Femtosecond-micrometer spatiotemporal alignment of particle and laser beams

粒子束和激光束的飞秒微米时空对准

• 批准号: 2123491
• 金额: --
• 依托单位: University of Strathclyde
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2018
• 资助国家: 英国
• 起止时间: 2018 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2123491
• 关键词: Femtosecond; micrometer; spatiotemporal; alignment; particle

Alastair Nutter will be developing a novel versatile method for spatiotemporal alignment and synchronization of particle and laser beams. The underlying principle was discovered as a key result of a multi-year experimental campaign obtained by the E210 collaboration at the Facility for Advanced Accelerator Experimental Tests (FACET) at the SLAC National Accelerator Laboratory at Stanford, one of our strategic partners. The project will be done co-funded by our partner at Helmholtz-Institute Dresden-Rossendorf (HZDR) in Germany. HZDR did not only agree to co-fund this PhD project directly, but will also be providing substantial resources into the burgeoning collaboration in terms of using beamtime at their PW-class laser system to the tune of ~10 weeks per year, and may be additionally investing into significant SCAPA beamtime (daily fees for the 350 TW laser at SCAPA are £ 3300). The student will be based at Strathclyde, but will also be placed at HZDR for extended times, in line with the international aspect of the Strathclyde CDT on Plasma-based Particle and Light Sources http://ppals.phys.strath.ac.uk/ . The coordinated interaction of intense laser and electron beams plays an ever-increasing role, for example for various pump-probe experiments and imaging of the ultrafast and ultrasmall. This requires precise techniques to measure and control temporal and spatial overlap of the interaction. We have discovered a fundamental effect which permits plasma-photonic synchronization and alignment of intense laser and electron beams with femtosecond and micrometer precision in a single robust apparatus. A laser-generated cold plasma filament picks up the electric field of a transient electron beam to varying degree, seed plasma electrons are heated by this coupling and perform complex oscillations which extend into ambient gas. Here, their non-relativistic energies are just right to generate substantial amount of additional plasma via impact ionization. This acts as a 'magnifying glass', transforming the specific femtosecond-micrometer interaction signature into visible plasma recombination / de-excitation light, which is observable on microsecond-millimeter scales.We have already exploited this basic effect to demonstrate combined spatiotemporal synchronization and alignment of the SLAC Stanford 20 GeV electron beam with a focused Ti:Sapphire laser with femtosecond-micrometer accuracy. This approach enables advanced diagnostics which will improve a wide range of pump-probe experiments substantially, and allows to realise advanced spatiotemporally resolved experiments which are hitherto not feasible. The phenomena also shed light on the previously hidden importance of impact ionization for instance in advanced plasma accelerator experiments. Supporting particle-in-cell simulations reveal fascinating dynamics over a wide range of time and length scales: The initial fs-scale kick by the electron beam is spread along the thin seed filament by plasma density waves and corresponding GV/m scale fields on the ps-scale, and impact ionization and recombination processes then take place on the ns-us time scale.In Stanford, we have been using a basic version of this effect, using an electron beam generated in a conventional linear accelerator. Alastair's PhD work will develop this method of spatiotemporal alignment further, such that it will be available in advanced shape when FACET-II, the follow-up plasma wakefield accelerator facility in Stanford will come online in 2019 for user-assisted commissioning. However, the effect has even wider applicability and can be used to enable advanced plasma wakefield acceleration at laser-plasma accelerator facilities such as SCAPA or HZDR. For this, the electron beam is generated not by a conventional accelerator, but by a laser-plasma-accelerator.

阿拉斯泰尔·纳特将开发一种新颖的多功能方法，用于粒子束和激光束的时空对准和同步。其基本原理是我们的战略合作伙伴之一、斯坦福大学 SLAC 国家加速器实验室的高级加速器实验测试设施 (FACET) 与 E210 合作进行的多年实验活动的关键结果。该项目将由我们的合作伙伴德国德累斯顿-罗森多夫亥姆霍兹研究所 (HZDR) 共同资助。 HZDR 不仅同意直接共同资助该博士项目，还将为新兴合作提供大量资源，以在其 PW 级激光系统上使用每年约 10 周的光束时间，并可能额外投资于大量 SCAPA 光束时间（SCAPA 350 TW 激光器的每日费用为 3300 英镑）。学生将在斯特拉斯克莱德学习，但也将在 HZDR 停留较长时间，这与斯特拉斯克莱德等离子体粒子和光源 CDT 的国际化相一致 http://ppals.phys.strath.ac.uk/ 。强激光束和电子束的协调相互作用发挥着越来越重要的作用，例如在各种泵浦探测实验以及超快和超小型成像中。这需要精确的技术来测量和控制交互的时间和空间重叠。我们发现了一种基本效应，可以在单个坚固的设备中以飞秒和微米精度实现等离子体光子同步和强激光束和电子束的对准。激光产生的冷等离子体灯丝不同程度地接收瞬态电子束的电场，种子等离子体电子通过这种耦合被加热，并执行复杂的振荡，并延伸到周围气体中。在这里，它们的非相对论能量正好可以通过碰撞电离产生大量额外的等离子体。它起到“放大镜”的作用，将特定的飞秒-微米相互作用特征转化为可见的等离子体复合/去激发光，可以在微秒-毫米尺度上观察到。我们已经利用这种基本效应来演示 SLAC 斯坦福 20 GeV 电子束与聚焦钛宝石激光器的组合时空同步和对准 具有飞秒微米精度。这种方法实现了先进的诊断，这将大大改善各种泵浦探针实验，并允许实现迄今为止不可行的先进的时空分辨实验。这些现象还揭示了碰撞电离先前隐藏的重要性，例如在先进等离子体加速器实验中。支持细胞内粒子模拟揭示了在广泛的时间和长度尺度上令人着迷的动力学：电子束的初始 fs 尺度冲击通过等离子体密度波和 ps 尺度上相应的 GV/m 尺度场沿着细种子丝传播，然后碰撞电离和重组过程发生在 ns-us 时间尺度上。在斯坦福大学，我们一直在使用这种效应的基本版本，使用在 传统的直线加速器。阿拉斯泰尔的博士工作将进一步开发这种时空对准方法，以便当斯坦福大学的后续等离子体尾场加速器设施 FACET-II 于 2019 年上线以进行用户辅助调试时，该方法将以先进的形式提供。然而，该效应具有更广泛的适用性，可用于在 SCAPA 或 HZDR 等激光等离子体加速器设施中实现先进的等离子体尾场加速。为此，电子束不是由传统加速器产生，而是由激光等离子体加速器产生。