1. LHC Beam Operation CommitteeJune, 14 th 20111 UFOs in the LHC Tobias Baer LBOC June, 14 th 2011 Acknowledgements: N. Garrel, B. Goddard, E.B. Holzer, S. Jackson, M. Misiowiec, E. Nebot, A. Nordt, J. Uythoven, J. Wenninger, C. Zamantzas

2. 2LHC Beam Operation CommitteeJune, 14 th 2011 Content 1. UFO Dumps2. Below Threshold UFOs3.UFOs at MKIs4.Outlook

3. 3LHC Beam Operation CommitteeJune, 14 th 2011 Content 1. UFO Dumps2. Below Threshold UFOs3.UFOs at MKIs4.Outlook

4. 4LHC Beam Operation CommitteeJune, 14 th 2011 UFO Dumps 18 beam dumps 18 beam dumps due to UFOs in 2010. UFOs are fast beam losses (loss duration some 10 turns) UFOs occur often at unconventional loss locations (e.g. in the arc) 11 beam dumps 11 beam dumps due to UFOs in 2011. 8 in injection region (2010: 2) 1 dump at 450 GeV. (6.6.2011)

5. 5LHC Beam Operation CommitteeJune, 14 th 2011 Content 1. UFO Dumps2. Below Threshold UFOs3.UFOs at MKIs4.Outlook

6. 6LHC Beam Operation CommitteeJune, 14 th 2011 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 8000 triggers Over 8000 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 -4 Gy/s (≈ 2 ‰ of threshold). 74 events remain of subset, of which 71 are clear UFOs (96%) and 3 are ambiguous cases.

7. 7LHC Beam Operation CommitteeJune, 14 th 2011 Events Below Threshold “threshold” = lowest threshold in standard arc cell. Most events are much below threshold. nominal threshold 7 TeV 628 candidate UFOs at 3.5 TeV. Signal RS05 > 5∙10 -4 Gy/s.

8. 8LHC Beam Operation CommitteeJune, 14 th 2011 Spatial UFO Distribution 3.5 TeV 3.5 TeV 1096 candidate UFOs. Signal RS05 > 5∙10 -4 Gy/s. The UFOs are distributed all around the machine. About 7% of all UFOs are around the MKIs. 53 candidate UFOs at MKI for Beam 2. gray areas around IRs are excluded from UFO detection. 450 GeV 450 GeV 591 candidate UFOs. Signal RS05 > 5∙10 -4 Gy/s. Mainly UFOs around MKIs

9. 9LHC Beam Operation CommitteeJune, 14 th 2011 10 UFOs/hour On average: 10 UFOs/hour UFO Rate in 2011 1904 candidate UFOs during stable beams. Signal RS05 > 2∙10 -4 Gy/s. Data scaled with 1.76 (detection efficiency from reference data) 228 b 36 bpi336b 36 bpi336b 72 bpi480b 36 bpi336b 72 bpi 480b 36 bpi480b 72 bpi624b 72 bpi 768b 72 bpi228 b 36 bpi480b 72 bpi768b 72 bpi 768b 108 bpi912b 108 bpi 1092b 108 bpi1092b 144 bpi

10. 10LHC Beam Operation CommitteeJune, 14 th 2011 Peak Signal 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. courtesy of E. Nebot

11. 11LHC Beam Operation CommitteeJune, 14 th 2011 Loss Duration T loss T loss : Given by fitting single function (Gaussian up to t=T loss, 1/t afterwards) to data. Loss duration Loss duration: UFOs have the tendency to become faster with increasing intensity. (cf. E.B. Holzer at Evian Dec. 2010) courtesy of E. Nebot

12. 12LHC Beam Operation CommitteeJune, 14 th 2011 Peak Signal vs Loss Duration Tendency that harder UFOs are faster. courtesy of E. Nebot

13. 13LHC Beam Operation CommitteeJune, 14 th 2011 Content 1. UFO Dumps2. Below Threshold UFOs3.UFOs at MKIs4.Outlook

14. 14LHC Beam Operation CommitteeJune, 14 th 2011 Beam dump on 6.6.2011 450 GeV. UFO at MKI in Pt. 2, at 450 GeV. MKIs TCT

15. 15LHC Beam Operation CommitteeJune, 14 th 2011 Beam dump 06.06.2011 From fit to losses (BLMEI.05L2.B1E10_MKI.D5L2.B1): 7.73 Gy/s Amplitude: 7.73 Gy/s (Threshold: 2.3 Gy/s) Width: 0.77 ms 0.47 m/s resulting speed of transiting dust particle = 0.47 m/s. (assuming ϵ n =2.2µm·rad) (cf. T. Baer 86 th LMC)

16. 16LHC Beam Operation CommitteeJune, 14 th 2011 Peak Losses 450 GeV Peak loss for MKI UFOs at 450 GeV. Threshold (RS1 = 2.3 Gy/s) 336 candidate UFOs at 450 GeV. Signal RS01 > 2∙10 -4 Gy/s. + 1 event with 3.5Gy/s (dump 06.06.2011)

17. 17LHC Beam Operation CommitteeJune, 14 th 2011 UFOs around Injection Region 679 UFOs 9 beam dumps. 679 UFOs around the MKIs caused 9 beam dumps. Most of the UFOs around the MKIs occur before going to stable beams.

18. 18LHC Beam Operation CommitteeJune, 14 th 2011 MKI UFOs During Scrubbing Typical scenario for MKI UFOs during scrubbing: Loss spikes occur in first few minutes after an injection and go away then. 2 hours

19. 19LHC Beam Operation CommitteeJune, 14 th 2011 UFOs at MKIs per fill Flashover Flashover of MKI D Pt.8 before Fill 1721 (vacuum valves moved in). Fill 1721: 21 MKI UFOs in Pt.8 2 MKI UFOs in Pt.2 Flashover

20. 20LHC Beam Operation CommitteeJune, 14 th 2011 Correlation with Vacuum Despite a large vacuum spike, there is no clear correlation with UFOs

21. 21LHC Beam Operation CommitteeJune, 14 th 2011 UFOs at MKIs 460 104 336 08.04. – 05.05. in total 460 fast loss events around MKIs. (104 around MKI in IP2, 336 around MKI in IP8). Distribution of first BLM which sees the loss: Left of IP2 Right of IP8 Beam direction

22. 22LHC Beam Operation CommitteeJune, 14 th 2011 Content 1. UFO Dumps2. Below Threshold UFOs3.UFOs at MKIs4.Outlook

23. 23LHC Beam Operation CommitteeJune, 14 th 2011 Next Steps Improve diagnostics. Acquisition of BLM Study Buffer for UFO events. Successful test during technical stop. Better localization of MKI UFOs. Additional BLMs during next Technical Stop. MD on MKI UFOs. MD on MKI UFOs. Better understanding of Quench Limit. Additional Simulations (F. Zimmermann, Y. Levinsen) Mitigation: Further increase of BLM thresholds... But: For higher energies thresholds need to be decreased.

24. 24LHC Beam Operation CommitteeJune, 14 th 2011 Summary 11 UFO related beam dumps 11 UFO related beam dumps in 2011 so far (18 in 2010). Over 5000 UFOs Over 5000 UFOs below dump threshold detected in 2011 so far. Most events at 3.5 TeV. UFO rate constant at 10 UFOs/hour at 3.5 TeV. Many UFOs around injection kicker magnets During scrubbing: increased UFO rate after each injection. Increased UFO rate after MKI Flashover. UFO MD Next steps: UFO MD, Improve the diagnostics, better understanding of quench limits, learn from simulations.

25. 25LHC Beam Operation CommitteeJune, 14 th 2011 Thank you for your Attention Tobias Baer CERN BE/OP Tobias.Baer@cern.ch Office: +41 22 76 75379 Further information: T. Baer, “UFOs in the LHC”, Joint DESY and University of Hamburg Accelerator Physics Seminar, May 2011. J. Wenninger, “Analysis attempt of dump UFOs”, LHC Machine Protection Panel, Geneva, March 2011. M. Sapinski, “Is the BLM system ready to go to higher intensities?”, Workshop on LHC Performance, Chamonix, Jan. 2011. E.B. Holzer, “Losses away from collimators: statistics and extrapolation”, LHC Beam Operation Workshop, Evian, Dec. 2010.

26. 26LHC Beam Operation CommitteeJune, 14 th 2011 Backup slides

27. 27LHC Beam Operation CommitteeJune, 14 th 2011 UFOs in 2010 18 beam dumps 18 beam dumps due to UFOs. (since 07.07.2010) 113 UFOs below threshold found in logging database. (E. Nebot) (03.08.2010 - 28.10.2010) UFO rate proportional to intensity. No dependency of peak signal on intensity. (cf. E.B. Holzer at Evian Dec. 2010) Loss duration has tendency to become faster with higher intensity. (cf. E.B. Holzer at Evian Dec. 2010) J. Wenninger

28. 28LHC Beam Operation CommitteeJune, 14 th 2011 Event Rate 113 events below threshold found in 2010. (E. Nebot) UFO rate UFO rate: proportional to beam intensity. courtesy of E. Nebot

29. 29LHC Beam Operation CommitteeJune, 14 th 2011 Calibration of T loss Correlation of T loss and width of Gaussian fitted to post mortem turn-by-turn data. courtesy of E. Nebot

30. 30LHC Beam Operation CommitteeJune, 14 th 2011 Fast Loss Event Rate 4.1 times less beam dumps After the increase of the BLM Threshold by a factor of 3 there were about 4.1 times less beam dumps due to fast loss events.

31. 31LHC Beam Operation CommitteeJune, 14 th 2011 UFO Algorithm 1.Losses (RS 4) of at least two BLMs within 40m are above 1E-4 Gy/s. 2.A BLM is not taken into account if It is at a TCT It is in IP3, IP6 or IP7 RS 2 / RS 1 > 0.55 (UFO average : 0.89). RS 3 / RS 2 > 0.45 (UFO average: 0.79). 3.The acquisition is skipped for a few seconds after injection warning and beam wire scan timing event.

32. 32LHC Beam Operation CommitteeJune, 14 th 2011 LHC UFO Buster LHC Console Manager -> Fixed Displays -> BLM -> UFO Buster

33. 33LHC Beam Operation CommitteeJune, 14 th 2011 UFO Detection For 2010: 113 UFOs below threshold found in logging database. (E. Nebot) UFO Buster. For 2011: Online UFO detection by UFO Buster. Detects UFOs in BLM concentrator data (1Hz). 5000 UFOs 5000 UFOs below threshold found so far. Most events are much below threshold. “threshold” = lowest threshold in standard arc cell. nominal arc threshold 7 TeV 4905 candidate UFOs at 3.5 TeV.

34. 34LHC Beam Operation CommitteeJune, 14 th 2011 Dump on 01.05.2011 Dump of BLMQI.04L2.B1E20_MQY on RS 3, 4 and 5 Dump of BLMQI.04L2.B1E20_MQY on 320µs, 640µs and 2.5ms integration time

35. 35LHC Beam Operation CommitteeJune, 14 th 2011 Dump on 01.05.2011 From fit to losses (BLMEI.05L2.B1E10_MKI.D5L2.B1): Amplitude: 0.63 Gy/s Width: 0.29 ms

36. 36LHC Beam Operation CommitteeJune, 14 th 2011 Correlation with Vacuum

37. 37LHC Beam Operation CommitteeJune, 14 th 2011 Dynamics of Dust Particles From simulations: Dust particle will be positively ionized and be repelled from the beam. Beam intensity: 2.3∙10 12 protons, Al object. Loss duration of a few ms. Losses become shorter for larger beam intensities. courtesy of F. Zimmermann

38. 38LHC Beam Operation CommitteeJune, 14 th 2011 Correlation with Wire Scanner From wire scans: linear dependency of BLM signal on beam energy courtesy of M. Sapinski (cf. Chamonix 2011)

39. 39LHC Beam Operation CommitteeJune, 14 th 2011 Layout of MKI Region

40. 40LHC Beam Operation CommitteeJune, 14 th 2011 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 of J. Wenninger (cf. MPP 25.03.2011)

41. 41LHC Beam Operation CommitteeJune, 14 th 2011 UFO Speed UFO speed: From free fall: The UFO speed corresponds to the expected speed for a free fall from the aperture. v u : UFO speed, σ b : transverse beam size, σ u : UFO size, σ T : temporal width of loss. 22 mm free fall ε norm = 2.5 µm·rad β = 150 m

42. 42LHC Beam Operation CommitteeJune, 14 th 2011 Known Dust Particle Sources Distributed ion pumps (PF-AR, HERA). Electrical Discharges (PF-AR). Movable Devices. Particles frozen or condensated at cold elements. (ANKA)