“Issues Effecting the Efficiency of Beam Commissioning” (Discussions and Decisions)

1. “Issues Effecting the Efficiency of Beam Commissioning”(Discussions and Decisions) Chamonix XIV, January 2005 Steve Myers

2. Object of this Session • Try to collect important issues and loose ends • Discuss their impact on efficiency of beam commissioning • Propose follow-up (TTC, MARIC, LTC…) and solutions • Same procedure used in the past and nearly all items for 2004 have already been treated during 2004 in LTC • Tendency to concentrate on problems etc might appear negative… not true

3. 1 Overview Beam Commissioning • Estimated 2 months (highly ambitious!) from 1st turn to 1st collisions (was 3 months in Chamonix 13) • Ensuring the tracking of all power supplies in the 8 sectors (needs tools, and beam time)

4. 1 Overview of Commissioning • Software needed for sliding bumps for efficiency • Many parameters, polarities, apertures etc can be checked • Beta Beating accuracy • Estimates of β beating with/without magnetic measurements of insertion and stand-alone quads • Accuracy of magnetic measurements, LEP experience? • Time needed to do necessary calibrations with beam • Algorithms and tools (difficulty of chains of quads)

5. 1 Overview of Commissioning • Ramp and Squeeze • Zero crossings for power converters cannot be avoided • ? Squeeze one IP at a time or all together? • ? Hybrid or combined ramp/squeeze • Beam Instrumentation • Instrumentation needs applications software: need for co-ordinated effort on applications • BLM understanding of measured signals is non-trivial • Systems commissioners to be nominated • Beam synchronized timing (BST) necessary for full functionality of the BI equipment

6. 2 Scheduling LHC Operation • 32 weeks operation, 16 weeks shutdown, 4 weeks MCO • Operation periods of 25 days beam, 3 days technical stop • 140 days of physics per year • 6 weeks testing for Machine Check-out !!! • Beam Scrubbing for electron cloud • Confidence in obtaining SEY < 1.3? • No limitation with 75ns operation • 25ns OK for Nb < 3.1010 p • Scrubbing needed for Nb > 5.1010 p • Scrubbing should be scheduled before shutdown for vacuum reasons, ??? radiation

7. 2 Scheduling LHC Operation • “Requirements” from the experiments (wish-list!) • Initially pile-up events 1-2 • 4fb-1 allows discovery of SM Higgs • 1fb-1 allows discovery of supersymmetry • LHCb dipole polarity to change on each run! • ALICE: reduce luminosity by increased beta • 75ns useful but 2 weeks enough! • 3 experiments taking data for lead ions • TOTEM, LHCf, etc…..

8. 2 Scheduling LHC Operation • My Summary of Experimental Requirements • Energy range 0.9—7.0Tev • Luminosity range 1025 – 1034 • Magnet settings: all possible variations of polarities and settings • Particles, protons and ions and … • No. of bunches 10 – 2880 • Beta values: complete range • Performance improvement in colliders is best achieved by repeating the same beam conditions run after run. • We need a greatly reduced prioritized list of operating conditions…LHCC/LHC Physics coordinator/JE

9. 3 Cryogenic and Vacuum Issues • Leaks in LHC Vacuum Beam System • localized He leak causing quenches likely not visible in beam lifetime or emittance. Helium front propagates slowly (few cm/hr) - only after weeks or months arriving at closest pressure gauges (placed every 300-400 m); • standard beam-loss monitoring system (every 53 m) may be unable to detect leak • solution: deploy mobile “BLM snake” with 2-m BLM spacing • alternative solution ?? • debunch test proton beam at injection & measure the electron current from gas ionization; large ionization cross section (Mbarn vs. barn) yields orders of magnitude higher sensitivity than BLM system; method was used at ISR and AA; response is fast due to high e- drift velocity; Technical Implications need to be worked out • Commissioning the DFB • manpower needed for commissioning, should be trained by Aug 2005

10. 4 Other Issues • Electrical Quality Assurance • Sector test is a MUST for optimization of ELQA • Staff needed after 2007 “polish contract” • Magnet Polarity • Oouuff! • Many potential problems uncovered. Great job done! Without this analysis we would have been in serious trouble with polarities • But, this is so important I would appreciate a second opinion, looked at from a different angle…just to be sure! • Quench protection System • Quote of the workshop “a faulty trigger a day keeps the Higgs away! • RF commissioning • Beam can survive an RF trip up to 50% of nominal

11. 4 Other Issues • Pre-commissioning BI systems • Still some possibilities for cable polarities errors • BUT easily tested with beam ( 2x 90 deg bumps) • BLM location confirmation, by placing source on each chamber one by one • Radiation doses in LHC beam cleaning • FLUKA is a “new” powerful tool for the calculations • There will be large doses for a collimation repair • External companies must be certified for work exposed to radiation

12. 5 Other issues • Lead Ion Injector Complex Commissioning • electron cooling delivered 16th Dec 2004 • ECR source was delivered from CEA Grenoble end Jan 2005 • LEIR conversion to be finished by Aug 2005 • Problem: delivery of vacuum bellows delayed by 4 months • Continuing the installation with old “spares” • VAC people propose NOT to continue installation with “old” bellows • Commissioning by 1st Mar 2006 • First beams in LHC possible in April 2008 • Conflict between AD operation and LEIR Operation in 2006 (same team) • Flexibility may be needed in order to allow parallel operation of LEIR and AD. Would allow some contingency in schedule for commissioning PS and SPS with ions

13. 5 Other issues • TI8/TT40 Tests • TI8 will need re-commissioning in 2006 • Tunnel temperature did not increase as predicted...needs follow up (TS dept) • EMC on temperature probes of extraction septum • Need a Mr. EMC for LHC **** • Injection and Transfer Lines • Injection can provoke damage.. 288 bunches, nominal current corresponds to 20 x the damage limit and 10,000 times the quench limit • Emittances are large and the aperture is small • Optics flexibility very desirable for beam transfer collimation (phase advances) • ?? More power converters or move collimators (question of finding space)

14. 5 Other issues • Safe Injection in the LHC • “Beam presence” signal a pre-requisite for high intensity injection • ? Add machine settings at time of injection of the “present beam” to condition • Detector equipment affecting beam operation • Magnets and compensators in all insertions • ZDC, VELO, RP IR5/IR1 • MPWG already involved, proposal soon • Who controls what? Answer CCC • Protection of detectors, beam dump interlock from experiments? • Experiment-Machine Interface and signal transfer • ATLAS lumi monitor (LUCID) useful for operations • Beam condition monitor from experiments • Possible background problems for ALICE/LHCb

15. 6 Effects of the Schedule Compression • Update on Installation Schedule • Summer 2007 taken as a “constraint” (sine qua non) •  need to gain at least 6 months •  advance the work for magnet interconnect •  skip cold QRL commissioning (risk analysis) •  magnet interconnect in parallel with QRL installation (risk analysis) •  AL must increase their production schedule • 1240 cold masses available by summer 2006 • SM18 magnet testing finished by end 2006 • Transport needs 20 cryo-magnets/ week • 90 weeks.. (Mar 05-Dec 06) • New Initial Planning (No limitation in resources) • Installation and HW commissioning finished 1st July 2007 • Sector test for 4 weeks, Nov-Dec 2006 • “no transport during X-Raying of welds” (RP) • Survey people to be working during magnet cool down (safety issue)

16. 6 Effects of the Schedule Compression • SM18 Magnet Testing • Enormous progress • Baseline 20% now was 30% Chamonix 13 • Need prioritization of quad testing (SSS and stand-alone) • Beta beating… see earlier • Controls • Good results from TI8/TT40 • Milestone approach very useful • LEIR this year will provide an acid test • Applications software: How to plan the production • LSA generic applications software • System commissioners

17. 7 Magnets (1.5) • Production of Dipoles and Quads • Tremendous progress • “last issue” austentic steel collars • “No strong reason to operate below 7TeV, except heat margin: better to reduce beam intensity..” • 30 additional dipole spares for FC in March • Magnet change will take 20 days (?including warm-up and cool-down?) • Other Magnets • Will MQTL be ready for sector test? (in house production) • Repair of magnets defined by “lack of staff”, radiation cool down, spares • MQXA, MQXB, MBX, MBRB, MBRS…. 6 months!! • MQM, MQY, MQTL …. 3 months !!

18. 7 Magnets (1.5) • Machine Optics vs Requirements • Warm-cold correlations not established for many quads • Integrated gradient (transfer function)… beta beating • Measurements needed for MQM, MQY ( plus the rest?) • Prioritization of quads which should be magnetically tested • Influence of the beam screen on the multi-poles • Magnetic measurements and RMS for commissioning • No on-line RMS • Faster magnetic measurements • 3Hz by improved digital integrator • 10Hz on sextupole measurements with Hall Plate • ? Continued measurement program after Jan 2007 on spares • Transfer functions with hysterisis are needed for beam commissioning

19. 7 Magnets (1.5) • Magnet Storage Issues • Preliminary Result • “Dipoles are like good wine, they improve with storage even at varying temperatures” • ? Influence of storage time and conditions on the cold diodes

20. 8 Machine Protection (1.5) • Overview • Beam dumped 3 turns after Beam Interlock signal is triggered • Beam presence needs to have machine settings included • Fast BCT monitor** (final safety net) • Fast magnet Current Decay Monitor for septa, D1 etc • Reaction time of 1ms for 0.3% current drop needed • Prototype tested and works…resources needed for operational device • ? Ions needs some additional studies wrt Machine protection • Collimators and Absorbers • Needing further discussion • Controls approach • Commissioning, squeeze etc • Minimal single stage cleaning/protection • Overcome possible beam loss limitations during commissioning

21. 8 Machine Protection (1.5) • A reduction of 0.5 sigma in cold aperture will result in factor 6 higher losses • => Support for conclusion that beta beat must be studied and the tight tolerances on beta-beat/orbit be reviewed. • Loss pattern shows loss spikes up to factor 10 above "simple" quench limit! •  advanced shower calculations, more detailed quench studies and estimates of BLM signal response needed •  commissioning of collimation and BLM systems.

22. 8 Machine Protection (1.5) • BDI for machine protection (in addition to BLM) • Excellent progress • Beam position interlock in IP6 for beam dump • Interlock for protection against asynchronous beam dump • Protection against oscillations and fast orbit changes • Beam Current Loss detector  fast interlock • Commissioning aspects of machine protection • Awareness of machine protection is now at the highest level • Fast losses, limits need to be verified by experiments (simulations) • Must be “safe” from the start • Formal, pre-testing, HW commissioning, • Same system as in SPS • Sector test invaluable

23. 8 Machine Protection (1.5) • Objects capable of touching the beams • 500 objects can touch the beam • Vacuum valves • Screens, stoppers, wire scanners, • Fast valves • Coherent approach needed for all objects which can touch the beam, Chamonix 14 (2004) • “Green Light for Operations” • MP system SIL2 ( 10-7/hour) but should be SIL3 (10-7–10-8/hour) • New analysis may move it to SIL3 • False dump rate 5% (? High)

24. 8 Machine Protection (1.5) • Quench Limits • Simulations and Comparisons with experiments is URGENTLY needed (was successfully done for HERA) • Damage Levels • Controlled experiment (SPS) with excellent albeit preliminary results • Work will continue

25. The END • Sincere thanks to: • Chair persons and scientific secretaries • All participants • Last and very importantly • Tjitske • Chamonix 2006: • strong motivation (following Chamonix 2005) to organise the workshop OUTSIDE CERN • More news after my MAPs