Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Thermodynamic Metrology Group

The Thermodynamic Metrology Group realizes, maintains, and disseminates the national measurement standards for temperature, humidity, pressure, vacuum, and leaks.

The group mission is to advance the state of the art in measurement of thermodynamic quantities. We have active efforts in optics, nano-photonics, and quantum-based metrology along with traditional precision measurements to advance U.S. industry. We collaborate nationally and internationally, and engage in metrology education and outreach.

Collaboration Opportunities

We invite collaboration on joint research, technology, and standards development projects. Want to work with us? Here’s how:

Or contact a project PI directly to learn how to get involved.

Research Projects and Programs

Cold Core Technology Platform

We are building a cold-atom based sensor program that represents a new approach to metrology—to establish a set of chip-scale tools that enable real-world use

Fixed Point Development : Non-Metals

We are developing new fixed points and new maintenance systems for use with Standard Platinum Resistance Thermometers (SPRTs) below the triple point of water

Photonic Dosimetry

As part of the NIST on a Chip program, the Photonic Dosimetry project is developing in-situ sub-micrometer ionizing-radiation dosimetry and calorimetry leading

Photonic Thermometry

Photonic Thermometry is a cutting-edge research program at NIST that aims to break the fundamental limitations of electrical resistance-based thermometry and

Reliable Vaccine Storage

We study provider-level vaccine storage and temperature monitoring methods to develop best practice guidance for public health audiences.

Measurement Services Projects and Programs


The NIST Thermodynamic Metrology Group maintains and develops national standards of humidity (in the range 1 nmol/mol to 0.6 mol/mol of water concentration)


The NIST Thermodynamic Metrology Group (TMG) provides critical research into pressure measurement capabilities improving uncertainties in user facilities and


The NIST Thermodynamic Metrology Group maintains and develops national standards of temperature (in the range 0.65 K to 2011 K), and supports calibration of all

Archive Projects and Programs

Acoustic Thermometry

By measuring the speed of sound in argon gas, we have determined thermodynamic temperature with unprecedented accuracy in the range 0 °C to 552 °C. Our results

Dynamic Pressure

Manufacturing processes by their very nature require a judicious, time-dependent use of pressure and temperature to transform a base material into a valuable

News and Updates

Hooked on Photonics? Math to the Rescue

Photonic thermometers – which measure temperature using light – have been around in optical fiber form for decades. These devices, called fiber Bragg gratings

A Primary Standard for Measuring Vacuum

A novel, quantum-based vacuum gauge system invented by researchers at the National Institute of Standards and Technology (NIST) has passed its first test to be


Opportunities for Fundamental Physics Research with Radioactive Molecules

Michail Athanasakis-Kaklamanakis, Mia Au, Jochen Ballof, Robert Berger, Anastasia Borschevsky, Alexander Breier, Dmitry Budker, Luke Caldwell, Christopher Charles, Vincenzo Cirigliano, Jordy de Vries, David DeMille, Jacek Jacek Dobaczewski, Ch. E. Dullmann, Ephraim Eliav, Ephraim Eliav, Jonathan Engel, Mingyu Fan, Victor Flambaum, Alyssa Gaiser, Ronald Garcia Ruiz, Konstantin Gaul, Thomas Geisen, Alexander Gottberg, Gerald Gwinner, Reinhard Heinke, Steven Hoekstra, Jason Holt, Nicholas Hutzler, Andrew Jayich, Stephan Malbrunot-Ettenauer, Takayuki Miyagi, Iain Moore, Petr Navratil, Witold Nazarewicz, Gerda Neyens, Eric Norrgard, Nicholas Nusgart, Lukas Pasteka, Roy Ready, Moritz Pascal Reiter, Mikael Reponen, Sebastian Rothe, Marianna Safronova, Andrea Shindler, Jaideep Singh, Leonid Skripnikov, Silviu-Marian Udrescu, Shane Wilkins
Radioactive molecules hold great promise for their discovery potential in diverse fields. The extreme nuclear properties of heavy, short-lived nuclei and the

Simulations of a frequency-chirped magneto-optical trap of MgF

Kayla Rodriguez, Nickolas Pilgram, Daniel Barker, Stephen Eckel, Eric Norrgard
We simulate the capture process of MgF molecules into a frequency-chirped molecular MOT. Our calculations show that by chirping the frequency, the MOT capture

Radiative Decay Rate and Branching Fractions of MgF

Eric Norrgard, Catherine Cooksey, Stephen Eckel, Nickolas Pilgram, Kayla Rodriguez, Howard W. Yoon, Yuly Andrea Chamorro Mena, Lukáš Pašteka, Anastasia Borschevsky
Here we report measured and calculated values of radiative decay rates and vibrational branching fractions for the A$^2\Pi$ state of MgF. The decay rate

Patents (pending and active, not including provisional)

Triple Point Immersion Cell Article (pending), US20210072098A1. Tew & Nanninga. March 11, 2021

Deformometer for determining deformation of an optical cavity optic, US Patent 10,935,370. Ahmed, Douglass, Eckel, Egan, Hendricks, Stone. Mar 2, 2021

Deformometer for determining deformation of an optical cavity optic, US Patent 10,816,325. Ahmed, Douglass, Eckel, Hendricks, Stone. Oct 27, 2020

Photonic calorimeter and process for performing calorimetry, US Patent 10,782,421. Tosh, Ahmed, Fitzgerald, Klimov. Sep 22, 2020

Photonic dosimeter and process for performing dosimetry, US Patent 10,718,872. Tosh, Ahmed, Fitzgerald, Klimov. Jul 21, 2020

Uniaxial counter-propagating monolaser atom trap (pending), US20200120785A1. Eckel, Barker, Fedchak, Scherschligt, Norrgard, Klimov. Apr 16, 2020

High-resolution photonic thermometer article (pending), US20200103594A1. Klimov, Douglass, Ahmed. Apr 2, 2020

Photonic quantum dew point sensor (pending), US20200041431A1. Herman, Klimov, Purdy. Feb 10, 2020

Optofluidic Flow Meter, US Patent 10,151,681 B2. Ahmed & Cooksey. Dec 11, 2018

Optical temperature sensor and use of same, US Patent 9,726,553. Ahmed, Semanick, Taylor, Fan, Hafezi, Xu, Strouse. Aug 8, 2017

Tools and Instruments

Leak Artifacts

Leak artifacts are calibrated in the range 1 x 10 -6 to 1 x 10 -13 mol/s (2 x 10 -2 to 2 x 10 -9 std. cm 3 /s at 0 °C). The calibration can be performed

Piston gauges and pressure transducers

Piston gauges are used to calibrate customer piston gauges and pressure sensing devices. Piston gauges are calibrated via a direct comparison to another piston


Press Coverage


Group Leader

Office Manager