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.

Search Publications by: James A. Fedchak (Fed)

Search Title, Abstract, Conference, Citation, Keyword or Author
Displaying 1 - 25 of 93

Effect of ''glancing'' collisions in the cold atom vacuum standard

February 12, 2025
Author(s)
Stephen Eckel, Daniel Barker, James A. Fedchak, Jacek Klos, Julia Scherschligt, Eite Tiesinga
We theoretically investigate the effect of "glancing" collisions on the ultra-high-vacuum pressure readings of the cold-atom vacuum standard (CAVS), based on either ultracold $^7$Li or $^87}$Rb atoms. Here, glancing collisions are those collisions between

Accurate measurement of the loss rate of cold atoms due to background gas collisions for the quantum-based cold atom vacuum standard

August 1, 2023
Author(s)
Daniel Barker, James A. Fedchak, Jacek Klos, Julia Scherschligt, Abrar Sheikh, Eite Tiesinga, Stephen Eckel
We present measurements of thermalized collisional rate coefficients for ultra-cold $^7$Li and $^87}$Rb colliding with room-temperature He, Ne, N$_2$, Ar, Kr, and Xe. In our experiments, a combined flowmeter and dynamic expansion system, a vacuum metrology

Precise Quantum Measurement of Vacuum with Cold Atoms

December 20, 2022
Author(s)
Daniel Barker, Bishnu Acharya, James A. Fedchak, Nikolai Klimov, Eric Norrgard, Julia Scherschligt, Eite Tiesinga, Stephen Eckel
We describe the cold-atom vacuum standards (CAVS) under development at the National Institute of Standards and Technology. The CAVS measures pressure in the ultra-high and extreme-high vacuum regimes by measuring the loss rate of sub-millikelvin sensor

The Digital NIST: Challenges and opportunities in the digital transformation of NIST's calibration services

September 21, 2022
Author(s)
Catherine Cooksey, James A. Fedchak, Robert Hanisch, Gregory (Greg) C. Cala, Damian Lauria, Raymond Plante, Benjamin Long, John S. Quintavalle, Manmohan Moodra
Early in 2022 NIST embarked on a pilot project to produce digital calibration reports and certificates of analysis for reference materials. The goal of the project was to produce a few examples of each for the purpose of assessing the scope and challenges

A constant pressure flowmeter for the extremely high vacuum

August 9, 2022
Author(s)
Stephen Eckel, Daniel Barker, James A. Fedchak, Emmanuel Newsome, Julia Scherschligt, Robert E. Vest
We demonstrate operation of a constant-pressure flowmeter capable of generating and accurately measuring flows as low as $1\times10^-13}$mol/s. Generation of such small flows is accomplished by using a small conductance element with $C\approx 25$nL/s

Comparison of two multiplexed portable cold atom vacuum standards

July 15, 2022
Author(s)
Lucas Ehinger, Bishnu Acharya, Daniel Barker, James A. Fedchak, Julia Scherschligt, Eite Tiesinga, Stephen Eckel
We compare the vacuum measured by two portable cold atom vacuum standards (pCAVS) based on ultracold $^7$Li atoms. Our pCAVS devices share the same laser system and measure the vacuum concurrently. The two pCAVS together detected a leak with a rate on the

Lambda-enhanced gray molasses in a tetrahedral laser beam geometry

March 14, 2022
Author(s)
Daniel Barker, Eric Norrgard, Nikolai Klimov, James A. Fedchak, Julia Scherschligt, Stephen Eckel
We report observation of sub-Doppler cooling of lithium using an irregular-tetrahedral laser beam arrangement, which is produced by a nanofabricated diffraction grating. We are able to capture 11(2) % of the lithium atoms from a grating magneto-optical

Erratum: Collisions of room temperature helium with ultra-cold lithium and the van-der-Waals bound state of HeLi [Phys. Rev. A 101, 012702 (2020)]

February 28, 2022
Author(s)
Constantinos Makrides, Daniel Barker, James A. Fedchak, Julia Scherschligt, Stephen Eckel, Eite Tiesinga
We have found an error in the computation of the thermally-averaged total elastic rate coefficient for the collision of a room-temperature helium atom with an ultra-cold lithium atom presented. We omitted the factor $2/\sqrt\pi}$ in the normalization over

Progress towards comparison of quantum and classical vacuum standards

September 22, 2021
Author(s)
Daniel Barker, Nikolai Klimov, Eite Tiesinga, James A. Fedchak, Julia Scherschligt, Stephen Eckel
We present our progress towards a comparison of NIST's cold atom primary vacuum standard and a dynamic expansion vacuum standard. The cold atom vacuum standard (CAVS) converts the loss rate of atoms from a magnetic trap to a vacuum pressure using ab initio

Quantum-Based Photonic Sensors for Pressure, Vacuum, and Temperature Measurements: A Vison of the Future with NIST on a Chip

September 17, 2021
Author(s)
Jay H. Hendricks, Zeeshan Ahmed, Daniel Barker, Kevin O. Douglass, Stephen Eckel, James A. Fedchak, Nikolai Klimov, Jacob Edmond Ricker, Julia Scherschligt
The NIST on a Chip (NOAC) program's central idea is the idea that measurement technology can be developed to enable metrology to be performed "outside the National Metrology Institute" by the crea-tion of deployed and often miniaturized standards. These

NIST on a Chip: Photonic and Quantum-Based Sensors for Measurements of Pressure, Vacuum, Temperature and Beyond!

April 29, 2021
Author(s)
Jay H. Hendricks, Zeeshan Ahmed, Daniel Barker, Stephen Eckel, James A. Fedchak, Nikolai Klimov, Julia Scherschligt
At the core of the NIST on a Chip (NoAC) program is the idea that measurement technology can be developed to enable metrology to be done "outside the National Metrology Institute" by virtue of deployed and often miniaturized standards (that can also serve

Outgassing rate comparison of seven geometrically similar vacuum chambers of different materials and heat treatments

April 23, 2021
Author(s)
James A. Fedchak, Julia Scherschligt, Sefer Avdiaj, Daniel Barker, Stephen Eckel, Ben Bowers, Scott O'Connell, Perry Henderson
We have measured the water and hydrogen outgassing rates of seven vacuum chambers of identical geometry but constructed of different materials and heat treatments. Chambers of five different materials were tested: 304L, 316L, and 316LN stainless steels