Grating-based dielectric laser-driven micro-accelerator

A beam of electrons was first observed to be accelerated with a 'gradient'—or energy transfer rate—of 300 MV/m, which is very high for present-day accelerators, in a device rather like a microchip. This was made of silica glass and powered by a commercial laser beam at the SLAC laboratory in the U.S. It opens the way to build a "particle accelerator on a chip" much more cheaply than conventional ones. However, few studies have been done of the all-important quality of the particle beam that can be obtained from such a micro-accelerator.

In an open access paper just published in the Physics of Plasmas journal, researchers investigated the beam quality for such a micro accelerator, by running complex numerical simulations. There, the beam is given the same properties as expected in the CLARA machine, which is a U.K. facility planned for the future. An electron bunch is fed into a specially shaped grating-like structure with 100 miniature cutouts called periods. Inside the device, it interacts with a pulse of energy from a laser. The important properties of the electrons that have been 'modulated,' or modified, are then examined in detail.

The researchers also studied possible influences on the quality of the beam. The particle simulations show that the best beam quality at the extreme 'accelerating gradient'—or rate of energy input—is up to 1.13 GV/m, while causing only a very small deterioration in quality of 3.6 percent.

This paper shows mathematically for the first time how to generate a beam with the desired quality in a micro-accelerator. It paves the way for actually constructing such a micro-accelerator in the future.

More information:
Y. Wei et al. Beam quality study for a grating-based dielectric laser-driven accelerator, Physics of Plasmas (2017). DOI: 10.1063/1.4975080

Provided by Cockcroft Institute