| 摘要 |
PURPOSE:To largely reduce the number of wires and simply enable multiplexing without requirement for improving freezing ability by applying equal constant voltage to superconducting loops of a plurality of SQUIDs and adding output current to be taken out. CONSTITUTION:Equal bias voltage is applied to superconducting loops 2a of a plurality of SQUIDs 2 through a bias voltage line 3a, and in order to cancel a change in flux input from an input coil 2b to the loop 2a, modulation MO current is supplied to an MO coil 2c to attain flux locking. Since output current from all of the loops 2a is taken out in a summed state, correlation between the summed current and a serial symbol C(t) is taken with a multiplier 5b provided on a flux lock loop 5 to integrate 5c one cycle so as to obtain the original MO current. In such a constitution, the number of the voltage lines 3a and current take-out lines 3d are two each irrespective of the SQUIDs 2 connected in parallel, so that they can be reduced to 4 + 2 lines, wherein numerous SQUIDs can be housed in series in a freezing vessel and simultaneous flux measurement is possible.
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