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CRYOGENICS PERFORMANCE AND OPERATION

CRYOGENICS PERFORMANCE AND OPERATION. L. Serio , on behalf of the LHC Cryogenics Operation and Cryogenics Performance Panel. Contents. Introduction on cooling down and commissioning time Tuning loops adjustment & CV910 puppets – acquired knowledge and expected improvement

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CRYOGENICS PERFORMANCE AND OPERATION

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  1. CRYOGENICS PERFORMANCE AND OPERATION L. Serio, on behalf of the LHC Cryogenics Operation and Cryogenics Performance Panel

  2. Contents • Introduction on cooling down and commissioning time • Tuning loops adjustment & CV910 puppets – acquired knowledge and expected improvement • Measured recovery time after quenches vs. theoretical expectations. DFBs filling • Availability study for cryogenic system - can system components or related services be improved to maximize overall availability • Improvement of He quality with new compressor. Translation to other sectors • Vacuum minor leaks' impact on 1.9 K stability - improved strategy for GLPT in 45/81 • Time to repair a fault occurring just before the week-end: is it adequate for running LHC? • Is recovery time after problems resource dependant? If so, can extra resource be made available when required eg weekends, nights? • Interlocks: New PIC-Cryo channels • Is it likely that if multiple sectors are commissioned, a cryo problem in one sector will not affect other sectors – thus allowing effort to be put elsewhere?

  3. Cool-down Global tuning And DFBs commissioning Powering (Big gain expected) (2-3 wks w.r.t 9 wks)

  4. LHC Cryogenics: duration of cool-down phases 9 d Design LHC 7-8 Final 21 d 80 K 14 d Sketches intended to illustrate achievements and ultimate expectations S. Claudet - Jul’07 3 d Design LHC 7-8 Final 14 d 20 K 7 d 1 d Design LHC 7-8 Final 14 d 4.5 K 3 d 1 d Design LHC 7-8 Final 21 d 1.9 K Excluding ELQA or extra-works : 4 d 14 d / 2 wks 70 d / 10 wks Design LHC 7-8 Final ELQA Total 28 d / 4 wks

  5. Data for LHC scheduling purposes • First time a given cryoplant type is used: 4-5 , 8-1 , 3-4 , 7-8: 8 wks + ELQA • Second time a given cryoplant type is used: 5-6 , 6-7: 6 wks + ELQA • For 2008 onwards: 4-5 , 3-4: 4 wks + ELQA • Warm-up: Complete sector: 4 wks the first time (Design: 2 wks) QRL + some cells: 2 wks Proposed durations with expected learning effects to be checked autumn 2007 S. Claudet - Jul’07

  6. Tuning loop adjustments • June 18: Simultaneous, sawtooth ramping of D2 and Q4

  7. Tuning loop adjustments

  8. Valves: Flow caracteristics Large sensitivity gain Installed R ~ 25 New R ~ 100

  9. Availability: From 7-8 to others Cryo Maintain ARC: 66% (Since 1st June) Cryo Maintain LSS: 85% (Since 1st May) DFBMs DFBAs Target LSS: 90% (incl. time lost for quench recovery) Target ARC: 80% (incl. time lost for quench recovery)

  10. Quench recovery for one quadrupole • Quench 720 A => TTregulation + 20 mK • Quench 2000 A => TTregulation + 200 mK & 5 minutes for Cryostart (2 K) • Quench 6500 A => TTregulation + 1.3 K & ~ 40 minutes for Cryostart (< 2 K) • New : Quench 2 x 6500 A => TTregul + 4 K & 2h30 for Cryostart (< 2 K) • => No effect on cold compressors • NB : Cryostart recovery time not yet optimised (presence output limit high on JT valve to limit overshoot)

  11. Recovery Time after Limited Resistive Transitions • 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).

  12. Interlocks: New PIC-Cryo channels • For operation reasons a cryo-start signal for 60 Amps will be implemented taking into account beam screen temperature (heat intercept) and eventually the thermal screen temperature • Details to be discussed with system owner and PIC team • To be implemented already for sector 4-5

  13. Helium quality for distribution • Improvement of He quality with for other refrigerators (sectors) • Problem only for ex-LEP cryoplants from Air Liquide for which the sub-cooler was just made for isothermal refrigeration (LEP) and not for non-isothermal refrigeration (LHC) • Problem identified Autumn’06 • Proposal received for modification, but no agreed yet • The change of refrigerator did not show big impact on commissioning. Major gain to be expected in pseudo liquefaction mode when re-filling after a stop

  14. Vacuum minor leaks • No major problems for stability /cooling power with the levels accepted in sector 7-8 • Can have (depending on the level) some impact on recovery time • More problematic is the leak (no connection) of the Y tube in the bayonet heat exchanger • Can still function with adjacent cell but increase in recovery of cryo start conditions (cooldown)

  15. Time to repair a fault outside working hours • Time to repair a fault occurring just before the week-end: is it adequate for running LHC? => We are not running the LHC we are commissioning it and cryogenics is part of the commissioning … • Is recovery time after problems resource dependant? If so, can extra resource be made available when required eg weekends, nights? • Efforts put on control logic (long term) rather than on manpower (short term) • Furthermore resources need to be trained or be expert in the domain for most of the problems encountered • Efforts and intervention are anyway already performed during the weekends and nights even if you do not realize it • Is it likely that if multiple sectors are commissioned, a cryo problem in one sector will not affect other sectors – thus allowing effort to be put elsewhere? =>YES, machines and teams independent

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