LIBD MeetingNovember 29 th 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, …

LIBD MeetingNovember 29 th Content 1. Lead MKI UFOs2. Update on MKI UFO MD results3. UFO size estimates4.IPAC Abstract

LIBD MeetingNovember 29 th Content 1. Lead MKI UFOs2. Update on MKI UFO MD results3. UFO size estimates4.IPAC Abstract

LIBD MeetingNovember 29 th Lead MKI UFOs MKI UFO at MKI.D5R8. 10 % of threshold 10 % of threshold at MQML.10L8. Losses are not localized as for protons. dispersion suppressor Highest loss is in the dispersion suppressor downstream of the IR (due to ion fragmentation). Horizontal dispersion MKI (UFO location) MQML.10L8 (highest loss) IP8 TCTH

LIBD MeetingNovember 29 th Content 1. Lead MKI UFOs2. Update on MKI UFO MD results3. UFO size estimates4.IPAC Abstract

LIBD MeetingNovember 29 th Delay of UFO events 57 UFO events In total 57 UFO events 44 at MKIs in Pt.8 (41 pulses) 13 at MKIs in Pt.2 (35 pulses) The distribution looks similar for the MKIs in Pt. 2 and Pt. 8. The first clear events occured 10.2ms after pulsing the MKIs. UFO detection in first ≈20ms is limited by transient losses during MKI pulse. zoomed 1 event at 1330 ms

LIBD MeetingNovember 29 th Delay of UFO events The distribution spreads out over a few hundred ms. The first event was observed about 3ms after MKI pulse (in IQC). 1 event at 1330 ms zoomed UFOs in IQC until

LIBD MeetingNovember 29 th UFO Location In Pt. 2 most UFOs occur at MKI.D5L2. In Pt. 8 the distribution is more equal. Beam candidate UFOs around MKI in Pt.2. Signal RS01 > 1∙10 -3 Gy/s. Pt. 2 Beam candidate UFOs around MKI in Pt.8. Signal RS01 > 1∙10 -3 Gy/s. Pt. 8

LIBD MeetingNovember 29 th Content 1. Lead MKI UFOs2. Update on MKI UFO MD results3. UFO size estimates4.IPAC Abstract

LIBD MeetingNovember 29 th Macro Particle Size F. Zimmermann at LMC 109

LIBD MeetingNovember 29 th Macro Particle Size UFO event on :09:18 I=1.02·10 14 protons, E=3.5 TeV, with n =2.5µm·rad, β x =158.5m, β y =29.5m, σ x =325µm, σ y =140µm. MaterialResulting mass (A)Radius of spherical object Al (l=39.7cm, ρ=2700kg/m 3 ) 5.53· µm Al 2 O 3 (l=24.8cm, ρ=3970kg/m 3 ) 5.08· µm Particle mass Nuclear interaction length Radius of large UFOs must be at least ≈40µm.

LIBD MeetingNovember 29 th Content 1. Lead MKI UFOs2. Update on MKI UFO MD results3. UFO size estimates4.IPAC Abstract

LIBD MeetingNovember 29 th 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.

LIBD MeetingNovember 29 th Thank you for your Attention Tobias Baer CERN BE/OP Office: Further information: T. Baer, “UFO update”, Mini-Chamonix Workshop, July R. Ballester, “Vibration analysis on an LHC kicker prototype for UFOs investigation”, EDMS Report No , August M. Sapinski, “Is the BLM system ready to go to higher intensities?”, Workshop on LHC Performance, Chamonix, Jan F. Zimmermann, “Interaction of macro-particles with the LHC proton beam”, IPAC’10.

LIBD MeetingNovember 29 th Backup slides

LIBD MeetingNovember 29 th temporal spatial amplitude Study buffer provides information about temporal and spatial distribution as well as amplitude of UFOs after MKI pulse. UFO at 09:54: s 2.56ms resolution Losses of unbuched beam at TDI UFOs beam

LIBD MeetingNovember 29 th Temporal Loss pattern Temporal loss pattern of the MKI UFO at :58:38 at three different BLMs left and right of IP8.

LIBD MeetingNovember 29 th Content UFO Dumps 2010/2011

LIBD MeetingNovember 29 th UFOs in the LHC 35 fast loss events led to a beam dump. Since July 2010, 35 fast loss events led to a beam dump. 18 in 2010, 17 in around MKIs. 6 dumps by experiments. 1 at 450 GeV. Typical characteristics: Loss duration: about 10 turns Often unconventional loss locations (e.g. in the arc) U FO The events are believed to be due to (Unidentified) Falling Objects (UFOs). Spatial and temporal loss profile of UFO on

LIBD MeetingNovember 29 th Beam dump on Dump on running sum 1-6.

LIBD MeetingNovember 29 th Beam dump 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)

LIBD MeetingNovember 29 th Content UFO Observations and Studies

LIBD MeetingNovember 29 th : Logged BLM data was analyzed and 113 sub-threshold UFO events were found. (E. Nebot) For 2011: Online UFO detection in 1Hz BLM data candidate UFOs Over 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 arc UFOs (≥cell 12) at 3.5 TeV with signal RS05 > 2∙10 -4 Gy/s.

LIBD MeetingNovember 29 th 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.

LIBD MeetingNovember 29 th 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.

LIBD MeetingNovember 29 th Intrafill UFO rate The UFO rate stays constant during a fill.

LIBD MeetingNovember 29 th 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

LIBD MeetingNovember 29 th 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

LIBD MeetingNovember 29 th 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

LIBD MeetingNovember 29 th Loss Duration UFOs have the tendency to become faster with increasing intensity. (cf. E.B. Holzer at Evian Dec. 2010) courtesy of E. Nebot

LIBD MeetingNovember 29 th Event Rate events below threshold found in (E. Nebot) UFO rate UFO rate: proportional to beam intensity. courtesy of E. Nebot

LIBD MeetingNovember 29 th UFOs Detection in : 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 triggers Over 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.

LIBD MeetingNovember 29 th 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.

LIBD MeetingNovember 29 th 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)

LIBD MeetingNovember 29 th 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

LIBD MeetingNovember 29 th UFO rate vs Bunch Intensity No dependency of UFO rate on buch intensity.

LIBD MeetingNovember 29 th Peak Signal vs Loss Duration Tendency that harder UFOs are faster. courtesy of E. Nebot

LIBD MeetingNovember 29 th 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

LIBD MeetingNovember 29 th Calibration of T loss Correlation of T loss and width of Gaussian fitted to post mortem turn-by-turn data. courtesy of E. Nebot

LIBD MeetingNovember 29 th 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 )

LIBD MeetingNovember 29 th 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

LIBD MeetingNovember 29 th Content UFOs around MKIs

LIBD MeetingNovember 29 th 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.

LIBD MeetingNovember 29 th Layout of MKI Region MKI.D MKI.CMKI.BMKI.A

LIBD MeetingNovember 29 th 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.

LIBD MeetingNovember 29 th 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

LIBD MeetingNovember 29 th 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

LIBD MeetingNovember 29 th Beam dump on GeV. UFO at MKI in Pt. 2, at 450 GeV. Small loss signal at Q5 (backscattering?). MKIs TCT

LIBD MeetingNovember 29 th Beam dump 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)

LIBD MeetingNovember 29 th 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

LIBD MeetingNovember 29 th 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

LIBD MeetingNovember 29 th 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 candidate UFOs around injection regions in Pt. 2 for fills reaching stable beams with >200 bunches. Signal RS01 > 1∙10 -2 Gy/s.

LIBD MeetingNovember 29 th 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.

LIBD MeetingNovember 29 th 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.

LIBD MeetingNovember 29 th 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 candidate UFOs around injection regions in Pt. 2 for fills reaching stable beams. Signal RS01 > 1∙10 -2 Gy/s.

LIBD MeetingNovember 29 th 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

LIBD MeetingNovember 29 th UFOs at MKIs – 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

LIBD MeetingNovember 29 th Correlation with Vacuum Despite a large vacuum spike, there is no clear correlation with UFOs

LIBD MeetingNovember 29 th Correlation with Vacuum

LIBD MeetingNovember 29 th Vacuum Correlation The pressure spike is seen on all MKI magnets. BLM MKI.C5L2 Vacuum MKI

LIBD MeetingNovember 29 th 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.

LIBD MeetingNovember 29 th Vacuum correlation (slow) The slow vacuum spike is correlated to the last injection. No correlation with UFOs

LIBD MeetingNovember 29 th UFOs in IQC Many additional events in IQC data for normal operation. Loss at Injection Candidate UFO

LIBD MeetingNovember 29 th Content MKI UFO MD

LIBD MeetingNovember 29 th 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)

LIBD MeetingNovember 29 th UFOs between kicker pulses The number of UFOs between kicker pulses decreased over time after the last injection with beam.

LIBD MeetingNovember 29 th 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

LIBD MeetingNovember 29 th ·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

LIBD MeetingNovember 29 th 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

LIBD MeetingNovember 29 th Content Conclusion and Summary

LIBD MeetingNovember 29 th 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)

LIBD MeetingNovember 29 th 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.

LIBD MeetingNovember 29 th 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?

LIBD MeetingNovember 29 th Summary and Conclusion 17 beam dumps 17 beam dumps due to UFOs in 2011 so far (18 in 2010). Over candidate UFOs 6.0 UFOs/hour Over 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.