The Josephson-Effect-Based Primary AC Power Standard at the PTB: Progress Report

The discovery of the Josephson effects 50 years ago initiated a revolution for electrical voltage metrology. This revolution started with single Josephson junctions delivering a few millivolt at most. Meanwhile, highly integrated series arrays containing more than 10 000 or even 300 000 junctions have been developed and fabricated for output voltages up to 10 V. Josephson voltage standards are nowadays used in many laboratories worldwide for dc applications. After their adoption for the representation of the unit of voltage in 1990, the focus of research shifted towards programmable Josephson series arrays. The increasing interest in highly precise ac voltages resulted in new developments for their metrological applications in the last 15 years. This paper summarizes the principal contributions from PTB to the present state of Josephson voltage standards with particular focus on developments and applications for ac standards in metrology and our proof-of-concept demonstrations. The presentation includes the two most promising versions of ac standards, being the programmable Josephson voltage standard based on binary divided series arrays and the Josephson arbitrary waveform synthesizer based on a pulse-driven series array.

Section: Applications Of Binary Josephson Arrayssupporting

confidence: 65%

Development and metrological applications of Josephson arrays at PTB

Behr¹,

Kieler²,

Kohlmann³

et al. 2012

“…The PJVS chip is flex-packaged [24] which gives rise to a uniform microwavepower distribution. In this work, the array cells are regrouped into ten sections containing 214, 72, 24,8,648,1944,4396,4400,13196 and 4400 junctions. The total number of available quantum-voltage steps is 15 255 in the configuration.…”

Section: Methodsmentioning

confidence: 99%

“…It has been one of key subjects in the field of electrical metrology to synthesize waveforms with calculable rootmean-square (rms) voltages utilizing a series array of non-hysteretic Josephson junctions. Synthesizers relying upon Josephson devices can be utilized for the calibration of thermal voltage converters (TVCs) [1,2], evaluation of thermoelectric transfer difference of TVCs [3][4][5] and development of power standards [6][7][8][9]. The pulse-driven Josephson standards [10][11][12][13][14][15] developed over the past decade are the most promising ac voltage sources, generating waveforms with quantum accuracy and extremely low harmonic distortion in a voltage range of V 300 mV.…”

Section: Introductionmentioning

confidence: 99%

Analog-to-digital conversion for low-frequency waveforms based on the Josephson voltage standard

Kim¹,

Kim²,

Kim³

et al. 2010

A waveform synthesizer adopting a superconductor-normal metal-superconductor junction array has been developed, which can generate arbitrary stepwise waveforms with a number of quantum-voltage steps up to 1 V level amplitude. As an application of the synthesizer, we have built a sampling voltmeter that measures the differential voltages between a sinusoidal waveform produced by a semiconductor-based ac source and the Josephson waveforms. We carried out extensive sampling measurements for a 50 Hz sine wave with 1 V amplitude, applying sampling apertures in the range of 55 μs t a 130 μs and using Josephson waveforms with 32, 60, 80 and 100 quantum steps. From the measurements, the amplitude of the ac waveform was determined with a type A uncertainty (k = 2) of 0.15 μV. Also, we elucidated how the phase jitter in the ac waveform is reflected in the overall uncertainty for the measurements. The type B uncertainty due to the jitter is at least one order of magnitude smaller than the type A uncertainty.

“…This will allow automation of the calibration processes for secondary standards and DVM linearity. Programmable arrays would simplify direct Josephson comparisons because polarity reversals could be carried out faster, equally spaced in time, and would therefore contribute to a reduction in residual thermal EMFs which contribute to the Type A uncertainty [45]. However, BIPM Josephson comparisons have shown that errors introduced in the measurement loop, even if they are small, can reach the 10 −10 level and be comparable to the most significant uncertainty components.…”

Section: Perspectivesmentioning

confidence: 99%

BIPM direct on-site Josephson voltage standard comparisons: 20 years of results

Solve¹,

Stöck²

2012

The discovery of the Josephson effect has for the first time given national metrology institutes (NMIs) the possibility of maintaining voltage references which are stable in time. In addition, the introduction in 1990 of a conventional value for the Josephson constant, KJ-90, has greatly improved world-wide consistency among representations of the volt. For 20 years, the Bureau International des Poids et Mesures (BIPM) has conducted an ongoing, direct, on-site key comparison of Josephson voltage standards among NMIs under the denominations BIPM.EM-K10.a (1 V) and BIPM.EM-K10.b (10 V) in the framework of the mutual recognition arrangement (CIPM MRA). The results of 41 comparisons illustrate the consistency among primary voltage standards and have demonstrated that a relative total uncertainty of a few parts in 1010 is achievable if a few precautions are taken with regard to the measurement set-up. Of particular importance are the grounding, efficient filters and high insulation resistance of the measurement leads, and clean microwave distribution along the propagation line to the Josephson array. This paper reviews the comparison scheme and technical issues that need to be taken into account to achieve a relative uncertainty at the level of a few parts in 1010 or even a few parts in 1011 in the best cases.