Planar Microwave Biased rf-SQUIDs with a Cryogenic HEMT amplifier

M. M�ck, Christoph Heiden

Michael Mück, D. Diehl, Christoph Heiden

Antonella Cavalleri, MASSIMO CERDONIO, Giorgio Fontana +5 more

Michael Mück, G. Hallmanns, Christoph Heiden +4 more

We report on the design and performance of a planar microwave rf-SQUID readout by a cryogenic preamplifier. The SQUID-sensor consists of a planar half-wavelength microstrip resonator, into which the SQUID-loop is integrated. The pump frequency is 1.7 GHz. The cryogenic preamplifier employs a microwave high electron mobility transistor (HEMT), located close to the SQUID sensor. Measurements of the flux noise and the fractional step rise parameter were carried out in the temperature range between 4.2 and 1.5 K. In an open loop white flux noise values of 2×10−6 Φ0/√Hz were obtained at 4.2 K.

H. Ahola, G. J. Ehnholm, P. �stman +1 more

Giorgio Fontana, R. Mezzena, Stefano Vitale +4 more

The design and performance of a planar microwave RF-SQUID (superconducting quantum interference device) read out by a cryogenic high-electron-mobility-transistor (HEMT) preamplifier are described. The SQUID sensor consists of a planar half-wavelength microstrip resonator, into which the SQUID loop is integrated. The SQUID is operated at a pump frequency of 1.7 GHz. The cryogenic preamplifier uses a microwave HEMT, located close to the SQUID sensor. Measurements of the flux noise and the fractional step rise parameter were carried out in the temperature range between 4.2 K and 1.5 K. In an open loop, a flux noise of 2*10/sup -6/ Phi /sub 0// square root Hz was measured at 4.2 K, resulting in an energy resolution of about 100 h. The design of a 3-GHz magnetometer is also described, and the preliminary results of the measurements are reported.>