Serial array high Tc SQUID magnetometer

SQUID magnetometers have been fabricated from series arrays of YBa2Cu3O7 dc SQUIDs by pulsed laser film deposition and ion mill patterning techniques. The array was designed either in linear chain with flux focusers or in meander structure. The arrays consisted of 50-130 step-edge junction SQUIDs and each SQUID had inductance of 20-40 pH with 2-5 mu m junction width. A linear array of 50 SQUIDs showed a modulation amplitude of 150 mu V which corresponds to a gain of similar to 10. One of 80 SQUID meander arrays had a gain of as high as 50. These results provide feasibility of the series array of SQUIDs in the direct readout SQUID amplifier circuitry with wide bandwidth. Larger number SQUID arrays and processes to increase the gain to the theoretical value need to be studied.