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Publications by
Jessica Golm

All publications of HI Jena

2019

T. Sieber, H. D. Gersem, J. Golm, D. Haider, N. Marsic, W. Müller, H. Reeg, M. Schmelz, F. Schmidl, M. Schwickert, P. Seidel, T. Stöhlker, R. Stolz, J. Tan, G. Tranquille, V. Tympel, and V. Zakosarenko
Next Generation Cryogenic Current Comparator (CCC) for nA Intensity Measurement
(2019)

Abstract: 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’ CCC, which was originally developed at PTB Braunschweig 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.

J. Golm, R. Neubert, F. Schmidl, P. Seidel, V. Tympel, T. Stöhlker, F. Kurian, D. M. Haider, M. Schwickert, T. Sieber, M. Schmelz, R. Stolz, V. Zakosarenko, M. F. Fernandes, C. P. Welsch, J. Tan, H. D. Gersem, N. Marsic, and W. F. O. Müller
Different Versions of Cryogenic Current Comparators with Magnetic Core for Beam Current Measurements
(2019)

Abstract: 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.

2018

P. Seidel, V. Tympel, R. Neubert, J. Golm, M. Schmelz, R. Stolz, V. Zakosarenko, T. Sieber, M. Schwickert, F. Kurian, F. Schmidl, and T. Stöhlker
Cryogenic Current Comparators for Larger Beamlines
IEEE Transactions on Applied Superconductivity 28, 1 (2018)

Abstract: The non-destructive measurement of charged particle beams with intensities below 1 μA represents still a challenge in current R&D efforts. Beam peak-intensities of modern high power accelerators are in the range of milli-amperes, but for a large number of experiments, the pulse lengths have to be increased by several orders of magnitude (slow extraction process) to avoid saturation in the detectors. At the same time, the intensities of exotic ion- or antiproton-beams – depending on the production yield – might be in the range of nano-amperes or even below. The solution of this measurement problem should moreover include the possibility to calibrate the electrical current with traceability to national standards.

2017

V. Tympel, J. Golm, R. Neubert, P. Seidel, M. Schmelz, R. Stolz, V. Zakosarenko, F. Kurian, M. Schwickert, T. Sieber, and Th. Stöhlker
The Next Generation of Cryogenic Current Comparators for Beam Monitoring
Proceedings of the 5th International Beam Instrumentation Conference, IBIC 2016 (2017)

Abstract: A new Cryogenic Current Comparator with eXtended Dimensions (CCC-XD), compared to earlier versions built for GSI, 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:
1) flux concentrator,
2) superconducting shield against external magnetic field and a
3) superconducting toroidal coil of niobium which is read out by a
4) Superconducting Quantum Interference Device (SQUID).
The new flux concentrator (1) comprises a specially designed highly-permeable core made of nano-crystalline material, in order to assure low-noise operation with high system bandwidth of up to 200 kHz. The superconducting shielding of niobium (2) is extended in its geometric dimensions compared to the predecessor CCC and thus will suppress (better -200 dB) disturbing magnetic fields of the beamline environment more effectively. For the CCD-XD readout, new SQUID sensors (4) with sub-μm Josephson junctions are used which enable the lowest possible noiselimited current resolution in combination with a good suppression of external disturbances. The CCC-XD system, together with a new dedicated cryostat, will be ready for testing in the CRYRING at GSI in spring 2017. For the application of a CCC in the antiproton storage ring at CERN a pulse shape correction has been developed and tested in parallel. Results from electrical measurements of two components (1 and 4) of the new CCC-XD setup will be presented in this work.

2016

M. Fernandes, R. Geithner, J. Golm, R. Neubert, M. Schwickert, Th. Stöhlker, J. Tan, and C. P. Welsch
Non-perturbative measurement of low-intensity charged particle beams
Superconductor Science and Technology 30, 015001 (2016)

Abstract: Non-perturbative measurements of low-intensity charged particle beams are particularly challenging to 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 rings at CERN, an absolute measurement of the beam intensity is essential to monitor the operation efficiency. Superconducting quantum interference device (SQUID) based cryogenic current comparators (CCC) have been used for measuring slow charged beams in the nA range, showing a very good current resolution. But these were unable to measure fast bunched beams, due to the slew-rate limitation of SQUID devices and presented a strong susceptibility to external perturbations. Here, we present a CCC system developed for the AD machine, which was optimised in terms of its current resolution, system stability, ability to cope with short bunched beams, and immunity to mechanical vibrations. This paper presents the monitor design and the first results from measurements with a low energy antiproton beam obtained in the AD in 2015. These are the first CCC beam current measurements ever performed in a synchrotron machine with both coasting and short bunched beams. It is shown that the system is able to stably measure the AD beam throughout the entire cycle, with a current resolution of 30 nA .

M. Fernandes, R. Geithner, J. Golm, R. Neubert, M. Schwickert, Th. Stöhlker, J. Tan, and C. P. Welsch
Non-perturbative measurement of low-intensity charged particle beams
Superconductor Science and Technology 30, 015001 (2016)

Abstract: Non-perturbative measurements of low-intensity charged particle beams are particularly challenging to 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 rings at CERN, an absolute measurement of the beam intensity is essential to monitor the operation efficiency. Superconducting quantum interference device (SQUID) based cryogenic current comparators (CCC) have been used for measuring slow charged beams in the nA range, showing a very good current resolution. But these were unable to measure fast bunched beams, due to the slew-rate limitation of SQUID devices and presented a strong susceptibility to external perturbations. Here, we present a CCC system developed for the AD machine, which was optimised in terms of its current resolution, system stability, ability to cope with short bunched beams, and immunity to mechanical vibrations. This paper presents the monitor design and the first results from measurements with a low energy antiproton beam obtained in the AD in 2015. These are the first CCC beam current measurements ever performed in a synchrotron machine with both coasting and short bunched beams. It is shown that the system is able to stably measure the AD beam throughout the entire cycle, with a current resolution of 30 nA .