Generation and acceleration of electron bunches from a plasma photocathode

• Published in: Nature physics Vol. 15; no. 11; pp. 1156 - 1160
• Main Authors: Deng, A., Karger, O. S., Heinemann, T., Knetsch, A., Scherkl, P., Manahan, G. G., Beaton, A., Ullmann, D., Wittig, G., Habib, A. F., Xi, Y., Litos, M. D., O’Shea, B. D., Gessner, S., Clarke, C. I., Green, S. Z., Lindstrøm, C. A., Adli, E., Zgadzaj, R., Downer, M. C., Andonian, G., Murokh, A., Bruhwiler, D. L., Cary, J. R., Hogan, M. J., Yakimenko, V., Rosenzweig, J. B., Hidding, B.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.11.2019; Nature Publishing Group; Nature Publishing Group (NPG)
• Subjects: 639/766/1960/1137; 639/766/419/1131; Acceleration; Atomic; Classical and Continuum Physics; Complex Systems; Condensed Matter Physics; Electron beams; Electrons; Emittance; Experimental particle physics; Free electron lasers; Helium; Helium plasma; Injection; Leptons; Letter; Light sources; Mathematical and Computational Physics; Molecular; Optical and Plasma Physics; Particle accelerators; Photocathodes; Physics; Physics and Astronomy; PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; Plasma; Plasma waves; Plasma-based accelerators; Relativism; Relativistic effects; Relativistic particles; Relativistic velocity; Theoretical
• ISSN: 1745-2473; 1745-2481
• DOI: 10.1038/s41567-019-0610-9

Plasma waves generated in the wake of intense, relativistic laser 1 , 2 or particle beams 3 , 4 can accelerate electron bunches to gigaelectronvolt energies in centimetre-scale distances. This allows the realization of compact accelerators with emerging applications ranging from modern light sources such as the free-electron laser to energy frontier lepton colliders. In a plasma wakefield accelerator, such multi-gigavolt-per-metre wakefields can accelerate witness electron bunches that are either externally injected 5 , 6 or captured from the background plasma 7 , 8 . Here we demonstrate optically triggered injection 9 – 11 and acceleration of electron bunches, generated in a multi-component hydrogen and helium plasma employing a spatially aligned and synchronized laser pulse. This ‘plasma photocathode’ decouples injection from wake excitation by liberating tunnel-ionized helium electrons directly inside the plasma cavity, where these cold electrons are then rapidly boosted to relativistic velocities. The injection regime can be accessed via optical 11 density down-ramp injection 12 – 16 and is an important step towards the generation of electron beams with unprecedented low transverse emittance, high current and 6D-brightness 17 . This experimental path opens numerous prospects for transformative plasma wakefield accelerator applications based on ultrahigh-brightness beams. Electron bunches are generated and accelerated to relativistic velocities by tunnel ionization of neutral gas species in a plasma. This represents a step towards ultra-bright, high-emittance beams in plasma wakefield accelerators. [This summary has been amended from ‘laser-plasma’ to ‘plasma wakefield’ accelerators.]