Application Driven Optimization of Cryogenic Current Comparators (CCC) for Beam Storage Rings

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...

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Bibliographic Details
Published in:IEEE transactions on applied superconductivity 2021-08, Vol.31 (5), p.1-4
Main Authors: Stapelfeld, Max, Schmidl, Frank, Seidel, Paul, Stuck, S., Tympel, Volker, Stohlker, Thomas, Haider, David, Schwickert, Marcus, Sieber, Thomas, Schmelz, Matthias, Schonau, Thomas, Stolz, Ronny
Format: Article
Language:English
Subjects:
Beam currents
Charged particles
Comparators
Current comparators
High pass filters
Inductance
Low pass filters
Magnetic cores
Magnetic field measurement
Magnetic noise
Magnetic permeability
magnetic sensors superconductivity
Magnetic shielding
measurement errors
Moving charged particles
Optimization
particle beam measurements sensors
Particle beams
Resistors
Slew rate
SQUIDs
Storage rings (particle accelerators)
superconducting coils
superconducting devices
Superconducting magnets
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Summary: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.
ISSN:1051-8223
1558-2515
DOI:10.1109/TASC.2021.3058082