Dephasingless Laser Wakefield Acceleration

Abstract

Laser wakefield accelerators (LWFAs) produce extremely high gradients enabling compact accelerators and radiation sources, but face design limitations, such as dephasing, occurring when trapped electrons outrun the accelerating phase of the wakefield. Here we combine spherical aberration with a novel cylindrically symmetric echelon optic to spatiotemporally structure an ultra-short, high-intensity laser pulse that can overcome dephasing by propagating at any velocity over any distance. The ponderomotive force of the spatiotemporally shaped pulse can drive a wakefield with a phase velocity equal to the speed of light in vacuum, preventing trapped electrons from outrunning the wake. Simulations in the linear regime and scaling laws in the bubble regime illustrate that this dephasingless LWFA can accelerate electrons to high energies in much shorter distances than a traditional LWFA-a single 4.5 m stage can accelerate electrons to TeV energies without the need for guiding structures. Forty years ago, Tajima and Dawson recognized that the axial electric fields of ponderomotively driven plasma waves far surpass those of conventional radiofrequency accelerators [1], launching the field of 'advanced accelerators'-disruptive concepts that promise smaller-scale, cheaper accelerators for high energy physics experiments and advanced light sources [2,3]. Since their seminal paper, a number of theoretical breakthroughs [4-7] and experimental demonstrations [8-14] of laser wakefield acceleration (LWFA) have made rapid progress toward that goal. Experiments recurrently achieve record-breaking electron energy gains underscored by the recent observation of a 7.8 GeV energy gain in only 20 cm [15]. In spite of this impressive progress, traditional LWFA faces a key design limitation of electrons outrunning the accelerating phase of the wakefield or dephasing.In traditional LWFA, a near-collimated laser pulse, either through channel or selfguiding, produces a ponderomotive force that travels subluminally at the group velocity (

PIC methods in astrophysics: simulations of relativistic jets and kinetic physics in astrophysical systems

“…In addition to studying astrophysical plasmas, the recent development of computational power allows the PIC simulation study of the interaction of plasmas and laser beams, such as the high-speed acceleration of electrons through the laser wakefield acceleration (LWFA) where an intense laser pulse is fired into a plasma creating a density wake whose electric field pushes charged particles like electrons (e.g., Esarey et al 2009;Palastro et al 2020). Furthermore, these new PIC simulations of laser-plasma Physics will be applied to studies of astrophysics.…”

Multi-GeV Laser Wakefield Electron Acceleration with PW Lasers

“…Besides the challenge of producing stable long-distance channels [50], curved channel technology will provide a useful method to control the directionality of electron beams and laser pulses [51]. In addition, recent theoretical and numerical studies proposed to overcome the dephasing length of LWFA, so-called phase-locked [52] or dephasingless [53] LWFA, by adapting the superluminal velocity of focal spot movement [54], which can be a way to maximize electron energy for given laser power.…”

Reciprocating propagation of laser pulse intensity in free space

“…Optical pulse propagation, including velocity and direction, is a very basic characteristic for applications like optical information/communication, laser-matter interaction, and so on [1][2][3][4][5][6]. In linear physics, an optical pulse propagates along a straight-line trajectory at the velocity of c/n, where c is the speed of light in the vacuum and n is the refractive index of the medium.…”