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Search Publications by: Jon R. Pratt (Fed)

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Displaying 26 - 50 of 129

A self-calibrating optomechanical force sensor with femtonewton resolution

December 10, 2014
Author(s)
John T. Melcher, Julian Stirling, Felipe Guzman, Jon R. Pratt, Gordon A. Shaw
We report the development of an ultrasensitive optomechanical sensor designed to improve the accuracy and precision of force measurements with atomic force microscopy. The sensors achieve quality factors of 4.3x10^6 (a 100-fold improvement over quartz

A constant from a mass, a mass from a constant

November 9, 2014
Author(s)
Jon R. Pratt, Stephan Schlamminger, David B. Newell, Leon S. Chao, Zeina J. Kubarych, Patrick J. Abbott, Yusi A. Cao, Frank C. Seifert, Darine El Haddad
NIST recently used a watt balance instrument known as NIST-3 to measure the Planck constant in terms of IPK with a relative uncertainty of approximately 45 parts in 10e9. Along the way to this new NIST value of h, the instrument was also employed to

THE CONSTRUCTION AND CHARACTERIZATION OF THE NIST-4 PERMANENT MAGNET SYSTEM

November 9, 2014
Author(s)
Leon S. Chao, Frank C. Seifert, Shisong Li, Darine El Haddad, Stephan Schlamminger, Jon R. Pratt
A watt balance is an electromagnetic force balancing instrument to realize the unit of mass at the kilogram level. The magnet system is one of the key components. Our group at the National Institute of Standards and Technology is currently building a next

Alignment and testing of the NIST Calculable Capacitor

August 24, 2014
Author(s)
Yicheng Wang, Felipe Guzman, Corey A. Stambaugh, Radek Smid, Hugo Zuniga Calvo, Andrew D. Koffman, Jon R. Pratt, John R. Lawall
This paper reports progress on the NIST effort to develop a new calculable capacitor, focusing on improvement of the guard electrode motion control as well as issues associated with the overall electrode alignment. Design of a multi-wavelength Fabry-Perot

Construction and Performance of the NIST-4 Magnet System

August 24, 2014
Author(s)
Frank C. Seifert, Alireza R. Panna, Leon S. Chao, Yusi A. Cao, Darine El Haddad, Shisong Li, Stephan Schlamminger, Jon R. Pratt, Heeju Choi, Lori Haley
A watt balance is a promising instrument to realize the unit of mass at the kilogram level. The magnet system is one of the key elements of such an instrument. For the new watt balance currently under construction at the National Institute of Standards and

Heterodyne interferometer with subnanometer accuracy

August 24, 2014
Author(s)
Darine El Haddad, Frank C. Seifert, Stephan Schlamminger, Leon S. Chao, David B. Newell, Jon R. Pratt
This paper gives a brief description of the laser interferometer system designed for the next generation watt balance experiment aimed to realize the unit of mass by direct link to Planck constant at the National Institute of Standards and Technology. The

The Design of the NEW NIST-4 Watt Balance

August 24, 2014
Author(s)
Leon S. Chao, Stephan Schlamminger, Frank C. Seifert, Yusi A. Cao, Darine El Haddad, David B. Newell, Jon R. Pratt
The design of the new permanent-magnet driven watt balance and novel mechanical features will demonstrate the high-precision capabilities of a large complex mass measurement system with expected overall uncertainties on the order of 3 parts in 10^8.

The Measurement of the Local Acceleration of Gravity for the NIST4 Watt Balance

August 24, 2014
Author(s)
David B. Newell, Jacques Liard, Leon S. Chao, Yusi A. Cao, Frank C. Seifert, Darine El Haddad, Jon R. Pratt, Stephan Schlamminger
A new watt balance is being constructed at NIST in preparation for the redefinition of the International System of Units and the realization of mass through an exact value of the Planck constant. We describe the procedures used and give results for the

Construction of a watt balance with the aim to realize the kilogram at the National Institute of Standards and Technology

August 1, 2014
Author(s)
Darine El Haddad, Leon Chao, Frank Seifert, David B. Newell, Jon R. Pratt, Stephan Schlamminger
A redefinition of the International System of Units, the SI, is impending and could occur as early as 2017. After redefinition a means to realize the unit of mass is required. A watt balance is a promising device to realize the unit of mass at the kilogram

Determination of the Planck constant at the National Institute of Standards and Technology

July 1, 2014
Author(s)
Stephan Schlamminger, Darine El Haddad, Frank C. Seifert, Leon S. Chao, David B. Newell, Ruimin Liu, Richard L. Steiner, Jon R. Pratt
In 2013, a new measurement of the Planck constant h was performed using a watt balance at the National Institute of Standards and Technology (NIST). The value is h=6.626 069 79(30) x 10^{-34} J s. The relative standard uncertainty of this determination is

A nonlinearity in permanent-magnet systems used in watt balances

June 25, 2014
Author(s)
Shisong Li, Stephan Schlamminger, Jon R. Pratt
In watt balances that employ permanent magnet systems to generate the magnetic flux the effects of the weighing current on the magnet systems can generate a systematic bias that can lead to an error in the result if not accounted for. In this article a

High Sensitivity Optomechanical Reference Accelerometer Over 10 kHz

June 5, 2014
Author(s)
Felipe Guzman, Lee M. Kumanchik, Jon R. Pratt, Jacob M. Taylor
We present an optically detected mechanical accelerometer that achieves a sensitivity of 100 ng/√Hz over a bandwidth of 10 kHz and is traceable. We have incorporated a Fabry-Perot fiber-optic micro-cavity that is currently capable of measuring the test

Determination of the Planck constant using a watt balance with a superconducting magnet system at the National Institute of Standards and Technology

March 31, 2014
Author(s)
Stephan Schlamminger, Darine El Haddad, Frank C. Seifert, Leon S. Chao, David B. Newell, Richard L. Steiner, Jon R. Pratt
In the past two years measurements were performed with a watt balance at the National Institute of Standards and Technology (NIST) to determine the Planck constant. A detailed analysis of these measurements and their uncertainties led to a value of h=6.626

How to weigh everything from atoms to apples using the revised SI

March 3, 2014
Author(s)
Jon R. Pratt
The fact that the unit of mass might soon be derived from the Planck constant, rather than from an artifact standard, can seem daunting and downright baffling when viewed from the vantage point of our day to day perception of mass. After all, at

Functional Constraints and the Design of a New Watt Balance

September 30, 2013
Author(s)
Leon S. Chao, Stephan Schlamminger, Jon R. Pratt
The functional constraints driving the design of the new permanent-magnet driven watt balance (NIST-4) outline the variables and compromises worthy of addressing. Construction according to these design parameters will demonstrate the high precision

The Planck constant, watt and vacuum balances, and an evolving Mise en pratique for the kilogram in North America

July 1, 2012
Author(s)
Jon R. Pratt, David B. Newell, Zeina J. Kubarych, Stephan Schlamminger, Darine El Haddad, Ruimin Liu, Edwin R. Williams, Dave Inglis, Barry M. Wood, Carlos Sanchez, Richard Green
We report preparations underway at the National Institute of Standards and Technology (NIST) in the United States and at the National Research Council (NRC) in Canada to support the redefinition of the international system of units (SI) and the development

Calibration of dynamic sensors for noncontact-atomic force microscopy

August 12, 2011
Author(s)
Gordon A. Shaw, Jon R. Pratt, Zeina J. Kubarych
Access to quantitative information on surface forces in noncontact-atomic force microscopy (NC-AFM) requires the accurate calibration of several key sensor parameters. This work outlines a dynamic method for calibrating the spring constant of tuning fork

An interferometric platform for studying AFM probe deflection

January 3, 2011
Author(s)
Jon R. Pratt, Lee Kumanchik, Tony L. Schmitz
This paper describes an interferometric platform for measuring the full-field deflection of atomic force microscope (AFM) probes and generic cantilevers during quasi-static loading. The platform consists of a scanning white light interferometer (SWLI)