Sapphire optical viewport for high pressure and temperature applications

Area of Science:

• Materials Science
• Optical Engineering
• Spectroscopy

Background:

• High-temperature and high-pressure environments pose challenges for optical components in spectroscopic applications.
• Conventional optical viewports often fail under extreme thermal and pressure gradients.
• Developing robust viewports is crucial for in-situ analysis of materials under demanding conditions.

Purpose of the Study:

• To design and demonstrate a novel soldered sapphire optical viewport.
• To mitigate thermally induced stress in optical viewports for high-pressure spectroscopy.
• To enable spectroscopic analysis of samples at high temperatures (20-450°C) and high pressures (10⁻⁶ mbar to 330 bar).

Main Methods:

• Active soldering of a sapphire window to a metal flange.
• Incorporation of two c-shaped rings made of different metallic materials to manage thermal stress.
• Construction and testing of a spectroscopic cell equipped with two such optical viewports.

Main Results:

• Successful operation of the spectroscopic cell with alkali metals in a noble gas environment.
• Demonstrated capability to withstand temperatures from 20-450°C and pressures from 10⁻⁶ mbar to 330 bar.
• Observed leakage rates below 30 mbar/day at the upper pressure range.

Conclusions:

• The designed soldered sapphire optical viewport is effective for high-temperature and high-pressure spectroscopic applications.
• The innovative stress-mitigation structure ensures reliable performance under extreme conditions.
• This viewport technology advances the capabilities for in-situ material analysis in demanding environments.