Bringing picosecond CO 2 lasers to the forefront of strong-field applications

Abstract

The picosecond CO₂ gas laser has proven a valuable tool in strong-field physics applications. We review the merits of this approach, taking as an example, the Brookhaven Accelerator Test Facility (ATF) that affords a platform for exploring novel methods of particle acceleration and radiation sources. To carry out this mission, the ATF is equipped with a picosecond terawatt CO₂ laser system, PITER-I. We describe the physical principles and architecture of this multi-stage laser system and its application in two high-energy physics projects. The first is the intense Thomson scattering of the CO₂ beam from 60 MeV electrons with production of one x-ray photon per electron that opened the possibility for a Compton gamma-source generating a polarized positron beam for the next generation of electron-positron colliders, such as the International Linear Collider (ILC) and the Compact Linear Collider (CLIC). The second is our new study of a high-brightness multi-MeV ion- and proton-beam source energized by this picosecond CO₂ laser. High-energy, collimated particle beams originate from the rear surface of the laser-irradiated foils. The expected advantage from using a CO₂ laser for this application, rather than an ultra-fast solid state laser, is the 100-fold increase in the electron ponderomotive potential due to the tenfold longer wavelength of the CO₂ laser. This innovation promises to substantially enhance energy efficiency and particle yield, and will facilitate the advancement of laser-driven ion accelerators towards practical applications. Finally, we address possibilities for generating CO₂ laser pulses of petawatt peak power and a few-cycles duration.