Advanced regimes of proton beam-driven plasma wake field acceleration

该项目旨在探索、分析和优化质子束形状和束成形技术，使在现有强子对撞机的基础上将电子的等离子体尾场加速到TeV能量范围内成为可能。到目前为止，只有激光脉冲或电子束被认为是等离子体尾迹场的驱动因素。然而，当等离子体尾迹场由激光脉冲或电子束驱动时，单个加速级的能量增益被限制在几十GeV，因此需要分级才能达到TeV范围的能量。这样的舞台在技术上是具有挑战性的。最近提出的质子驱动的尾波场加速(Caldwell等人，自然物理学5,363(2009))有可能在一个加速阶段使电子超过TeV能量。然而，该方案需要将质子束纵向压缩到亚毫米级，如果用传统技术完成这一要求也是很高的。在这个项目中，我们将探索基于等离子体的束流压缩和整形技术，与传统的方法相结合，应该能够产生适合于驱动尾迹场的质子束。其中包括外部种子横向两流不稳定，外部源尾迹场对光束的截断，以及等离子体诱导的能量斜坡。

The project is aimed at quest, analysis, and optimization of proton beam shapes and beam shaping techniques that would open a possibility of plasma wakefield acceleration of electrons to TeV-range energies on the basis of existing hadron colliders. Up to now, only laser pulses or electron bunches were considered as drivers for plasma wake fields. However, when the plasma wake field is driven by a laser pulse or by an electron beam, the energy gain in a single accelerating stage is limited to a few tens GeV, so that a staging is necessary to reach the TeV-range energies. Such staging is technically challenging. The recently proposed proton-driven wake field acceleration (Caldwell et al., Nature Physics 5, 363 (2009)) has the potential of bringing electrons beyond the TeV energy in a single acceleration stage. Yet, the scheme requires a longitudinal compression of the proton beam to the sub-millimeter scale, which is also demanding if accomplished with conventional techniques. In this project, we are going to search for plasma-based techniques of beam compression and shaping which, in combination with the conventional methods, should produce the proton beam suitable for driving the wake field. These include an externally seeded transverse two-stream instability, beam chopping by the wake field of an external source, and plasma-induced energy ramping.