Enhanced X-ray free-electron laser performance with optical klystron and helical undulators

Area of Science:

• Physics
• Accelerator Physics
• Photon Science

Background:

• X-ray free-electron lasers (FELs) are crucial for advanced research.
• Optimizing FEL performance is key to enabling new scientific discoveries.
• Current FEL designs face limitations in efficiency and accessibility.

Purpose of the Study:

• To demonstrate improved performance of an X-ray FEL using optical klystron and helical undulators.
• To compare the performance with standard planar undulator configurations.
• To assess the impact on FEL saturation length and pulse energy.

Main Methods:

• Utilized the Athos soft X-ray beamline at SwissFEL.
• Employed variable-polarization undulators with magnetic chicanes for optical klystron implementation.
• Conducted experiments at soft X-ray wavelengths (1.24 nm and 3.10 nm).

Main Results:

• Achieved a ~35% reduction in FEL saturation length by combining optical klystron and helical undulators.
• Attributed roughly half of the saturation length improvement to each component (optical klystron and helical undulator).
• Observed a 20% to 50% increase in pulse energy with helical undulators compared to planar ones.

Conclusions:

• The combined use of optical klystron and helical undulators significantly enhances FEL performance.
• This advancement contributes to the development of more compact, high-power, and efficient FELs.
• The findings aim to make FEL technology more affordable and accessible for broader scientific applications.