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

Abstract

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.

Ultralow-emittance measurement of high-quality electron beams from a laser wakefield accelerator

“…4(b) it can be found that the e beam is self-injected into the second bucket longitudinally, which leads to small transverse momentum and transverse position. This longitudinal self-injection mechanism will lead to a low transverse emittance in the acceleration process 8,28 . After being seeded into the base of the first bucket, the e beam experiences the highest accelerating field and maintains a small transverse momentum for re-acceleration, as shown in Fig.…”

“…To realize the practical applications of LWFAs 19,20,26 , low-emittance e beams 27,28 are required specially to minimize the degradation over long-distance propagation. The transverse emittance, a nontrivial experimental parameter of high-energy e beams, needs to be measured.…”

Erratum: Great moments in kinetic theory: 150 years of Maxwell's (other) equations (2017 Eur. J. Phys. 38 065103)

“…This outstanding feature promises a dramatic miniaturisation of future accelerators and an according reduction of costs. Present efforts within the field of plasmabased accelerators are directed towards the generation of a large number of electrons, occupying a small (transverse) phase-space volume [34][35][36][37][38], and the subsequent acceleration to great energies while maintaining the populated volume [39][40][41]. The transverse quality of a beam is quantified by the transverse phase-space emittance (see e.g.…”

Brilliant GeV electron beam with narrow energy spread generated by a laser plasma accelerator

“…The injection length of self-injection is typically a few hundreds of microns [15,23], and the divergence of injected electrons is typically a few milliradians [33][34][35]. Several controlled injection schemes were proposed, such as the density transition injection [36][37][38][39], multipulse colliding injection [40][41][42][43][44] and ionization injection [45][46][47][48][49][50][51][52][53][54], but the production of GeV electron beam with narrow energy spread (≲0.5%) remains to be challenging.…”