Design Criteria for Flux-Shield Variable Inductors

摘要

Design equations are developed for three configurations of Flux-Shield Inductors. At cryogenic temperatures where conductors support zero magnetic flux, it is shown that there is an optimum shape factor of 2.2 for the ratio of diameter to length which yields a minimum quantity of superconductive shield material for any given inductor tuning ratio. Comparing shield volume of the 'two-coil-one-shield' configuration and the 'three-coil-two-shield' configuration against the 'one-coil-one-shield' configuration gives relative volume factors for each, as follows: V = 1 for the one-coil, V = 0.25 for the two-coil, and V = 0.16 for the three-coil. Experimental verification at room temperature shows discrepancies with predictions of less than 5% for coils which have small turn-to-turn spacing. (Author)