Recent results and future challenges for the NIST charged-capacitor experiment

This paper reports on recent results in some of the work toward developing a new capacitance standard using single electron tunneling (SET) devices. In particular, we plan on using a SET pump to charge a cryogenic standard capacitor and measure the voltage that develops. In this paper, we summarize: 1) measurements of the ratio of two capacitors in a bridge configuration, using a SET transistor as the null detector and 2) stability and leakage measurements on the cryogenic capacitors. We then discuss in detail several of the possible challenges, including the effects of stray capacitance and line impedance, and resulting requirements on the sensitivity of the SET null detector.