Creation of a flux-free environment

For the proper operation of flux sensitive cryogenic devices such as those in Josephson computers a nearly zero field environment is essential. Since shieldings based on ferromagnetic mu-metal has been found to be not effective enough, superconducting shieldings are required. In this paper flux penetration into superconducting disks of ideal and non-ideal shape is investigated with respect to flux free regions in the disk. Based on the experimental results of the linear dimension of flux free belts in disk shaped type-I superconductors an arrangement is proposed to create flux free regions large enough for practical applications.