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The NIST Johnson noise thermometry system for the determination of the Boltzmann constant



Nathan Flowers-Jacobs, Alessio Pollarolo, Kevin Coakley, Adam C. Weis, Anna Fox, Horst Rogalla, Weston L. Tew, Samuel Benz


In preparation for the redefinition of the International System of Units (SI), five different electronic measurements of the Boltzmann constant have been performed using different Johnson noise thermometry (JNT) systems over the past seven years. In this paper, we describe in detail the JNT system and uncertainty components associated with the most recent National Institute of Standards and Technology (NIST) determination of the Boltzmann constant: k = 1.380642 9(69) × 10−23 J/K, with a relative standard uncertainty of 5.0 × 10−6 and relative offset of −4.05 × 10−6 from the Committee on Data for Science and Technology (CODATA) 2014 recommended value. We discuss the input circuits and the approach we used to match the frequency response of two noise sources. We present new measurements of the correlated noise of the 4 K on-chip resistors in the quantum- accurate, pseudorandom, voltage-noise source, which we used to estimate the correlated, frequency-dependent, nonthermal noise in our system. Finally, we contrast our system with those used in other measurements and speculate on future improvements.
Journal of Research (NIST JRES) -


Boltzmann equation, correlation, digital-analog conversion, Josephson arrays, measurement units, noise measurement, quantization, signal synthesis, standards, temperature.


Flowers-Jacobs, N. , Pollarolo, A. , Coakley, K. , Weis, A. , Fox, A. , Rogalla, H. , Tew, W. and Benz, S. (2017), The NIST Johnson noise thermometry system for the determination of the Boltzmann constant, Journal of Research (NIST JRES), National Institute of Standards and Technology, Gaithersburg, MD, [online],, (Accessed July 21, 2024)


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Created December 28, 2017, Updated October 12, 2021