Enabling Real-Time Impedance Measurements of Operational Superconducting Circuits of Accelerator Magnets

Impedance measurements of superconducting circuits routinely serve as means to anticipate their dynamic response and validate their electrical integrity. Usual procedures involve performing tests on non-powered systems during commissioning and maintenance periods. However, impedance measurements might have a strong potential in diagnostics of powered superconducting circuits as well. In particular, they should allow for on-line fault monitoring, enhanced quench detection, and deeper insight into the electrical properties of the circuits such as impedance variations or non-linear effects in the operational conditions. This paper outlines the design of an experimental platform enabling such an evaluation. In essence, this system is capable of injecting electrical stimuli into a magnet circuit and capturing the response. The acquired data are processed in order to extract circuit characteristics, in particular the impedance and its temporal evolution. In addition to discussing key design considerations related to measurement performance such as bandwidth, resolution, and sensitivity, the paper explores how to maintain transparent operation with respect to peripheral components such as the power converters and quench protection systems. Finally, the paper presents the validation campaign of the designed solution. The validation consists of two stages, including non-powered and powered superconducting circuits. The former case compares performance of the system to a state-of-the-art industrial impedance analyser, while the latter focuses on the impact the system has on peripheral components. Presented conclusions provide guidelines for front-end instrumentation design and data processing in order to enhance performance evaluation of superconducting circuits in their entire operational spectrum

The ALICE experiment at the CERN LHC

ALICE (A Large Ion Collider Experiment) is a general-purpose, heavy-ion detector at the CERN LHC which focuses on QCD, the strong-interaction sector of the Standard Model. It is designed to address the physics of strongly interacting matter and the quark-gluon plasma at extreme values of energy density and temperature in nucleus-nucleus collisions. Besides running with Pb ions, the physics programme includes collisions with lighter ions, lower energy running and dedicated proton-nucleus runs. ALICE will also take data with proton beams at the top LHC energy to collect reference data for the heavy-ion programme and to address several QCD topics for which ALICE is complementary to the other LHC detectors. The ALICE detector has been built by a collaboration including currently over 1000 physicists and engineers from 105 Institutes in 30 countries. Its overall dimensions are 161626 m3 with a total weight of approximately 10 000 t. The experiment consists of 18 different detector systems each with its own specific technology choice and design constraints, driven both by the physics requirements and the experimental conditions expected at LHC. The most stringent design constraint is to cope with the extreme particle multiplicity anticipated in central Pb-Pb collisions. The different subsystems were optimized to provide high-momentum resolution as well as excellent Particle Identification (PID) over a broad range in momentum, up to the highest multiplicities predicted for LHC. This will allow for comprehensive studies of hadrons, electrons, muons, and photons produced in the collision of heavy nuclei. Most detector systems are scheduled to be installed and ready for data taking by mid-2008 when the LHC is scheduled to start operation, with the exception of parts of the Photon Spectrometer (PHOS), Transition Radiation Detector (TRD) and Electro Magnetic Calorimeter (EMCal). These detectors will be completed for the high-luminosity ion run expected in 2010. This paper describes in detail the detector components as installed for the first data taking in the summer of 2008

Next Generation of Quench Detection Systems for the High-Luminosity Upgrade of the LHC

Abstract: The foreseen upgrade of the large hadron collider (LHC) for high-luminosity operation will incorporate a new generation of high field superconducting magnets. In particular, the current inner triplet magnets in LHC experiments A Toroidal LHC Apparatus (ATLAS) and Compact Muon Solenoid (CMS) in points 1 and 5 will be replaced by novel large aperture Nb3 Sn quadrupole magnets. In addition, there will be a variety of new magnets based on NbTi conductors. For the magnet powering, the novel MgB2 based superconducting links will be used, thus allowing the installation of sensitive equipment such as power converters in radiation-free areas of the LHC. The protection of the superconducting elements will be ensured by various elements such as quench heaters and the recently developed coupling-loss induced quench system, which are triggered by a dedicated set of quench detection systems. These custom-made systems are the result of a complete new development and adapted to the specific features of the newly installed superconducting elements. This concerns in particular the Nb3 Sn based magnets, requiring an effective rejection of voltage spikes resulting from flux jumps and a dynamic setting of detection parameters when energizing the magnet. The new detection systems will be complemented by data acquisition systems, offering significantly higher sampling rates and resolution than previously installed systems

An Approach to Reliability Assessment of Complex Systems at CERN

This paper presents the systematic approach Reliability Requirements and Initial Risk Evaluation (RIRE) developed and used at CERN. RIRE is a four-step procedure, which provides a framework for the experience based derivation of quantitative reliability targets for CERN’s accelerator systems. These targets are not subject to statutory regulations. RIRE shows the risks posed by a system and prioritizes subsequent, more detailed analyses, such as Fault Tree. The application of RIRE to the quench detection system of the LHC super conducting magnets is shown in this paper. From this example is concluded that RIRE is suitable for the analysis of a complex system with context dependent functions.This paper presents the systematic approach Reliability Requirements and Initial Risk Evaluation (RIRE) developed and used at CERN. RIRE is a four-step procedure, which provides a framework for the experience based derivation of quantitative reliability targets for CERN’s accelerator systems. These targets are not subject to statutory regulations. RIRE shows the risks posed by a system and prioritizes subsequent, more detailed analyses, such as Fault Tree. The application of RIRE to the quench detection system of the LHC super conducting magnets is shown in this paper. From this example it is concluded that RIRE is suitable for the analysis of a complex system with context dependent functions

An Approach to Reliability Assessment of Complex Systems at CERN

This paper presents the systematic approach Reliability Requirements and Initial Risk Evaluation (RIRE) developed and used at CERN. RIRE is a four-step procedure, which provides a framework for the experience based derivation of quantitative reliability targets for CERN’s accelerator systems. These targets are not subject to statutory regulations. RIRE shows the risks posed by a system and prioritizes subsequent, more detailed analyses, such as Fault Tree. The application of RIRE to the quench detection system of the LHC super conducting magnets is shown in this paper. From this example is concluded that RIRE is suitable for the analysis of a complex system with context dependent functions.This paper presents the systematic approach Reliability Requirements and Initial Risk Evaluation (RIRE) developed and used at CERN. RIRE is a four-step procedure, which provides a framework for the experience based derivation of quantitative reliability targets for CERN’s accelerator systems. These targets are not subject to statutory regulations. RIRE shows the risks posed by a system and prioritizes subsequent, more detailed analyses, such as Fault Tree. The application of RIRE to the quench detection system of the LHC super conducting magnets is shown in this paper. From this example it is concluded that RIRE is suitable for the analysis of a complex system with context dependent functions

Next Generation of Quench Detection Systems for the High-Luminosity Upgrade of the LHC

Abstract: The foreseen upgrade of the large hadron collider (LHC) for high-luminosity operation will incorporate a new generation of high field superconducting magnets. In particular, the current inner triplet magnets in LHC experiments A Toroidal LHC Apparatus (ATLAS) and Compact Muon Solenoid (CMS) in points 1 and 5 will be replaced by novel large aperture Nb3 Sn quadrupole magnets. In addition, there will be a variety of new magnets based on NbTi conductors. For the magnet powering, the novel MgB2 based superconducting links will be used, thus allowing the installation of sensitive equipment such as power converters in radiation-free areas of the LHC. The protection of the superconducting elements will be ensured by various elements such as quench heaters and the recently developed coupling-loss induced quench system, which are triggered by a dedicated set of quench detection systems. These custom-made systems are the result of a complete new development and adapted to the specific features of the newly installed superconducting elements. This concerns in particular the Nb3 Sn based magnets, requiring an effective rejection of voltage spikes resulting from flux jumps and a dynamic setting of detection parameters when energizing the magnet. The new detection systems will be complemented by data acquisition systems, offering significantly higher sampling rates and resolution than previously installed systems

Upgrade of the Protection System for the Superconducting Elements of the LHC During LS1

During the first long shutdown (LS1) of the Large Hadron Collider (LHC), the protection system for the superconducting elements of the LHC will substantially be upgraded with the principal objectives to extend its diagnostic capabilities and to enhance the system immunity to ionizing radiation. All proposed measures will improve the overall system dependability as well. The supervision of the quench heater circuits of the LHC main dipoles will be enhanced by adding additional measurement channels for the discharge current and increasing the sampling frequency and resolution of the related data acquisition systems. By these measures it will be possible to identify potential fault states of the quench heater circuits, which may affect the integrity of the concerned magnets. At this occasion all main dipole protection systems will be submitted to general overhaul after four years of successful operation. Within the radiation to electronics project, the upgrade of the protection systems will be concluded by installing the latest versions of radiation tolerant quench detection electronics. In addition some equipment will be relocated to shielded areas

New Quench Detection System to Enhance Protection of the Individually Powered Magnets in the Large Hadron Collider

To further improve the existing Quench Detection System (QDS) of individually powered magnets installed in the Large Hadron Collider (LHC), a new radiation tolerant electronic board was developed. The board provides three signal acquisition channels. It is able to acquire with different and configurable signal resolution and acquisition rate the analog signals of different properties. These enhancements enable the application of different quench detection algorithms depending on the protected magnet. Additionally, the board can be used with newly developed current derivative sensors for reliable detection of symmetric quenches. The new system supports both open and closed loop current sensors

Enhanced Diagnostic Systems for the Supervision of the Superconducting Circuits of the LHC

Being an integral part of the protection system for the superconducting circuits of the LHC, the data acquisition systems used for the circuit supervision underwent a substantial upgrade during the first long shutdown of the LHC. The sampling rates and resolution of most of the acquired signals increased significantly. Newly added measurements channels like for the supervision of the quench heater circuits of the LHC main dipoles allow identifying specific fault states. All LHC main circuits are meanwhile equipped with earth voltage feelers allowing monitoring the electrical insulation strength, especially during the fast discharges. The protection system for the bus-bar splices is now capable to operate in different modes. By this measure, it is possible fulfilling the requirements for different specific tests like the warm bus-bar measurements and current stabilizer continuity measurements (CSCM) without field interventions