LHC Cryogenics for sector 45 and Perspectives

1. LHC Cryogenics for sector 45andPerspectives S. Claudet, for LHC cryogenics HWC Review, 28 Fev’08

2. Content • Cryo Performance & Operation • - Availability for cryogenic system • - Recovery time after quenches: what can we expect? • - Operation overnight and over the weekend: is it possible? • - Operation with several sectors in parallel, what will change? • - Presence in the CCC • - Level measurements: Correct Helium level for operation? • Achieved performance and plans • MTBF, MTTR and quench recovery • Consolidation activities • Manpower and distribution • Summary LHC Cryo - HWC review for sector 45

3. LHC sector 4-5: 1st cool-down Cool-down 300K - 80K Cool-down 80K - 4.5K Warm-up started Leaky flexible hoses in DFBA’s and hesitations due to PIM’s findings during summer Major perturbations: - Air leaks into sub-atm circuits - Levels in stand-alone magnets - Tuning valves for DFB’s Towards 2.1 K HWC @ 1.9 K Improved cool-down speed w.r.t 7-8 ( Now much closer to our final expectations as for 5-6) More than 8 months in total, for about 8 weeks of powering ! X-mas LHC Cryo - HWC review for sector 45

4. LHC 4-5: Evolution of temperature Global powering 25Jan’08 Stop of 1.8K Ref. unit due to vacuum interlock Quench of dipoles 13Feb’08 Stop of 1.8K Ref. unit due to water stop US45 21Jan’08 Stop of 18kW due to oil system Quench of Quads MTBF: 11 days MTTR: 48 hrs >=Wk06: ARC + RF + LSS5L + LSS4R LHC Cryo - HWC review for sector 45

5. Availability: From 7-8 to others Cryo Maintain ARC: 63% (Since 14Jan08) Cryo Maintain LSS: 70% - 93% (Since 21Jan08 or 01Feb08) Stand-alone levels DFB’s valves ELQA 7-8 (2007): 85% for LSS (>1st May’07) 66% for ARC (>1st Jun’07) Target 4-5: 90% for LSS 80% for ARC For future sectors, we maintain our objectives with work on recovery time But as well we try to give Cryo Start/Maintain earlyer ! LHC Cryo - HWC review for sector 45

6. Recovery Time after Limited Resistive Transitions Now: 2 to 3 times slower (Predictions at design stage) Achieved or achievable • More than 14 cells or full sector:recovery up to 48 hours • In case of fast discharge (even w/o quench): 2 h recovery (heating due to eddy currents). LHC Cryo - HWC review for sector 45

7. Recovering a quench 2. Larger He Qty released (criteria!): > Pre-cooling required before LHe re-filling > Perturbation of global process, to be done by expert 1. Small He Qty released: > Usual 1.9K cooling valve at max. opening > Self adapting and global process kept OK Alternative 1. considered less perturbating for HWC, ideas to make it automatic and < 10 h for a dipole > 10 kA LHC Cryo - HWC review for sector 45

8. Availability • MTBF: • Less perturbations due to EL or CV systems • First results of global effort of teams to work together • To be further improved for beams to circulate one day! • MTTR: • Experience so far with cold compressors helped pump-down to 15mbar to be successful at each try! • Conservative approach to prevent spoiling 15mbar conditions (2hrs more versus 2 days lost!) • Ideas to make it more automatic are being tested • We will never compensate the time delay for Y lines ! • Quench recovery: • A simple and safe solution is being studied for automation LHC Cryo - HWC review for sector 45

9. Content • Achieved performance and plans • MTBF, MTTR and quench recovery • Consolidation activities • Manpower and distribution • Summary LHC Cryo - HWC review for sector 45

10. Consolidation activities • Valve plugs: • Changed for all JT valves (CV910) => Nominal features now • Evaluation to change few valves at return module (line D) • Refrigeration and local distribution: • P6_QULA crossed lines fixed early 2008 • P6_QSRA heat-exchanger by-pass done (Feb’08) [P4 in Mar’08] • P2_QURA subcooler being changed [P8 to be decided] • Air leak to sub-atmospheric circuits: • More systematic checks before being sub-atm. organised • Investigations for minor adaptations on QUI’s LHC Cryo - HWC review for sector 45

11. Consolidations on DFB’s Calibrated level gages and protective covers Electromagnetic proportional valves Pulse width modulation command signal, no feedback, sensitive to DP Max flow 0.05 g/s at DP=33mbar Anti-condensation systems on current leads chimneys Spare valves being gathered, ready for exchange Possible adjustment being tested Online filters being tested LHC Cryo - HWC review for sector 45

12. Levels for stand-alones Large impedance ! LHe level gauge Cold mass Set-point • Proposal for the time being: • All stand-alone magnets are being equipped with valves @300K • Capillaries will be installed on request • BUT individual adjustment of setting required! (evolution ?) LHC Cryo - HWC review for sector 45

13. 4.5K stand-alone magnets Cool-down to < 10K Adjust instrumentation LT/EH Control LHe at 50% Fill-up and boil-off to determine appropriate set-point DFB’s Cool-down shield (if any) Cool-down leads at 150K, then cool-down phase separator Adjust instrumentation LT/EH Control LHe at nominal Fill-up and boil-off to determine appropriate set-point Tuning of Temp. control loops LHC Cryogenic commissioning • 2 K magnets in ARC • LT/EH at return modules • LT of SSS in ARC • EH at lowest point • EH of cold masses & beam screens • Possible pump-down and cool-down of magnets, including tests with cold compressors Identified and tuned for sector 4-5, Now being implement for sector 5-6 during the two weeks after ARC magnets @ 4.5K LHC Cryo - HWC review for sector 45

14. Content • Achieved performance and plans • MTBF, MTTR and quench recovery • Consolidation activities • Manpower and distribution • Summary LHC Cryo - HWC review for sector 45

15. Affectations LHC Cryo CRG-OA LHC Cryo OP No Tel SdC Team Leader: S. Claudet + M. Soubiran (Analyse fonctionnelle) + Industrial partner teams in local control rooms (≈ 23 personnes ALLS) LHC Cryo - HWC review for sector 45

16. Working periods • CERN staff: • Normal working hours + overtime when needed • On-call service: 1 Operator (direct) + 1 Engineer (back-up) Now: mostly to guarantee safety and helium inventory • Expert assistance in CCC for specific tests • Industrial partner: • Normal working hours + overtime when needed • On-call service: 1 Operator (direct) + 1 Operator (direct) • Afternoon shifts (14h-22h): 2 Operators, mostly for LN2 trucks • Saturdays: 2 Operators, for LN2 trucks and interventions HWC activities already possible up to 22h and Saturdays ! Investigations for 1 Operator in CCC (2 shifts) after logistics with LN2 trucks LHC Cryo - HWC review for sector 45

17. Challenge for Spring’08 Preparing tools to help having a quick global overview, and identify what needs to be delegated to local tuning teams LHC Cryo - HWC review for sector 45

18. Summary • All cryogenic features of sector 4-5 have been tested and validated, except multi-cell quenches! • Learning curves for transients on the good way, with automation in progress • Methodology for cryogenic commissioning of DFB’s and cryogenic instrumentation started for sector 4-5, now in place • OP team structure adapted in January 2008 to face parallelism (x8) • This continues to pay now, already for sector 5-6 [and 7-8, 8-1, 2-3] • Once cool-downs are well advanced, ideas to redeploy resources LHC Cryo - HWC review for sector 45