Seeding of Self-Modulation using Truncated Seed Bunches as a Path to High Gradient Acceleration

N. Z. van Gils; E. Belli; M. Bergamaschi; A. Clairembaud; A. Gerbershagen; E. Gschwendtner; H. Jaworska; J. Mezger; M. Moreira; P. Muggli; F. Pannell; L. Ranc; M. Turner; the AWAKE Collaboration

arXiv · 2603.29472

Seeding of Self-Modulation using Truncated Seed Bunches as a Path to High Gradient Acceleration

N. Z. van Gils·E. Belli·M. Bergamaschi·A. Clairembaud·A. Gerbershagen·E. Gschwendtner·H. Jaworska·J. Mezger·M. Moreira·P. Muggli·F. Pannell·L. Ranc·M. Turner·the AWAKE Collaboration

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Abstract

This manuscript proposes a method to enable controlled high-gradient particle acceleration when requiring self-modulation of the drive bunch. While electron bunch seeding of self-modulation (eSSM) has been realised at a plasma electron density $n_\mathrm{pe}\cong10^{14}\mathrm{cm}^{-3}$, it has not been demonstrated at higher plasma densities due to limitations of available seed bunch properties. As experimentally shown in this manuscript, truncating available seed bunches with a relativistic ionisation front allows these limitations to be overcome. This seeding method is called truncated electron bunch seeding of self-modulation (teSSM) and experiments confirm that -- when using teSSM -- self-modulation becomes reproducible at $n_\mathrm{pe}=7\times10^{14}\mathrm{cm}^{-3}$. Additionally, the seed wakefield amplitude is also increased, which is known to be advantageous because it shortens the length needed to reach self-modulation saturation. The presented results establish teSSM as a method for achieving controlled, high-gradient particle acceleration with long drivers and available seed bunches.

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N. Z. van Gils, E. Belli, M. Bergamaschi, A. Clairembaud, A. Gerbershagen, E. Gschwendtner, H. Jaworska, J. Mezger, M. Moreira, P. Muggli, F. Pannell, L. Ranc, M. Turner, the AWAKE Collaboration. 2026-03-31. Seeding of Self-Modulation using Truncated Seed Bunches as a Path to High Gradient Acceleration. https://arxiv.org/abs/2603.29472

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