Supershielding: trapping of magnetic fields

In a new methodology called "supershielding," a variety of open systems of current-carrying conductors can be designed such that their magnetic fields are surprisingly well confined, leading to significant improvements in shielding applications. As an application and further elucidation of the method, we present the details for two concentric spheres with polar caps removed. To good approximation, the magnetic field is trapped inside the outer sphere, provided the currents on both spheres obey "supershielding conditions." Slotted concentric cylinders are also considered.