Microfluidic liquid sheets as large-area targets for high repetition XFELs

Area of Science:

• Physics
• Chemistry
• Materials Science

Background:

• High-intensity X-ray free electron lasers (XFELs) pose a significant challenge due to their potential to damage delicate solution-phase samples.
• Sample damage can affect molecular, electronic, and macroscopic structures, compromising experimental data.
• Existing cylindrical microjets are susceptible to damage, especially with high-repetition-rate XFELs requiring large sample volumes.

Purpose of the Study:

• To investigate the use of a large surface area liquid sheet microjet as an alternative sample target for XFEL experiments.
• To characterize the dimensions of microfluidic liquid sheets produced by different nozzle designs.
• To assess the feasibility of in-vacuum operation and sample recirculation for XFEL applications.

Main Methods:

• Fabrication of three nozzle styles from isotropically etched glass for liquid sheet generation.
• Systematic study of microfluidic liquid sheet dimensions (length, width, thickness gradients) as a function of liquid flow rate.
• Experimental demonstration of in-vacuum operation and sample recirculation capabilities.

Main Results:

• The liquid sheet microjet allows for an increased incident X-ray spot size, effectively lowering the X-ray intensity below the damage threshold.
• Detailed characterization of liquid sheet dimensions was achieved for various nozzle designs and flow rates.
• Successful demonstration of in-vacuum operation and sample recirculation, crucial for high-repetition-rate XFELs.

Conclusions:

• The liquid sheet microjet is a viable alternative to cylindrical microjets for mitigating XFEL-induced sample damage.
• This approach enables the use of high-intensity XFELs with reduced sample volumes, making experiments more efficient.
• Further investigation into the effects of intense XFEL pulses on liquid sheet structure is warranted.