Neil M Zimmerman et al 2006 Metrologia 43 383 doi:10.1088/0026-1394/43/5/007
Neil M Zimmerman, Brian J Simonds and Yicheng Wang
Show affiliationsIn attempting to develop a capacitance standard based on the charge of the electron, one question which has been open for many years is the frequency dependence of the vacuum-gap cryogenic capacitor; the crucial difficulty has been: How do we measure frequency dependence down to 0.01 Hz? In this paper, we succeed in putting an upper bound on the frequency dependence, from 0.01 Hz to 1 kHz, of about 2 × 10−7. We do this by considering a model for the dispersion in the surface insulating films on the surface of the Cu electrodes; the crucial prediction of this model is that the dispersion falls to very low values at low temperatures. By measuring the frequency dependence over a restricted range of frequencies, we have verified this prediction, and thus provide adequate support to conclude that the model is correct. We also point out that, independent of the capacitance standard, this cryogenic capacitor provides a frequency-independent standard for measurements in fields such as the low-temperature dynamics of amorphous materials.
06.30.Ka Basic electromagnetic quantities
06.20.fb Standards and calibration
06.20.Dk Measurement and error theory
07.20.Mc Cryogenics; refrigerators, low-temperature equipment
Issue 5 (October 2006)
Received 11 April 2006, accepted for publication 23 May 2006
Published 6 September 2006
Neil M Zimmerman et al 2006 Metrologia 43 383
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