“issues effecting the efficiency of beam commissioning” (discussions and decisions)

Chamonix 2005 Summary Session 9.ppt) CERN Auditorium Feb 2, 2005

“Issues Effecting the Efficiency of Beam Commissioning”

(Discussions and Decisions)

Chamonix XIV, January 2005

Steve Myers

2Chamonix 2005 Summary Session 9.ppt) CERN Auditorium Feb 2, 2005

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


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)


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)


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


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



“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…..



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


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


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


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


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


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)


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


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)


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


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 !!


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


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


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



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.



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



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)



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


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

“issues effecting the efficiency of beam commissioning” (discussions and decisions)

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