Picovoltmeter based on a high transition temperature SQUID

Abstract

We have fabricated and tested picovoltmeters in which the voltage source is connected in series with a calibrated resistor and a coil inductively coupled to a high-transition temperature superconducting quantum interference device operating at 77 K. The coil consists of either seven or ten turns of copper wire or of two turns patterned in a film of YBa2Cu3O7-x(YBCO). The lowest voltage noise achieved at 1 Hz was 30 pV Hz-1/2 and 2.3 pV Hz-1/2 for input coils made of copper and YBCO, respectively. © 1995 American Institute of Physics.