studied. This project, through experiments and modeling, will answer some basic questions. First, since present stopping models are dependent on the effective charge state Z* of the projectile, how does the modification of Z* depend on the characteristics of the plasma that it passes through? Which current theoretical model closely predicts this interactions and over which conditions? Second, what foundational platform would need to be developed to study ion stopping power in plasmas to bridge cold stopping to hot plasma stopping data?This program is being carried out with two laboratories in France, namely LULI (Laboratoire pour l'Utilisation des Lasers Intenses at Ecole Polytechnique) and CELIA (Centre Lasers Intenses et Applications at Université de Bordeaux). LULI houses unique experimental capability available there, namely their flexible high-power, multi-beams laser user facility. With this system, the multiple laser beams will allow matter to be heated to several eV temperatures at solid density (i.e. WDM plasmas), create a broadband ion beam up to tens of MeV, and provide short duration probe beams for diagnostics. Diagnostics fielded fall into two categories: those that measure the characteristics of the ion beams and those that provide information of the plasma conditions that the ion beam had passed through. With the PIC and QMD codes which have been adapted to simulating short pulse laser-plasma interactions developed at CELIA, the experimental effort will be grounded in theory. Most importantly on a broader scale, this approach will aid in verifying and validating simulations that are currently being developed both in the US and in Europe. Also, this research will compliment and develop platforms for studying WDM at X-FELs, accelerators, and HiPER (the European laser fusion project), all of which will ultimately prepare experiments at the National Ignition Facility (NIF).