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LHC Project Workshop: Beam Dumping System Requirements

Discussion on operational states, beam commissioning, LBDS beam tests, TCDQ positioning, and safety aspects for LHC project.

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LHC Project Workshop: Beam Dumping System Requirements

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  1. Chamonix 2006 – LHC Project Workshop What is required to get the beam safely out of the LHC B.Goddard AB/BT Input from E.Carlier, J.Uythoven, R.Assmann, V.Kain, J.Wenninger + others http://proj-lbds.web.cern.ch/proj-lbds/ Chamonix 2006 - LHC Project

  2. Outline of talk • Beam dumping system : • Operational states and sequencing • Beam commissioning – what, when and how: • Overview of beam commissioning needed • Fitting into the overall LHC commissioning • Breakdown of individual LBDS beam tests • TCDQ positioning • Discussion points and conclusion Chamonix 2006 - LHC Project

  3. Scope I will focus on ‘Stage I’ as detailed earlier by Roger 1 pilot 43 bunches (41010 p+) 156 bunches ( 91010 p+) Requirements for ‘Stage II’ are basically more of the same Chamonix 2006 - LHC Project

  4. Reminder • Dilution kicker system MKB is staged (2H, 2V) • Limits extracted intensity at 7 TeV to 50% of nominal • For 25ns spacing, this is a limit onsingle bunch intensity, NOT on total in LHC • Not an issue for “Stage I” : could safely dump full beam intensity up to about 2 TeV – (no interlock - rather unlikely to be needed in first few months…) Allowed dumped intensity (staged MKB) BTVDD trace – full dilution BTVDD trace – staged MKB Chamonix 2006 - LHC Project

  5. Q: “when is the LBDS needed….”? See J.Wenninger’s presentation ! • System tests, HWC and Reliability Run to validate internal dependencies of LBDS subsystems, and connection with MP systems (including BIS) no operational Beam Dump system = no Beam permit • However….LBDS can be “operational” for pilot intensity, but “not operational” for 43 bunch running  need representation of “operational state” (LHC sequencer) A: “day 1” Chamonix 2006 - LHC Project

  6. “Bootstrapping” the LBDS operational state Need to drive LBDS operational state from “Not ready” to “Ready for beam” Diagnostics IPOC, XPOC Beam dump triggered Not ready . Arming procedure Ready for no beam Ready for pilot Tests with pilot beam Ready for beam LBDS operational states • BUT LBDS “Ready for beam” can’t distinguish between 1 or 2808 bunches of 1011 p+ • need formal representation of the progress of the LHC commissioning process could envisage MCS + SIS (plus sequencer?) to manage this Chamonix 2006 - LHC Project

  7. Safety critical aspects of the LBDS • Signal from beam interlock system (test in HWC/RR) • No trigger = no beam dump • Energy tracking • Potentially catastrophic (whole beam at “any” amplitude) • MKD retriggering (test in HWC/RR) • No retriggering could put whole 7 TeV beam at ~10s • TCDQ setting • Wrong w.r.t. orbit exposes LHC arc / triplets / collimators. • System self-tests and post-mortem • Undetected ‘dead’ MKD severely reduces reliability • Aperture, optics and orbit • Dump with bad orbit could damage extraction elements MSD, TCDS or MKB • MKD – MKB connection and sweep form • Insufficient dilution could damage TDE, BTVDD and TDE entrance window • Abort gap ‘protection’ • Beam in the abort gaps risks quench, or TCT/LHC damage if TCDQ position error • Fault tolerance with 14/15 MKD • The system is designed to operate safely with only 14 out of the 15 MKDs Nearly all aspects need beam commissioning (validation or optimisation) Chamonix 2006 - LHC Project

  8. LBDS beam commissioning in phase I • Pilot beam: • Before first extraction…. • Before first ramp… • During ramp… • At 7 TeV… • Before moving to potentially unsafe beam: • Interlock commissioning • TCDQ positioning • 43 bunches • Before first extraction… • Before first ramp… • 156 bunches • Before first ramp… Chamonix 2006 - LHC Project

  9. Before first extraction… Circulating beam, 1 pilot at 450 GeV • Optics and other measurements in IR6 • Beta, dispersion, orbit correction, stability • Commission dedicated LBDS BDI for circulating beam • Synch BPM, BLMs (MKD, MSD, TCDS, TCDQ), check direct LBDS interlock BLM • Aperture measurement with circulating beam • MSD, TCDS, MKD, TCDQM Opening for circulating beam (H plane) at TCDS and MSD 15.3 mm (n1=6.5) 20.8 mm (n1=7.0) Chamonix 2006 - LHC Project

  10. Before first pilot ramp…i Extracted beam: 1 pilot @ 450 GeV (inject & dump) • First extraction • Into “Inject & Dump” mode • “Rough” extraction timing • Adjust RF synch  MKD kick delay, S signal from IR6 BPM (UA access for each delay trim!) • Commission extraction line BDI • BTV (SE, D, DD), BPM (SE, D), BLMs, BCTs Any major problems will be apparent at this stage! Chamonix 2006 - LHC Project

  11. Before first pilot ramp…ii Extracted beam: 1 pilot @ 450 GeV (inject & dump) • Verification of extraction trajectory and aperture • Vary orbit in IR6 and measure aperture at TCDS/MSD/TD line • Optimise extraction trajectory (orbit, MKD, MSD); define ‘reference’ (UA access for MKD trim!) • Define limits for interlock BPM reference • Explicit check that aperture is adequate for 14/15 MKD case • Unplugging 1 MKD is not desirable (interlocks to be strapped, undo HWC/RR validation, etc.) • Prefer to check by varying orbit in IR6 (1/15 of 270 mrad…) Opening for extracted beam (H plane) at TCDS and MSD Extracted beam aperture vs IR6 orbit { MKD sweep Chamonix 2006 - LHC Project

  12. Before first pilot ramp…iii Extracted beam: 1 pilot @ 450 GeV (inject & dump) • Logging and fixed displays • Checks that the beam related data is being correctly acquired and displayed • XPOC basic functionality (trajectory, BLMs, BCT, kickers, BTVDD, …) • Check that XPOC validation is working correctly for pilot setup • Issue: safe change of configuration when changing beam. With MCS/SIS/sequencer? • BDI Post-Mortem data • Check that all beam-dependant transient signals from the LBDS systems are being PM’d Chamonix 2006 - LHC Project

  13. Before first pilot ramp…iv 89 ms MKD kick waveform measurements • Important for aperture at TCDS/MSD • BPMD, BTVDD and BLMs. inject & dump, vary injected bunch bucket (5 meas. points) MKB sweep measurements • Important for MKB and TD line aperture • BPMD and BTVDD. inject & dump, vary injected bunch bucket (≈10 meas. points) Extracted beam: 1 pilot @ 450 GeV (inject & dump) MKD kicker waveforms (current signal) BTVDD ‘screenshot’ bunch 1 bunch 1300 Chamonix 2006 - LHC Project

  14. During ramp with pilot… Extracted beam: 1 pilot @ 450-7000 GeV (dump in ramp) • MKD, MKB kicker and MSD septum energy tracking • Extract single pilot at pre-defined energies in the ramp (calibrated points) • Adjustment of kicker lookup tables means UA access • Time-consuming if done as dedicated measurement….need to organise in a quasi-parasitic way • Extraction with 2 pilots during the ramp is also needed to verify the abort gap timing… combine? MKD lookup table calibration data Chamonix 2006 - LHC Project

  15. Before moving to unsafe beams…i bunch 1 turn n 270 mrad kick bunch 2808 turn n-1 3 mrad kick Extracted beam: 2 pilots @ 450 GeV (inject & dump) MKD kicker “fine” timing adjustment • Inject 2 pilots into positions 1 and 2808 (3.0 ms spacing) • Fine adjustment of MKD timing (IR6 synch BPMs and RF frequency) • Acquire last turn of bunch 2808 in LHC to verify MKD kick (0.5 s or 3 mrad) MKD kick waveform 3.0 ms Note: this also needs to be checked through the ramp… Chamonix 2006 - LHC Project

  16. Before moving to unsafe beams…ii Circulating beam: safe beam @ 450 GeV • Abort gap “watchdog” • Commission the link between the LBDS and the injections • Fine timing between IR6 and injections needs to be adjusted with beam • Interlock BPMs for IR6 maximum orbit • Interlocked to around ±3.6 mm. Threshold setting and tests Chamonix 2006 - LHC Project

  17. Before moving to unsafe beams…iii TCDQ Circulating beam: 1 pilot @ 450 GeV • Adjustment of TCDQ/TCS jaws to 450 GeV position (≈10 s) • Beam axis wrt jaw, adjustment of jaw tilt, movement cross-calibration • TCS – 2 jaws - more accurate movement - tighter setting (by ≈1 s) • Needs BLMs and collimator controls • Orbit at TCDQ • Measurement of beam axis Circulating beam: safe beam @ 450-7000 GeV • Establish TCDQ movement function during ramp • Interdependence with collimation system Circulating beam: safe beam @ 7 TeV • Establish TCDQ movement function during squeeze • Accurate adjustment of TCDQ and TCS jaws in final position • Establish reference settings for target b* during next phase of commissioning • Interdependence with collimation system Interdependency on collimation settings, and on orbit feedback Iterations (changes of orbit, b-beat, b*) to finalise TCDQ reference function This looks like a major workup! Chamonix 2006 - LHC Project

  18. Alternative for TCDQ setting during phase I… TCDQ protects arc at 450 GeV and TCTs/triplets at 7 TeV squeezed • 450 GeV - set TCDQ/TCS system up at ±10 s • Rely on ±4 mm interlock to protect arc (maximum excursion at TCDQ is ≈2 s ) • Asynch dump with 156b, max. 2 bunches in interval 7-12 s  Safe for 450 GeV • 7 TeV - pilot near to damage level - set TCDQ/TCS at ±10 s • Rely on 2-jawed TCS to protect the TCTs – don’t worry about the orbit • Keep TCTs at ≈20 s protected for any orbit in IR6 (limits b* to 2 m) • Can then (if needed) delay final orbit feedback + TCDQ beam position + SW interlock full commissioning to b* <2 m • Should improve operational efficiency during stage I • Need to check through all detailed implications • Protection level with TCS - decide safe combinations of intensity/filling pattern • Optics control/knowledge at TCDQ, TCTs and triplets (plus orbit at TCTs/triplets) Chamonix 2006 - LHC Project

  19. Before first 43b ramp… Extracted beam: 43b @ 450 GeV (inject, fill & dump?) • Start with 43 pilots, to keep below the damage threshold • When this is OK, move to 43 bunches of 41010 for validation • Losses in extraction channel and along the dump line • Reduced sweep with staged MKB means generous TD aperture • Check BDI response • Logging, PM and XPOC validations • Establish new reference data for XPOC… BPMD BTVDD Chamonix 2006 - LHC Project

  20. Before first 156b ramp… Extracted beam: 156b @ 450 GeV (inject, fill & dump?) • As per 43b activities… • Plus…..TDE thermal behaviour? • ≈10 kW for nominal beam at 7 TeV every 10 hours • Could load with ≈4 kW with repeated inject, fill & dump of 156 bunches… Chamonix 2006 - LHC Project

  21. LBDS beam commissioning – pilot beam = time consuming Chamonix 2006 - LHC Project

  22. LBDS beam commissioning – 43b Chamonix 2006 - LHC Project

  23. LBDS beam commissioning – 156b This is essentially the same list of activities as from pilot to 43b. It will be essentially the same list for all major changes in LHC beam (filling pattern, significant intensity steps, optics, emittance, …) Chamonix 2006 - LHC Project

  24. Unfinished business… • Inject and dump mode • Needed from first extractions, for efficient commissioning • Details to finalise (timing, PM/logging,, multiple injections, turn delays, HW,SW) • Diagnostics • Split between IPOC, XPOC, logging and PM; XPOC configurations • Abort gap monitoring and cleaning in phase I • Assumed not needed for protection - could be important for efficiency • Topic for another day… • Ensuring that only ‘authorised’ beam can be used • Operational states and allowed LHC beam conditions – MCS, SIS and sequencer • Halo at TCDQ • Effect of “minimum collimation” strategy – risk of frequent Q4 quenches • FLUKA energy deposition simulations give cause for concern – work ongoing • Beam 2 will be worse….not checked yet Chamonix 2006 - LHC Project

  25. Conclusion LBDS beam commissioning for phase I operation: • will depend heavily on HWC/RR; • Validation of subsystem interconnectivity and reliability assumptions • Many key elements will be fully commissioned without beam • requires careful commissioning with pilot beam; • At 450 GeV before extraction, to check the optics and aperture • At 450 GeV in “Inject & Dump” mode, to check the LBDS functioning • During the ramp, to check the energy tracking • requires specific checks when LHC beam changes; • To verify instrument response, diagnostics and losses • can be somewhat relaxed for difficult TCDQ/TCS positioning; • By taking advantage of limited b* squeeze and number of bunches Chamonix 2006 - LHC Project

  26. Chamonix 2006 - LHC Project

  27. LBDS functional dependencies - overview Chamonix 2006 - LHC Project

  28. External “subsystems” requiring beam LHC control system Ethernet LBDS DCCTs Access BPM IR6 Fast timing (RF synch) BLM6 TCDQ position Direct triggers (to TSU) Slow timing Abort gap monitor Emergency stop status IR6 PM trigger Mains & UPS status IR6 orbit feedback External outputs External inputs Machine Protection interfaces SLP Injection BICinterface Software interlock LHC beam permit loop Chamonix 2006 - LHC Project

  29. Primary LBDS failure catalogue

  30. Lookup tables in the LBDS • Lookup tables within Beam Energy Tracking sub-system to convert physical measurements to energy • Conversion of main bending currents to energy • Conversion of energy to kicker voltage references • Conversion of extraction septa currents to energy • Conversion of ring quadrupole Q4 currents to energy • Conversion of kicker voltages to energy Modification (e.g. adjust MKD strength)  reprogram local FPGAs E.Carlier Chamonix 2006 - LHC Project

  31. Look-Up Tables - Which Type and Where Tracking Interlock Logic |EbeamB – EbeamKiMi|>0.5% * EbeamB EbeamKi UmeasKi Normalisation to Beam Energy Kicker HV Generators Q4 & SeptaMagnets ImeasMi EbeamMi Acquisition Settings Normalisation to Beam Energy Operational Settings Kicker HV Generators Main Bends UrefKi ImeasA EbeamA Reference Normalisation to Beam Energy Main Bends Imeas B EbeamB Dump Trigger Request Interlock Acquisition Tracking First Order Interpolation Memory Map Chamonix 2006 - LHC Project

  32. Energy tracking performance Chamonix 2006 - LHC Project

  33. “Bootstrapping” the LBDS operational state • BUT LBDS “Ready for beam” can’t distinguish between 1 or 2808 bunches of 1011 p+ • need formal representation of the progress of the LHC commissioning process could envisage MCS + SIS (plus sequencer?) to manage this Ready for pilot LBDS “Ready for pilot” commission pilot prepare for 43 bunches Ready for 43 bunches commission 43 bunches prepare for 156 bunches Ready for 156 bunches LBDS always “Ready for beam” commission 156 bunches prepare for 936 bunches Ready for 936 bunches commission 936 bunches prepare for 2808 bunches Ready for 2808 bunches commission 2808 bunches LHC state Inside each activity are commissioning steps for LBDS, which must be completed and “signed-off” before overall LHC is declared “Ready” for next stage. Chamonix 2006 - LHC Project

  34. Areas for concern – halo at TCDQ • Halo at TCDQ • Effect of “minimum collimation” strategy • High load on TCDQ risks frequent Q4 quenches • Load from beam tracking: input for FLUKA energy deposition simulations • Beam 2 will be worse – not checked yet Thermal load in Q4 coil due to halo nominal cleaning no beam cleaning 0.03mW/cm3 15mW/cm3 A.Presland Chamonix 2006 - LHC Project

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