GSI, Darmstadt, Germany
TEMF, TU Darmstadt, Darmstadt, Germany
IPHT, Jena, Germany
FSU Jena, Jena, Germany
IOQ, Jena, Germany
HIJ, Jena, Germany
Supracon AG, Jena, Germany
The Cryogenic Current Comparator (CCC) at the heavy-ion storage ring CRYRING@ESR at GSI provides a calibrated non-destructive measurement of beam current with a resolution of 10 nA or better. With traditional diagnostics in storage rings or transfer lines a non-interceptive absolute intensity measurement of weak ion beams (< 1 µA) is already challenging for bunched beams and virtually impossible for coasting beams. Therefore, at these currents the CCC is the only diagnostics instrumentation that gives reliable values for the beam intensity independently of the measured ion species and without the need for tedious calibration procedures. Herein, after a brief review of the diagnostic setup, an overview of the operation of the CCC with different stored ion beams at CRYRING is presented. The current reading of the CCC is compared to the intensity signal of various standard instrumentations including a Parametric Current Transformer (PCT), an Ionization Profile Monitor (IPM) and the Beam Position Monitors (BPMs). It was shown that the CCC is a reliable instrument to monitor changes of the beam current in the range of nA.
HIJ, Jena, Germany
GSI, Darmstadt, Germany
IOQ, Jena, Germany
IPHT, Jena, Germany
FSU Jena, Jena, Germany
Supracon AG, Jena, Germany
Cryogenic Current Comparators (CCC) are presently used at CERN-AD (100 mm beamline diameter) and in the FAIR project at CRYRING (150 mm beamline diameter) for non-destructive absolute measurement of beam currents below 20 ’A (current resolution 10 nA). Both sensor versions (CERN-Nb-CCC and FAIR-Nb-CCC-XD) use niobium as superconductor for the DC-transformer and magnetic shielding. The integrated flux concentrators have an inductance of below 100 ’H at 4.2 Kelvin. The new Sm-series (smart & small) is designed for a beamline diameter of 63 mm and uses lead for the superconducting shield. The first sensor (IFK-Pb-DCCC-Sm-200) has two core-based pickup coils (2x 100 µH at 4.2 K) and two SQUID units, to eliminate Barkhausen current jumps as part of the low frequency 1/f-noise. During the construction some basic experiments on noise behavior (fluctuation’dissipation theorem, white noise below 2 pA/sqrt(Hz)) and magnetic shielding (flux concentrator and shielding as LC circuit resonance , additional mu-metal shielding) were undertaken, the results of which are presented here. Finally, a current resolution of 500 pA could be achieved in the laboratory.
