A cryogenic current comparator for beam diagnostics in the FAIR project

A cryogenic current comparator(CCC) is based on the properties of ideal superconductors to expel magnetic flux from the bulk material through shielding currents on the surface of the material. As this effect is only dependent on the magnetic field, the CCC allows measuring the magnetic field, e.g. generated by a passing ion beam, they can be measured non-destructively with a high precision. In figure 1 the main components of a CCC are shown. The magnetic field of the beam current creates shielding currents on the superconducting magnetic ring structure, which are transformed with a torodial single turn pick-up coil and its ferromagnetic core. The signal from the pickup coil is feed to a LTS DC SQUID and measured via the external electronics.