Magnets

1. Magnets PS & SPS Days 18 & 19th January 2006 K.H. Mess, W. Kalbreier,D. Smekens, Th. Zickler CERN

2. Overview

3. PS Booster Magnets – Present Situation • The main problem encountered was the ageing of the rubber water hoses and seals causing water leaks. • Water leaks: - Many stops in 1998 & 1999 to repair leaks on seals of flexible hoses. - All hoses and seals have been replaced in the 4 following shutdowns. - No leaks thereafter except in 2004 after the installation of 21 non-conform hoses replaced during start-up. - 1 water collector leaking due to Cu erosion on QDE42 in 2003. - 1 water collector leaking on BHZ162 in 2005. - Water leaks in transfer line magnets from BOOSTER to PS in 7-2005 in BT2-BTV20 (leaking gasket) & DT1-DVT10 (repaired via 5 brazings).

4. PS Booster Magnets - Modifications • No major changes on the Booster magnet system in 2005. • Standard annual maintenance (adjustment of flow meters, control of bus bar connections, etc…). • A detailed inspection and a study to improve the cooling circuit will be started before the Booster start up. • The foreseen replacement of the water hoses has to be postponed to the next shut down due to the workload on the PS main magnets. • High pressure tests on DT1-DVT10 foreseen. Actions will be taken according to the test results. • We assume the risk of failures during 2006 low, but preventive maintenance and future improvements are indispensable to keep the machine operational (particular in context with the new 900 ms cycling scheme). • A more detailed study to identify further weak points and to improve the reliability of the Booster magnets will follow next shut down 2006/07 (water connections, interlock, etc…).

5. PS Auxiliary Magnets • A number of changes and modifications in the PS straight sections have be done in 2005. • For more details refer to the presentation “PS Ring” by R. Brown.

6. PS Main Magnets – Status before 2005 • During the annual routine HV test before the 2003 start-up the coil insulation on 2 PS main magnets was destroyed by breakdown. A following detailed analysis and inspection of the 45 years old PS main magnets revealed that: • 90% of the magnets in original state from the late 50s. • Preventive maintenance and developments have been done until 1987, but since then only broken components have been repaired. • Many components have already approached or are even beyond their expected life time and showed heavy degradation induced by radiation. • On many magnets the coil insulation was deteriorated and over larger areas no more adhering to the Al-conductor. • Insufficient spare coils with good insulation existed. • The cable insulation of the pole face windings was falling apart when touched. • The bus bar insulation is fragile and extremely liable to breakdowns during handling.

7. Risk Analysis of PS Main Magnet Components * Down time does not include any cooling down time

8. PS Magnet Consolidation Program The 18 months shut down of the PS in 2005/06 offered an unique chance to repair a significant number of PS magnets. Therefore, in summer 2003 it was decided to launch the PS Magnet Consolidation Project split into two phases : • Phase I for 2003-2006: Refurbishment of the weakest 40 PS Main Magnets • Phase II in 2006-2013: Refurbishment of the remaining 60 PS Main Magnets (still to be funded). The split has the following reasons: • Budget: The total amount of 20 MCHF was not available, whereas the amount needed for the first phase of about 7 MCHF could be allocated. • Personnel: The strain on the personnel involved in LHC, CNGS & other project under full construction (magnets, vacuum, transport, survey) would have been too high for doing all magnets in 2003-2006.

9. PS Magnet Selection Criteria 100 main magnet units are installed in the PS tunnel, 91 of them are still in original state (72 even on original position). The following criteria have been applied to find out the weakest magnets : • The total integrated dose received between 1959 and 2004. • The actual radioactivity. • State of the electrical insulation of the main coils. • State of the electrical insulation of the PFW cables. • Voltage seen by the main coils during operation. The sequence of the magnet removal and refurbishment is determined by: • Actual radioactivity: less radioactive magnets first. • Accessibility: magnets difficult to uninstall are removed when personnel involved has sufficient experience. • Survey constraints: important to avoid removing adjacent magnets from the PS ring at the same time.

10. PS Main Magnet Modifications in 2005 • New Main Coils • The production of 232 new main coils is still ongoing at BINP/ Novosibirsk. • Conductor and coil shape identical to old coils. • Type of coil insulation has been changed to present standard. • New Pole Face Windings • The production of 240 new PFW ongoing at Sigmphi/France. • Conductor configuration identical to old PFW. • Cable insulation and epoxy insulation changed to present standard. • New Back Leg Winding Cables (identical configuration). • Figure of Eight windings not changed. • Bus bars not changed. • All cables on the magnet replaced (radiation hard insulation). • Repair of the two central magnet blocks.

11. PS Main Magnet Test and Commissioning • Every repaired magnet tested individually before re-installation in the tunnel (hydraulic, resistance, insulation, polarity, interlock, etc…) • Magnetic field excited by the main windings, FoE windings or the BLW cannot have changed - it is determied by the pole shape of the iron yoke. • Comparison of the magnetic behavior of the new and the old PFW – no difference measured. • No systematic magnetic measurements of the new PFW, but very strict control of the conductor positioning before final molding (more precise than magnetic control). • Extended hardware tests period foreseen to identify and solve any possible problem before the PS start up in April 2006. • The commissioning includes: • HV test of main coils, FoE, PFW, BLW. • Visual and audio patrol (all windings powered). • Thermographic inspection to control the quality of the electrical connections. • Polarity checks: PFW, FoE, BLW.

12. Actual Status and Risk Expectations 2005: • Serious delays of 10 months in the coil production at BINP and the PFW production. • The refurbishment of the first magnet started only beginning of August and the first magnet re-installed by mid of September. • Thanks to the big effort and the motivation of the entire refurbishment team the magnet refurbishment rate could have been significantly increased. • By the end of the year, 25 magnets repaired successfully. 2006: • The 25 weakest magnets chosen for the refurbishment campaign. • All 25 magnets re-installed in the tunnel. • A careful commissioning will reveal any problem before the PS start. • The risk of magnet failure in 2006 will be much lower than in the past. • Start up of the PS with 4 operational spare magnets available.

13. East Area Magnets • MNP23 (new type) in F61S (PS tunnel) • Magnet breakdown due to erosion and corrosion problems. • Replacement by new magnet with improved water cooling system (cooling of each half-turn). • Identical magnetic properties, but position slightly shifted downstream. • MNP23 (old type) in T9 (target area) • High leakage current most likely due to low resistive cooling water. • No replacement, but tests before start up. • Q120 in F61S (PS tunnel) • One magnet leaking, other still OK. • Replacement of one or both magnets to be decided end of February according to the arrival of the new magnets actually in production. • Q120 in target area • Replacement not possible before start up, but repaired leak done in 2002 is still OK.

14. SPS Main Magnets • Interventions in the SPS reduced to a minimum in order to limit costs and manpower working on LHC and CNGS transfer lines. • No major changes on the SPS main magnet system in 2005. • The modification of the extraction channel and the replacement of the electro-static septum in LSS6 made a re-arrangement of the surrounding magnets necessary (see also following presentation by J. Borburgh): • All horizontal Bumpers and Correctors displaced. • QFA quad replaced by QF type to avoid interference. • This intervention increases the commissioning work, but no risk for the SPS start up in 2006. • Installation of the upstream part of TI2  no issue for the SPS start up. • Installation of TT41 for CNGS  no issue for the SPS start up. • Replacement of 7 main dipoles (MBB) due to erosion problems on the copper manifolds of the water cooling system. • No diagnostic possible  difficult to make any prediction. • Problem could re-occur on any of the 744 main dipoles.

15. North Area Magnets • The long cooling down time in 2005 allowed interventions on highly radioactive equipment in the SPS and in the North Area. • No modifications. • Time consuming, but low cost magnet maintenance in the target areas. • No risk for the start up in 2006.

16. Conclusion • PS Booster: minimal risk during start up due to possible problems in the water cooling circuits. • PS Main Magnet system: Extended tests and commissioning should reveal possible problems (polarity, electrical connections, …) before the start of the PS. A minor risk remains due to the complexity of the system and the extend of the refurbishment program. • East Area: Risk of delayed start up due to the late arrival of spare components. • SPS: no major modifications in 2005, therefore no risk apart from possible corrosion problems in the cooling water manifolds (not predictable). • North Area: no risk expected (only maintenance, but no changes).

17. DT1-DVT10 • Return

18. Insulation breakdown after HV test • Return

19. PFW cable insulation • Return

20. Damaged main coil insulation • Return

21. Thermography during power test • Return

22. PS Magnet Refurbishment Team • Return

23. PFW before molding • Next

24. Finished PFW • Return

25. Lose lamination on the central blocks • Next

26. Test set up • Next

27. Broken lamination on MU 61 • Next

28. Repaired magnet blocks • Return

29. New MNP 23 coil • Return

30. LSS6 Extraction channel towards TT60/TI2 • Return

31. Water leak on MBB • Return