Chamonix XIV Workshop 2005 Commissioning the DFBs

1. Chamonix XIV Workshop 2005 Commissioning the DFBs A. Perin, V. Benda AT/ACR Acknowledgements: C. Davison, V. Fontanive, T. Goiffon, R. Marie, L. Metral, AT-ACRR. Folch, M. Genet, V. Kleimenov, Ph. Trilhe, T. Kuryka, TS-MME

2. Outline • Main characteristics of the DFBs • The DFB project / strategy • Pre-installation tests • Installation of the DFBs • Commissioning the DFBs • In situ maintenance / repair • Possible faults and expected downtime

3. Location of the DFBs in the LHC DFBA DFBL DFBA DFBL DFBA DFBA DFBM DFBM DFBM DFBM DFBA DFBA DFBM DFBA DFBM DFBA DFBM DFBM DFBM

4. Main characteristics of the DFBs: variants 23 DFBM: powering standalone magnets Leads and chimneys 16 DFBA: powering the LHC arcs 5 DFBL: powering the superconducting links

5. Main characteristics of the DFBs: variants • Numerous variants: 44 DFBs, 31 variants (drawings sets) • DFBAs are in the beam lines, high mechanical constraints • Highly integrated into LHC machine • Sensitive components (current leads, busbars, lambda plates) • Very diverse components: cryogenic, electrical, vacuum, etc. • High number of interfaces • Allow the in situ exchange of current leads

6. Main functionalities of the DFBs • Current supply to the LHC cryomagnets • 1200 current leads, 2900 kA total current, 44 boxes, incorporating from 2 to 71 current leads in 3 main types • Arc termination • applies only to DFBAs • end of arc forces compensation • supply of cryogenics to arc magnets • beam pipes continuity support & alignment: precise alignment under vacuum & cold conditions • DFBL: Cryogenic fluids for the superconducting links DFBAP IR 8 right

7. Main characteristics of the DFBs • Cryogenics • Current leads operation in 4.5 K saturated LHe bath • Controls: liquid helium and helium gas flow for the current leads • Max. pressure for DFBs 0.35 MPa • DFBA supply/exit of GHe for E line

8. Main characteristics of the DFBs • Electrical • Concentration of all types of busbars in very small space • Significant quantity of electrical interconnects: 1200 current leads to busbars, 1800 busbar to busbar, ranging from 120A to 13’000A • Insulation vacuum • No vacuum barrier: DFB share the vacuum of the magnets they power • Beam vacuum (DFBAs only) • Actively cooled beam pipes with beam screens • Cold-warm transitions • DFBs must be installed to pump/cool down arcs and MS magnets • DFBs must be fully operational to power the magnets

9. Strategy for production and tests of the DFBs • Global strategy • Test as much as possible before installation • 31 variants: no spare unit • Only spare parts will be produced • Current leads + related components • Instrumentation, control valves, etc. • Production • Modular construction: the same modules are found in all DFBs • Standardized current lead cartridges • Ancillary equipment • The DFBs will be produced and validated as complete systems including • All instrumentation • Proximity piping and warm control valves • Electrical splitting boxes • All ancillary equipment • As far as possible the units will be transported with all accessories installed • Testing • Extensive warm testing will be performed on all DFBs: vacuum, electrical, geometry, pre-alignment, etc. • Warm tests will be performed on complete units • All current leads will be cold tested • 1 unit is planned to be tested in operating conditions with full electrical powering

10. Type test: Cold tests of DFB in SM18 • Fundamental tests:parameters which can make DFB not functional : • Powering to I max • LHe level stability • High voltage test at working condition • Deformation (beam pipe) • Quench behavior of bus-bars • Transient condition • Very useful tests:parameters which will help to optimize DFB function and shorten commissioning • LHe level maximum and minimum • Cool down/warm up time • Varying of GHe temperature for CL 5-30 K • Explore all non nominal operating conditions • Useful tests: parameters confirming the technical choices: • Quality of splices contact • Temperature measurement (shield etc.) • Pressure drop measurement • Temperature measurement of GHe leaving CL (icing & condensation – HV test problem) • Stop CL heating and restart with ice on it • If cold test cannot be performed: most likely consequence is a much longer commissioning time for the initial DFBs with possible very late discovery of more important problems

11. Installation of the DFBs • When to install the DFBs? • DFBs are cryogenically and electrically connected to the magnets • DFBs will be installed during the interconnection period of the corresponding sector • DFBAs can be installed when Q7 is installed, in 8L, 2L, 2R Q6 must be installed first • DFBMs need the corresponding magnet to be installed first • DFBLs need the corresponding superconducting link to be installed first • Transport • non standard device (in particular height!), specific equipment for transport and final positioning • For DFBAs final positioning is similar to a magnet • Operations for local installation • Preliminary alignment #1 • Electrical and mechanical internal interconnections • Electrical and mechanical internal interconnections to magnets or DSL • Connection to the QRL (if applicable) or DSL • Connection to warm gas recovery • Connection of warm instrumentation / AC power cabling • Connection of DC power cables

12. Installation of the DFBs: required dates • DFBs will be installed during the interconnection period of the corresponding sector • on average 1 sector / 6 weeks

13. Commissioning the DFBs • Commissioning rate will be very high: 1 sector / 6 weeks, will require dedicated personnel • No experience exists for devices of this size • DFBs are tightly integrated with magnets: commissioning is not independent! Any delay in DFB commissioning will will delay commissioning of LHC • Warm commissioning • Commissioning of local equipment and instrumentation performed in workshop before installation as far as possible • Insulation vacuum commissioning with the corresponding magnets (see presentation 62 by P. Cruikshank) • All cryogenic circuits shall be tested for leaks • Operation of all control valves and instrumentation shall be checked • Electrical commissioning: continuity and HV (see presentation 53 by D. Bozzini) • Precise alignment of beam pipes after pumping and pressure tests (if applicable) • Beam vacuum commissioning will include cold and warm beam pipes operations (see presentation 32 by V. Baglin) • … • Cold commissioning • Cool down of the DFB • Cannot be done completely in parallel with the magnets because of pressure in header D (1 MPa) is not compatible with DFB/current leads design pressure (0.35 MPa) • Sequence shall be defined in coordination with magnet cool down • Cool down time depending on DFB type and local conditions, varying from 2 to 5 days • Commissioning of the DFBL depends on the superconducting links • Precise alignment of beam pipes after pumping and pressure tests (if needed) • Operation of individual current leads / collective powering / ramps will be required • Definition of all operational parameters for the control system • …

14. Commissioning the DFBs: tunnel access Water cooled cables Transformers Instrumentatio rack

15. Consequences of faults (warm comm.) • General approach • Complex system, mixing electrical and cryogenic equipment: experience shows that the first commissioning can be much longer than expected ! • DFBs are geometrically tightly integrated in the LHC and an integral part of the powering system • No spare DFBs! Replacement of faulty DFB is not possible! • In situ repair of internal components is very difficult if not impossible! • Access to external components is difficult • But: essentially passive cold components and all instrumentation exchangeable. Moderate effort to replace current leads. Complete system extensively tested on in workshop • Problems most likely to appear during warm commissioning

16. Consequences of faults (cold comm.) • Problems most likely to appear during cold commissioning

17. Repair / modification of internal components • Current lead fault • Faulty instrumentation: use backup • Replacement of current lead: • Can be done in situ • Requires warm up of cell + break vacuum • Operation can then be performed in estimated 1 to 2 days 50K connection 20K connection CL splice View of a DFB with removed cover • Leaks • to insulation vacuum: if accessible from door, possible in situ, if not requires disconnection of the DFB and repair in the workshop. Minimum downtime: 30 days + warm up + cool down • to beam vacuum:requires disconnection of the DFB and repair in the workshop. Most probably will require extensive disassembly. Minimum downtime: 60 days+ warmup + cool down • Electrical circuits swapped / continuity / splice problems / high voltage faults • Swapped wires: requires access to splices. Minimum downtime: 3 days+ warmup + cool down • Discontinuity: if problem at splice, can be done in situ (see above), if not requires extensive disassembly, in such a case minimum downtime 60 days+ warmup + cool down • Bad splice:Minimum downtime: 3 days+ warmup + cool down • HV fault: if problem at splice, can be done in situ (see above), if not requires extensive disassembly, in such a case minimum downtime 60 days+ warmup + cool down

18. Conclusions • Each DFB is unique: no spare DFB will be available. All delay in DFBs will have a direct impact on LHC commissioning. • In order to reduce the commissioning time in the LHC tunnel, all ancillary equipment will be installed on the DFBs and tested before tunnel installation • Extensive testing at room temperature is required before installation • Data gathered during a cold test of one DFB (“type test”) can greatly reduce the commissioning time • The current leads can be replaced in situ with a moderate effort • The splices are accessible in situ with moderate effort • Any access, except to splices, to the internal components will most probably require the disconnection of the DFB with a minimum downtime of several months • Beam commissioning cannot be performed with non working DFBs • The DFBs must be commissioned together with the magnets they are powering • The specific pressure requirements of the DFBs imply a specific cool down sequence • Without cold test, displacement of the beam pipes can only be validated with a a circulating beam • Appropriate resources (not available at the moment!) are necessary to comply with the installation rate required by LHC schedule.