High-TC rf superconducting quantum interference device readout with a cryogenic preamplifier
Dongfeng He, M. Tachiki, Hideo Itozaki
A high-TC rf superconducting quantum interference device (SQUID) readout with a cryogenic preamplifier was developed. The noise figure of the preamplifier at 350MHz was about 0.92dB at room temperature and 0.35dB at 77K. For a high-TC yttrium barium copper oxide rf SQUID coupled with a lumped element tank circuit with a resonant frequency of about 360MHz, the white flux noise was about 25μΦ0∕√Hz and 22μΦ0∕√Hz when the preamplifier was at room temperature and at 77K, respectively. The flux noise was only reduced by about 12% using the cryogenic preamplifier. As the thermal noise of the SQUID and the noise generated by the tank circuit are already higher than the preamplifier noise, cooling the preamplifier has only a small effect of the system noise, when the SQUID is operated at 77K. Lower operating temperatures, e.g., when using a SQUID made from MgB2, might justify the use of a cooled preamplifier.
Review of Scientific Instruments•Jun 1, 2006•0 citations