Context and project goals
Plasma acceleration of electrons has been a growing area of research since a plasma medium can sustain accelerating forces that are hundreds of times higher than those of conventional particle accelerators. A primary motivation for advancing plasma accelerator technology is their potential use in future colliders, where collisions between tightly focused electron and positron beams can shed light on the nature of physics beyond the standard model. Colliders require electron beams with both high charge and excellent quality. Thus, solving the problem of generating high-quality electrons in plasma accelerators represents a high-impact and challenging area of research, with novel approaches actively pursued using advanced simulation tools.
A promising breakthrough involves a fully optical strategy, in which emerging techniques for controlling the spatiotemporal properties of a laser pulse are utilized to create high-charge, low-emittance bunch with a specially shaped current profile. The shaped current profile is key to producing a final beam with low energy spread as it creates a uniform accelerating force that ensures all electrons reach nearly the same final energy —an essential requirement for collider applications.
Central to this method is the “flying focus” technique, which utilizes a form of structured light where the peak intensity of a laser pulse can propagate at an arbitrarily chosen velocity, including faster than the speed of light in vacuum. This precise spatiotemporal manipulation of the laser pulse enables new modalities for electron injection and acceleration in plasma.
Computational Methods
The complexity of modeling laser-plasma interactions at the required resolution, specifically at a wavelength of 400 nm, is addressed by leveraging the SeaWulf High-Performance Computing (HPC) Cluster. Such high-resolution simulations are necessary, given the inadequacy of standard analytical models for these phenomena.
The Osiris particle-in-cell (PIC) code, developed in collaboration with UCLA, serves as the main computational tool. Its ‘arbitrary laser pulse’ module provides an analytic framework for understanding and simulating flying focus propagation, supporting fully self-consistent simulations driven by the available HPC resources.
Research Team
This research is led by Professor Navid Vafaei-Najafabadi’s group at Stony Brook University, in a dedicated collaboration with the Laboratory for Laser Energetics at the University of Rochester, the Accelerator Test Facility for experimental validation, the University of California, Los Angeles (UCLA) for simulation code support, and the University of Texas at Austin.
Potential Impact
This novel approach constitutes the only plasma-based method that currently meets the key performance targets proposed by the particle physics community for future high-energy plasma colliders. Furthermore, the theoretical framework developed in this paper allows tuning and scaling beam parameters for different experimental needs. This makes our approach flexible and potentially useful across a wide range of applications in advanced accelerator research.
Publication Status
This work is under review at Physical Review X and is available as a preprint at arXiv: 10.48550/arXiv.2503.09557
Figure: Production of collider-quality electron beams with a flying focus photoinjector. In the first stage, a long-wave infrared laser pulse partially ionizes a gas and drives a nonlinear plasma wave. A trailing, shorter-wavelength flying focus pulse further ionizes the gas within the plasma wave, creating a moving ionization front. The electrons freed by the moving ionization front form a bunch with a trapezoidal current profile. In the second stage, the trapezoidal bunch is injected into the accelerating phase of a plasma wave driven by an electron beam. The trapezoidal shape of the bunch flattens the accelerating field of the plasma wave, ensuring uniform acceleration across the bunch. This bunch is accelerated to 20 GeV over 2-meters and has an energy spread of less than 1%, which meets the quality requirements for a collider. These results are obtained through high-resolution PIC simulations performed on the SeaWulf HPC cluster.
Visualization of the flying focus injection technique: A CO_2 driver pulse drives a nonlinear plasma wave, while a trailing flying focus pulse (injector) further ionizes the gas within the wave. The flying focus pulse creates a moving ionization front leading to a trapezoidal current profile that is ideal for beam loading in a subsequent acceleration stage. High resolution particle –in-cell (PIC) simulations performed on the SeaWulf cluster reveal how flying focus injection offers precise control over electron trapping and accelerator performance —enables high-quality electron beam generation in advanced accelerator research, from particle colliders to compact light sources.