Different versions of Cryogenic Current Comparators with magnetic core for beam current measurements

For more than 20 years Cryogenic Current Comparators (CCC) are used to measure the current of charged particle beams with low intensity (nA-range). The device was first established at GSI in Darmstadt and was improved over the past two decades by the cooperation of institutes in Jena, GSI and CERN. The improved versions differ in material parameters and electronics to increase the resolution, and in dimensions in order to meet the requirements of the respective application. The device allows non-destructive measurements of the charged particle beam current. The azimuthal magnetic field which is excited by the beam current is detected by a low-temperature Superconducting Quantum Interference Device (SQUID) sensor. A complex shaped superconductor cooled down to 4.2 K is used as magnetic shielding and a high permeability core serves as flux concentrator. Three versions of the low-temperature superconducting CCC shall be presented in this work: (#1) GSI-Pb-CCC which was running at GSI Darmstadt in a transfer line, (#2) CERN-Nb-CCC currently installed in the Antiproton Decelerator at CERN and (#3) GSI-Nb-CCC-XD which will start operation in the CRYRING at GSI 2019. Noise, signal and drift measurements were performed in the Cryo-Detector Lab at the University of Jena.