1. UFO Study Working GroupAugust 12 th 20111 Update on UFO Studies Tobias Baer August, 12 th 2011 Acknowledgements: G. Arduini, W. Bartmann, M. Barnes, C. Bracco, M. Ferro-Luzzi, N. Garrel, B. Goddard, E.B. Holzer, M. Jimenez, V. Mertens, M. Misiowiec, E. Nebot, L. Norderhaug Drosdal, A. Nordt, J. Uythoven, J. Wenninger, C. Zamantzas, F. Zimmermann, …

2. UFO Study Working GroupAugust 12 th 20112 Content 1. Update on UFO Statistics2. Results from MKI UFO MD3. Outlook and Summary

3. UFO Study Working GroupAugust 12 th 20113 Content 1. Update on UFO Statistics2. Results from MKI UFO MD3. Outlook and Summary

4. UFO Study Working GroupAugust 12 th 20114 UFO rate On average 6.2 UFOs/hour. By now: 34 UFO related beam dumps. 5152 candidate UFOs in cell 12 or larger during stable beams. Fills with at least 1 hour stable beams are considered.

5. UFO Study Working GroupAugust 12 th 20115 UFOs vs. Dust Particles 3670 arc UFOs (>cell 12) at 3.5 TeV with signal RS01 > 1∙10 -3 Gy/s.

6. UFO Study Working GroupAugust 12 th 20116 Number of MKI UFOs 9.4 MKI UFOs per fill On average: 9.4 MKI UFOs per fill (5.4 at MKI.L2 and 3.9 at MKI.R8). After MKI flashover 1042 candidate UFOs around injection regions in Pt. 2 and Pt.8 for fills reaching stable beams with >200 bunches. MKI UFO storms in Pt. 2

7. UFO Study Working GroupAugust 12 th 20117 Number of Large MKI UFOs B1 The large number of strong MKI UFOs in Pt. 2 disappeared in the fills after the technical stop. MKI Beam 1 160 candidate UFOs around injection regions in Pt. 2 for fills reaching stable beams with >200 bunches. Signal RS01 > 1∙10 -2 Gy/s.

8. UFO Study Working GroupAugust 12 th 20118 Vacuum Valve Movement orangeblue green Closure of vacuum valves. orange: Several valves closed, blue: VVGST.193.5L2 and VVGST.3.5L2 closed, green: status unknown for several valves. VVGST.101.5L2.B VVGST.101.5L2.R VVGST.136.5L2.B VVGST.136.5L2.R VVGST.140.5L2.R VVGST.175.5L2.B VVGST.175.5L2.R VVGST.101.5L2.B VVGST.101.5L2.R VVGST.140.5L2.B VVGST.140.5L2.R VVGST.175.5L2.B VVGST.175.5L2.R VVGST.193.5L2.B VVGST.21.5L2.B VVGST.21.5L2.R VVGST.3.5L2.B VVGST.56.5L2.B VVGST.56.5L2.R VVGST.61.5L2.B VVGST.61.5L2.R VVGST.96.5L2.B VVGST.96.5L2.R VVGST.101.5L2.B VVGST.101.5L2.R VVGST.136.5L2.B VVGST.136.5L2.R VVGST.140.5L2.B VVGST.140.5L2.R VVGST.175.5L2.B VVGST.175.5L2.R VVGST.193.5L2.B VVGST.21.5L2.B VVGST.21.5L2.R VVGST.3.5L2.B VVGST.56.5L2.B VVGST.56.5L2.R VVGST.61.5L2.B VVGST.61.5L2.R VVGST.96.5L2.B VVGST.96.5L2.R MKI Beam 1 152 candidate UFOs around injection regions in Pt. 2 for fills reaching stable beams. Signal RS01 > 1∙10 -2 Gy/s.

9. UFO Study Working GroupAugust 12 th 20119 Content 1. Update on UFO Statistics2. Results from MKI UFO MD3. Outlook and Summary

10. UFO Study Working GroupAugust 12 th 201110 MKI UFO MD UFO type loss pattern In 17 cases: UFO type loss pattern 21 pulses of MKIs, 43 UFO type loss pattern observed. UFO type loss pattern within the second of MKI pulse. In 17 cases: UFO type loss pattern within the second of MKI pulse. Pulses MKI-A Pulses MKI-D Losses at MKI-D (green) and MKI-A (brown)

11. UFO Study Working GroupAugust 12 th 201111 MKI UFO MD In 2 cases: UFO recorded by BLM injection capture buffer. TDI 4R8 MKI D 5R8 UFO Kicker pulse beam Spatial loss patternTemporal loss pattern

12. UFO Study Working GroupAugust 12 th 201112 UFO Dynamics From fit to losses (MKI-D): 1.8·10 -2 Gy/s Amplitude: 1.8·10 -2 Gy/s (Threshold: 11.6 Gy/s) 160 µs Temporal Width: 160 µs 3.0 m/s resulting speed of transiting dust particle = 3.0 m/s. (assuming ϵ n =2.5µm·rad) 7.6 ms 658 m/s² Time delay to kicker pulse: 7.6 ms resulting acceleration (assuming constant particle acceleration): 658 m/s² 5.0 m/s resulting speed during interaction with beam: 5.0 m/s

13. UFO Study Working GroupAugust 12 th 201113 UFO Dynamics From fit to losses (MKI-D): 3.7·10 -3 Gy/s Amplitude: 3.7·10 -3 Gy/s (Threshold: 11.6 Gy/s) 218µs Temporal Width: 218µs 2.2 m/s resulting speed of transiting dust particle = 2.2 m/s. (assuming ϵ n =2.5µm·rad) 4.3 ms 2055 m/s² Time delay to kicker pulse: 4.3 ms resulting acceleration (assuming constant particle acceleration): 2055 m/s² 8.8 m/s resulting speed during interaction with beam: 8.8 m/s

14. UFO Study Working GroupAugust 12 th 201114 UFOs in IQC Many additional events in IQC data for normal operation. Loss at Injection Candidate UFO

15. UFO Study Working GroupAugust 12 th 201115 UFOs in IQC Delay of UFOs w.r.t. injection.

16. UFO Study Working GroupAugust 12 th 201116 Content 1. Update on UFO Statistics2. Results from MKI UFO MD3. Outlook and Summary

17. UFO Study Working GroupAugust 12 th 201117 Outlook MKI UFO MD (Sunday 28.08.). Improve diagnostics and statistics for UFO events after kicker pulse (longer BLM study buffer). Study MKI asymmetry. Study B1/B2 (a)symmetry. Pulse MKQA. Improve diagnostics. BLM Study Buffer. FLUKA Simulations of MKI UFOs. Open MKI and search for dust particles. Dust particle dynamics model.

18. UFO Study Working GroupAugust 12 th 201118 Summary UFO rate decreased from 10 to 5 UFOs/hour since April. The MKI.B1 UFO storms disappeared soon after the TS. Still unclear why the UFO storms suddenly appeared and disappeared. From UFO MD: UFO type losses often directly after pulsing of MKIs. UFO type losses often directly after pulsing of MKIs. Very fast acceleration of dust particles and complex macro particle dynamics. Asymmetry between the four MKIs. The number of UFOs between kicker pulses decreased over time after the last injection with beam. Many UFO studies underway. How about dust particle experiment?

19. UFO Study Working GroupAugust 12 th 201119 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.

20. UFO Study Working GroupAugust 12 th 201120 Backup slides

21. UFO Study Working GroupAugust 12 th 201121 Content 1. UFO Dumps 2010/2011

22. UFO Study Working GroupAugust 12 th 201122 UFO related Beam Dumps 29 beam dumps 29 beam dumps due to UFOs in 2010 (18) and 2011 (11). 10 dumps around MKIs. 1 dump at 450 GeV. Temporal width of a few turns. Dump often on running sum with 640µs or 2.5ms integration time. Max Loss amplitude (extrapolated): 7.7 Gy/s Beam dump on 01.05.2011 L2 MKI D TCT

23. UFO Study Working GroupAugust 12 th 201123 Beam dump on 29.05.2011 Dump on running sum 1-6.

24. UFO Study Working GroupAugust 12 th 201124 Beam dump 29.05.2011 From fit to losses (BLMQI.28L8.B1E10_MQ): 2.4 Gy/s Amplitude: 2.4 Gy/s (Threshold: 2.1 Gy/s) 97 µs Temporal Width: 97 µs 3.6 m/s resulting speed of transiting dust particle = 3.6 m/s. (assuming ϵ n =2.5µm·rad) (also cf. J. Wenninger at MPP March 2011)

25. UFO Study Working GroupAugust 12 th 201125 UFO Dumps in 2011 8 dumps due to UFO in injection region. Timestamp (local)LocationLoss RS1 [Gy/s]Fillnumber# bunchesIntensity 01.05.2011 14:58:23MKI.D5L20.2017527629.00E+13 29.05.2011 04:46:13Q28.L82.5018139121.11E+14 31.05.2011 06:22:03MKI.D5L22.50182210921.33E+14 31.05.2011 22:20:38MKI.D5L22.00182810921.24E+14 02.06.2011 21:50:17MQXA.R80.50183910921.24E+14 03.06.2011 18:24:50MKI.D5R80.20184310921.34E+14 04.06.2011 20:20:38MKI.D5L20.10184710921.29E+14 05.06.2011 06:56:37MKI.D5L20.50185110921.29E+14 06.06.2011 13:15:24MKI.D5L23.49185511041.31E+14 08.06.2011 19:04:29MKI.D5L22.13185810921.30E+14 16.06.2011 03:28:33MQX.L80.50187010921.27E+14 courtesy of J. Wenninger

26. UFO Study Working GroupAugust 12 th 201126 Content 2. Below Threshold UFOs

27. UFO Study Working GroupAugust 12 th 201127 Event Rate 2010 113 events below threshold found in 2010. (E. Nebot) UFO rate UFO rate: proportional to beam intensity. courtesy of E. Nebot

28. UFO Study Working GroupAugust 12 th 201128 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.

29. UFO Study Working GroupAugust 12 th 201129 Spatial UFO Distribution 3.5 TeV 3.5 TeV 2759 candidate UFOs. Signal RS05 > 2∙10 -4 Gy/s. MKIs Many UFOs around MKIs. BLMQI.19R3.B1I10_MQ: 50 UFOs. Arc locations with many UFOs: BLMQI.19R3.B1I10_MQ: 50 UFOs. BLMQI.25R3.B2E10_MQ: 53 UFOs. BLMQI.28R7.B2I10_MQ: 47 UFOs. 450 GeV 450 GeV 151 candidate UFOs. Signal RS05 > 2∙10 -4 Gy/s. 26.4. – 22.5., 9.6. – 21.6.2011 Mainly UFOs around MKIs gray areas around IRs are excluded from UFO detection.

30. UFO Study Working GroupAugust 12 th 201130 Spatial UFO Distribution MKIs Many UFOs around MKIs. Arc locations with many UFOs: (on average ≈2.5 UFOs per cell and beam) BLMQI.16L3.B2E10_MQ: 32 UFOs. BLMQI.19R3.B1I10_MQ: 50 UFOs. BLMQI.25R3.B2E10_MQ: 53 UFOs. BLMQI.32L5.B1I10_MQ: 34 UFOs. BLMQI.28L6.B2I10_MQ: 33 UFOs. BLMQI.28R7.B2I10_MQ: 47 UFOs. BLMQI.28L8.B1E10_MQ: 37 UFOs. 3.5 TeV 3.5 TeV 2759 candidate UFOs. Signal RS05 > 2∙10 -4 Gy/s. gray areas around IRs are excluded from UFO detection.

31. UFO Study Working GroupAugust 12 th 201131 Weighted Spatial UFO Distribution The weighted spatial distribution is dominated by a few large amplitude UFOs. 28L8 around WS/BSRT MKIs 5875 candidate UFOs at 3.5 TeV. Gray areas around IRs are excluded from UFO detection.

32. UFO Study Working GroupAugust 12 th 201132 Normalized UFO rate 2194 candidate UFOs during stable beams in fills with at least 1 hour stable beams. Signal RS05 > 2∙10 -4 Gy/s. Data scaled with 1.76 (detection efficiency from reference data)

33. UFO Study Working GroupAugust 12 th 201133 Intrafill UFO rate The UFO rate stays constant during a fill. 1312 candidate UFOs during stable beams in 18 fills with at least 10 hours stable beams. Signal RS05 > 2∙10 -4 Gy/s.

34. UFO Study Working GroupAugust 12 th 201134 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

35. UFO Study Working GroupAugust 12 th 201135 UFO rate vs Bunch Intensity No dependency of UFO rate on buch intensity.

36. UFO Study Working GroupAugust 12 th 201136 Peak Signal vs Loss Duration Tendency that harder UFOs are faster. courtesy of E. Nebot

37. UFO Study Working GroupAugust 12 th 201137 Loss Duration T loss T loss : Given by fitting single function (Gaussian up to t=T loss, 1/t afterwards) to data. ) courtesy of E. Nebot

38. UFO Study Working GroupAugust 12 th 201138 Calibration of T loss Correlation of T loss and width of Gaussian fitted to post mortem turn-by-turn data. courtesy of E. Nebot

39. UFO Study Working GroupAugust 12 th 201139 Loss Duration UFOs have the tendency to become faster with increasing intensity. (cf. E.B. Holzer at Evian Dec. 2010) courtesy of E. Nebot

40. UFO Study Working GroupAugust 12 th 201140 Energy Dependency Ufo amplitude:Linear dependency Ufo amplitude: Linear dependency of BLM signal on beam energy observed (from wire scans). (cf. M. Sapinski at Chamonix 2011) BLM Thresholds: factor 5 smaller BLM Thresholds: Arc Thresholds at 7 TeV are about a factor 5 smaller than at 3.5 TeV. UFO rate: UFO rate: At 450 GeV: extremely rare. During 1.38 TeV run: 3 UFOs in 36.5 h. At 3.5 TeV: 8 UFOs/h. courtesy of M. Sapinski (cf. Chamonix 2011)

41. UFO Study Working GroupAugust 12 th 201141 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)

42. UFO Study Working GroupAugust 12 th 201142 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

43. UFO Study Working GroupAugust 12 th 201143 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

44. UFO Study Working GroupAugust 12 th 201144 Content 3.UFOs at MKIs

45. UFO Study Working GroupAugust 12 th 201145 Layout of MKI Region

46. UFO Study Working GroupAugust 12 th 201146 Beam dump on 6.6.2011 450 GeV. UFO at MKI in Pt. 2, at 450 GeV. Small loss signal at Q5 (backscattering?). MKIs TCT

47. UFO Study Working GroupAugust 12 th 201147 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) (Brennan Goddard)

48. UFO Study Working GroupAugust 12 th 201148 MKI UFOs During Scrubbing Typical scenario for MKI UFOs during scrubbing: The MKI UFO rate is increased for about 10 minutes after each injection. 2 hours

49. UFO Study Working GroupAugust 12 th 201149 Most MKI UFOs occur shortly after the last injections. Time of MKI UFOs 479 candidate UFOs around injection regions for fills lasting at least 3 hours after last injection.

50. UFO Study Working GroupAugust 12 th 201150 MKI UFO Storms Fill 1898 (26 th June): 15 UFOs MKI B1, 7 UFOs MKI B2. 14 UFOs at MKI B1 within 40 min. Highest UFO: 34% of Threshold at TCTH.4L2 (RS1, RS2) at 3.5 TeV. Fill 1900 (27 th June): 32 UFOs MKI B1, 5 UFOs MKI B2. 17 UFOs at MKI B1 within 6 min. 17 UFOs at MKI B1 within 6 min. 65% Highest UFO: 65% of Threshold at MQY.04L2 (RS6) at 3.5 TeV. Fill 1901 (28 th June): 41 UFOs MKI B1, 12 UFOs MKI B2. 16 UFOs at MKI B1 in 2:20 min. 16 UFOs at MKI B1 in 2:20 min. Mostly at 450 GeV (12 min. at 450 GeV after last injection). 63% Highest UFO: 63% of Threshold at TCTH.4L2 (RS8) at 450 GeV.

51. UFO Study Working GroupAugust 12 th 201151 Number of large MKI UFOs B2 The number of large MKI UFOs in Pt. 8 did not increase. MKI Beam 2 70 candidate UFOs around injection regions in Pt. 8 for fills reaching stable beams. Signal RS01 > 1∙10 -2 Gy/s.

52. UFO Study Working GroupAugust 12 th 201152 BLM with Highest Loss Distribution of BLM with the highest loss RS05. 62 candidate UFOs around injection regions in Pt. 8 between 24.06. and 29.06.2011. 440 candidate UFOs around injection regions in Pt. 8 between 14.04. and 23.06.2011. (before installation of additional BLMs)

53. UFO Study Working GroupAugust 12 th 201153 UFO Location Sometimes BLMs upstream of the BLM with the highest have only slighly smaller losses.  Analyzing first BLM above minsignal (as defined in plot) BLMQI.05R8.B1I10_MQY minsignal = 75% of difference in log scale. UFO BLM First BLM to see UFO

54. UFO Study Working GroupAugust 12 th 201154 Start of UFOs in Pt. 8 62 candidate UFOs around injection regions in Pt. 8 between 24.06. and 29.06.2011. Distribution of first BLM to see UFO. Less UFOs are detected to start at MKI A. 190 candidate UFOs around injection regions in Pt. 8 between 01.05. and 31.05.2011. (before installation of additional BLMs) In the past most of the UFOs were observed to start at MKI D. (cf. presentation at MPP, May 13 th 2011)

55. UFO Study Working GroupAugust 12 th 201155 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

56. UFO Study Working GroupAugust 12 th 201156 Correlation with Vacuum Despite a large vacuum spike, there is no clear correlation with UFOs

57. UFO Study Working GroupAugust 12 th 201157 Correlation with Vacuum

58. UFO Study Working GroupAugust 12 th 201158 Vacuum Correlation The pressure spike is seen on all MKI magnets. BLM MKI.C5L2 Vacuum MKI

59. UFO Study Working GroupAugust 12 th 201159 Dust Particles in the LHC Samples from non-operational and old equipment. But not representative for the LHC… 1mm Dust particles in Penning gauge from lab. courtesy of N. Garrel and V. Mertens Dust particles in ceramic test beam tube.

60. UFO Study Working GroupAugust 12 th 201160 Vacuum correlation (slow) The slow vacuum spike is correlated to the last injection. No correlation with UFOs

61. UFO Study Working GroupAugust 12 th 201161 MKI UFOs at MKI pulse 1.4∙10 -2 Gy/s The peak loss at the MKI D in the second of the kicker pulse are 1.4∙10 -2 Gy/s (40µs running sum). TDI MKI D

62. UFO Study Working GroupAugust 12 th 201162 1.4·10 -3 Gy/s The peak loss at the MKI D at injection is one order of magnitude smaller (1.4·10 -3 Gy/s). Losses at MKI Loss at Kicker pulse

63. UFO Study Working GroupAugust 12 th 201163 UFOs between kicker pulses The number of UFOs between kicker pulses decreased over time after the last injection with beam.

64. UFO Study Working GroupAugust 12 th 201164 Content 3.Conclusion and Summary

65. UFO Study Working GroupAugust 12 th 201165 Known Dust Particle Sources Distributed ion pumps (PF-AR, HERA). No ion pumps in LHC arcs. Electrical Discharges (PF-AR). Movable Devices (LHC). Particles frozen to or condensated at cold elements. (ANKA)

66. UFO Study Working GroupAugust 12 th 201166 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 UFOs detected in 2011 so far. Strong energy dependency expected. First Indication that UFO rate might decrease over time. Many UFOs around injection kicker magnets Pulsing the injection kicker magnets directly induces UFOs. During scrubbing: increased UFO rate after each injection. Increased UFO rate after MKI Flashover. Continuous improvements of diagnostics are ongoing.

67. UFO Study Working GroupAugust 12 th 201167 Next Steps Continuous improvement of diagnostics. Adjust injection capture buffer and BLM capture buffer for UFO events. Analysis of additional BLMs around MKIs (installed during last TS). Continue MKI UFO MD. Study UFO production mechanism (MKI UFO storms). Study dust particle dynamics. Search for dust particles in MKIs. MKI vibration measurements. Better understanding of Quench Limit. Additional Simulations Mitigation Mitigation: Further increase of BLM thresholds... But: For higher energies thresholds need to be decreased.

68. UFO Study Working GroupAugust 12 th 201168 Conclusion For 2011: For 2011: Arc UFOs: No sign that the situation will become worse. Arc UFOs: No sign that the situation will become worse. Few dumps are expected. MKI UFO Storms might be critical. MKI UFOs: MKI UFO Storms might be critical. Large effort underway to understand mechanism, in lab and in LHC. Beyond 2011: Beyond 2011: aggressive scaling with beam energy! Intermediate energy step would be very helpful for extrapolations to nominal energy. Observations show an aggressive scaling with beam energy! Situation could be significantly worse above 3.5TeV. Intermediate energy step would be very helpful for extrapolations to nominal energy.