The Multipoles Factory: an element of the LHC control (original) (raw)

Parametric field modeling for the lhc main magnets in operating conditions

2007 IEEE Particle Accelerator Conference (PAC), 2007

The first beam injections and current ramps in the LHC will require a prediction of the settings of the magnet current as well as the main correctors. For this reason we are developing a parametric model of the magnetic field generated by the LHC magnets that will provide the field dependence on current, ramp-rate, time, and history. The model of the field is fitted on magnetic field measurements performed during the acceptance tests of the magnets before their installation in the machine. In this paper we summarize the different steps necessary to select the relevant data and identify the parameters: the data extraction, the filtering and the validation of the measurements, and the fitting procedure that is used to obtain the parameters from the experimental results. The main result reported is a summary of the value of the parameters obtained with the above procedure, and describing the behavior of the magnetic field in the LHC main dipoles and quadrupoles.

The magnetic model of the LHC in the early phase of beam commissioning

…, 2010

The relation between field and current in each family of the Large Hadron Collider magnets is modelled with a set of empirical equations (FiDeL) whose free parameters are fit on magnetic measurements. They take into account residual magnetization, persistent currents, hysteresis, saturation, decay and snapback during initial part of the ramp. Here we give a first summary of the reconstruction of the magnetic field properties based on the beam observables (orbit, tune, coupling, chromaticity) and a comparison with the expectations. The most critical issues for the machine performance in terms of knowledge of the relation magnetic field vs current are pointed out.

Numerical Field Calculation in Support of the Hardware Commissioning of the LHC

IEEE Transactions on Applied Superconductivity, 2000

The hardware commissioning of the Large Hadron Collider (LHC) required the testing and qualification of the cryogenic and vacuum system, as well as the electrical systems for the powering of more than 10000 superconducting magnets. Non-conformities had to be resolved within a tight schedule. In this paper we focus on the role that electromagnetic field computation has played during hardware commissioning in terms of analysis of magnet quench, electromagnetic force calculations in busbars and splices, as well as field-quality prediction for the optimization of powering cycles.

The magnetic model of the large hadron collider

2011

The magnetic model of the LHC is based on a fit of the magnetic measurements through equations that model the field components (geometric, saturation, persistent) at different currents. In this paper we will review the main results related to the magnetic model during the run of the LHC in 2010-2011: with a top energy of 3.5 TeV, all components of the model but the saturation are visible. We first review the main results relative to the decay at injection plateau, dependence on powering history, and snapback at the beginning of the ramp for both tune and chromaticity. We discuss the precision obtained in tracking the magnets during the ramp, where the persistent current components gradually disappear. We conclude by presenting the behaviour of the quadrupoles model during the squeeze.

The Magnetic Field Model of the Large Hadron Collider: Overview of Operation at 3.5 and 4 TeV

2012

The magnetic model of the LHC is based on a fit of the magnetic measurements through equations that model the field components (geometric, saturation, persistent) at different currents. In this paper we will review the main results related to the magnetic model during the run of the LHC in 2010-2011: with a top energy of 3.5 TeV, all components of the model but the saturation are visible. We first review the main results relative to the decay at injection plateau, dependence on powering history, and snapback at the beginning of the ramp for both tune and chromaticity. We discuss the precision obtained in tracking the magnets during the ramp, where the persistent current components gradually disappear. We conclude by presenting the behaviour of the quadrupoles model during the squeeze.

Field display system for the forecast of beam momentum and betatron frequencies in LHC

1995

requirement. acceleration. The described system forms an important tool for meeting this synchronization of the magnetic fields is of vital importance during particle simultaneous measurements in dipole and quadrupoles. Precise expected betatron frequencies can be calculated from the results of the both at steady field conditions and during particle acceleration. The information about the focussing parameters. Measurements are performed momentum at central orbit. Reference quadrupoles provide the hysteresis and remanent field effects, and thus the value of particle characteristics such as the field integral in the bending magnets including reference dipole provides information about magnet excitation reference magnets connected in series with the main ring magnet strings. A (LHC). The method is based on magnetic field measurements in a set of momentum and betatron frequencies in the CERN Large Hadron Collider This note describes a measurement system for the forecast of particle Abstract KN. Henrichsen BEAM MOMENTUM AND BETATRON FREQUENCIES IN LHC FIELD DISPLAY SYSTEM FOR THE FORECAST OF 9 @5 LHC Note 308 CERN AT/95-02 (MA) CERN'AT'95'°2

Measurement and scaling laws of the sextupole component in the LHC dipole magnets

IPAC

One of the main requirements for the magnet operation of the Large Hadron Collider at CERN is the correction of the dynamic multipole errors produced. In particular, integrated sextupole errors in the main dipoles must be kept well below 0.1 units to ensure acceptable chromaticity. The feed-forward control of the LHC magnets is based on the Field Description for the LHC (FiDeL), a semi-empirical mathematical model capable of forecasting the magnet's behaviours in order to suitably power the corrector scheme. Measurement campaign were recently undertaken to validate the model making use of a novel Fast rotating-coil Magnetic Measurement Equipment (FAME), able to detect superconductor decay and snapback transient with unprecedented accuracy and temporal resolution. We discuss in this paper the test setup and some measurement results confirming the FiDeL model.

Production Follow-Up of the LHC Main Dipoles Through Magnetic Measurements at Room Temperature

IEEE Transactions on Appiled Superconductivity, 2004

In this paper we review the tools used for controlling the production of the LHC main dipoles through warm magnetic measurements. For the collared coil measurements, control limits are based on the statistics relative to the pre-series production. For the cold mass, the difference between collared coil and cold mass is considered, allowing a very stringent test. In both cases, measurements are split in straight part average, variations and coil ends contributions. Two different alarm levels exist in case the measured field is out of limits. The analysis can be carried out at the manufacturer and allows detection of anomalies in the measured magnetic field. These can be either due to wrong measurements or caused by assembly defects. Techniques used to work out information on the magnet assembly from the field harmonics are outlined. We summarize the experience gathered on about 180 collared coils and 120 cold masses, pointing out the bad cases and investigating the reliability of the measurements.

Compensation of third-harmonic field error in LHC main dipole magnets

2010 IEEE Instrumentation & Measurement Technology Conference Proceedings, 2010

One of the main requirements for the operations of the Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN) is a suitable correction of multipole errors in magnetic field. The feed-forward control of the LHC is based on the Field Description for the LHC (FiDel), capable of forecasting the magnet's behavior in order to generate adequate current ramps for main and corrector magnets. Magnetic measurements campaigns aimed at validating the model underlying FiDel highlighted the need for improving the harmonic compensation of the third-harmonic (b3) component of the main LHC dipoles. In this paper, the results of a new measurement campaign for b3 harmonic compensation, carried out through the new Fast Acquisition Measurement Equipment (FAME), are reported. In particular, the mechanism and the measurement procedure of the compensation, as well as the new perspectives opened by preliminary experimental results, are illustrated.

A system for series magnetic measurements of the LHC main quadrupoles

IEEE Transactions on Appiled Superconductivity, 2002

More than 400 twin aperture lattice quadrupoles are needed for the Large Hadron Collider (LHC) which is under construction at CERN. The main quadrupole is assembled with correction magnets in a common cryostat called the Short Straight Section (SSS). We plan to measure all SSSs in cold conditions with an unprecedented accuracy: integrated gradient of the field within 150 ppm, harmonics in a range of 1 to 5 ppm, magnetic axis of all elements within 0.1 mm and their field direction within 0.2 mrad. In this paper we describe the automatic measurement system that we have designed, built, and calibrated. Based on the results obtained on the two first prototypes of the SSSs (SSS3 and SSS4) we show that this system meets all above requirements.