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Proceedings of the 10th International Beam Instrumentation Conference, IBIC2021, Pohang, Rep. of Korea 10th International Beam Instrumentation Conference, IBIC 2021, Pohang, Republic of Corea, 24 May 2021 - 28 May 2021; JACoW Publishing, Geneva, Switzerland 4 pages (2021). doi:10.18429/JACOW-IBIC2021-WEOB02, Accurate non-destructive measurement of the absolute intensity of weak ion beams ( 1 uA) in storage rings is often restricted to special beam conditions and, even then, is associated with large uncertainties and tedious calibration procedures. However, experiments with rare ions in particular depend on excellent current resolution. In order to make these beams accessible, the Cryogenic Current Comparator (CCC) monitors deviations of the DC beam current on a scale of nA and compares the signal to a calibrated reference current. At the heavy-ion storage ring CRYRING at GSI a CCC prototype for FAIR was installed and first results of the commissioning are reported here. Preceding the operation with beam, a careful design of the beamline helium cryostat was required to provide the stable cryogenic environment needed for CCC operation. Mechanical and electro-magnetic perturbations that interfere with measurement of the beam’s faint magnetic field are suppressed by the internal structure of the system and a superconducting magnetic shield, while the remaining interference can be filtered with adequate signal processing. In this way, a current resolution in the nA range was demonstrated., Published by JACoW Publishing, Geneva, Switzerland

The Cryogenic Current Comparator (CCC) extends the measurement range of traditional non-destructive current monitors used in accelerator beamlines down to a few nano-amperes of direct beam current. This is achieved by a cryogenic environment of liquid helium around the beamline, in which the beam’s magnetic field is measured with a Superconducting Quantum Interference Device (SQUID), which is itself enclosed in a superconducting shielding structure. For this purpose, a versatile UHV-beamline cryostat was designed for the CCCs at FAIR and is currently in production. It is built for long-term autonomous operation with a closed helium re-liquefaction cycle and with good access to all inner components. The design is supported by simulations of the cryostat’s mechanical eigenmodes to minimize the excitation by vibrations in an accelerator environment. A prototype at GSI has demonstrated the self-contained cryogenic operation in combination with a 15 l/day re-liquefier. The cryostat will be used in CRYRING to compare the FAIR-CCC-X with newly developed CCC-types for 150 mm beamlines. Both which will supply a nA current reading during commissioning and for the experiments., Proceedings of the 8th International Beam Instrumentation Conference, IBIC2019, Malmö, Sweden

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 generated by the beam current is detected by low temperature Superconducting Quantum Interference Device (SQUID) current sensors. 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 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 be operating in the CRYRING at GSI 2019. Noise, signal and drift measurements were performed in the Cryo-Detector Lab at the University of Jena., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

The storage of low current beams as well as the long extraction times from the synchrotrons at FAIR require non-destructive beam intensity monitoring with a current resolution of nanoampere. To fulfill this requirement, the concept of the Cryogenic Current Comparator (CCC), based on the low temperature SQUID, is used to obtain an extremely sensitive beam current transformer. During the last years, CCCs have been installed to do measurements of the spill structure in the extraction line of GSI SIS18 and for current monitoring in the CERN Antiproton Decelerator. From these experiences lessons can be learned to facilitate further developments. The goal of the ongoing research is to improve the robustness of the CCC towards external influences, such as vibrations, stray fields and He-pressure variations, as well as to develop a cost-efficient concept for the superconducting shield and the cryostat., Proceedings of the 7\textsuperscript{th} Int. Beam Instrumentation Conf., IBIC2018, Shanghai, China

The principle of non-destructive measurement of ion beams by detection of the azimuthal magnetic field, using low temperature Superconducting Quantum Interference Device (SQUID) sensors, has been established at GSI already in the mid 90's. After more recent developments at Jena, GSI and CERN, a CCC was installed in the CERN Antiproton Decelerator (AD) and is operated there routinely as the first stand-alone CCC system. For the Facility for Antiproton and Ion Research (FAIR) a new version of the CCC with eXtended Dimensions (CCC-XD) - especially with a larger inner diameter and adapted parameters - was constructed and first lab tests have already been performed. In parallel, a concept for a dedicated UHV beamline cryostat has been worked out. The CCC-XD system - together with the new cryostat - will be ready for testing in the CRYRING at GSI before the end of 2018. In this contribution, experimental results for the resolution, frequency range, slew rate and pulse-signal obtained by electrical laboratory measurements with the CCC-XD are presented., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

A new Cryogenic Current Comparator with eXtended Dimensions (CCC-XD) is currently under development for a non-destructive, highly sensitive monitoring of nA-intensities of beams for larger beamline diameters planned for the new FAIR accelerator facility at GSI. The CCC consists of a superconducting coil which is read out by a Superconducting Quantum Interference Device (SQUID), a flux concentrator and a superconducting shield. The new flux concentrator comprises of a specially designed, highly permeable core made of nanocrystalline material in order to assure a low-noise operation and a high system bandwidth of up to 200 kHz. The superconducting shielding of niobium has extended geometric dimensions and will suppress disturbing magnetic fields of the beamline environment effectively. New SQUID sensors with sub-μm-Josephson junctions enable extreme low-noise signals and high disturbance-suppression. The CCC-XD system and the new dedicated cryostat will be ready for testing in the CRYRING at GSI in 2017. Results from electrical measurements with the components of the new CCC-XD Setup will be presented in this work., Proceedings of the 5th Int. Beam Instrumentation Conf., IBIC2016, Barcelona, Spain