Experimental Study of Plasma Wakefield Acceleration at VELA/CLARA Facility at Daresbury Laboratory

自从Tajima和Dawson提出这个想法以来，等离子体加速器在过去的几十年里取得了巨大的进步。目前，激光尾迹加速器(LWFA)可以通过毫米到厘米的等离子体单元获得多GeV能级的单能电子。电子束驱动的等离子体尾场加速(PWFA)在一米长的等离子体结构中实现了42GeV超相对论电子束的能量倍增，最近在SLAC小面装置上实现了高效率的束流加速。在这些实验中测得的加速梯度可以在10-100GeV/m的范围内，比目前传统的射频粒子加速器大3-4个数量级。由于等离子体尾波场加速器有望实现未来能量前沿机的小型化，因此对等离子体尾波场加速器的超高加速梯度、等离子体透镜(等离子体聚焦)、高转换比、等离子体不稳定性等关键问题的研究是紧凑型光源和基于这种新型加速方案的对撞机等新一代设备的关键。与ASTEC和斯特拉斯克莱德大学的同事们合作，我们目前正在达雷伯里实验室准备第一个使用Vela/Clara束流的英国束流驱动的等离子体尾场加速实验。第一个实验将演示等离子体透镜的强聚焦效应。后续的实验将研究上述其他关键问题，包括束-等离子体相互作用的全模型、等离子体池的工程设计和制造、实验装置的调试和实验数据的分析。

Plasma accelerators have made tremendous progress in the last few decades since the inception of the idea from Tajima and Dawson. Nowadays, laser wakefield accelerators (LWFA) could achieve multi-GeV level, mono-energetic electrons through millimeter to centimeter plasma cells. Electron beam driven plasma wakefield acceleration (PWFA) has demonstrated energy doubling for an ultra relativistic 42 GeV electron beam in a meter long plasma structure and recently realized the high efficiency beam acceleration at SLAC FACET facility. The accelerating gradients measured in these experiments can be in the range of 10-100 GeV/m, which are 3-4 orders of magnitude larger than that in todays' conventional RF-based particle accelerators. Since plasma wakefield accelerators hold great promise to miniature the future energy frontier machines, the research on the key issues, e.g. the ultrahigh accelerating gradients, plasma lens (plasma focusing), high transformer ratio, plasma instabilities of the plasma wakefield accelerators are critical for the new generation facility such as compact light sources and colliders based on this novel acceleration scheme. Working together with colleagues from ASTeC and the University of Strathclyde, we are currently preparing for the first UK based beam driven plasma wakefield acceleration experiment at Darebury laboratory using the VELA/CLARA beam. The first experiment will demonstrate the plasma lens strong focusing effect. The follow-up experiment will investigate other key issues as above-mentioned.The study will include full modelling of beam-plasma interaction, engineering design and manufacture of plasma cell, commissioning of the experimental facility and analysing the experimental data.