A Magnetic Monopole Detector Utilizing Superconducting Elements

An electromagnetic detector has been built to extend the search for magnetic monopoles to the lunar sample returned during the Apollo missions. It is sensitive to the minimum magnetic charge allowed by Dirac's theory and permits analysis of a sample without changing any of its properties. The apparatus consists of a superconducting niobium sensing coil with a core at room temperature, shorted by a superconducting mechanical switch and protected against the effects of variable ambient magnetic field by an adequate shield made of superconducting lead. Characteristic features, performance, and sample containers are described.