16 June 2006LHC Machine Advisory Committee1/20 LHC Machine Advisory Committee Commissioning the Beam Dumping System Brennan Goddard AB/BT Input from E.Carlier, L.Ducimetière, M.Gyr, L.Jensen, J.Uythoven, V.Mertens, R.Assmann, V.Kain, R.Schmidt, M.Lamont, W.Weterings + many others

16 June 2006LHC Machine Advisory Committee2/20 Outline Beam dumping system overview : –Principles –Layout –Safety critical aspects Commissioning without beam : –Individual System Tests –Hardware Commissioning –Reliability Run Commissioning with beam: –Overview of individual LHC Beam Dump System (LBDS) beam tests –Known problem areas Ongoing work Conclusion

16 June 2006LHC Machine Advisory Committee3/20 LHC beam dump principle (and acronyms) Dump block Dilution kickers Extraction kicker Extraction septum Passive diluter

16 June 2006LHC Machine Advisory Committee4/20 TD62 TD68 UD62 UD68 UP62 UP68 UJ62 UJ68 UJ63 UJ67 UA67 RA63 UA63 Underground kicker installations around P6 Extraction kicker generators, cables and magnets RA67 Dilution kicker generators, cables and magnets

16 June 2006LHC Machine Advisory Committee5/20 Also a lot of sub-system interconnectivity Example: critical triggering/retriggering –Synchronised to abort gap (internal PLL locks to rev. freq.) –Parallel path with 1 turn delay by-passes synchronisation system –Retriggering system detects any trigger and re-distributes –Large amount of redundancy with crossed trigger lines – all needs commissioning 2 of 15 generators shown

16 June 2006LHC Machine Advisory Committee6/20 Safety critical aspects of the LBDS Signal from beam interlock system (test in Hardware Commissioning/Reliability Run) –No trigger = no beam dump Energy tracking (test in HC/RR & with beam) –Potentially catastrophic (whole beam at “any” amplitude) Extraction kicker retriggering (test in HC/RR) –No retriggering could put whole 7 TeV beam at ~10  Mobile diluter TCDQ setting (test with beam) –Wrong w.r.t. orbit exposes LHC arc / triplets / collimators. System self-tests and post-mortem (test in HC/RR & with beam) –Undetected ‘dead’ extraction kicker severely reduces reliability Aperture, optics and orbit (test with beam) –Dump with bad orbit could damage extraction elements (septa, diluters) Extraction-dilution kicker connection and sweep form (test in HC/RR & with beam) –Insufficient dilution could damage dump block, entrance window and screens Abort gap ‘protection’ (test with beam) –Beam in the abort gaps risks quench, or aperture damage if TCDQ wrongly positioned Fault tolerance with 14/15 extraction kickers (test in HC/RR & with beam) –The system is designed to operate safely with only 14 out of the 15 kickers Nearly all aspects need beam commissioning (validation or optimisation) Increasing severity

16 June 2006LHC Machine Advisory Committee7/20 Reminder – staged dilution system Dilution kicker system MKB is staged (2/4 H, 2/6 V installed at startup) –Made for budget profile reasons, with argument that anyway intensity  50% in first 2 years Limit on single bunch intensity (not possible to fill 50% of the ring with full intensity bunches…) –Can dump full beam intensity up to ~2 TeV…but safer to limit the intensity at injection –Remaining MKBs installed in 08/09 shutdown (conditional on actual installation/commissioning) Allowed dumped intensity (staged MKB) Nominal beam, full dilution50% nominal beam, staged MKB

16 June 2006LHC Machine Advisory Committee8/20 Individual System tests Equipment groups provide tested sub-systems ready for Hardware commissioning –Entry/exit condition, procedures & requirements defined with sub-system engineers and HC team –Formal Test Procedures for most LBDS sub-systems presently in preparation

16 June 2006LHC Machine Advisory Committee9/20 Individual System tests Example: outline of Individual System Tests for extraction kickers –Details of Individual System Tests for the equipment Pulse the system and check all signals at 450 GeV equivalent voltage; Measurement of the pulse form (magnet current); Set up system timing without beam (adjustment of trigger voltage); Commission Internal diagnostics and post-operational check; Ramp the system and check all signals up to 7 TeV equivalent voltage; Set up kick strengths (adjust settings for different beam energies), Stability and reproducibility measurements at 7 TeV equivalent voltage –Estimated duration 4 weeks per beam for MKD, 1.5 weeks per beam for MKB –Services required Electrical distribution system; Fire detection system; UPS system; Ethernet network infrastructure; Distribution of the LHC timing; Vacuum (ceramic chambers, interconnects, sector valves, pumps, gauges, bake-out) –Special safety or access conditions No access limitations during the HV conditioning and tests (systems designed such that contact with HV is not possible: All HV components contained in grounded metallic containers or racks, disconnection or opening not possible without special tools); Yellow flashers and Emergency Stops in RA and UAs next to equipment –Impact on transport or other activities in the zone In principle No: however, basic considerations to enhance personnel safety may lead to implementation of transport restrictions during IST, or other additional safety measures.

16 June 2006LHC Machine Advisory Committee10/20 Hardware Commissioning Hardware Commissioning to provide commissioned LBDS system to LHC OP –Defined with HC Team and system engineers – Formal HC Test Procedures exist in draft form; still to be finalised and approved

16 June 2006LHC Machine Advisory Committee11/20 Hardware Commissioning Main emphasis will be on testing the interconnections between the sub-system components and the connections to external systems –Critical link to beam permit loop –Signals from other systems (RF, PO) –Control and data exchange –Direct triggers (access, local BLM) –Links to Safe LHC parameters and Injection kickers –Internal and External Post-Mortem processes ?

16 June 2006LHC Machine Advisory Committee12/20 Reliability Run System “burn-in” by AB/BT and LHC OP in final configuration from CCC. –System debugged, and reliability assumptions measured. –Discover hidden flaws –Check sub-system interdependencies Test pulsed systems after realistic waiting times; –Generate statistics to give upper bounds on failure rates –Validate reliability calculations; –Bathtub reliability curve: if problems found, take time to repair and check statistics again ‘Debugging’ phase –obvious/frequent faults are found and repaired. ‘Statistics gathering’ phase –‘operational’ system reliability can be estimated and compared to calculated values. ‘Fault injection’ phase –test (where feasible) functioning of error/fault detectors, fault tolerance and surveillance After each dump action perform full Internal and External post-operational checks on pulse generators and power converters –Check all currents and voltages in tolerance, relative to look-up tables. –Look for trends and correlations in measured signals –Determine if any parameter is outside margin Impact of final LHC HC scenario and planning needs to be evaluated

16 June 2006LHC Machine Advisory Committee13/20 Reliability Run – what can be learnt? Draft programme exists but detailed and coherent methodology to be elaborated Schedule: need 3 months to make any meaningful conclusions –Needs system operating with connections to external components –Much shorter period will not allow quantification of reliability assumptions Estimate MKD failure rate upper bound for test duration T, to try to demonstrate the design hypothesis: (failure rate per MKD branch ≤10 -4 /h). –Expect ~4 failures in 3 months for assumed /h rate. A type I censored reliability testing with fixed duration T and pulsing frequency f is performed. The sampling distribution is Binomial. The curves in the figure are the one-sided 95% failure rate confidence intervals for 75% effective running time, f =1/h, T = 1,2,3 and 4 months and number of failures from 0 to 30.

16 June 2006LHC Machine Advisory Committee14/20 Beam Commissioning AB/BT and LHC OP to provide dump system ready for each new operational phase –LBDS will be “commissioned” for a defined operational parameter space. –Entry/exit condition, procedures & requirements fairly well defined with sub- system engineers and HC team. –Formal Test Procedures for most LBDS sub-systems presently in preparation – to be finalised and approved. Methods, requirements and steps already analysed in detail for LHC phase I (up to 156 bunches) –Still to be fitted in to overall machine protection and beam commissioning plan –Procedures and steps now being formalised with LHC OP – substantial work Implications with collimation being addressed –e.g. Halo load on TCDQ diluter for reduced collimation scheme

16 June 2006LHC Machine Advisory Committee15/20 Entry conditions for beam commissioning defined LHC Commissioning Procedures repository

16 June 2006LHC Machine Advisory Committee16/20 LBDS beam commissioning – pilot beam LBDS beam commissioning activityLHC modeBeam typeEnergy GeV With initial 450 GeV/c circulating beam IR6 optics measurementsInjectionCirculating 1 pilot450 Commission dedicated LBDS BDI in IR6InjectionCirculating 1 pilot450 Extraction element aperture measurementsInjectionCirculating 1 pilot450 Commission SW interlock on beam position at TCDQInjectionCirculating, safe beam450 Commission IR6 orbit BPM interlockInjectionCirculating, safe beam450 Commission abort gap watchdogInjectionCirculating, safe beam450 TCDQ “injection setting” positioningInjectionCirculating, safe beam450 Orbit feedback / stability checks at TCDQInjectionCirculating, safe beam450 With 450 GeV/c extracted beam First extractions: rough timing adjustmentInject & dumpExtract 1 pilot450 TD line BDI commissioningInject & dumpExtract 1 pilot450 Extraction trajectory and aperture measurementsInject & dumpExtract 1 pilot450 Check of aperture and trajectory with 14/15 MKDInject & dumpExtract 1 pilot450 Data diagnostics: IPOC, logging, FDs, PMInject & dumpExtract 1 pilot450 Verification of post-operational checks (IPOC, XPOC)Inject & dumpExtract 1 pilot450 MKD waveform overshoot measurementsInject & dumpExtract 1 pilot450 MKB sweep measurementsInject & dumpExtract 1 pilot450 Fine timing and amplitude adjustmentInject & dumpExtract 2 pilots450 Through the energy ramp 450 – 7000 GeV/c Energy tracking measurementsRampExtract 1 pilot TCDQ position function through rampRampCirculating, safe beam Fine timing and amplitude in rampRampExtract 2 pilots At 7000 GeV/c TCDQ positioning function through squeezeAdjust/squeezeCirculating, safe beam ms Extraction kicker waveform measurements -Importance: high (defines aperture at TCDS/MSD) -Tools: BPMD, BTVDD and BLMs. -Mode: inject & dump. -Intensity: Pilot bunch -Method: vary injected bunch bucket (6 measurement points). Calculate kick at MKD and compare to tolerance limits from MKD system measurements

16 June 2006LHC Machine Advisory Committee17/20 LBDS beam commissioning – intensity increase LBDS beam commissioning activityLHC modeBeam typeEnergy GeV With 450 GeV/c circulating beam Orbit feedback / stability checks at TCDQInjectionCirculating450 Checks of EMC on BI and control signalsInjectionCirculating450 Test response of abort gap monitorInjectionCirculating450 Check abort gap cleaningInjectionCirculating450 With 450 GeV/c extracted beam Extraction trajectory checksInject & dumpExtract450 TD line beam instrumentation checksInject & dumpExtract450 Data diagnostics: check XPOC responseInject & dumpExtract450 Define new references for correctly executed beam dumpInject & dumpExtract450 TDE thermal responseInject & dumpExtract450 Beam loss profiles (extraction, TD lines and TDE)Inject & dumpExtract450 Through the energy ramp Energy tracking and abort gap timing checksRampExtract during ramp At 7 TeV Checks of EMC on BI and control signalsAdjust/squeezeCirculating7000 Test response of abort gap monitorAdjust/squeezeCirculating7000 Check abort gap cleaningAdjust/squeezeCirculating7000 Data diagnostics: check XPOC responseAdjust/squeezeExtract7000 Define new references for correctly executed beam dumpAdjust/squeezeExtract7000 TCDQ positioning at 7 TeVAdjust/squeezeCirculating7000 Each commissioning step (intensity increase, # bunches) needs LBDS (re)tests –Must be completed before operation with the new beam conditions can be allowed –Method to enforce this ‘allowed’ LHC operational configuration still to be finalised

16 June 2006LHC Machine Advisory Committee18/20 Known “problem” areas – TCDQ TCDQ diluter (+ TCS collimator) protects aperture against particles in abort gap –unsynchronised dumps, extraction kicker pre-triggers, uncaptured beam Setting-up of this diluter will be time-consuming –Interdependency on collimation settings, and on orbit feedback –Iterations (changes of orbit,  -beat,  *) to finalise TCDQ reference/interlock function Can by-pass some setting-up stages for early operation –450 GeV - set TCDQ/TCS system up at ±10  Rely on ±4 mm interlock to protect arc (maximum excursion at TCDQ is ≈2  ) Asynch dump with 156b, max. 1 bunch in interval 7-12  Safe for 450 GeV –7 TeV - pilot near to damage level - set TCDQ/TCS at ±10  Rely on 2-jawed TCS to protect the TCTs – don’t worry about the orbit Keep TCTs at ≈20   protected for any orbit in IR6 (limits  * to  2 m) Can then (if needed) delay full commissioning (final orbit feedback, fine TCDQ / beam positioning, SW interlock) to  * <2 m Will be simpler and should improve operational efficiency during stage I –Need to check optics control/knowledge, plus orbit at aperture limitations

16 June 2006LHC Machine Advisory Committee19/20 Areas where work is still ongoing Formalisation of the various commissioning procedures –Individual system tests – outline drafted –Test Procedures to be made and approved –Hardware Commissioning – draft Test Procedure to be updated and approved –Reliability Run – Test Procedure to be written –Beam Commissioning – details exist – being incorporated in LHC OP commissioning procedures Inject-and-dump mode –Needed from first extractions, for efficient commissioning –Concept exists: details to finalise (timing, multiple injections, turn delays, HW,SW, logging) Diagnostics –Internal and External post-operational checks – definition and prototyping phase now in progress Configuration management –Measurement, test and commissioning results to be maintained, plus operational data and settings –Management of critical settings (MCS) – reference management needs subset of MCS presently in definition Ensuring that only ‘authorised’ beam can be used –Operational states and allowed LHC beam conditions still to be defined in adequate detail –Wider issue of OP software for machine protection (MCS, SIS, sequencer, …) outstanding Abort gap monitoring and cleaning –Details still to be worked out (limits, how to operate damper for cleaning, losses) Halo at TCDQ - effect of “minimum collimation” strategy on energy deposition in Q4 –FLUKA energy deposition simulations results show TCDQ is a concern – intense study ongoing Operation with ions - intercepting devices (diluters, dump block, entrance window) –Checks of effects of BI response and optics/orbit control – FLUKA work now being defined Wide-ranging and heavy workload for LBDS project – low in dedicated resources in AB/BT and rely heavily on various collaborators

16 June 2006LHC Machine Advisory Committee20/20 Conclusion LHC Beam Dump system commissioning : Starts with the Individual System Tests; Will depend heavily on careful Hardware Commissioning; –Many key elements and connections will be fully commissioned without beam; Requires a Reliability Run to guarantee safety of the system; –Validation of subsystem interconnectivity and reliability assumptions; –Debugging and fault finding in initial ‘simulated’ operational period; Requires careful tests and checks with beam; –A lot can be done with pilot beam; At 450 GeV before extraction, to check the optics and aperture; At 450 GeV in “Inject & Dump” mode, to check system functionality; During the ramp, to check the energy tracking and timing; –Requires specific checks when LHC beam conditions change; To verify instrument response, diagnostics and losses; –Can be somewhat relaxed for difficult TCDQ/TCS positioning in early stages; Take advantage of limited  * squeeze and limited number of bunches; Still a lot of work to be done