Compact x-ray free-electron laser from a laser-plasma accelerator using a transverse-gradient undulator

Area of Science:

• Physics
• Accelerator Science
• Optics

Background:

• Compact laser-plasma accelerators generate high-energy electron beams.
• These beams have low emittance and high peak current but significant energy spread.
• Large energy spread limits applications in coherent free-electron laser (FEL) radiation generation.

Purpose of the Study:

• To present a method for compensating the effects of beam energy spread in FELs.
• To enable the use of laser-plasma accelerator electron beams for coherent FEL radiation.

Main Methods:

• Introducing transverse field variation into the FEL undulator.
• Utilizing a transverse gradient undulator.
• Employing a properly dispersed electron beam.
• Conducting theoretical analysis and numerical simulations.

Main Results:

• The proposed method significantly reduces the impact of electron energy spread and jitter on FEL performance.
• Demonstrated effectiveness for both self-amplified spontaneous emission and seeded FELs.
• Validated for extreme ultraviolet and soft x-ray FELs.

Conclusions:

• The transverse gradient undulator technique is effective in mitigating electron energy spread issues.
• This method broadens the applicability of laser-plasma accelerators for advanced FEL applications.
• Enables high-quality coherent radiation generation from compact accelerator sources.