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MKI UFOs

MKI UFOs. LIBD Meeting Tobias Baer November, 29 th 2011. Acknowledgements : M. Barnes, C. Bracco, N. Garrel , B. Goddard, S. Jackson, V. Mertens , M. Misiowiec , E. Nebot, A. Nordt, J. Uythoven, J. Wenninger, C. Zamantzas, F. Zimmermann, …. Content. Content. Lead MKI UFOs.

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MKI UFOs

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  1. MKI UFOs • LIBD Meeting Tobias Baer November, 29th 2011 Acknowledgements:M. Barnes, C. Bracco, N. Garrel, B. Goddard, S. Jackson, V. Mertens, M. Misiowiec,E. Nebot, A. Nordt, J. Uythoven, J. Wenninger, C. Zamantzas, F. Zimmermann, …

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  4. Lead MKI UFOs • MKI UFO at MKI.D5R8. • 10 % of threshold at MQML.10L8.Losses are not localized as for protons. • Highest loss is in the dispersion suppressor downstream of the IR (due to ion fragmentation). IP8 MQML.10L8 (highestloss) MKI (UFO location) TCTH Horizontal dispersion

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  6. Delay of UFO events • In total 57 UFO events • 44 at MKIs in Pt.8 (41 pulses) • 13 at MKIs in Pt.2 (35 pulses) • The distributionlookssimilarforthe MKIs in Pt. 2 and Pt. 8. • The firstcleareventsoccured 10.2ms after pulsingthe MKIs.UFO detection in first ≈20ms is limited by transient lossesduring MKI pulse. 1 eventat 1330 ms zoomed

  7. Delay of UFO events • The distributionspreads out over a fewhundredms. The firstevent was observedabout 3ms after MKI pulse (in IQC). 1 eventat 1330 ms UFOs in IQC until 11.08.2011 zoomed

  8. UFO Location • In Pt. 2 most UFOs occuratMKI.D5L2. In Pt. 8 thedistributionismoreequal. 270 candidate UFOs around MKI in Pt.8. Signal RS01 > 1∙10-3Gy/s. Beam 2 Beam 1 Pt. 8 Pt. 2 174 candidate UFOs around MKI in Pt.2. Signal RS01 > 1∙10-3Gy/s.

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  10. MacroParticleSize F. Zimmermann at LMC 109

  11. MacroParticle Size • From FLUKA simulations:4.07·1011interactions per Gy atBLMEI.05L2.B1E10_MKI.D5L2.B1 at 3.5 TeV. • Peak lossof 8.45 Gy/s correspondsto 3.44·1012interactions/s. • With (r << σ) Radius of large UFOs must beat least ≈40µm. UFO event on 16.07.2011 14:09:18 Particlemass I=1.02·1014protons, E=3.5 TeV, with ԑn=2.5µm·rad, βx=158.5m, βy=29.5m, σx=325µm, σy=140µm. Nuclearinteractionlength

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  13. IPAC Abstract • UFOs in the LHC • T. Baer, M. Barnes, N. Fuster Martinez (U. Valencia), N. Garrel, B. Goddard,E.B. Holzer, A. Lechner, V. Mertens, E. Nebot del Busto, A. Nordt, J. Uythoven,J. Wenninger, F. Zimmermann, … • One of the major known limitations for nominal operation of the Large Hadron Collider is so called UFOs (Unidentified Falling Objects). UFOs are thought to be micrometer to millimeter sized dust particles which lead to fast beam losses, with a duration of the order of 10 turns, when they interact with the beam. The first UFO events were observed in July 2010 and they have caused 35 protection beam dumps since then. In 2011, the diagnostics for such events were significantly improved, dedicated experiments and measurements in the LHC and in the laboratory were made and complemented by simulations and theoretical studies. This allows estimates of the properties, dynamics and production mechanisms of the dust particles. The state of knowledge, extrapolations to nominal LHC parameters and mitigation strategies are presented.

  14. Thank you • for your Attention • Tobias Baer • CERN BE/OP • Tobias.Baer@cern.ch • Office: +41 22 76 75379 • Further information: • T. Baer, “UFO update”, Mini-Chamonix Workshop, July 2011. • R. Ballester, “Vibration analysis on an LHC kicker prototype for UFOs investigation”, EDMS Report No. 1153686, August 2011. • M. Sapinski, “Is the BLM system ready to go to higher intensities?”, Workshop on LHC Performance, Chamonix, Jan. 2011. • F. Zimmermann, “Interaction of macro-particles with the LHC proton beam”, IPAC’10.

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  16. UFO at 09:54:28 • Study bufferprovidesinformationabouttemporalandspatialdistributionaswellasamplitudeof UFOs after MKI pulse. beam Lossesofunbuched beam at TDI 11.2s2.56ms resolution UFOs

  17. Temporal Loss pattern Temporal losspatternofthe MKI UFO at 24.11.2011 13:58:38 atthree different BLMs leftandrightof IP8.

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  19. UFOs in the LHC • Since July 2010, 35 fast loss events led to a beam dump. • 18 in 2010, 17 in 2011. 13 around MKIs. 6 dumps by experiments. 1 at 450 GeV. • Typical characteristics: • Loss duration: about 10 turns • Oftenunconventionallosslocations (e.g. in thearc) • The events are believed to be due to (Unidentified) Falling Objects (UFOs). Spatialand temporal lossprofileof UFO on 23.08.2010

  20. Beam dump on 29.05.2011 • Dump on running sum 1-6.

  21. Beam dump 29.05.2011 • From fit to losses (BLMQI.28L8.B1E10_MQ): • Amplitude: 2.4 Gy/s (Threshold: 2.1 Gy/s) • Temporal Width: 97 µs resulting speed of transiting dust particle = 3.6 m/s.(assuming ϵn=2.5µm·rad) (also cf. J. Wenninger at MPP March 2011)

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  23. UFOs Below Dump Threshold • 2010: Logged BLM data was analyzed and 113 sub-threshold UFO events were found.(E. Nebot) • For 2011: Online UFO detection in 1Hz BLM data. • Over 10000 candidate UFOsbelow threshold found. • Most events are much below threshold. • Between 2010 and 2011,UFO related beam dumpswere reduced by increasingthe BLM thresholds for losseson ms scale by a factor 5. 2780 arc UFOs (≥cell 12) at 3.5 TeVwith signal RS05 > 2∙10-4Gy/s. Distribution ofarc UFOs.

  24. Spatial UFO Distribution 3.5 TeV3686 candidate UFOs. Signal RS05 > 2∙10-4Gy/s. Red:Signal RS01 > 1∙10-2Gy/s. 450 GeV486 candidate UFOs. • Signal RS05 > 2∙10-4Gy/s. Mainly UFOs around MKIs UFOs occur all aroundthemachine. ManyUFOs aroundinjectionkickermagnets (MKIs). gray areas around IRs are excluded from UFO detection.

  25. UFO rate • On average 6.0 UFOs/hour. • Nointensitydependencyforabove a fewhundredbunches. 5238 candidate UFOs in cell 12 or larger during stable beams. Fills with at least 1 hour stable beams are considered.

  26. Intrafill UFO rate • The UFO rate stays constant during a fill. 3375 candidate arc UFOs (cell 12) during stable beams in 31 fills with at least 10 hours stable beams.

  27. Energy Dependency • Ufo amplitude:At 7 TeVabout3 timeshigherthanat 3.5TeV.(from wire scans).(E. Nebot, IPAC 2011) • BLM thresholds: Arc thresholds at7 TeV are about a factor 5 smallerthan at 3.5 TeV. • UFO rate: Noenergydependencywouldbecompetativewithobservations. (E. Nebot, IPAC 2011) • From 2011 data: 82 UFO beam dumpsbyarc UFOs for 7 TeV(comparedto 2 actualdumpsat 3.5 TeV). E. Nebot Wirescanduringramp

  28. UFOs and Dust Particle Distribution • The measured distribution of dust particles in SM12/Bat113 would explain the UFO distribution. 3670 arc UFOs (>cell 12) at 3.5 TeVwith signal RS01 > 1∙10-3Gy/s. courtesy of J. M. Jimenez

  29. Dynamics of Dust Particles • From simulations: • Dust particle will be positively ionized and be repelled from the beam. • Loss duration of a few ms. • Losses become faster for larger beam intensities. 2.3∙1012 protonsround Al Object 4.6∙1013 protons3.5 TeV courtesy of F. Zimmermann

  30. Loss Duration • UFOs have the tendency to become faster with increasing intensity. (cf. E.B. Holzer at Evian Dec. 2010) courtesy ofE. Nebot

  31. Event Rate 2010 • 113 events below threshold found in 2010. (E. Nebot) • UFO rate: proportional tobeam intensity. courtesy ofE. Nebot

  32. UFOs Detection in 2011 • 2010: 113 UFOs below threshold found in logging database. (E. Nebot) • 2011: Online UFO detection from live BLM data.Losses (RS 4) of two BLMs in 40m are above 1E-4 Gy/s.RS 2 / RS 1 > 0.55 (UFO average : 0.89). RS 3 / RS 2 > 0.45 (UFO average: 0.79). • Over 10000 triggers so far. • From subset of about 300 manually verified triggers: About 65% are UFOs, 15% ambiguous cases, 20% are false triggers. • For most analysis additional cut. E.g.: Only flat top UFOs, loss of UFO BLM (RS05) > 2∙10-4Gy/s (≈ 2 ‰ of threshold). 74 events remain of subset, of which 71 are clear UFOs (96%) and 3 are ambiguous cases.

  33. Weighted Spatial UFO Distribution • The weighted spatial distribution isdominated by a few large amplitude UFOs. MKIs 5875 candidate UFOs at 3.5 TeV. Gray areas around IRs are excluded from UFO detection. around WS/BSRT 28L8

  34. Normalized UFO rate 2194 candidate UFOs during stable beams in fills with at least 1 hour stable beams.Signal RS05 > 2∙10-4Gy/s. Data scaled with 1.76 (detection efficiency from reference data)

  35. Peak Signal courtesy ofE. Nebot • No clear dependency of peak loss on intensity. (cf. E.B. Holzer at Evian Dec. 2010) • No clear dependency of peak loss on bunch intensity.

  36. UFO rate vsBunchIntensity • Nodependencyof UFO rate on buch intensity.

  37. Peak Signal vs Loss Duration • Tendency that harder UFOs are faster. courtesy ofE. Nebot

  38. Loss Duration • Tloss: Given by fitting single function (Gaussian up to t=Tloss, 1/t afterwards) to data. • ) courtesy ofE. Nebot

  39. Calibration of Tloss • Correlation of Tloss and width of Gaussian fitted topost mortem turn-by-turn data. courtesy ofE. Nebot

  40. UFO size • Two extreme cases: • UFO much larger than beam: the beam is imaging the UFO. • UFO much smaller than beam: the UFO is imaging the beam. Most UFO shapes are Gaussian, thus most UFOs are expected to be smaller than the beam. • From FLUKA simulations: size ≈ 1 μm. (cf. M. Sapinski, F. Zimmermann at Chamonix 2011) courtesy ofJ. Wenninger(cf. MPP 25.03.2011)

  41. UFO Speed • UFO speed: • From free fall: • The UFO speed corresponds to the expected speed for a free fall from the aperture. εnorm = 2.5 µm·rad β = 150 m 22 mm free fall vu: UFO speed, σb: transverse beam size, σu: UFO size,σT: temporal width of loss.

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  43. MKI UFOs • 13 beam dumps due to UFOs around the injection kicker magnets (MKIs)10 dumps at MKI.D5L2 • In total ≈1500 UFOs around MKIs 614 in Pt.2 and 874 in Pt.8 • Most events within 30min after the last injection. 479 candidate UFOs around injection regions for fills lasting at least 3 hours after last injection.

  44. Layout of MKI Region MKI.D MKI.C MKI.B MKI.A

  45. UFOs at MKIs • In Pt.2 most MKI UFOs startatthe BLM after MKI.D5L2. • In Pt.8 less UFOs start at the MKI.A5R8. Beam direction Beam direction 174 candidate UFOs around MKI in Pt.2. Signal RS01 > 1∙10-3Gy/s. 270 candidate UFOs around MKI in Pt.8. Signal RS01 > 1∙10-3Gy/s. Right of IP8 Left of IP2

  46. MKI UFO MD • 21 pulses of MKIs, 43 UFO type loss pattern observed. • In 17 cases: UFO type loss pattern within the second of MKI pulse. • In 2 cases: UFO recorded by BLM injection capture buffer. TDI 4R8 beam MKI D 5R8 UFO Kicker pulse Spatial loss pattern Temporal loss pattern

  47. UFO Dynamics • From fit tolosses (MKI-D): • Amplitude: 1.8·10-2Gy/s (Threshold: 11.6 Gy/s) • Temporal Width: 160 µs • Time delay to kicker pulse: 7.6 ms • resulting acceleration (constant particle acceleration): 658 m/s² • resulting speed during interaction with beam: 5.0 m/s • UFO type loss signal observed after many normal injections. 7.6ms

  48. Beam dump on 6.6.2011 • UFO at MKI in Pt. 2, at 450 GeV. • Small loss signal at Q5 (backscattering?). TCT MKIs

  49. Beam dump 06.06.2011 • From fit to losses (BLMEI.05L2.B1E10_MKI.D5L2.B1): • Amplitude: 7.73 Gy/s (Threshold: 2.3 Gy/s) • Width: 0.77 ms resulting speed of transiting dust particle = 0.47 m/s.(assuming ϵn=2.2µm·rad) (Brennan Goddard)

  50. MKI UFOs DuringScrubbing • Typical scenario for MKI UFOs during scrubbing: The MKI UFO rate is increased for about 10 minutes after each injection. 2 hours

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