The field description for the Large Hadron Collider

This thesis deals with the formulation of a static and dynamic field model as well as a set of scaling laws that together form the core of the feed-forward control system. This work also includes numerous magnetic measurements on the superconducting magnets in cryogenic conditions which enable the extraction of the parameters used in the model

The Dependence of the Field Decay on the Powering History of the LHC Superconducting Dipole Magnets

The decay of the allowed multipoles in the Large Hadron Collider (LHC) dipoles is expected to perturb the beam stability during the particle injection. The decay amplitude is largely affected by the powering history of the magnet and is particularly dependent on the pre-cycle flat-top current and duration as well as the pre-injection preparation duration. With possible prospects of having different genres of cycles during the LHC operation, the powering history effect must be taken into account in the Field Description Model for the LHC and must hence be corrected during machine operation. This paper presents the results of the modelling of this phenomenon

The Field Description Model for the LHC Quadrupole Superconducting Magnets

The LHC control system requires an accurate forecast of the magnetic field and the multipole field errors to reduce the burden on the beam-based feed-back. The Field Description for the LHC (FIDEL) is the core of this forecast system and is based on the identification and physical decomposition of the effects that contribute to the total field in the magnet apertures. The effects are quantified using the data obtained from series magnetic measurements at CERN and they are consequently modelled empirically or theoretically depending on the complexity of the physical phenomena. This paper presents a description of the methodology used to model the field of the LHC magnets particularly focusing on the results obtained for the LHC main quadrupoles (MQ) and insertion region wide aperture quadrupoles (MQY)

MDA-driven development of standard-compliant OSS components: the OSS/J inventory case-study.

The telecommunications-oriented Operational Support Systems (OSS) industry have recognised the value of technology independent modelling of OSS solutions as a way to reduce cost, add agility, validate and verify solution designs against architectural guidelines of an enterprise and most importantly provide traceability in the design methodology process. The challenges faced by the OSS community is how MDA tools can deliver the promise of advanced meta-modelling, model definition and validation and model transformation for both OSS software components and integration logic in the larger OSS landscape. This paper describes how an advanced extensible meta-modelling tool is used to build an OSS component following best practice industry guidelines. Extended MOF, extended executable OCL and a powerful transformation language are used to capture the constraints in the meta-models as well as models followed by complete, 100% code generation from models. Furthermore, meta-models are also developed to capture graphical user interface elements in conjunction with the inventory data models, which are then automatically translated into code. This work is the precursor for defining extensive meta-models for a component-based OSS infrastructure based on industry best practice, for adding high degree of formality to model specifications and for enabling the verification of domain requirements by executing the models through model snapshot creation, way before system implementation takes place

Dependence of the Static and Dynamic Field Quality of the LHC Superconducting Dipole Magnets on the Pre-Cycle Ramp Rate

The allowed multipoles in the Large Hadron Collider (LHC) superconducting dipole magnets decay whilst on a constant current plateau. It is known that the decay amplitude is largely affected by the powering history of the magnet, and particularly by the pre-cycle flat top current and duration and the pre-injection preparation duration. Recently, it was observed that the decay amplitude is also highly dependent on the pre-cycle ramp rate, which has an indirect effect also on the sample of data taken at constant field along the magnet loadlines. This is an important consideration to be included in the Field Description for the LHC (FiDeL), to cope with the difference between the test procedure followed for series tests and the expected cycles during the machine operation. This paper presents the results of the measurements performed to investigate this phenomenon and describes the method included in FiDeL to represent this dependence

Focusing Strength Measurements of the Main Quadrupoles for the LHC

More than 1100 quadrupole magnets of different types are needed for the Large Hadron Collider (LHC) which is in the construction stage at CERN. The most challenging parameter to measure on these quadrupoles is the integrated gradient (Gdl). An absolute accuracy of 0.1% is needed to control the beta beating. In this paper we briefly describe the whole set of equipment used for Gdl measurements: Automated Scanner system, Single Stretched Wire system and Twin Coils system, concentrating mostly on their absolute accuracies. Most of the possible inherent effects that can introduce systematic errors are discussed along with their preventive methods. In the frame of this qualification some of the magnets were tested with two systems. The results of the intersystem cross-calibrations are presented. In addition, the qualification of the measurement system used at the magnet manufacturer's is based on results of more than 40 quadrupole assemblies tested in cold conditions at CERN and in warm conditions at the vendor site

Measurement and Effects of the Magnetic Hysteresis on the LHC Crossing Angle and Separation Bumps

The superconducting orbit corrector magnets (MCBC, MCBY and MCBX) in the Large Hadron Collider (LHC) at CERN will be used to generate parallel separation and crossing angles at the interaction points during the different phases that will bring the LHC beams into collision. However, the field errors generated by the inherent hysteresis in the operation region of the orbit correctors may lead to unwanted orbit perturbations that could have a critical effect on luminosity. This paper presents the results obtained from dedicated cryogenic measurements on the orbit correctors and the resulting simulations performed to quantify the impact of the hysteresis on the LHC orbit

Electrical and Magnetic Performance of the LHC Short Straight Sections

The Short Straight Section (SSS) for the Large Hadron Collider arcs, containing in a common cryostat the lattice quadrupoles and correction magnets, have now entered series production. The foremost features of the lattice quadrupole magnets are a two-in-one structure containing two 56 mm aperture, two-layers coils wound from 15.1 mm wide NbTi cables, enclosed by the stainless steel collars and ferromagnetic yoke, and inserted into the inertia tube. Systematic cryogenic tests are performed at CERN in order to qualify these magnets with respect to their cryogenic and electrical integrity, the quench performance and the field quality in all operating conditions. This paper reports the main results obtained during tests and measurements in superfluid helium. The electrical characteristics, the insulation measurements and the quench performance are compared to the specifications and expected performances for these magnets. The field in the main quadrupole is measured using three independent systems: 10-m long twin rotating coils, an automatic scanner, and single stretched wire. A particular emphasis is given to the integrated transfer function which has a spread of around 12 units rms in the production and is a critical issue. The do-decapole harmonic component, which required trimming through a change in coil shims, is also discussed. Finally, the magnetic axis measurements at room temperature and at 1.9 K, providing the nominal vertical shift for installation are reported

A Demonstration Experiment for the Forecast of Magnetic Field and Field Errors in the Large Hadron Collider

In order to reduce the burden on the beam-based feedback, the Large Hadron Collider control system is equipped with the Field Description for the LHC (FiDeL) which provides a forecast of the magnetic field and the multipole field errors. FiDeL has recently been extensively tested at CERN to determine main field tracking, multipole forecasting and compensation accuracy. This paper describes the rationale behind the tests, the procedures employed to power the main magnets and their correctors, and finally, we present the results obtained. We also give an indication of the prediction accuracy that the system can deliver during the operation of the LHC and we discuss the implications that these will have on the machine performance