The Electron Counting Capacitance Standard currently pursued at PTB aims to close the Quantum Metrological Triangle with a final precision of a few parts in 10^7. This paper reports the considerable progress recently achieved with a new generation of single-electron tunnelling devices. A five-junction R-pump was operated with a relative charge transfer error of five electrons in 10^7, and was used to successfully perform single-electron charging of a cryogenic capacitor. The preliminary result for the single-electron charge quantum has an uncertainty of less than two parts in 10^6 and is consistent with the value of the elementary charge.
@article{arxiv.1107.1616,
title = {Electron Counting Capacitance Standard with an improved five-junction R-pump},
author = {Benedetta Camarota and Hansjoerg Scherer and Mark W Keller and Sergey V Lotkhov and Gerd-Dietmar Willenberg and Franz Josef Ahlers},
journal= {arXiv preprint arXiv:1107.1616},
year = {2015}
}