Development of AC Quantum Hall Measurements at CMI

This paper describes results and equipment involved in experiments with realization of quantum impedance standard, based on ac quantum Hall resistance standard. CMI developed cryogenic probe with TO-8 holder and coaxial wiring, device holder and digitally assisted (DA) bridge suitable for ac measurements of quantum Hall effect. Experiments were performed at liquid helium temperatures with GaAs devices placed in double shielded holders.