Laser plasma x-ray source for ultrafast time-resolved x-ray absorption spectroscopy.

Area of Science:

• Atomic and Molecular Physics
• Plasma Physics
• Spectroscopy

Background:

• Ultrafast x-ray absorption spectroscopy (XAS) requires stable, high-flux X-ray sources for time-resolved measurements.
• Existing laboratory-based XAS sources often face limitations in flux, stability, or spectral characteristics.
• Developing compact, efficient X-ray sources is crucial for advancing materials science and chemistry research.

Purpose of the Study:

• To develop and characterize a novel laser-driven x-ray plasma source for ultrafast XAS.
• To assess the source's stability and spectral properties for reliable spectroscopic measurements.
• To demonstrate the source's capability by acquiring a static XAS spectrum.

Main Methods:

• Utilized a 1 kHz, 20 W, femtosecond pulsed infrared laser interacting with a water target to generate x-rays.
• Investigated x-ray spectra, plasma temperature, and photon flux by varying laser energy and pulse duration.
• Employed a polycapillary optic to focus the x-rays and characterized source stability through single-pulse measurements.

Main Results:

• Achieved a 75 μm FWHM x-ray spot size with approximately 10^6 photons/s.
• Demonstrated source stability with an 8% standard deviation in x-ray flux per pulse, primarily due to laser pointing.
• Confirmed low variability in x-ray spectral shape across single pulses, validating data summation for spectral acquisition.

Conclusions:

• The developed water-jet based laser-driven plasma source is a promising candidate for laboratory-based time-resolved XAS.
• The source exhibits sufficient stability and spectral characteristics for acquiring high-quality XAS data.
• This technology facilitates advanced spectroscopic studies of materials and chemical processes at ultrafast timescales.