| AVS 65th International Symposium & Exhibition | |
| Vacuum Technology Division | Monday Sessions |
| Session VT-MoM |
| Session: | Vacuum Measurement |
| Presenter: | Jay Hendricks, National Institute of Standards and Technology |
| Authors: | J. Hendricks, National Institute of Standards and Technology J.E. Ricker, National Institute of Standards and Technology K.O. Douglass, National Institute of Standards and Technology G. Brucker, MKS Instruments, Inc., Pressure and Vacuum Measurement Group E. Fuchs, MKS Instruments, Inc., Pressure and Vacuum Measurement Group A. Ocepek, MKS Instruments, Inc., Pressure and Vacuum Measurement Group P. Sullivan, MKS Instruments, Inc., Pressure and Vacuum Measurement Group S. Venkatesan, MKS Instruments, Inc., Pressure and Vacuum Measurement Group |
| Correspondent: | Click to Email |
Over the past 5 years, NIST has worked to develop a new pressure standard based on the fundamental properties of gas refractive index that will replace mercury manometers at national metrology institutes and has potential to be developed as a commercially manufactured product. The new pressure standard is based a first-principles quantum-chemistry calculations of gas refractive index and is a new route to realizing the pascal. NIST has now built and tested a fixed-length optical cavity (FLOC), which consists a pair of Fabry–Pérot cavities within a single block of ultralow-expansion glass. The change in optical path length between the two cavities (one at vacuum and one at the pressure to be measured) depends on the gas refractive index, density, and atomic or molecular properties. Helium's atomic properties were calculated from first principles, so the refractivity measurement leads to a determination of density, which provides a determination of pressure. While helium’s refractive index has now been calculated by theory, the value of nitrogen refractive index remains too difficult for current computational theory to handle. Using the NIST mercury manometer along with helium’s theoretical value of refractive index in a FLOC has resulted in a new experimental value for nitrogen refractive index to be determined. This enables the FLOC to be used with nitrogen as a pressure standard with direct primary traceability to NIST. Moving forward, the FLOC technology is so promising as a pressure standard, that NIST has joined with MKS under a Collaborative Research and Development Agreement (CRADA). The aim of this partnership is technology transfer to the market place, with the aim to develop a small, portable prototype need for real world metrology operations for industrial applications in gas pressure metrology. The current status of NIST-MKS CRADA will be briefly presented and discussed.