Low-noise measurements of the quantized hall resistance using an improved cryogenic current comparator bridge

Abstract

Significant improvements have been made on the bridge based on a cryogenic current comparator (CCC bridge) that is used at the Bureau International des Poids et Mesures, France (BIPM), for measurements of the quantized Hall resistance (QHR). Specifically, a SQUID (superconducting quantum interference device)-based DC nanovoltmeter and a new CCC with an increased number of turns have been built and incorporated into the bridge. QHR measurements with a very low noise level (2 parts in 10/sup 9/ of the ratio of the QHR to a 100- Omega standard) have been carried out using this improved bridge. >