Controlled injection for Multi-pulse laser wakefield accelerators

多脉冲激光尾场加速器的受控注入

• 批准号: 2196609
• 金额: --
• 依托单位: University of Oxford
• 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-2196609
• 关键词: Controlled; injection; Multi; pulse; laser

Context, aims and objectivesLaser-driven plasma accelerators can already accelerate electrons (and, in principle, positrons) to multi-GeV energies in accelerator stages only a few centimetres long. However, several issues must be overcome before these systems can realize their enormous promise: (i) the shot-to-shot jitter of the bunch parameters is too high for many applications; (ii) the lasers used to drive the accelerator operate at only a few pulses per second, which is too low for applications such as driving compact light sources; and (iii) the driving lasers are very inefficient (below 0.1%), which will be an issue for long-term applications such as driving particle colliders. In an effort to address the low repetition rate and efficiency of the driving lasers used at present, our group has proposed that a train of low-energy laser pulses could be used to drive the plasma wave, rather than a single high energy pulse. If the pulses in the train are spaced by the plasma period then the wakefields add coherently to produce a plasma wave with an amplitude which grows towards the back of the pulse train. This approach, known, as multi-pulse laser wakefield acceleration (MP-LWFA), could enable novel lasers to be employed which cannot easily generate high energy pulses, but which can generate few-milijoule laser pulses at mulit-kilohertz pulse repetition rates, with high efficiency. The MP-LWFA approach therefore offers a route to achieving compact accelerators able to generate GeV-scale electron bunches at high repetition rates, and in turn a route to a new generation of compact light sources. In order to address the issues of high shot-to-jot jitter of the bunch parameters it will be necessary to develop strategies for controlling the injection and trapping of electrons into the plasma wakefield. This is especially challenging for the linear, or quasi-linear, plasma wakefields driven by a MP-LWFA. The objectives of this work are to develop methods for controlling electron injection into the quasi-linear wakefields produced by MP-LWFAs. Methodology: Two methods for controlling injection will be explored: (i) ionization injection using additional laser pulses; and (ii) injection at plasma density ramps. These possible methods will be explored both experimentally and through numerical simulations. The experimental work will be undertaken in our labs in Oxford and at national laser facilities such as the Central Laser Facility at Rutherford Appleton Laboratory. Numerical simulations will be undertaken using particle-in-cell (PIC) codes run on national and local computer cluster facilities.

背景、目的和目标激光驱动的等离子体加速器已经可以在仅有几厘米长的加速器级中将电子（原则上还可以是正电子）加速到多GeV能量。然而，在这些系统实现其巨大前景之前，必须克服几个问题：(i) 束参数的逐次抖动对于许多应用来说太高； (ii) 用于驱动加速器的激光器每秒仅运行几个脉冲，这对于驱动紧凑型光源等应用来说太低了； (iii) 驱动激光器的效率非常低（低于 0.1%），这对于驱动粒子对撞机等长期应用来说将是一个问题。为了解决目前使用的驱动激光器重复率和效率低的问题，我们的小组提出可以使用一系列低能量激光脉冲来驱动等离子体波，而不是单个高能量脉冲。如果脉冲串中的脉冲按等离子体周期间隔，则尾场相干地相加，产生等离子体波，其振幅朝脉冲串的后面增长。这种方法被称为多脉冲激光尾场加速（MP-LWFA），可以使用新型激光器，这种激光器不能轻易产生高能脉冲，但可以以千赫兹脉冲重复率产生几毫焦耳激光脉冲，效率很高。因此，MP-LWFA 方法提供了一条实现紧凑型加速器的途径，该加速器能够以高重复率产生 GeV 级电子束，进而提供了一条通往新一代紧凑型光源的途径。为了解决束参数的高点间抖动问题，有必要制定控制电子注入和捕获到等离子体尾场的策略。这对于 MP-LWFA 驱动的线性或准线性等离子体尾场来说尤其具有挑战性。这项工作的目标是开发控制电子注入 MP-LWFA 产生的准线性尾场的方法。方法：将探索两种控制注射的方法：（i）使用附加激光脉冲的电离注射； (ii) 以等离子体密度斜坡注射。这些可能的方法将通过实验和数值模拟进行探索。实验工作将在我们位于牛津的实验室和国家激光设施（例如卢瑟福阿普尔顿实验室的中央激光设施）进行。将使用在国家和地方计算机集群设施上运行的细胞内粒子（PIC）代码进行数值模拟。