High-Quality Electron Beams from Beam-Driven Plasma Accelerators by Wakefield-Induced Ionization Injection

• Published in: arXiv.org 2015-06
• Main Authors: A Martinez de la Ossa, Grebenyuk, J, Mehrling, T, Schaper, L, Osterhoff, J
• Format: Article
• Language: English
• Subjects: Acceleration; Electron beams; Emittance; Helium; Hydrogen plasma; Ionization; Particle accelerators; Particle in cell technique; Plasma; Plasma accelerators; Plasma waves; Trapping
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1309.1900

We propose a new and simple strategy for controlled ionization-induced trapping of electrons in a beam-driven plasma accelerator. The presented method directly exploits electric wakefields to ionize electrons from a dopant gas and capture them into a well-defined volume of the accelerating and focusing wake phase, leading to high-quality witness-bunches. This injection principle is explained by example of three-dimensional particle-in-cell (PIC) calculations using the code OSIRIS. In these simulations a high-current-density electron-beam driver excites plasma waves in the blow-out regime inside a fully-ionized hydrogen plasma of density \(5\times10^{17} \mathrm{cm^{-3}}\). Within an embedded \(100 \mathrm{\mu m}\) long plasma column contaminated with neutral helium gas, the wakefields trigger ionization, trapping of a defined fraction of the released electrons, and subsequent acceleration. The hereby generated electron beam features a \(1.5 \mathrm{kA}\) peak current, \(1.5 \mathrm{\mu m}\) transverse normalized emittance, an uncorrelated energy spread of 0.3% on a GeV-energy scale, and few femtosecond bunch length.