Ice-Cold Plasma Electron Beams Prepare to Power Future Hard X-ray Laser Beams

Scientists chart a path to sub-femtosecond hard X-ray Free-Electron-Laser pulses powered by compact plasma-based accelerators.

Schematic of a plasma wakefield accelerator using optical laser beams and electron driver, escort, and witness beams for generating bright, coherent X-ray laser beams with attosecond duration and sub-Angstrom wavelength. — Image courtesy of the University of Strathclyde

The Science

Scientists have developed a blueprint for producing ultrabright and ultrashort pulses of electron beams for the next generation of particle accelerator science. The study shows how to produce “ice-cold” and ultrabright electron beams in a new type of accelerator called a plasma wakefield accelerator (PWFA). The scheme relies on a novel plasma concept in which the beams are first born in the plasma and then carefully “escorted” out without a loss of quality in a single plasma stage. This enables the PWFA-generated beams to produce bright X-ray pulses with extremely short durations and tiny wavelengths. This could enable new scientific tools such as X-ray free-electron-lasers (XFELs) that can see matter at smaller scales and faster speeds than now possible.

The Impact

This study suggests that electron beams with sufficient quality to produce hard X-ray FEL pulses can be produced and preserved in precisely tailored PWFAs. The scheme has the potential to solve the problem of preserving the quality of electron beams from plasmas. This is a critical step toward the use of such drivers for future light sources. It may also open novel opportunities in complementary compact accelerators and in high-energy physics research.

Summary

Novel complementary accelerator technologies and their applications in photon science and high-energy physics is an active field of research. A team from the United States and the United Kingdom working at the National Energy Research Scientific Computing Center (NERSC), a Department of Energy (DOE) Office of Science user facility, has moved one step closer to generating bright, high-quality electron beams thanks to a new trick using PWFAs. Inside a PWFA, the technique uses a pair of lasers in a novel plasma photocathode to first generate an electron beam (via tunneling ionization) and then carefully extract it (via beam-loading produced by an escort beam). The resulting beam can be orders of magnitude brighter than traditional beams used in accelerators.

The research shows how to produce, extract, and isolate these ultrabright beams in a beam transport line without charge and quality loss. In undulators, such electron beams can then produce bright sub-femtosecond hard X-ray pulses like what is produced at the Linac Coherent Light Source (LCLS) at SLAC National Accelerator Laboratory, but in a much shorter distance. Several aspects of this new PWFA scheme may be tested at the SLAC’s Facility for Advanced Accelerator Experimental Tests (FACET-II), a DOE user facility. In the long term, researchers envision that compact high-brightness beams from PWFAs could lead to complementary compact XFELs and to more exotic research such as coherent photon-photon colliders.

Contact

Ahmad Fahim Habib
University of Strathclyde
[email protected]

Bernhard Hidding
Heinrich Heine University
[email protected]

Funding

Funding for this research was provided by the DOE Office of Science, Basic Energy Sciences, the European Research Council, and the Science and Technology Facilities Council of United Kingdom. The research used resources at the National Energy Research Scientific Computing Center (NERSC), a DOE Office of Science user facility, and the Shaheen Petrochemical Project of South Korea.