Field Description of the LHC FiDeL - Status and Plan Presented by L. Bottura based on contributions of many MARIC and LHCCWG

Outline Objective of FiDeL Some details on the Field Model Interface to LSA (LHC control) Interface to off-line LHC model (through WISE to MAD) Status and plan Milestones of validation

Objective and targets of FiDeL The Field Description of the LHC (FiDeL) aims at predicting the magnetic state of any magnet, magnet assembly or magnet circuit in the LHC, following arbitrary operating cycles, to an agreed accuracy, as practical for accelerator control and beam dynamics studies FiDeL clients: The high-level LHC control software (LSA), requires a parameterization of transfer function and harmonics of the main magnet and corrector circuits to Prepare machine settings for injection, define the ramp, and reach coast conditions Provide trims for correction circuits during constant current plateaus, and especially to follow the field drift at injection Provide trims for correction currents during the energy ramp, and especially during the snap-back at the beginning of the acceleration The off-line LHC model (MAD), through WISE, requires a snap- shot of the deviations from nominal optics (field errors) in all magnets at an arbitrary time to perform studies on the LHC beams

Magnet normalization cycles to be defined in the operation and recovery procedures An overall view and FiDeL scope AB TS-IC AT-MAS AT-MEL AT-MTM AT-MAS AT-MTM TS-SU AB-OP AT AB-ABP FiDeL scope

FiDeL field model concept Parametric model Unified description of the field and field errors C n applicable to all LHC magnets Set of parametric equations for 7 physical components Geometric (+ BS offset) Persistent Saturation Residual magnetization Decay Snap-back Ramp Field parameters Adapt the parametric equations to fit the measured or expected behaviours of the magnets Set of ≈20 parameters, classified in 2 categories: Shape parameters, equal for all magnets of the same type and family (e.g. all MB’s with inner cable 01B) Amplitude parameters, specific to each magnet (e.g. geometric C n ) Field Model Phys.Rev. Special Topics, Accelerators and Beams, 9, , 2006

Field model “components” Seven components of different physical origin to describe the field and field errors In addition: residual magnetization and ramp (not visible above) The same model applies to single magnets and to string of magnets

Interface to LSA Produce calibration functions (reproducible components) Set ramp Compute and correct dynamic errors in real- time (non-reproducible components) Java implementation of FiDeL field model (AB-OP) Field model parameters for all LHC circuits (AT, AB-OP triggers import of new configuration) Feed-back from operation (AB-OP, AT consulted) Oracle database of circuit parameters (AB-OP)

Interface to MAD Simulate LHC at the best of our knowledge of magnetic field and alignment Quantify effect of systematic and random errors Oracle database of magnet parameters, included in the database of circuit parameters (AB-OP) magnet parameters (AT) implementation of FiDeL field model substitutes present link to magnetic data extraction

Status Proposal of 1 year ago: Mandate the FQWG to Complete the definition of the project (interfaces, responsibilities, deliverables) Compile above in a RDD to be agreed with AB-OP (LHC controls) and AB-ABP (MAD) Propose participation of AT groups (MEL/MAS ( * ) /MTM are natural candidates) Provide the structure for coordination and follow-up of progress Spin-off the team that will be in charge of the LHC magnetics We had 6 formal meetings (several informal) to: Agree on an implementation proposal with participation from three groups in AT and AB-OP Bond in a team the core of people concerned with and by the work Define and pursue the data selection, sorting and re- analysis Identify critical issues in the definition of the interfaces (configuration and cycle databases, sign conventions) ( * ) Now MCS

Project information Scope of the work Minutes of meetings Mailing list Documentation Data repository (!)

Implementation plan TaskHR needed (man-month) DueDone (%) Model Specification131/3/2007 Create FiDeL data structures331/3/2007≈ 30 Implement FiDeL Engine431/3/2007 test 30/9/2007 stable Normalisation cycles230/4/2007≈ 25 Magnetic data consolidation2030/6/2007≈ 50 MB/MQ/correctors powering and tracking test 630/6/2007 Sector powering test36/2007 sector 78 9/2007 sector 45 Adapt WISE interface to FiDeL230/9/2007

Magnetic data consolidation Verify the validity of magnet acceptance data (i.e. ID cards) Select from measurement databases the (additional) data necessary to the field model (e.g. current values between injection and flat-top) Perform data reduction using uniform (standard) methods Store results in a web- based repository MB warm (AT-MCS) done, cold (AT-MTM) 90 % MQ warm (AT-MCS) and cold (AT-MTM) done MQM warm (AT-MEL+AT-MCS) done, cold (AT-MTM) in progress MQY warm (AT-MEL) and cold (AT-MTM) in progress MQTL warm (AT-MEL) and cold (AT-MTM) in progress MQXA, MQXB warm and cold data recovered (AT-MCS) for MQXA, to be done for MQXB Correctors Warm (AT-MEL) and cold (AT-MTM) in progress D1…D4 (TBD) NC magnets (TBD) Experimental magnets (TBD)

Issues for the coming 3 months Reference frames and conventions (beam direction vs. measurement frame) Magnetic data MQY warm (permeability correction, on-going) MQXB (inquiries sent, not clear what is and will be available) Normal-conducting magnets (data sources and formats are very diverse) Experimental magnets (TBD) Modeling Synthesis of magnetic data to the level relevant for modeling (build integrals over series connected circuits) Implement semi-automated fitting procedures for massive data treatment Verification of the quality and (if needed) adapt the parametric model

Tracking tests in SM-18 What is the test ? Equip spare magnets (2 MB’s + 1 or 2 MQ’s) with existing field measurement instrumentation Generate nominal (7 TeV) ramps in the main magnets and in the correctors using LSA and the FiDeL field model Run the ramp and measure field and field errors Diagnose result (B1 vs. specified ramp, B2/B1 tracking, b3 and b5 correction) Where and when ? In the existing SM-18 test benches (Jun 2007) Why is it useful ? Detailed study of the accuracy of the field model Test of the prediction capability for different powering cycles Difference among series tests and LHC, e.g. the issue of precycles at 50 A/s (series tests) vs. 10 A/s (LHC) Effect of deviation from nominal operating conditions (e.g. waiting times) Effectiveness of recovery procedures (yet to be defined)

Test LHC ramps during HC What is the test ? Generate the nominal ramp in all power circuits of a sector (commissioned) using LSA and the FiDeL field model Run the ramp from CCC through LSA Diagnose result (current and expected field tracking vs. specified ramp) Where and when ? 7-8 (May-Jun 2007) Maximum energy < 7 TeV 4-5 and/or 8-1 (Aug-Sep 2007) 7 TeV ramp+squeeze, RT trims Why is it useful ? Proof of readiness for the data structures and implementation Early feed-back on ramp down-load and real-time trim mechanisms (LSA) Verification of hardware limits, especially on corrector circuits (voltage swings) and quench protection hardware (voltage thresholds)

Scope of FiDeL discussion AB TS-IC AT-MAS AT-MEL AT-MTM AT-MAS AT-MTM TS-SU AB-OP AT AB-ABP FiDeL scope FiDeL range

A FiDeL project team ? So far we have worked as an informal interdepartmental team, fostered by the FQWG The resources required by this work are significant: A team of ≈ 10 people working part-time The estimate is ≈ 40 man-months for the work up to the main deliverable, mainly in AT About 1/3 have been engaged to date Opinions are discordant as to the adequacy of the estimate The estimate does not consider adjustments and maintenance, which will be a natural follow-up of the work The validation milestones have hardware implications, mainly in SM-18 This is a good time to have a formal assignment of the work-packages, and consolidate the framework of this collaboration

Acknowledgements It is a pleasure to work with a motivated and committed team: Laurent Deniau (secretary for the team), Mario Di Castro, Per Hagen, Vittorio Remondino, David Sernelius, Nicholas Sammut, Stephane Sanfilippo, Ezio Todesco, Walter Venturini-Delsolaro in collaboration with our colleagues in AB: Ilya Agapov, Massimo Giovannozzi, Mike Lamont, Frank Schmidt, Marek Strzelczyk with the advice of some old wise men: Jean-Pierre Koutchouk, Louis Walckiers, Rob Wolf