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

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

Design and Manufacturing of the First Industrial-Grade CLIQ Units for the Protection of Superconducting Magnets for the High-Luminosity LHC Project at CERN

The newly developed concept of Coupling-Loss Induced Quench (CLIQ) used in the domain of superconducting magnets quench protection has opened a new path towards efficient magnet protection. Subsequently to the first trials using ad hoc solutions in order to confirm functionality and performance of the method, two pre-series of three units each with different hardware configurations have been recently manufactured at CERN. Starting from the design phase, the hardware realization follows industrial standards and associated quality control. At the same time aspects related to the long term operation of the units have also been addressed. This paper discusses the design and manufacturing issues, the construction details and the decisions made on choices considering their operation in test stations and in a final accelerator environment. The results of the tests of these units before connecting them to a superconducting magnet will be presented and analyzed

Commissioning of the LHC Magnet Powering System in 2009

On 19th September 2008 the Large Hadron Collider (LHC) experienced a serious incident, caused by a defective electrical joint, which stopped beam operation just a few days after its beginning. During the following 14 months the damage was repaired, additional protection systems were installed and the measures to avoid a similar incident were taken, i.e. new layer of the Magnet Quench Protection System (nQPS) and more efficient He release valves. As a consequence, a large number of powering tests had to be repeated or carried out for the first time. The re-commissioning of the already existing systems as well as the commissioning of the new ones was carefully studied, then performed taking into account the history of each of the eight LHC sectors (either warmed-up or left at floating temperature). Moreover, a campaign of measurements of the bus-bar splice resistances as well as the ones internal to the cold masses was carried out with the original and the nQPS in order to spot out non conformities, thus assessing the risk of the LHC operation for the initial energy level. This paper discusses how the guidelines for the LHC 2009 re-commissioning were defined, providing a general principle to be used for the future re-commissionin

Beam-induced Quench Tests of LHC Magnets

At the end of the LHC Run1 a 48-hour quench-test campaign took place to investigate the quench levels of superconducting magnets for loss durations from nanoseconds to tens of seconds. The longitudinal losses produced extended from one meter to hundreds of meters and the number of lost protons varied from 10⁸ to 10¹³. The results of these and other, previously conducted quench experiments, allow the quench levels of several types of LHC magnets under various loss conditions to be assessed. The quench levels are expected to limit LHC performance in the case of steady-state losses in the interaction regions and also in the case of fast losses initiated by dust particles all around the ring. It is therefore required to accurately adjust beam loss abort thresholds in order to maximize the operation time. A detailed discussion of these quench test results and a proposal for additional tests after the LHC restart is presented

A New Cryogenic Test Facility for Large and Heavy Superconducting Magnets

CERN has recently designed and constructed a new cryogenic facility for testing large and heavy superconducting magnets at liquid helium temperatures. The facility, erected in a large assembly hall with cranes capable of up to 100 t, provides a cooling capacity of 1.2 kW at 4.5 K equivalent, 15-kW LN$_2$ cooling and warming capabilities for up to three magnets in parallel. The facility provides the required technical infrastructure for continuous and reliable operation. Test capabilities comprise electrical, cryogenics, vacuum and mechanical verification, and validation at ambient and liquid helium temperatures. A comprehensive survey and magnetic measurement system, comprising a hall-probe mapper, a rotating-coil magnetometer, a stretched wire, a translating fluxmeter, and a laser tracker, allows the detailed measurement of the magnetic field strength and quality on a large volume. The magnetic axes of the quadrupoles can be established within $\pm 0.2$ mm at $1 \sigma$ accuracy. The facility has been equipped with power supplies, three converters of $\pm 500$ A/120 V, and six converters of $\pm 600$ A/40 V, as well as the required energy extraction, quench protection, data acquisition, and interlocks for the testing of superconducting magnets for the FAIR project, currently under construction at the GSI Research Center, in Darmstadt, Germany. The versatile design of the facility, its layout, and testing capabilities complements CERN's other test infrastructures for large superconducting magnets. We report on the design, construction, and commissioning of the facility as well as the expected capabilities and performances for future tests of large and heavy superconducting magnets