HIJ, Jena, Germany
IPHT, Jena, Germany
TEMF, TU Darmstadt, Darmstadt, Germany
FSU Jena, Jena, Germany
GSI, Darmstadt, Germany
IOQ, Jena, Germany
CERN, Geneva, Switzerland
Supracon AG, Jena, Germany
The non-destructive and highly sensitive measurement of a charged particle beam is of utmost importance for modern particle accelerator facilities. A Cryogenic Current Comparator (CCC) can be used to measure beam currents in the nA-range. Therein, charged particles passing through a superconducting toroid induce screening currents at the surface of the toroid, which are measured via SQUIDs. Classical CCC beam monitors make use of a high magnetic permeability core as a flux-concentrator for the pickup coil. The core increases the pickup inductance and thus coupling to the beam, but unfortunately also raises low-frequency noise and thermal drift. In the new concept from the Leibniz Institute of Photonic Technology the Coreless Cryogenic Current Comparator (4C) completely omits this core and instead uses highly sensitive SQUIDs featuring sub-micron cross-type Josephson tunnel junctions. Combined with a new shielding geometry a compact and comparably lightweight design has been developed, which exhibits a current sensitivity of about 6 pA/sqrt(Hz) in the white noise region and a measured shielding factor of about 134 dB*.
* V. Zakosarenko et al., Coreless SQUID-based cryogenic current comparator for non-destructive intensity diagnostics of charged particle beams, Supercond. Sci. Technol. 32 (2019) 014002.
