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The novel method focuses laser light by sending an optical pulse (yellow lines) to the right to reflect from a radial echelon (rightmost element); the pulse then reflects from an axiparabola (leftmost element) to control when each ring comes to focus.
The novel method focuses laser light by sending an optical pulse (yellow lines) to the right to reflect from a radial echelon (rightmost element); the pulse then reflects from an axiparabola (leftmost element) to control when each ring comes to focus.
Image courtesy of Dustin H. Froula, University of Rochester

The Science

Particle accelerators are large, complex machines for studying the most basic particles and forces that underpin our universe. A new paradigm in particle accelerator design paves the way to dramatically smaller accelerators. The novel concept is called a dephasing less laser wakefield accelerator (DLWFA). The concept uses a new technology called "flying focus." This technology combines special optics to shape an ultra-short, high-intensity laser pulse. The DLWFA concept would produce an accelerator that would use laser light to accelerate particles to very high energy levels in very little space.

The Impact

Particle accelerators work by accelerating charged particles, such as protons or electrons, at speeds close to the speed of light. They then smash those particles into a target or other particles. High energy physicists study the particles and radiation released in these collisions. However, conventional radiofrequency accelerators are close to the limits of how much energy they can push to particles. Researchers are developing advanced accelerator concepts to reach new energy levels. The flying focus technology could transform accelerators. Because the new concept needs much less space, future accelerators could be many times smaller than the accelerators of today.

Summary

Particle accelerators currently use electrical fields generated by radio waves to accelerate particles. These accelerators must be bigger and bigger—and thus more complex and expensive—to produce more power to reach faster particle speeds for new scientific research. A new approach, plasma wakefield machines, would use plasma instead of radio waves. In this study, researchers describe a novel dephasing less laser wakefield accelerator (DLWFA) concept based on the recently demonstrated "flying focus" technology. The concept could help achieve new power levels and acceleration in a relatively small building.

The flying focus uses a combination of mirrors and other optics to focus a laser. The force of the 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 show that this DLWFA can accelerate electrons to high energies in just 4.5 meters, 40 times shorter than a traditional LWFA. The flying focus technology could enable LWFAs to overcome some of the challenges facing future linear colliders. Decoupling the velocity of the wakefield from the plasma density and removing the need to guide the laser over long distances removes two significant constraints in a conventional LWFA and enables a dephasingless laser plasma accelerator that could provide electron beam energies limited only by the available laser power.

Contact

Dustin H. Froula
Associate Professor, Physics Department, Plasma Physics Experimental Group Leader, Laboratory for Laser Energetics
University of Rochester
dustin.froula@rochester.edu

John Palastro
Plasma Physics Theory Group Leader, Laboratory for Laser Energetics
University of Rochester
jpal@lle.rochester.edu

Funding

This research was funded by the Department of Energy (DOE) Office of Science, Fusion Energy Sciences program; the DOE National Nuclear Security Administration; the University of Rochester; and the New York State Energy Research and Development Authority.

Publications

Palastro, J.P. et al., “Dephasingless Laser Wakefield Acceleration.” Phys. Rev. Lett. 124, 134802 – Published 31 March 2020. [https://doi.org/10.1103/PhysRevLett.124.134802]

Related Links

Physics Viewpoint: Lining Up for Wakefield Acceleration

University of Rochester Press Release: New Laser Technique Will Allow More Powerful—and Smaller—Particle Accelerators