The National Institute of Standards and Technology (NIST) has developed a practical implementation (mise en pratique) for realizing the new kilogram definition in a high vacuum environment. This new definition, part of the revised International System of Units (SI) adopted in 2019, requires Planck’s constant to be used as the basis for the kilogram.
NIST’s Mass & Force Group has created a sequence of steps to address the challenge of transferring the new kilogram definition from vacuum to air, where mass metrology is typically performed. This involves realizing the new kilogram in the NIST Watt Balance, transferring the realization to air, disseminating it to the U.S. Measurement System, and storing the Kibble Balance realized kilogram in a vacuum environment.
The key steps in the mise en pratique include:
1. Realizing the new kilogram in the NIST Watt Balance
2. Transferring the realization from vacuum to air
3. Disseminating to the U.S. Measurement System
4. Storing the Kibble Balance realized kilogram in a vacuum environment
The realization can be transferred to other artifacts using either a precision vacuum mass comparator or a magnetic suspension instrument that enables direct comparison of mass in vacuum and air. The NIST-4 Kibble balance is used infrequently due to its complexity, necessitating an ensemble or “pool” of kilogram artifacts that act as a “flywheel” in between realizations. This ensemble is stored in either high vacuum or laboratory air, ensuring accurate dissemination of the kilogram’s mass value.
Source: https://www.nist.gov/programs-projects/nist-mise-en-pratique-new-kilogram-definition
Keywords: quantum, metrology, measurement
