Sequential read-out architecture for multi-channel SQUID systems

摘要

The authors describe a novel multi-channel sequential SQUID read-out technique that requires fewer wires than conventional units and also simplifies the electronics significantly. They designed and experimentally tested the sequential read-out electronics with up to 8 channels using LTS 8x8 mm(sup 2) magnetometers with about 3fT/(radical)Hz field resolution. They have investigated noise performance, amplitude-frequency characteristics, and cross- talk of the sequential read-out electronics for 2, 4, and 8 channels. They observed field resolution better than 4fT/(radical)Hz, 6fT/(radical)Hz, and 9fT/(radical)Hz for 2-, 4-, and 8-channel versions, respectively. They observed 10 kHz frequency bandwidth for the 8-channel version using 200 kHz modulation frequency. Cross-talk better than (minus)90dB was measured for this system. A single-channel simulation was used to estimate the field resolution for systems with up to 128 channels. They found that the expected field resolution can be better than 15fT/(radical)Hz, 20fT/(radical)Hz, and 30fT/(radical)Hz for 32-, 64-, and 128-channel systems, respectively, with the sequential read-out technique.