Direct JVS Comparison between NIST and SNL to Support NCSLI JVS ILC 2011

摘要

The National Conference of Standard Laboratories International (NCSLI) is scheduled to start its 9th Josephson Voltage Standard (JVS) Interlaboratory Comparison (ILC) in March 2011. Sandia National Laboratories (SNL) is the pivot lab for this comparison of JVS systems that are currently in operation at several U.S. companies and national laboratories. In order to ensure the uniformity and traceability of the representation of the volt based on the Josephson constant 1990 in all the participating labs, the National Institute of Standards and Technology (NIST) DC Volt Lab and SNL performed a direct JVS comparison from December 6, 2010 to December 10, 2010 at the SNL, Albuquerque, NM. In this JVS comparison, the difference between the NIST CJVS and the SNL JVS was found to be -2.08 nV +- 2.88 nV at 10 V (k velence 2). The large number of measurement data points enabled research investigations, such as the evaluation of the impact of the null detector's gain error and the filter network on the comparison result. The team discovered that the polarization of the dielectric material of the SNL cryoprobe filter capacitors could affect the comparison outcome. The difference between the two JVSs was reduced from -6.50 nV to -2.08 nV by extending the waiting period for the capacitor recovery from polarization to equilibrium. An in-situ JVS comparison between the NIST CJVS and the SNL JVS via a set of Zener transfer standards at 10 V was also carried out. The difference was 12 nV +- 21 nV at 10 V (k velence 2). This result is consistent with the results from similar past JVS ILC comparisons. The same set of Zeners will be used in the JVS ILC that is scheduled to begin in March 2011. The result of this direct JVS comparison achieved an uncertainty level comparable to the international key comparison BIPM.EM.K10.b in the Bureau International des Poids et Mesures (BIPM) Key Comparison Data Base (KCDB). This bilateral JVS comparison has confirmed that SNL is capable of performing its role as the pivot lab in the upcoming NCSLI JVS ILC. The results of the NCSLI JVS ILC will allow its participants to establish a voltage measurement link to NIST via the pivot lab SNL.