Title :
Optimum sensitivity of an externally shielded cryogenic current comparator
Author :
Early, Murray D. ; Jones, Keith
Author_Institution :
Meas. Standards Lab., New Zealand
fDate :
4/1/1997 12:00:00 AM
Abstract :
The sensitivity of an overlapped-tube cryogenic current comparator (CCC) has been calculated including the effect of a cylindrical external shield. Dimensions of the shield, tube and pick-up coil can be optimized to give maximum sensitivity. The sensitivity in the case of a fixed radius shield has been numerically investigated and a CCC based on an optimized design has been constructed. A single sensitivity measurement indicates that the cylindrical-shield model is accurate to within about 20% of the measured value. This is a significant improvement compared with a simplified ring model of the shield or neglecting the shield entirely
Keywords :
SQUIDs; bridge instruments; coils; cryogenics; current comparators; quantum Hall effect; shielding; cylindrical external shield; cylindrical-shield model; externally shielded cryogenic current comparator; fixed radius shield; pick-up coil; quantum Hall resistance bridges; sensitivity measurement; Cryogenics; Design optimization; Electrical resistance measurement; Equations; Equivalent circuits; Geometry; Inductance; Superconducting coils; Superconducting epitaxial layers; Wire;
Journal_Title :
Instrumentation and Measurement, IEEE Transactions on
