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arXiv · 1805.03272

Amplitude enhancement of the self-modulated plasma wakefields

Y. Li·G. Xia·K. V. Lotov·A. P. Sosedkin·Y. Zhao·S. J. Gessner
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Abstract

Seeded Self-modulation (SSM) has been demonstrated to transform a long proton bunch into many equidistant micro-bunches (e.g., the AWAKE case), which then resonantly excite strong wakefields. However, the wakefields in a uniform plasma suffer from a quick amplitude drop after reaching the peak. This is caused by a significant decrease of the wake phase velocity during self-modulation. A large number of protons slip out of focusing and decelerating regions and get lost, and thus cannot contribute to the wakefield growth. Previously suggested solutions incorporate a sharp or a linear plasma longitudinal density increase which can compensate the backward phase shift and therefore enhance the wakefields. In this paper, we propose a new plasma density profile, which can further boost the wakefield amplitude by 30%. More importantly, almost 24% of protons initially located along one plasma period survive in a micro-bunch after modulation. The underlying physics is discussed.

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Y. Li, G. Xia, K. V. Lotov, A. P. Sosedkin, Y. Zhao, S. J. Gessner. 2018-05-08. Amplitude enhancement of the self-modulated plasma wakefields. https://doi.org/10.1088/1742-6596%2F1067%2F4%2F042009

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