Postdoctoral researcher / Precision Measurement of Thermophysical Quantities

Overview

NIST seeks a postdoctoral researcher with an interest in the precision measurement of thermophysical quantities. Example quantities of interest include thermodynamic temperature, pressure, refractive index, thermal expansion, density virial coefficients, magnetic susceptibility. A unifying principle of the work is that all measurements are based on precision optical interferometry.

For example, one branch of interest is to develop a cryogenic gas thermometer. The working principle is refractive index gas thermometry, using a Fabry-Perot cavity resonator filled with helium gas; temperature is derived from the ideal gas law. The system targets a temperature range of 4 K to 303 K, with current art performance realizing the SI unit kelvin.

Another branch of interest is the development of an accurate, air-based dilatometer to measure the thermal expansion coefficient of materials important to dimensional metrology. The working principle is displacement interferometry with a linear slide translation stage. The system targets accuracy of about on the thermal expansion coefficient in the temperature range 283 K to 313 K.

A third branch of interest is to measure the magnetic susceptibility of gases important to thermodynamic metrology. The working principle is a “Faraday balance”, which consists of balancing a suspended dumbbell in a magnetic field; as the volume around the dumbbell is filled with the test (diamagnetic) gas, the dumbbell will rotate, and the magnetic susceptibility is proportional to the rotation. The undertaking aims to resolve large disagreements between historic measurement and recent ab initio calculation of the magnetic susceptibility of helium, neon, argon, and nitrogen.

Qualifications

• PhD in Physics, Chemistry, or Chemical or Electrical Engineering
• Experience with optics, laser control and feedback electronics, and temperature and pressure measurements
• Experience with frequency metrology (optical and rf)
• Familiarity with measurement uncertainty and error analysis
• Ability to work with the python programming language.

Research Proposal

Key responsibilities will include but are not limited to:

• Conduct research and development into precision interferometry, and its application to the measurement of thermophysical quantities
• Instrumentation of apparatus, including optical, electrical, mechanical, and control automation
• Instrument control, data acquisition and curation, and final analysis all performed in python
• Publishing results of research to relevant journals and presentation at conferences