Laser-Induced Linear-Field Particle Acceleration in Free Space

Abstract

Linear-field particle acceleration in free space (which is distinct from geometries like the linac that requires components in the vicinity of the particle) has been studied for over 20 years, and its ability to eventually produce high-quality, high energy multi-particle bunches has remained a subject of great interest. Arguments can certainly be made that linear-field particle acceleration in free space is very doubtful given that first-order electron-photon interactions are forbidden in free space. Nevertheless, we chose to develop an accurate and truly predictive theoretical formalism to explore this remote possibility when intense, few-cycle electromagnetic pulses are used in a computational experiment. The formalism includes exact treatment of Maxwell’s equations and exact treatment of the interaction among the multiple individual particles at near and far field. Several surprising results emerge. We find that electrons interacting with intense laser pulses in free space are capable of gaining substantial amounts of energy that scale linearly with the field amplitude. For example, 30 keV electrons (2.5% energy spread) are accelerated to 61 MeV (0.5% spread) and to 205 MeV (0.25% spread) using 250 mJ and 2.5 J lasers respectively. These findings carry important implications for our understanding of ultrafast electron-photon interactions in strong fields.

Attosecond coherent control of free-electron wave functions using semi-infinite light fields

“…Such an electron–photon–matter interaction creates optical field components with a frequency–momentum decomposition that lies outside the light cone, allowing emission/absorption to take place. This type of interaction, which is forbidden in free-space 12 , 13 , is regularly exploited for generating radiation and for accelerating charged particles. Recently, it has also prompted the development of photon-induced near-field electron microscopy (PINEM) 11 , 14 – 16 .…”

Sub-cycle dynamics in relativistic nanoplasma acceleration

“…I L > 10 18 Wcm −2 ) from TW-PW lasers generate MeV-GeV femtosecond electron bunches 16–20 in gas targets or keV-MeV electrons 21–24 from solid or overdense plasma targets. Furthermore, direct vacuum laser acceleration (VLA) 25–30 utilizing these lasers has also been proposed due to its accelerating field, >1 TVm −1 , significantly exceeding that of low-density plasma accelerators (≈0.1 TVm −1 ). Only the sub-cycle confinement of these relativistic interactions 31 , where the electron oscillatory velocities are comparable to the speed of light, would generate sub-fs electron pulses 32,33 , providing even isolated bunches with quasi-single-cycle lasers 34,35 .…”

Editorial: Lasers in Accelerator Science and Secondary Emission Light Source Technology

“…Future laser-based or laser-enabled accelerator and light source technologies could tap into an incredibly broad range of methodologies, including but not limited to well-underway approaches like laser wakefield acceleration [15][16][17][18] and seeded [9] and echo-enabled harmonic generation in FELs [19,20] as well as more exploratory compact accelerator concepts such as free-space [21][22][23], terahertz [24][25][26], and on-chip [27][28][29] accelerators, among many others. Rather than a competition for the best possible future technology, these approaches answer to vastly differing scientific and technological needs, from large-scale colliders for exploration of fundamental physics [16,30] to compact systems for radiation therapy [27], to name a few.…”