Compact single-shot soft X-ray photon spectrometer for free-electron laser diagnostics

Area of Science:

• Physics
• Optics
• Spectroscopy

Background:

• Free-electron laser (FEL) photon spectra are crucial for time-resolved experiments and machine optimization.
• Accurate spectral diagnostics are needed for understanding and controlling FEL light properties.

Purpose of the Study:

• To develop a compact, single-shot photon spectrometer for diagnosing soft X-ray spectra.
• To enable spectral monitoring in space-limited environments downstream of an endstation.

Main Methods:

• Utilized an array of off-axis Fresnel zone plates (FZPs) as transmission-imaging gratings.
• Employed a cerium-doped yttrium aluminum garnet (Ce:YAG) scintillator and microscope objective for imaging.
• Designed to operate in segmented energy ranges covering tens of electronvolts for specific atomic absorption edges (C, N, O, Ne).

Main Results:

• Demonstrated spectrometer performance at a 120 Hz repetition rate.
• Achieved sub-electronvolt energy resolution for soft X-ray spectra.
• The detection scheme is extendable to 200 kHz spectral collection using a fast CMOS line-scan camera.

Conclusions:

• The developed compact photon spectrometer is effective for soft X-ray spectral diagnosis.
• Offers a valuable tool for FEL optimization and time-resolved studies.
• Its compact design facilitates integration in space-constrained experimental setups.