Electron injection and emittance control by transverse colliding pulses in a laser-plasma accelerator

• Published in: Physical review special topics. PRST-AB. Accelerators and beams 2014-05, Vol.17 (5), p.051303, Article 051303
• Main Authors: Chen, M., Esarey, E., Geddes, C. G. R., Cormier-Michel, E., Schroeder, C. B., Bulanov, S. S., Benedetti, C., Yu, L. L., Rykovanov, S., Bruhwiler, D. L., Leemans, W. P.
• Format: Article
• Language: English
• Subjects: Charge simulation; Electron beams; Emittance; Lasers; Plasma; Plasma accelerators; Plasma waves; Ponderomotive forces; Stability; Trapped charge
• ISSN: 1098-4402; 1098-4402; 2469-9888
• DOI: 10.1103/PhysRevSTAB.17.051303

A method to inject electron beams with controllable transverse emittances in a laser-plasma accelerators is proposed and analyzed. It uses two colliding laser pulses that propagate transversely to the plasma wave. For colliding pulses with equal frequencies, a beam with very low emittance is generated when the collision is close to the density peak of the plasma wave. Electrons near the axis are accelerated longitudinally by the ponderomotive force of the colliding pulses, accelerated transversely by the beat wave, and subsequently injected into the second bucket of the wake. Ionization is used to increase the transverse injection area and the final trapped charge. Simulations show that the transverse emittance can be less than the 0.1 mm mrad level, which is important for many applications. For colliding laser pulses with different frequencies, the beat wave can produce asymmetric injection, which can enhance betatron radiation generated by the electron beam.