Low noise HTS dc-SQUID flip-chip magnetometers and gradiometers

We have fabricated HTS dc-SQUID flip-chip sensors with a large area multila yer flux transformers. Different layouts of the flux transformers provide a large variety of magnetometers and planar gradiometers. For the magnetomet ers a resolution similar to 6 fT/root Hz end the planar gradiometers a reso lution of about similar to 30 fTcm(.)root Hz were routinely obtained at 77 K. The noise was nearly white down to frequencies of few Hz. The sensors we re vacuum-tight encapsulated together with a heater and a feedback coil. Th is makes the handling of the sensors more reproducible and convenient. Prod uction of the magnetometers end gradiometers in small series was proven.