Broadband beam applications of plasma wakefield accelerators

激光等离子体加速器可以产生相对论能量的电子束和厘米级距离的大电流，这要归功于等离子体可以维持的巨大电场-与传统的粒子加速器相比，等离子体加速器的主要吸引力是更大的数量级。来自等离子体加速器的束的能量扩散固有地倾向于是宽的。虽然通常不理想，但存在独特的应用程序，该功能是一种资产。事实上，用等离子体加速器产生宽带光束比产生单能光束更容易-因此宽带光束具有更高的TRL。受益于这种宽带波束的应用将在这项工作中开发。一个应用是在实验室中再现空间辐射[1]。太空辐射是宽带的，对船上的电子设备和宇航员构成危险。利用等离子体加速器精确再现空间辐射为先进的辐射硬度测试开辟了道路。类似的宽带低能量射束可用于肿瘤治疗。这项相关的申请是由斯特拉斯克莱德[2]与工业界合作申请的专利。辐射的宽带特性允许深度-剂量沉积分布，其可以针对表面肿瘤定制，从而消除了常规加速器会发生的对周围健康组织的照射。要研究的第三个应用是使用相对宽带的电子束在更高的能量的数百兆电子伏的顺序。这种光束是混合等离子体韦克菲尔德加速器的理想驱动器[3]，该方法有望实现等离子体韦克菲尔德加速器能量和亮度转换器，因此当与等离子体光电阴极耦合时，可以实现比现有技术更亮100，000倍的光束[4]。这是一个非常成功的实验推力在欧洲的合作[5，6]。就在最近，关于这一主题的突破性出版物被《自然通讯》杂志接受，由斯特拉斯克莱德和HZDR之间的前联合博士生作为第一作者之一获得[6]。同样，拟议工作的博士生将由HZDR共同资助，并将致力于宽带电子束的上述三种应用。该项目的另一个合作伙伴将是斯坦福大学，我们将在那里提供FACET-II等离子体光电阴极的批准E-310实验，同时还将在斯特拉斯克莱德的SCAPA和HZDR的DRACO激光等离子体设施进行开发和测试。等离子体光电阴极的开发及其应用前景由ERC NeXeplant资助[7]。该学生将探索等离子体加速器操作的基础激光等离子体物理学，旨在稳定，宽带光束及其应用。将利用SCAPA的内部能力来解决这些问题，并辅之以在HZDR的DRACO设施进行的实验，该设施与SCAPA规模相似。在与人类发展报告合作方面有着良好的记录，包括联合编写高级别文件，如[5，6]。此外，HZDR还与他们的工业合作伙伴OncoRay共同积极开展医学癌症治疗，并对太空辐射复制有着浓厚的兴趣。因此，他们是这个学生的理想合作伙伴。该项目的主要目标是将上述三个应用推力的TRL提高至少一个点。这将包括SCAPA的建模和实验活动，包括作为英国Cockcroft研究所和ERC NeXtreme项目合作采购的新kHz激光器和光束线，DRACo和斯坦福大学的光束线。该学生将被嵌入斯特拉斯克莱德博士培训中心PPALS [8]，作为以前的学生，包括斯特拉斯克莱德-HZDR联合博士生，他是[6]的第一作者之一。

Laser-plasma accelerators can generate electron beams with relativistic energies and large current on centimetre-scale distance, thanks to the huge electric fields a plasma can sustain - the chief attraction of plasma accelerators compared to conventional particle accelerators that are orders of magnitude larger. The energy spread of beams from plasma accelerators inherently tends to be broad. While generally not desirable, there are unique applications for which this feature is an asset. In fact, producing broadband beams with plasma accelerators is easier than to produce monoenergetic beams - broadband beams therefore have higher TRL. Applications that profit from such broadband beams shall be developed in this work. One application is the reproduction of space radiation in the laboratory [1]. Space radiation is broadband, and a danger to electronics and astronauts onboard. Exact reproduction of space radiation with plasma accelerators opens up a path to advanced radiation hardness testing. Similar broadband, low energy beams can be used for surficial cancer therapy. This related application is patented by Strathclyde [2] in collaboration with industry. The broadband character of the radiation allows a depth-dose deposition profile that can be tailored to surface tumours, thus eliminating irradiation of surrounding healthy tissue as would occur with conventional accelerators. The third application to be investigated is using relatively broadband electron beams at higher energies of the order of hundreds of MeV. Such beams are ideal drivers for hybrid plasma wakefield accelerators [3], an approach that promises to allow plasma wakefield accelerator energy and brightness converters and therefore beams 100,000 x brighter than state-of-the-art to be realized when coupled with plasma photocathodes [4]. This is now an experimentally very successful thrust in a European collaboration [5,6]. Just recently, a breakthrough publication on this topic was accepted in Nature Communications, obtained by a previous joint PhD student between Strathclyde and HZDR as one of the first authors [6]. The PhD student for the proposed work likewise would be co-funded by HZDR and would be working on the above three applications of broadband electron beams. Another partner in this project will be Stanford University, where we will deliver the approved E-310 experiment on the plasma photocathode at FACET-II, which in parallel is also to be developed and tested at Strathclyde's SCAPA and HZDR's DRACO laser-plasma facilities. The plasma photocathode development and its prospects for applications are co-funded by the ERC NeXource grant [7]. The studentship will explore fundamental laser-plasma-physics underlying the operation of plasma accelerators aiming at stable, broadband beams and its applications. SCAPA's in-house capabilities will be exploited to address these questions, complemented by experiments at HZDR's DRACO facility, which is of similar scale as SCAPA. A strong track record exists in collaboration with HZDR, including joint high-level papers such as [5,6]. In addition, HZDR is also active in medical cancer therapy jointly with their industrial partner OncoRay, and has strong interest in space radiation reproduction. They are therefore the ideal partner for this studentship. Main aims of the project are to increase the TRL of the above mentioned three application thrusts by at least one point. That will include modelling and experimental campaigns at SCAPA, including the new kHz laser and beamline procured as collaboration between the UK Cockcroft Institute and the ERC NeXource project, the beamlines at DRACo and at Stanford. The student will be embedded in the Strathclyde Centre for Doctoral Training PPALS [8], as previous students including the joint Strathclyde-HZDR PhD student who was one of the first authors of [6].