A spiral-transmission-line technique for detecting slot apertures in shield enclosures

This note presents another concept, SPIRA, for monitoring the integrity of a shield enclosure. In this concept a helically wound conductor is used as a transmission line in conjunction with the shield enclosure. This type of structure produces an external magnetic field with a strong component parallel to the axis of the helix. This allows the helix to lie parallel to potential slot apertures in the shield enclosure. A similar helix is used on the other side of the shield wall to monitor penetrating magnetic fields.