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Search Publications by: Patrick Egan (Fed)

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Displaying 1 - 25 of 34

Wavemeter calibration by frequency comb

November 7, 2024
Author(s)
Patrick Egan
Upgrades to the vacuum-wavelength calibration service at NIST are reported. The instrumentation centerpiece is an optical frequency comb tied to a GPS-disciplined oscillator, thereby providing direct traceability to the SI second. Historically, the service

Expansivity of fused quartz glass measured within 6 x 10^-10 K^-1

September 11, 2024
Author(s)
Patrick Egan
A method is described to measure the thermal expansion coefficient of fused quartz glass. The measurement principle is to monitor the change in resonance frequency of a Fabry–Perot cavity as its temperature changes; the Fabry–Perot cavity is made from

Optical n(p, T_90) measurement suite 3: results at l = 1542 nm

August 3, 2024
Author(s)
Patrick Egan, Yuanchao Yang
Single-isotherm n(p, T90) results are reported for the gases Ar, N2, H2O, and D2O at vacuum wavelength λ = 1542.383(1) nm. The argon and nitrogen isotherms were measured near 303 K; the water isotherms were measured near 373 K. Combined with the two

Optical n(p, T_90) measurement suite 2: H_2O and D_2O

May 28, 2024
Author(s)
Patrick Egan, Yuanchao Yang
A suite of measurements of refractive index n(p, T_90) is reported for gas phase ordinary water H_2O and heavy water D_2O. The methodology is optical refractive index gas metrology, operating at laser wavelength 633 nm and covering the range (293 T_90 43

Working equation for a Fabry-Perot cavity based optical pressure standard

May 1, 2024
Author(s)
Yuanchao Yang, Patrick Egan, Tom Rubin
From basics of Fabry-Perot (FP) resonator and roundtrip phase, a complete working equation for a FP cavity based optical pressure standard (OPS) is derived and presented which includes corrections of reflection phase-shift, diffraction and pressure-induced

Optical n(p, T_90) measurement suite 1: He, Ar, and N_2

November 23, 2023
Author(s)
Patrick Egan, Yuanchao Yang
An n(p, T90) measurement suite is reported for the gases helium, argon, and nitrogen. The methodology is optical refractive-index gas metrology, operating at laser wavelength 633 nm and covering the temperature range (293 T 433) K and pressures p 0.5

D-to-A_eff converter

August 1, 2022
Author(s)
Patrick Egan, Eric S. Stanfield, John R. Stoup
Recent developments in diameter metrology at NIST have enabled the dimensional characterization of piston-cylinder assemblies (PCA) with unprecedented precision. For the newest generation of PCA, standard uncertainty on measurement of outer diameter is 12

Shrinks When It's Colder

August 1, 2022
Author(s)
Patrick Egan
Thermal expansion can be a leading cause of uncertainty in length metrology. A cell-based refractometer has been designed at NIST which targets 10^-6} relative uncertainty in the measurement of helium refractivity; in terms of refractive index at ambient

Towards Photonic based Pascal Realization as a Primary Pressure Standard

February 7, 2019
Author(s)
Jacob E. Ricker, Jay H. Hendricks, Patrick F. Egan, Jack Stone, Kevin O. Douglass, Gregory Scace
New techniques using refractometry have enabled gas pressure to be measured using laser interferometry. Two key techniques have been studied at NIST which include the Fixed Length Optical Cavity (FLOC) and the Variable Length Optical Cavity (VLOC). The

Design of a cell-based refractometer with small end-effects

July 7, 2018
Author(s)
Patrick Egan, Jack A. Stone Jr.
In cell-based laser refractometers, interferometer pathlength uncertainty introduced by deformation and stress in the windows through which the beams pass can be the chief factor limiting measurement accuracy. The fractional contribution of pathlength

Candidates to Replace R-12 as a Radiating Gas in Cherenkov Detectors

April 14, 2018
Author(s)
Allan H. Harvey, Yauheni Paulechka, Patrick F. Egan
Dichlorodifluoromethane (R-12) has been used as a radiating gas in pressure threshold Cherenkov detectors for high-energy particle physics. However, that ozone-depleting compound is becoming unavailable due to the Montreal Protocol. To find a replacement

Quantum for Pressure

January 5, 2018
Author(s)
Jay H. Hendricks, Patrick F. Egan, Jacob E. Ricker, Jack A. Stone Jr., Kevin O. Douglass, Gregory F. Strouse
A team of NIST scientists is working to fundamentally change the way that the unit of pressure is realized and disseminated, an effort that will lead to the elimination of mercury barometer pressure standards.

Perspectives for a new realization of the pascal by optical methods

October 24, 2017
Author(s)
Jay H. Hendricks, Karl Jousten, Jack A. Stone Jr., Patrick F. Egan, Tom Rubin, Christof Gaiser, Rene Schodel, James A. Fedchak, Jacob E. Ricker, Jens Fluegge, Stephen P. Eckel, Julia K. Scherschligt, Daniel S. Barker, Kevin O. Douglass, Gregory F. Strouse, Uwe Sterr, Waldimir Sabuga
Since the beginning of measurement of pressure in the 17th century, the unit of pressure has been defined by the relationship of force per unit area. The present state of optical technology now offers the possibility of using a thermodynamic definition

Cell-based refractometer for pascal realization

July 24, 2017
Author(s)
Patrick F. Egan, Jack A. Stone Jr., Jacob E. Ricker, Jay H. Hendricks, Gregory F. Strouse
We describe a method for determining density of helium via measurements of optical refractivity. In combination with the equation of state, this allows realization of the pascal. Our apparatus is based on the integration of a gas triple-cell into a quasi

Stuck in a moment: A view from the MIRE

April 20, 2017
Author(s)
Patrick Egan, Jack A. Stone Jr., Jacob Edmond Ricker, Jay H. Hendricks
The next-generation pressure standards will be realized via gas density and the equation of state. One way to access the density is through a measurement of gas refractivity, underpinned by the theoretical calculations that predict the relationship between

Laser Refractometer as a Transfer Standard of the Pascal

July 9, 2016
Author(s)
Patrick Egan, Jack A. Stone Jr., Jacob Edmond Ricker, Jay H. Hendricks
We have developed a new low pressure sensor which is based on the measurement of (nitrogen) gas refractivity inside a Fabry-Perot (FP) cavity. We compare pressure determinations via this laser refractometer to that of well-established ultrasonic manometers

MEASURING PRESSURE AND VACUUM WITH LIGHT: A NEW PHOTONIC, QUANTUM-BASED, PRESSURE STANDARD

September 3, 2015
Author(s)
Jay H. Hendricks, Jacob E. Ricker, Jack A. Stone Jr., Patrick F. Egan, Gregory E. Scace, Gregory F. Strouse, Douglas A. Olson, Donavon Gerty
The future of pressure and vacuum measurement will rely on lasers and Fabry-Perot optical cavities, and will be based on fundamental physics of light interacting with a gas. Light interacts at the quantum level with matter such that light travels at a

Performance of a dual Fabry-Perot cavity refractometer

August 18, 2015
Author(s)
Patrick F. Egan, Jack A. Stone Jr., Jay H. Hendricks, Jacob E. Ricker, Gregory E. Scace, Gregory F. Strouse
We have built and characterized a refractometer that utilizes two Fabry-Perot cavities formed on a dimensionally stable spacer. In the typical mode of operation, one cavity is held at vacuum and the other cavity is filled with nitrogen gas. The

Clearing the fog for best in the world air-wavelength

July 1, 2015
Author(s)
Patrick F. Egan, Jack A. Stone Jr.
Laser interferometry, the basis for modern length metrology, achieves very high accuracies as a consequence of the stable, well-known frequencies of laser sources. However, length measurements in air also require corrections based on precise knowledge of

In Search of Better Pressure Standards

August 1, 2014
Author(s)
Jay H. Hendricks, Jacob E. Ricker, Patrick F. Egan, Gregory F. Strouse
Based on highly accurate optical interferometry and fundamental quantum calculations, researchers at the National Institute of Standards and Technology (NIST) in the US are developing an improved definition of the SI unit for pressure that will consign the