Fiber-optic cavity sensing of hydrogen diffusion.

Area of Science:

• Materials Science
• Optical Sensors
• Chemical Engineering

Background:

• Hydrogen diffusion in silica is crucial for understanding material degradation and performance in various applications.
• Accurate measurement of hydrogen diffusion coefficients is essential for material science and engineering.
• Existing methods for measuring hydrogen diffusion can be complex and time-consuming.

Purpose of the Study:

• To present a novel fiber-optic cavity sensor for real-time monitoring of hydrogen diffusion.
• To validate the sensor's performance against a theoretical diffusion model.
• To determine the diffusion coefficient of hydrogen in silica using the developed sensor.

Main Methods:

• Implementation of a cavity ringdown spectroscopy scheme within a silica-based single-mode fiber.
• Exposure of the fiber-optic sensor to gaseous hydrogen at normal pressure.
• Measurement of ringdown times during hydrogen diffusion and comparison with a theoretical model.

Main Results:

• The developed fiber-optic cavity sensor successfully monitored hydrogen diffusion into and out of silica fibers.
• Measured ringdown times showed excellent agreement with the theoretical diffusion model.
• The diffusion coefficient of hydrogen in silica was determined to be D = (3.02 ± 0.07) x 10⁻¹⁵ m²/s at 30°C.

Conclusions:

• The novel fiber-optic cavity sensor provides a reliable and accurate method for studying hydrogen diffusion in silica.
• The sensor's ability to determine the diffusion coefficient offers valuable insights for materials science applications.
• This technique presents a promising approach for in-situ monitoring of hydrogen-material interactions.