The Cryogenic Current Comparator (CCC) is a superconducting device for measurement of low intensity beams with magnetic fields in the range of fT. It uses a Superconducting Quantum Interference Device (SQUID) as an ultrasensitive magnetometer and an elaborated superconducting shield for its protection from external magnetic fields. The system is operated in a helium bath cryostat, which has to fulfill many requirements, such as being non-magnetic, pressure/temperature stable (mK), vibration dampening, UHV fit, bakable, compact and accessible for maintenance and repair. First operation of a CCC as beam current monitor was achieved in the 90s at GSI. The idea has been updated for measurement of slow extracted beams and exotic ions at FAIR, and since 2014 there has been steady optimization by an international collaboration of expert institutes. Looking at noise figures and current resolution as well as practical applicability and costs, a Dual-Core CCC (DCCC) has turned out as best candidate for FAIR. In parallel to detector development the cryostat has been investigated and improved. It has recently achieved stand-alone operation, which is a main requirement for FAIR.

This article studies the impact of mechanical deformations on the performance of a coaxial-type cryogenic current comparator (CCC). Such deformations may become a concern as the size of the CCC increases (e.g., when used as a diagnostic device in a particle accelerator facility involving beamlines with a large diameter). In addition to static deformations, this article also discusses the effect of mechanical vibrations on the CCC performance.

Non-destructive measurements of nA beam currents in particle beam storage rings by detecting the azimuthal magnetic field generated by moving charged particles with a Cryogenic Current Comparator (CCC) are well established. The detection of beam currents with small amplitudes with a CCC in a storage ring demands a high slew rate which is caused by the rapid change of the beam current exceeding the operational limit of the SQUID in flux-locked loop mode. Previous solutions to increase the slew rate used a LCR first-order low-pass filter were a small resistor, unfortunately, dominated the current noise of the CCC. In this work we present a novel take by adding a second resonator into the CCC which in turn allows for higher resistances of the LCR low-pass filter and therefore lower thermal current noise. A second challenge connected with this CCC approach is the residual magnetization of the highly permeable magnetic core and the resulting shielding currents in the superconducting circuits of the CCC. The timing of a storage ring in the range of minutes opens a way to reduce these DC currents using a LR high-pass filter. Using serial sub-micro ohm resistors, time constants in the hour range can be achieved to improve the stability and performance of the CCC system.

In this paper, open loop and closed loop Tunneling Magnetoresistance (TMR) DC Current Transformers (DCCTs) for ion beam diagnostics are presented. The DCCTs employ MR sensors to measure the DC component of the accelerator’s ion beam. A comparative study between Giant Magnetoresistance (GMR) and TMR sensors is presented to illustrate the sensor selection criterion for the DCCT application. The two proposed DCCTs are studied in open and closed loop configurations. A closed loop feedback electronic system is designed to generate a feedback current equivalent to the ion beam current such that the sensor operates at zero flux. Furthermore, theoretical and experimental results for the TMR-based DCCT including noise analysis are presented for both open loop and closed loop configurations. Both configurations’ minimum detectable currents are in the range of microampere. The proposed closed loop hardware prototype has a settling time of less than 15 μs. The measured minimum detectable currents for the open and closed loop TMR-based DCCTs are 128.2 μA/Hz and 10.14 μA/Hz at 1 Hz, respectively.

This paper presents a new shield configuration for cryogenic current comparators (CCCs), namely the folded coaxial geometry. An analytical model describing its shielding performance is first developed, and then validated by means of finite element simulations. Thanks to this model, the fundamental properties of the new shield are highlighted. Additionally, this paper compares the volumetric performance of the folded coaxial shield to the one of a ring shield, the latter being installed in many CCCs for measuring particle beam currents in accelerator facilities.

A Cryogenic Current Comparator (CCC) is an extremely sensitive DC-Beam Transformer based on superconducting SQUID technology. Recently, a CCC without a toroidal core and with an axially oriented magnetic shielding has been developed at the Institute of Photonic Technologies (IPHT) Jena/Germany. It represents a compact and lightweight alternative to the ‘classical’ CC, which was originally developed at PTB Braunschweig/Germany and is successfully in operation in accelerators at GSI and CERN. Excellent low-frequency noise performance was demonstrated with a prototype of this new CCC-type. Current measurements and further tests are ongoing, first results are presented together with simulation calculations for the magnetic shielding. The construction from lead as well as simplified manufacturing results in drastically reduced costs compared to formerly used Nb-CCCs. Reduced weight also puts less constraints on the cryostat. Based on highly sensitive SQUIDs, the new prototype device shows a current sensitivity of about 6 pA/Hz1/2 in the white noise region. The measured and calculated shielding factor is ~135 dB. These values, together with a significant cost reduction resulting also from a compact cryostat design opens up the way for widespread use of CCCs in modern accelerator facilities.

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.

The new version of a cryogenic current comparator with eXtended dimensions (CCC-XD) for the beam monitoring of charged particles, which is currently in the optimization cycle, is presented herein. The CCC-XD is designed for a nondestructive, highly sensitive monitoring of a few nA beam intensities for 150-mm beamline diameters at the Facility for Antiproton and Ion Research at GSI (Helmholtz Center of Heavy Ion Research). The new CCC comprises a combined superconducting pickup loop, a magnetic shield, and a ferrite core with superconducting quantum interference device based readout. Compared to the previous CCC currently running at CERN, the niobium shield exhibits enlarged geometric dimensions, which results in a more effective suppression of magnetic stray fields from the beamline environment. First results of laboratory measurements as well as simulations of the electrical behavior are presented in this paper. The CCC-XD system—in combination with a newly developed cryostat—will be ready for testing in the beamline of CRYRING at GSI in 2018.

We present the beam instrumentation of CRYRING@ESR, a low-energy experiment facility at the GSI Helmholtz-Centre for heavy ion research. The 1.44 Tm synchrotron and storage ring, formerly hosted at the Manne Siegbahn laboratory in Stockholm, Sweden, was modified in its configuration and installed behind the existing ESR, the experimental storage ring. As the first machine within the ongoing FAIR project, the facility for antiproton and ion research, it is built on the future timing system and frameworks for data supply and acquisition. Throughout the past year CRYRING was commissioned including its electron cooler with hydrogen beams from the local linear accelerator. Storage, acceleration and cooling have been demonstrated. The contribution provides an overview of the beam instrumentation. The design of the detector systems and their current performance are presented. Emphasis is given to beam position monitors, detectors for intensity measurements, and the ionization profile monitors.

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.

Nowadays, cryogenic current comparators (CCCs) are among the most accurate devices for measuring extremely small electric currents. This feature motivates the use of CCCs for beam instrumentation in particle accelerators. This paper presents and discusses some numerical techniques to assess the performance of such devices. In particular a 2.5D finite element model is developed. Finally, by exploiting the available numerical tools, an optimisation of the CCC geometrical dimensions is performed and analysed.