Superconducting beam charge monitors for antiproton storage rings

A Cryogenic Current Comparator (CCC) is a new type of instruments for monitoring charged beams like ions or antiprotons. Using superconducting effects is it possible to create a nondestructive, contactless and easy to calibrate beam measurement system with a high current resolution in amplitude and time. The Meissner effect enables an effective magnetic shielding of the system. The screening current enables creation of DC-transformers and therefore a DC-current measurement system. The combination of two Josephson-junctions and coils form a superconducting quantum interference device (SQUID) in an analog magnetic feedback of the flux-locked loop (FLL), which is linearizing the SQUID’s transfer function. The performance of the CCC system opens beam currents range between 1 nA and 20 µA. Installations at the Antiproton Decelerator at CERN and GSI in Darmstadt shows a strong correlation between SEM/longitudinal-Schottky and CCC signals including the known spill pattern but with a better signal to noise ratio.