Commissioning of accelerator systems - magnets

1. Commissioning of accelerator systems - magnets Presented by W. Venturini Delsolaro On behalf of many people (in HWC, FIDEL, MPP) Particular thanks to Adriaan, Andrzej, Jean-Pierre, Frank, Jörg, Luca, Massimo, Rob, Mike, Roberto, and Rüdiger LHCCWG Meeting, 8 May 2007

2. Outline (Brief) overview of the magnet system(s) Hardware commissioning enterprise Questions for beam commissioning Conclusion, open issues

3. Overview of the magnet system Chapters 7,8, and 9 of the LHC design report 28 powering sub sectors (EDMS 361532)

4. Main magnets in the arcs: MB and MQ sextupole corrector (MCS) quadrupole MQF orbit corrector quadrupole MQD quadrupole MQF MCB MCB main dipole MB main dipole MB main dipole MB main dipole MB main dipole MB main dipole MB lattice sextupole (MS) special corrector (MQS) lattice sextupole (MS) decapole octupole corrector (MCDO) special corrector (MO) special corrector (MO) lattice sextupole (MS) Picture stolen from Rüdiger’s talk

5. Correction magnets

6. SSS circuits (EDMS doc 104157)

7. Matching sections and dispersion suppressors

8. Separation regions and final focus

9. Hardware commissioning HWC was long prepared and documented within the Hardware Commissioning Working Group, now HWC coordination: http://hcc.web.cern.ch/hcc/ Strategy for hardware commissioning (EDMS 382004) Individual System Tests: QPS, EE, PIC, ELQA Hardware Commissioning Activities SC, PIC1, PIC2, PCS, PLI, PNO, PAC LHC-D-HCP-0001(EDMS 477145): “General Procedure for the commissioning of the electrical circuits of a sector” LHC-D-HCP-0003(EDMS 519716): “Powering of the superconducting circuits of a sector up to nominal current” Detailed procedures prepared by MPP Training day on 29 March 2007: all presentations can be found on: http://indico.cern.ch/conferenceTimeTable.py?confId=13360

10. The magnet system shaping the LHC beam is the innermost “hand” of a complex “body” behind it Hardware commissioning is now checking this up completely: for example heat runs to validate the functionality of cooling, ventilation, power controls, etc QPS DFB PC PIC Cryogenics and Vacuum EE Magnet system Networks Electric Power Cooling Ventilation

11. Questions to be addressed What will be the status of the system when we start beam commissioning? Which signals are available in the control room? What needs to be measured with beam? What is the commissioning plan with beam (if any). Is any special beam time required to commission the system? How can the system affect beam operation?

12. What will be the status of the system when we start beam commissioning? The goal of HWC is to release all systems ready to be operated at their nominal performance level, OR, more realistically, with a complete list of NON CONFORMITIES First experience with sector 7-8 shows that we may have to accept some limitations, translating in current ratings lower than nominal for some circuits However, sector 7-8 is (hopefully) not fully representative: it is used as a “playground” to validate and tune HWC procedures Moreover it will be reopened, allowing repairs to be done before commissioning with beam A list of magnet circuits not needed for the first phases of beam commissioning was presented at Divonne 2006 (M. Giovannozzi) Expected values for the number of quenches during HWC have been given by P. Pugnat in the same workshop Hardware commissioning is completed by a dry run (powering all circuits “at unison” through the whole machine cycle)

13. MPP recommendations for 600A circuits in sector 7-8, first run

14. Magnet performance panel The MPP (& the CPP) are expected to actively contribute to the Hardware Commissioning effort by: participating to the definition of the procedures, analyzing the data gathered, supplying all the information necessary and timely validating the continuation of the commissioning procedures interpreting the data and depending on it allowing/refusing the execution of the following step of the test procedure in case of failure, the MPP/CPP is expected to perform in-depth diagnostics to unblock the situation or escalate the problem via Hardware Commissioning Coordination R. Saban at the HWC training day

15. ICC LTC, MARIC HWC coordination MPP HWC teams Non conformities: can affect machine performance, but they may be tolerated for the first stages of beam commissioning depending on the circuits concerned During series tests of magnets, this was eventually handled by the MEB. How do we deal with NC during the HWC, when correcting actions might still be possible? Escalation of Non Conformities (simplified, see details in: http://indico.cern.ch/sessionDisplay.py?sessionId=1&slotId=0&confId=13360#2007-03-29) Very BIG Troubles ! LHCCWG ?

16. So, what will be the status of the system at the start of beam commissioning ? “It depends on the type of non conformities found during HWC and on the their outcome” This can have an influence on the procedures of beam commissioning  the LHCCWG needs up-to-date forecasts of the expected performance of circuits

17. Which signals are available in the control room? Fixed displays for Power Converters status (LSA) GPMA application for voltages, currents, logic states, etc (Labview) Circuits that do not quench will not produce any QPS PM data Courtesy A. Rijllart

18. What needs to be measured with beam? Polarities Calibration of orbit correctors Matching of MB fields over the octants Gross tune errors Beta Beat Alignment errors Calibration of lattice correctors and MCS spool pieces MB/MQ tracking Transfer functions of some critical elements (D1, D2) at 450 GeV and 7 TeV Quench levels for BLM thresholds (see Laurette’s talk ) Time lags for correctors with parallel resistors on automatic feedback

19. What is the commissioning plan with beam Is any special beam time required to commission the system? (1) SETTINGS AND TRIMS of MAGNETIC FIELDS Involves almost all phases of beam commissioning: Pre cycling, MB, MQ, MCB, MCBC, MCBY transfer functions (A-1, A-2) Stability and reproducibility (A-4) MB and MQ errors, MQS, MQT, MQTL, MS, MCS transfer functions (A-4) MCD transfer functions? (A-5) Dynamic field model, refined MCS transfer functions (A-8) Transfer functions of D1, D2 (A-9) MQM, MQY hysteresis models (A-11) Probably more input needed for stages B, C, D FIRST SETTINGS WILL COME FROM FIDEL

20. Friday 4/4/2007 … first SPS turn: based on trajectory measurement, the current in the MB was changed by some 1.6 A, and the beam went from a few turns to a few millions! Then the new injection level was joined by interpolation to the higher energy points, to allow the power converters ramping the magnets: quick and efficient. But LHC Beam based corrections will have to be integrated in the magnetic model (see Luca and Mike’s talks at Divonne 2006) Cumbersome? The complexity is such that we cannot just “trim around”, there needs to be a coherent frame Corrections based on Beam Measurements

21. Field Description for LHC project http://fidel.web.cern.ch/fidel/ How will this work?

22. The problem is how to adjust the model parameters based on beam measurements: If the model incorporates “blindly” all trims that turn out to “work” in the CCC, it will rapidly loose physical sense becoming totally ad hoc. On the other hand, the model must be open to revisions based on experience. But it has to remain physical=possible to extrapolate We need to understand the beam and the magnets at the same time, as the magnet system has enormous influence on the beam Issues: 1. Automatic feedback corrections superimposed through real time channels should be taken into account for a correct analysis 2. Trims based on beam measurements come as field/current increments, not as Fidel components. They cannot be directly incorporated into the model, but need to be analyzed to be correctly decomposed.

23. What is the commissioning plan with beam Is any special beam time required to commission the system? (2) POWER PERFORMANCE: quenches are of 3 types Natural: hopefully most during HWC. Consequence will be unscheduled down time, GPMA should give green light to go ahead.No need to plan for any beam time False triggers estimate rates are available in the LHC report. Diagnosis based on timing of logical states, but causes might be difficult to find out. Consistency check foreseen before powering. No need to plan for any beam time Beam induced: may lead to reconsider optics, collimator settings, BLM thresholds the level of beam loss induced quenches will be assessed either via “quench and learn” to set BLM thresholds, or parasitically. At least one good argument supports the first option: if the damage level and the quench level are close at high energy for some type of losses, and if energy scaling is reliable, then quench and learn at 450 GeV will validly protect the machine. (See Laurette’s talk) Foreseen at the beginning of the phase A1.5 (increasing intensity)

24. How do we deal with quenches during beam operation PM analysis Manual and GPMA Circuit release Automatic, operation, MPP Recycling prescriptions Normally never beyond a powering sub sector Events that do not give rise to recycling: in general, quench of magnets with no decay

25. Magnet pre cycling: depends on the level of performance reached during Hardware commissioning Prescriptions being prepared by R. Wolf with FIDEL Example: simple cycling against degaussing of correctors MCBXA33

26. Time lags for correctors with parallel resistors τwill depend on current (L varies up to 30%) To be taken into account when tuning the PID And in the settings generation for the ramp, for example for snapback compensation L(I) Rpar

27. Conclusions The status of the magnet system at the end of hardware commissioning will have direct impact on machine energy, optics and “tunability”, and on operation procedures. Keep an eye on expected performance. Software for automatic PM analysis aims at minimizing the need of expert support to release powering after quenches Pre cycling prescriptions being prepared Tracking test in SM18 is in preparation Corrections based on beam measurements: how to integrate them in the magnetic model?