The LCLS variable-energy hard X-ray single-shot spectrometer.

Area of Science:

• X-ray spectroscopy
• Accelerator physics
• Free-electron laser technology

Background:

• Accurate characterization of free-electron laser (FEL) spectra is crucial for experimental success and accelerator optimization.
• Existing methods may lack the necessary resolution or single-shot capability for dynamic FEL processes.
• The Linac Coherent Light Source (LCLS) requires advanced diagnostics for its high-intensity X-ray beams.

Purpose of the Study:

• To report the design, implementation, and performance of a novel variable-energy hard X-ray single-shot spectrometer (HXSSS).
• To provide single-shot spectral measurements for LCLS FEL users and accelerator physicists.
• To validate the HXSSS's capability for optimizing FEL performance and lasing mechanisms.

Main Methods:

• Utilized a cylindrically bent silicon thin crystal for polychromatic X-ray beam dispersion.
• Employed a detector system comprising a Ce:YAG scintillator, optical imaging, and a low-noise pixelated camera.
• Integrated the spectrometer into the LCLS experimental environment for real-time spectral analysis.

Main Results:

• Achieved single-shot spectrum measurements with a spectral range exceeding 2% and a resolution of 2 × 10⁻⁵.
• Successfully operated within the designed energy range of 4 to 20 keV.
• Demonstrated the HXSSS's effectiveness during commissioning, meeting all performance goals.

Conclusions:

• The HXSSS is a high-performance instrument for characterizing hard X-ray FEL spectra.
• It significantly enhances the capabilities for FEL research and accelerator development at LCLS.
• The spectrometer's single-shot capability is vital for experiments sensitive to FEL spectral variations.