Optimized Cryogenic Current Comparator for CERN's Low-Energy Antiproton Facilities

Non-perturbative measurement of low-intensity charged particle beams is particularly challenging for beam diagnostics due to the low amplitude of the induced electromagnetic fields. In the low-energy Antiproton Decelerator (AD) and the future Extra Low ENergy Antiproton (ELENA) rings at CERN, an absolute measurement of the beam intensity is essential to monitor operational efficiency and provide important calibration data for all AD experiments. Cryogenic Current Comparators (CCC) based on Superconducting QUantum Interference Device (SQUID) have in the past been used for the measurement of beams in the nA range, showing a very good current resolution. However these were unable to provide a measurement of short bunched beams, due to the slew-rate limitation of SQUID devices and their strong susceptibility to external perturbations. Here, we present the measurements and results obtained during 2016 with a CCC system developed for the Antiproton Decelerator, which has been optimized to overcome these earlier limitations in terms of current resolution, system stability, the ability to cope with short bunched beams, and immunity to mechanical vibrations.