1. LHC UFO Study Working GroupSeptember 15 th 20111 UFOs since TS#4 LHC UFO Study Group Tobias Baer September, 15 th 2011 Acknowledgements: B. Goddard, S. Grishin, E.B. Holzer, S. Jackson, M. Jimenez, A. Lechner, V. Mertens, M. Misiowiec, E. Nebot, A. Nordt, J. Uythoven, J. Wenninger, C. Zamantzas, F. Zimmermann, …

2. LHC UFO Study Working GroupSeptember 15 th 20112 No obvious changes after the technical stop. (apart from intensity ramp up) Now constantly below 5 UFOs/hour. UFO rate 5533 candidate UFOs in cell 12 or larger during stable beams. Fills with at least hour stable beams are considered. TS #4 TS #3 TS #2

3. LHC UFO Study Working GroupSeptember 15 th 20113 BLMMI repositioning Moved BLMMI.05L2.B1E31_MQY and BLMMI.05R8.B2E31_MQY during TS#4 in order to have a better localization of UFOs starting at MKI-D. Limited by cable margin in Pt.2 Still about 1m margin in Pt.8.

4. LHC UFO Study Working GroupSeptember 15 th 20114 UFO at MKI.D5L2 UFO on 08.09.2011: 0.3% of dump threshold. at 737 GeV. Signal from UFO also measured by BLMMI.05L2.B1E31_MQY But only 9.5% of signal after MKI.D5L2. BLMMI.05L2.B1E31_MQY

5. LHC UFO Study Working GroupSeptember 15 th 20115 UFO at MKI.D5R8 UFO on 09.09.2011: 11% of dump threshold. at 3.5 TeV. Signal from UFO also measured by BLMMI.05R8.B2E31_MQY But only 3.5% of signal after MKI.D5L2. BLMMI.05R8.B2E31_MQY

6. LHC UFO Study Working GroupSeptember 15 th 20116 UFO at MKI.D5R8 UFO on 14.09.2011 0.3% of dump threshold at 2471 GeV not Signal from UFO not measured by BLMMI.05R8.B2E31_MQY MKI.D5R8

7. LHC UFO Study Working GroupSeptember 15 th 20117 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”, IPAC’11, TUPC137, September 2011. F. Zimmermann, “Simulation Studies of Macro-particles Falling into the LHC Proton Beam”, IPAC’11, MOPS017, September 2011. E. Nebot del Busto, “Analysis of Fast Losses in the LHC with the BLM System”, IPAC’11, TUPC136, September 2011. A. Lechner, “FLUKA Simulations of UFO induced Losses in IR2”, MKI UFO Meeting, August 2011. R. Ballester, “Vibration analysis on an LHC kicker prototype for UFOs investigation”, EDMS Report No. 1153686, August 2011.

8. LHC UFO Study Working GroupSeptember 15 th 20118 Backup slides

9. LHC UFO Study Working GroupSeptember 15 th 20119 Content UFO Dumps 2010/2011

10. LHC UFO Study Working GroupSeptember 15 th 201110 Beam dump on 29.05.2011 Dump on running sum 1-6.

11. LHC UFO Study Working GroupSeptember 15 th 201111 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)

12. LHC UFO Study Working GroupSeptember 15 th 201112 Content UFO Observations and Studies

13. LHC UFO Study Working GroupSeptember 15 th 201113 Event Rate 2010 113 events below threshold found in 2010. (E. Nebot) UFO rate UFO rate: proportional to beam intensity. courtesy of E. Nebot

14. LHC UFO Study Working GroupSeptember 15 th 201114 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 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 -4 Gy/s (≈ 2 ‰ of threshold). 74 events remain of subset, of which 71 are clear UFOs (96%) and 3 are ambiguous cases.

15. LHC UFO Study Working GroupSeptember 15 th 201115 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. 10000 candidate UFOs Over 10000 candidate UFOs below threshold found. Most events are much below threshold. Between 2010 and 2011, UFO related beam dumps were reduced by increasing the BLM thresholds for losses on ms scale by a factor 5. UFOs Below Dump Threshold Distribution of arc UFOs. 2780 arc UFOs (≥cell 12) at 3.5 TeV with signal RS05 > 2∙10 -4 Gy/s.

16. LHC UFO Study Working GroupSeptember 15 th 201116 Spatial UFO Distribution 3.5 TeV 3.5 TeV 3686 candidate UFOs. Signal RS05 > 2∙10 -4 Gy/s. Red: Signal RS01 > 1∙10 -2 Gy/s. UFOs occur all around the machine. injection kicker magnets (MKIs). Many UFOs around injection kicker magnets (MKIs). 450 GeV 450 GeV 486 candidate UFOs. Signal RS05 > 2∙10 -4 Gy/s. Mainly UFOs around MKIs gray areas around IRs are excluded from UFO detection.

17. LHC UFO Study Working GroupSeptember 15 th 201117 On average 6.0 UFOs/hour. No intensity dependency for above a few hundred bunches. UFO rate 5238 candidate UFOs in cell 12 or larger during stable beams. Fills with at least 1 hour stable beams are considered.

18. LHC UFO Study Working GroupSeptember 15 th 201118 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.

19. LHC UFO Study Working GroupSeptember 15 th 201119 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)

20. LHC UFO Study Working GroupSeptember 15 th 201120 Intrafill UFO rate The UFO rate stays constant during a fill.

21. LHC UFO Study Working GroupSeptember 15 th 201121 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

22. LHC UFO Study Working GroupSeptember 15 th 201122 UFO rate vs Bunch Intensity No dependency of UFO rate on buch intensity.

23. LHC UFO Study Working GroupSeptember 15 th 201123 Peak Signal vs Loss Duration Tendency that harder UFOs are faster. courtesy of E. Nebot

24. LHC UFO Study Working GroupSeptember 15 th 201124 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

25. LHC UFO Study Working GroupSeptember 15 th 201125 Calibration of T loss Correlation of T loss and width of Gaussian fitted to post mortem turn-by-turn data. courtesy of E. Nebot

26. LHC UFO Study Working GroupSeptember 15 th 201126 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)

27. LHC UFO Study Working GroupSeptember 15 th 201127 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

28. LHC UFO Study Working GroupSeptember 15 th 201128 UFOs and Dust Particle Distribution 3670 arc UFOs (>cell 12) at 3.5 TeV with signal RS01 > 1∙10 -3 Gy/s. courtesy of J. M. Jimenez

29. LHC UFO Study Working GroupSeptember 15 th 201129 Ufo amplitude: 3 times higher Ufo amplitude: At 7 TeV about 3 times higher than at 3.5TeV. (from wire scans). (E. Nebot, IPAC 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: No energy dependency would be competative with observations. (E. Nebot, IPAC 2011) From 2011 data: 82 UFO beam dumps by arc UFOs for 7 TeV From 2011 data: 82 UFO beam dumps by arc UFOs for 7 TeV (compared to 2 actual dumps at 3.5 TeV). Energy Dependency Wire scan during ramp E. Nebot

30. LHC UFO Study Working GroupSeptember 15 th 201130 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. courtesy of F. Zimmermann 4.6∙10 13 protons 3.5 TeV 2.3∙10 12 protons round Al Object

31. LHC UFO Study Working GroupSeptember 15 th 201131 Loss Duration UFOs have the tendency to become faster with increasing intensity. (cf. E.B. Holzer at Evian Dec. 2010) courtesy of E. Nebot

32. LHC UFO Study Working GroupSeptember 15 th 201132 Content UFOs around MKIs

33. LHC UFO Study Working GroupSeptember 15 th 201133 13 beam dumps MKI.D5L2 13 beam dumps due to UFOs around the injection kicker magnets (MKIs) 10 dumps at MKI.D5L2 ≈1500 UFOs around MKIs In total ≈1500 UFOs around MKIs 614 in Pt.2 and 874 in Pt.8 Most events within 30min after the last injection. MKI UFOs 479 candidate UFOs around injection regions for fills lasting at least 3 hours after last injection.

34. LHC UFO Study Working GroupSeptember 15 th 201134 Layout of MKI Region MKI.D MKI.CMKI.BMKI.A

35. LHC UFO Study Working GroupSeptember 15 th 201135 UFOs at MKIs In Pt.2 most MKI UFOs start at the BLM after MKI.D5L2. In Pt.8 less UFOs start at the MKI.A5R8. Left of IP2 Beam direction 174 candidate UFOs around MKI in Pt.2. Signal RS01 > 1∙10 -3 Gy/s. Right of IP8 Beam direction 270 candidate UFOs around MKI in Pt.8. Signal RS01 > 1∙10 -3 Gy/s.

36. LHC UFO Study Working GroupSeptember 15 th 201136 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

37. LHC UFO Study Working GroupSeptember 15 th 201137 MKI UFO MD 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. In 2 cases: UFO recorded by BLM injection capture buffer. TDI 4R8 MKI D 5R8 UFO Kicker pulse beam Spatial loss patternTemporal loss pattern

38. LHC UFO Study Working GroupSeptember 15 th 201138 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 7.6 ms Time delay to kicker pulse: 7.6 ms 658 m/s² resulting acceleration (constant particle acceleration): 658 m/s² 5.0 m/s resulting speed during interaction with beam: 5.0 m/s UFO type loss signal observed after many normal injections. 7.6ms

39. LHC UFO Study Working GroupSeptember 15 th 201139 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

40. LHC UFO Study Working GroupSeptember 15 th 201140 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)

41. LHC UFO Study Working GroupSeptember 15 th 201141 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

42. LHC UFO Study Working GroupSeptember 15 th 201142 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

43. LHC UFO Study Working GroupSeptember 15 th 201143 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.

44. LHC UFO Study Working GroupSeptember 15 th 201144 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.

45. LHC UFO Study Working GroupSeptember 15 th 201145 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.

46. LHC UFO Study Working GroupSeptember 15 th 201146 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.

47. LHC UFO Study Working GroupSeptember 15 th 201147 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

48. LHC UFO Study Working GroupSeptember 15 th 201148 Correlation with Vacuum Despite a large vacuum spike, there is no clear correlation with UFOs

49. LHC UFO Study Working GroupSeptember 15 th 201149 Correlation with Vacuum

50. LHC UFO Study Working GroupSeptember 15 th 201150 Vacuum Correlation The pressure spike is seen on all MKI magnets. BLM MKI.C5L2 Vacuum MKI

51. LHC UFO Study Working GroupSeptember 15 th 201151 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.

52. LHC UFO Study Working GroupSeptember 15 th 201152 Vacuum correlation (slow) The slow vacuum spike is correlated to the last injection. No correlation with UFOs

53. LHC UFO Study Working GroupSeptember 15 th 201153 UFOs in IQC Many additional events in IQC data for normal operation. Loss at Injection Candidate UFO

54. LHC UFO Study Working GroupSeptember 15 th 201154 Content MKI UFO MD

55. LHC UFO Study Working GroupSeptember 15 th 201155 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)

56. LHC UFO Study Working GroupSeptember 15 th 201156 UFOs between kicker pulses The number of UFOs between kicker pulses decreased over time after the last injection with beam.

57. LHC UFO Study Working GroupSeptember 15 th 201157 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

58. LHC UFO Study Working GroupSeptember 15 th 201158 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

59. LHC UFO Study Working GroupSeptember 15 th 201159 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

60. LHC UFO Study Working GroupSeptember 15 th 201160 Content Conclusion and Summary

61. LHC UFO Study Working GroupSeptember 15 th 201161 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)

62. LHC UFO Study Working GroupSeptember 15 th 201162 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 (but observed storms disappeared again). 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.

63. LHC UFO Study Working GroupSeptember 15 th 201163 Next Steps MKI UFO MD (28.08.). Study MKI/MKQA UFOs with improved diagnostics and better statistics. Study dust particle dynamics. Improve diagnostics (during next TS). Dedicated turn-by-turn BLM Study Buffer. Improved BLM data logging. FLUKA simulations on MKI UFOs. Open MKI and search for dust particles. Dust particle dynamics model. Better understanding of Quench Limit. Mitigation Mitigation: Further increase of BLM thresholds... But: Do we have enough margin at higher energies?

64. LHC UFO Study Working GroupSeptember 15 th 201164 Summary and Conclusion 17 beam dumps 17 beam dumps due to UFOs in 2011 so far (18 in 2010). Over 10000 candidate UFOs 6.0 UFOs/hour Over 10000 candidate UFOs below threshold detected. On average 6.0 UFOs/hour during stable beams in the arcs. Micrometer sized macroparticles are the most plausible explanation. Many UFOs around injection kicker magnets. Many MKI UFOs observed directly after kicker pulsing/injection. aggressive scaling with beam 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. Large effort underway to understand UFO mechanism. Measurements in LHC, lab measurements, simulations, theories.