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Experience making transfer functions for LEP R. Wolf, AT-MEL-MC

Introduction Magnet & Control data base tables Making of the Transfer function Work to be done for LHC (looking back to LEP) Conclusion. Experience making transfer functions for LEP R. Wolf, AT-MEL-MC. Introduction. LEP Technically simpler, no time dependence, warm

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Experience making transfer functions for LEP R. Wolf, AT-MEL-MC

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  1. Introduction Magnet & Control data base tables Making of the Transfer function Work to be done for LHC (looking back to LEP) Conclusion Experience making transfer functions for LEPR. Wolf, AT-MEL-MC 1

  2. Introduction • LEP Technically simpler, no time dependence, warm • However several LEP specific corrections to apply to the transfer functions. • Administratively simpler. On the AT side only one group involved. Now there are 3 (MAS, MTM, MEL). • All magnets measured magnetically (at room temperature) + 8 superconducting low-beta quadrupoles measured at 4.2K. • Validated transfer function measurements of each LEP magnet, including correctors, stored in Oracle database tables of the magnet database. • Only transfer functions of circuits present in the control system database. 2

  3. Magnet & Control data base tables 3

  4. (Intermediate) Magnet DB: Transfer functions of individual magnets 4

  5. Making of the LEP Transfer functions 1 From data in the intermediate magnet database 5

  6. Making of the LEP Transfer functions 2 • Additional corrections/parameters • Proximity correction on transfer function for orbit correctors • Ramp Starting delays according to the vacuumchamber type (compensation of main component of vacuum chamber eddy currents) • Current to inject in main quadrupoles and sextupoles to compensate for quadrupole and sextupole components of vacuumchamber eddy currents • Setup cycling of the magnet circuits was to be defined. • Finally in all LEP lifetime 494 distinct transfer functions and 66 distinct cycles were made and put in the control database. 6

  7. Control DB: Magnet Families (circuits)1164 entries 7

  8. Control DB: Transfer functions of circuits 8

  9. Control DB: Cycles 9

  10. The work to be done (looking back to LEP) • First stage and main job: defining and making all appropriate measurements. • Complete putting validated results in tables (Oracle in the LEP case) so as to be reasonably well accessible. • Agree with the operations people what is needed for LHC and in which format (AT & AB) • Second stage (up to 1-st circulating beam) • Make intermediate measurement DB for easy access, which is suitable for automatic generation of the field model for all circuits. • Implement the magnet-related part of the control database (AB’s job) • Determine transfer function and setup cycles for circuits with help of the layout database(s) • Make various corrections/improvements based on measurements going on in parallel/cold-warm correlations/...... 10

  11. The work to be done (looking back to LEP) • Third stage (first two(?)years beam) • Make various corrections/improvements based on magnetic and machine measurements going on in parallel. This is certain to be more important than in LEP because of the time-dependent nature of the field of the magnets build with rutherford cables • Fourth stage (from year three). • Important improvements to machine coming closer (luminosity upgrade...) • Not to forget stage 1.5, the sector test.............. 11

  12. Conclusion • Measurements to be completed and valid data to be properly stored for all magnets. • It is urgent to agree with AB on the information to transmit and on it’s format. Operation people should be systematically involved from now on. • Need to appoint an AT person who is full-time responsible for the practical transmission of the field model in the control system and who should have professional database support. • On going magnetic measurement program and improvement of the field model to be expected for at least two years after start-up. 12

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