Fully coherent x-ray pulses from a regenerative-amplifier free-electron laser

Area of Science:

• Physics
• X-ray Science
• Laser Technology

Background:

• Free-electron lasers (FELs) are crucial for generating high-intensity radiation.
• Current single-pass Self-Amplified Spontaneous Emission (SASE) FELs have limitations in coherence and spectral brightness.
• Producing fully coherent, hard x-ray pulses remains a significant challenge.

Purpose of the Study:

• To propose and analyze a novel regenerative-amplifier free-electron laser (FEL) design.
• To achieve fully coherent, hard x-ray pulses with enhanced spectral brightness.
• To overcome the limitations of existing SASE FEL technologies.

Main Methods:

• Utilizing narrow-bandwidth Bragg crystals to create an x-ray feedback loop.
• Employing a regenerative amplification scheme with a short undulator.
• Leveraging a bunch train to spectrally filter and re-inject radiation for repeated interaction.

Main Results:

• The proposed FEL design achieves regenerative amplification of x-ray pulses.
• The spectral brightness of the generated x-ray pulses is 2-3 orders of magnitude higher than SASE FELs.
• The method allows for effective transmission of x rays outside the crystal bandwidth.

Conclusions:

• The regenerative-amplifier FEL offers a promising pathway to high-brightness, coherent hard x-ray sources.
• This technique significantly enhances the performance of FELs for advanced scientific applications.
• The proposed method represents a substantial advancement in x-ray generation technology.