Stable, tunable, quasimonoenergetic electron beams produced in a laser wakefield near the threshold for self-injection

• Published in: Physical review special topics. PRST-AB. Accelerators and beams Vol. 16; no. 3; p. 031302
• Main Authors: Banerjee, S., Kalmykov, S. Y., Powers, N. D., Golovin, G., Ramanathan, V., Cunningham, N. J., Brown, K. J., Chen, S., Ghebregziabher, I., Shadwick, B. A., Umstadter, D. P., Cowan, B. M., Bruhwiler, D. L., Beck, A., Lefebvre, E.
• Format: Journal Article
• Language: English
• Published: College Park American Physical Society 25.03.2013
• Subjects: Electron beams; Electrons; Gas jets; Lasers; Particle in cell technique
• ISSN: 1098-4402; 1098-4402; 2469-9888
• DOI: 10.1103/PhysRevSTAB.16.031302

Stable operation of a laser-plasma accelerator near the threshold for electron self-injection in the blowout regime has been demonstrated with 25–60 TW, 30 fs laser pulses focused into a 3–4 millimeter length gas jet. Nearly Gaussian shape and high nanosecond contrast of the focused pulse appear to be critically important for controllable, tunable generation of 250–430 MeV electron bunches with a low-energy spread, ∼10pC charge, a few-mrad divergence and pointing stability, and a vanishingly small low-energy background. The physical nature of the near-threshold behavior is examined using three-dimensional particle-in-cell simulations. Simulations indicate that properly locating the nonlinear focus of the laser pulse within the plasma suppresses continuous injection, thus reducing the low-energy tail of the electron beam.