PCTFE as a solution to birefringence in atom trap viewports.

Area of Science:

• Materials Science
• Optical Engineering
• Vacuum Technology

Background:

• Stress-induced birefringence in optical viewports can compromise sensitive measurements.
• Traditional glass-to-metal seals may introduce undesirable optical distortions.
• Ultra-high vacuum (UHV) compatibility is essential for advanced scientific instrumentation.

Purpose of the Study:

• To develop and characterize novel optical viewports utilizing polychlorotrifluoroethylene (PCTFE) for glass-to-metal seals.
• To minimize stress-induced birefringence in UHV optical viewports.
• To evaluate the UHV performance and gas permeation properties of PCTFE seals.

Main Methods:

• Fabrication of optical viewports with PCTFE glass-to-metal seals.
• Measurement of stress-induced birefringence using Stokes parameter S3.
• Achieved ultra-high vacuum levels and partial pressure of air.
• Gas permeation studies, including helium diffusion and upper limits for nitrogen, oxygen, and argon.

Main Results:

• Successfully developed PCTFE-sealed optical viewports.
• Maintained a high Stokes parameter S3 of 0.9986, indicating minimal birefringence.
• Achieved excellent UHV performance with partial air pressure below 5 × 10⁻¹¹ Torr.
• Quantified helium diffusion and established upper limits for other noble gas permeation through PCTFE.

Conclusions:

• PCTFE is a viable material for glass-to-metal seals in UHV optical viewports, effectively reducing birefringence.
• The developed viewports meet stringent UHV requirements for demanding optical applications.
• PCTFE's low gas permeation properties suggest potential for use in noble gas sample transport systems.