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At the CERN Super Proton Synchrotron (SPS) the proton beam is supplied to the fixed target experiments in the North Area facility (NA) via a slow extraction process, taking place at 400 GeV. The monitoring of the spill quality during the extraction, lasting 4.8 seconds with the present SPS setup, is of high interest for minimising beam losses and providing the users with uniform proton-on-target rates. The monitor development challenges include the need for detecting, sampling, processing and publishing the data at rates ranging from few hundred Hz to support the present operation to several hundreds of MHz to serve future experiments proposed within the Physics Beyond Collider (PBC) programme. This paper will give an overview of the ongoing studies for optimizing the existing monitors performances and of the R dedicated to future developments. Different techniques are being explored, from Secondary Emission Monitors to Optical Transition Radiation (OTR), Gas Scintillation and Cherenkov detectors. Expected ultimate limitations from the various methods will be presented, together with 2022 experimental results, for example with a recently refurbished OTR detector., Proceedings of the 11th International Beam Instrumentation Conference, IBIC2022, Kraków, Poland

The LHC injectors Upgrade (LIU) program has been fully implemented during the second long shutdown (LS2), which took place in 2019-20. In this context, new or upgraded beam instrumentation was developed to cope with H⁻ beam in LINAC4 and the new Proton Synchrotron Booster (PSB) injection systems which would provide high brightness proton beams in the rest of the injector complex. After a short overview of the newly installed diagnostics, the main focus of this paper will move to the instruments already commissioned with the beam. This will include LINAC4 diagnostics, the PSB H⁰/H⁻ monitor, the PSB Trajectory Measurement System, and the PS beam gas ionization monitor. In addition, particular emphasis will be given to the first operational experience with the new generation of fast wire scanners installed in all injector synchronous., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

A Cryogenic Current Comparator (CCC) is a non-destructive, metrological-traceable charged particle beam intensity measurement system for the nano-ampere range. Using superconducting shielding and coils, low temperature Superconducting Quantum Interference Devices (SQUIDs) and highly permeable flux-concentrators, the CCC can operate in the frequency range from DC to several kHz or hundreds of kHz depending on the requirement of the application. Also, the white noise level can be optimized down to 2 pA/sqrt(Hz) at 2.16 K. This work compares three different Pb- and Nb-based CCC-sensors developed at the Institute of Solid State Physics and Leibniz Institute of Photonic Technology at Jena, Germany: CERN-Nb-CCC, optimized for applica-tion at CERN Antiproton Decelerator (AD) in 2015 with a free inner diameter of 185 mm; GSI-Pb-CCC, designed for GSI-Darmstadt with a free inner diameter of 145 mm, 1996 completed, 2014 upgraded; GSI-Nb-CCC-XD, de-signed for the GSI/FAIR-project with a free inner diame-ter of 250 mm, 2017 completed. The results of noise, small-signal, slew-rate, and drift measurements done 2015 and 2018 in the Cryo-Detector Lab at the University of Jena are presented here.

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*.

The CERN Linac4 has been successfully commissioned to its nominal energy and will provide 160 MeV H⁻ ions for charge-exchange injection into the Proton Synchrotron Booster (PSB) from 2020. A complete set of beam diagnostic devices has been installed along the accelerating structures and the transfer line for safe and efficient operation. This includes two longitudinal Bunch Shape Monitors (BSM) developed by the Institute for Nuclear Research (INR, Moscow). Setting-up the RF cavities of Linac4 involves beam loading observations, time-of-flight measurements and reconstruction of the longitudinal emittance from phase profile measurements. In this paper the BSM is presented along with some results obtained during accelerator commissioning, including a comparison with phase measurements performed using the Beam Position Monitor system., Proceedings of the 7\textsuperscript{th} Int. Beam Instrumentation Conf., IBIC2018, Shanghai, China

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., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

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., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

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*.

A Cryogenic Current Comparator (CCC) is a non-destructive, metrological-traceable charged particle beam intensity measurement system for the nano-ampere range. Using superconducting shielding and coils, low temperature Superconducting Quantum Interference Devices (SQUIDs) and highly permeable flux-concentrators, the CCC can operate in the frequency range from DC to several kHz or hundreds of kHz depending on the requirement of the application. Also, the white noise level can be optimized down to 2 pA/sqrt(Hz) at 2.16 K. This work compares three different Pb- and Nb-based CCC-sensors developed at the Institute of Solid State Physics and Leibniz Institute of Photonic Technology at Jena, Germany: CERN-Nb-CCC, optimized for applica-tion at CERN Antiproton Decelerator (AD) in 2015 with a free inner diameter of 185 mm; GSI-Pb-CCC, designed for GSI-Darmstadt with a free inner diameter of 145 mm, 1996 completed, 2014 upgraded; GSI-Nb-CCC-XD, de-signed for the GSI/FAIR-project with a free inner diame-ter of 250 mm, 2017 completed. The results of noise, small-signal, slew-rate, and drift measurements done 2015 and 2018 in the Cryo-Detector Lab at the University of Jena are presented here.

The storage of low current beams as well as the long extraction times from the synchrotrons at FAIR require non-destructive beam intensity monitoring with a current resolution of nanoampere. To fulfill this requirement, the concept of the Cryogenic Current Comparator (CCC), based on the low temperature SQUID, is used to obtain an extremely sensitive beam current transformer. During the last years, CCCs have been installed to do measurements of the spill structure in the extraction line of GSI SIS18 and for current monitoring in the CERN Antiproton Decelerator. From these experiences lessons can be learned to facilitate further developments. The goal of the ongoing research is to improve the robustness of the CCC towards external influences, such as vibrations, stray fields and He-pressure variations, as well as to develop a cost-efficient concept for the superconducting shield and the cryostat., Proceedings of the 7\textsuperscript{th} Int. Beam Instrumentation Conf., IBIC2018, Shanghai, China

Triggered by the need for current measurement in the nA range for slow extracted beams and for the beams in the storage rings at FAIR and CERN, the idea of the CCC as a current transformer has been revitalized during the last ten years. Compared to the first prototype, developed at GSI in the 90s, the second generation of CCCs is based on the possibility of detailed simulation of superconducting magnetic shielding properties, new nano-crystalline materials for the magnetic ring-cores, and on superior commercially available SQUID systems. In 2014, nA resolution measurements at 2 kHz bandwidth demonstrated the possibility of spill analysis at slow extracted beams from GSI SIS18. In the following year, the first stand-alone CCC system, including a cryostat with separate He liquefier, started operation in the CERN AD. Although the existing systems show an outstanding current resolution, their cost efficiency and robustness, as well as noise and vibration sensitivity can still be improved, which is subject of ongoing research. In this contribution recent results of our CCC tests are shown and future developments are discussed., Proceedings of the 6th Int. Beam Instrumentation Conf., IBIC2017, Grand Rapids, MI, USA

Low-intensity charged particle beams are particularly challenging for non-perturbative beam diagnostics due to the small amplitude of induced electromagnetic fields. The Antiproton Decelerator (AD) and Extra Low ENergy Antiproton (ELENA) rings at CERN decelerate beams containing 10⁷ antiprotons. An absolute intensity measurement of the circulating beam is essential to monitor the operational efficiency and to provide important calibration data for the antimatter experiments. This paper reviews the design of an operational Cryogenic Current Comparator (CCC) based on Superconducting QUantum Interference Device (SQUID) for current and intensity monitoring in the AD. Such a system has been operational throughout 2017, relying on a stand-alone cryogenic infrastructure based on a pulse-tube cryocooler. System performance is presented and correlated with different working environments, confirming a resolution in the nanoampere range., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

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., Proceedings of the 5th Int. Beam Instrumentation Conf., IBIC2016, Barcelona, Spain

The construction, installation and initial commissioning of CERN's LINAC4 was completed in 2016 with H⁻ ions successfully accelerated to its top energy of 160 MeV. The accelerator is equipped with a large number of beam diagnostic systems that are essential to monitor, control and optimize the beam parameters. A general overview of the installed systems and their functional specifications will be followed by a summary of the most relevant results. This includes transverse profile monitors (wire scanners, wire grids and a laser profile monitor), beam position and phase monitors (whose ToF measurements were essential for adjusting RF cavity parameters), beam loss monitors, beam current transformers and longitudinal beam shape monitors. This contribution will also cover the beam instrumentation for the so-called PSB Half Sector Test, which has been temporarily installed in the LINAC4 transfer line to study H⁻ stripping efficiency. At this facility it was possible to test the new H⁰/H⁻ beam current monitor, designed to monitor the stripping efficiency and an essential element of the beam interlock system when the LINAC4 is connected to the PSB in 2019., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

Several laboratories have shown the potential of Cryogenic Current Comparators (CCC) for an absolute measurement of beam intensity down to the nA level. This type of current monitor relies on the use of Superconducting QUantum Interference Device (SQUID) magnetometers and superconductor magnetic shields. CERN, in collaboration with GSI Helmholtz Centre for Heavy Ion Research, Jena University, and the Helmholtz Institute Jena are currently developing an improved version of such a current monitor for the Antiproton Decelerator (AD) and Extra Low ENergy Antiproton (ELENA) rings. The primary goals are a better current measurement accuracy and overall enhanced system availability. This contribution presents the design of the CCC, an estimation of its resolution, dynamic limitations of the SQUID, as well as a description of the modifications to the coupling circuit and cryostat that were required to optimize the monitor for the anticipated beam parameters. First results from beam measurements are also presented. To our knowledge these are the first CCC beam current measurements performed in a synchrotron and the first to be performed with both coasting and bunched beams., Proceedings of the 4th International Beam Instrumentation Conference, IBIC2015, Melbourne, Australia

CERN’s Proton Synchrotron Booster (PSB) is undergoing a major upgrade program in the frame of the LHC Injectors Upgrade (LIU) project. During the first long LHC shutdown (LS1) some parts of the upgrade have already been implemented, and the machine has been successfully re-commissioned. More work is planned for the upcoming end-of-year technical stops, notably in 2016/17, while most of the upgrade is planned to take place during the second long LHC shutdown (LS2). We report on the upgrade items already completed and commissioned, the first Run 2 beam performance and give a status of the ongoing design and integration work., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

As part of the CERN LHC injector chain upgrade, LINAC4 will accelerate H⁻ ions to 160 MeV, replacing the old 50 MeV proton linac. The ion source, the Low Energy Beam Transfer (LEBT) line, the 3 MeV Radio Frequency Quadrupole and the Medium Energy Beam Transfer (MEBT) line hosting a chopper, have been first commissioned in a dedicated test stand and are now tested in the LINAC4 tunnel. Diagnostics devices are installed in the LEBT and MEBT line and in a movable diagnostics test bench which is temporarily added to the MEBT exit. The paper gives an overview of all the instruments used, including beam current transformers, beam position monitors, wire scanners and wire grids for transverse profile measurements, a longitudinal bunch shape monitor and a slit-and-grid emittance meter. The movable test bench also includes a spectrometer that allows measuring the beam energy spread in conjunction with a wire grid. The present understanding of the instrumentation performance is discussed and the measurement results that allowed characterizing the 3 MeV beam in the LINAC4 tunnel are summarized., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

As part of the CERN LHC injector chain upgrade, LINAC4 will accelerate H^{−} ions to 160 MeV, replacing the old 50 MeV proton linac. The ion source, the Low Energy Beam Transfer (LEBT) line, the 3 MeV Radio Frequency Quadrupole and the Medium Energy Beam Transfer (MEBT) line hosting a chopper, have been first commissioned in a dedicated test stand and are now tested in the LINAC4 tunnel. Diagnostics devices are installed in the LEBT and MEBT line and in a movable diagnostics test bench which is temporarily added to the MEBT exit. The paper gives an overview of all the instruments used, including beam current transformers, beam position monitors, wire scanners and wire grids for transverse profile measurements, a longitudinal bunch shape monitor and a slit-and-grid emittance meter. The movable test bench also includes a spectrometer that allows measuring the beam energy spread in conjunction with a wire grid. The present understanding of the instrumentation performance is discussed and the measurement results that allowed characterizing the 3 MeV beam in the LINAC4 tunnel are summarized.

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*., Proceedings of the 8th International Beam Instrumentation Conference, IBIC2019, Malmö, Sweden

A Cryogenic Current Comparator (CCC) is a non-destructive, metrological-traceable charged particle beam intensity measurement system for the nano-ampere range. Using superconducting shielding and coils, low temperature Superconducting Quantum Interference Devices (SQUIDs) and highly permeable flux-concentrators, the CCC can operate in the frequency range from DC to several kHz or hundreds of kHz depending on the requirement of the application. Also, the white noise level can be optimized down to 2 pA/sqrt(Hz) at 2.16 K. This work compares three different Pb- and Nb-based CCC-sensors developed at the Institute of Solid State Physics and Leibniz Institute of Photonic Technology at Jena, Germany: CERN-Nb-CCC, optimized for applica-tion at CERN Antiproton Decelerator (AD) in 2015 with a free inner diameter of 185 mm; GSI-Pb-CCC, designed for GSI-Darmstadt with a free inner diameter of 145 mm, 1996 completed, 2014 upgraded; GSI-Nb-CCC-XD, de-signed for the GSI/FAIR-project with a free inner diame-ter of 250 mm, 2017 completed. The results of noise, small-signal, slew-rate, and drift measurements done 2015 and 2018 in the Cryo-Detector Lab at the University of Jena are presented here., Proceedings of the 7\textsuperscript{th} Int. Beam Instrumentation Conf., IBIC2018, Shanghai, China

Linac4 is a normal conducting 160 MeV H⁻ linear accelerator presently being installed and progressively commissioned at CERN. It will replace the ageing 50 MeV Linac2 as injector of the PS Booster (PSB), increasing at the same time its brightness by a factor of two thanks to the higher injection energy. This will be the first step of a program to increase the beam intensity in the LHC injectors for the needs of the High-Luminosity LHC project. After a series of beam measurements on a dedicated test stand the 3 MeV Linac4 front-end, including ion source, RFQ and a beam chopping line, has been recommissioned at its final position in the Linac4 tunnel. Commissioning of the following section, the Drift Tube Linac, is starting. Beam commissioning will take place in steps of increasing energy, to reach the final 160 MeV in 2015. An extended beam measurement phase including testing of stripping equipment for the PSB and a year-long test run to assess and improve Linac4 reliability will take place in 2016, prior to the connection of Linac4 to the PSB that will take place during the next long LHC shut-down., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

In the low-energy Antiproton Decelerator (AD) and the Extra Low ENergy Antiproton (ELENA) rings at CERN, an absolute measurement of the beam intensity is essential to commission and troubleshoot the different accelerator systems, to measure the operational efficiency, and to provide calibration information for the different experiments using the antiproton (p) beam. Both the AD and ELENA are synchrotron decelerators, operating with both bunched and debunched - Direct Current (DC) - beams. The beam currents can be smaller than 100 nA, and the total number of circulating particles is of the order of 10^7. Non-intercepting measurements of low-intensity charged particle beams are particularly challenging due to the low amplitude of the induced electromagnetic fields. This is even more difficult for DC beams. The most common diagnostics that are able to measure DC beams are the DC Current Transformers (DCCTs), but these present considerable limitations when used to measure low-intensity beams, since these are limited in current resolution to 1 µA. In the AD a longitudinal-Schottky (Schottky) monitor is currently used for intensity measurements but this presents several limitations, including accuracy errors above 10 %. Several laboratories have shown in the past the potential of Superconducting QUantum Interference Device (SQUID)-based Cryogenic Current Comparator (CCC), using Low-Temperature Superconductors (LTS) technology, to measure beam current intensities of slowly varying beams in the nano-ampere range. However, previous CCC beam monitors suffered from a strong susceptibility to mechanical vibrations, and ElectroMagnetic Interference (EMI) perturbations, and also presented limited availability which limited their operational use. Additionally, these were never able to cope with short bunched beams in a synchrotron accelerator. In the present work a CCC system was developed for the AD machine. This monitor was optimised in terms of its current resolution, ability to cope with short bunched beams and overall system stability. Also, a dedicated cryostat was designed and fabricated to house the CCC, and to be installed in the AD beam line, aiming at decoupling external mechanical vibrations from the monitor, and to have a reduced heat in-leak, allowing for a standalone operation with an external liquid helium reliquefier. The new monitor was characterized in laboratory and different measurements are presented. Measurements with real beam were also performed in the AD, and the resolution and accuracy of beam current and beam intensity measurements were assessed. Optimal beam current resolutions of 2.5 nA, and beam intensity resolutions of 1.2 × 10^4 charges (at the highest beam energy) were obtained. However, the limiting factor in the obtained absolute measurement accuracy was the observed drift of the zero beam baseline, which could amount to 25 nA. These are the first CCC beam current and intensity measurements ever performed in a synchrotron machine with both coasting and short bunched beams. Future improvements could be obtained by studying the origin and effect of the external perturbations causing the observed drift, leading to the implementation of mitigation and compensation techniques.