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,
Slide 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
Slide 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.
Slide 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
Slide 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
Slide 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
Slide 7
LHC UFO Study Working GroupSeptember 15 th 20117 Thank you for
your Attention Tobias Baer CERN BE/OP [email protected] Office:
+41 22 76 75379 Further information: T. Baer, UFOs in the LHC,
IPAC11, TUPC137, September 2011. F. Zimmermann, Simulation Studies
of Macro-particles Falling into the LHC Proton Beam, IPAC11,
MOPS017, September 2011. E. Nebot del Busto, Analysis of Fast
Losses in the LHC with the BLM System, IPAC11, 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.
Slide 8
LHC UFO Study Working GroupSeptember 15 th 20118 Backup
slides
Slide 9
LHC UFO Study Working GroupSeptember 15 th 20119 Content UFO
Dumps 2010/2011
Slide 10
LHC UFO Study Working GroupSeptember 15 th 201110 Beam dump on
29.05.2011 Dump on running sum 1-6.
Slide 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 s Temporal Width: 97 s
3.6 m/s resulting speed of transiting dust particle = 3.6 m/s.
(assuming n =2.5mrad) (also cf. J. Wenninger at MPP March
2011)
Slide 12
LHC UFO Study Working GroupSeptember 15 th 201112 Content UFO
Observations and Studies
Slide 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
Slide 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)
> 210 -4 Gy/s ( 2 of threshold). 74 events remain of subset, of
which 71 are clear UFOs (96%) and 3 are ambiguous cases.
Slide 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 > 210 -4 Gy/s.
Slide 16
LHC UFO Study Working GroupSeptember 15 th 201116 Spatial UFO
Distribution 3.5 TeV 3.5 TeV 3686 candidate UFOs. Signal RS05 >
210 -4 Gy/s. Red: Signal RS01 > 110 -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 > 210 -4 Gy/s. Mainly UFOs around
MKIs gray areas around IRs are excluded from UFO detection.
Slide 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.
Slide 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.
Slide 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 > 210 -4 Gy/s. Data
scaled with 1.76 (detection efficiency from reference data)
Slide 20
LHC UFO Study Working GroupSeptember 15 th 201120 Intrafill UFO
rate The UFO rate stays constant during a fill.
Slide 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
Slide 22
LHC UFO Study Working GroupSeptember 15 th 201122 UFO rate vs
Bunch Intensity No dependency of UFO rate on buch intensity.
Slide 23
LHC UFO Study Working GroupSeptember 15 th 201123 Peak Signal
vs Loss Duration Tendency that harder UFOs are faster. courtesy of
E. Nebot
Slide 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
Slide 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
Slide 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 m. (cf. M. Sapinski,
F. Zimmermann at Chamonix 2011) courtesy of J. Wenninger (cf. MPP
25.03.2011)
Slide 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, b :
transverse beam size, u : UFO size, T : temporal width of loss. 22
mm free fall norm = 2.5 mrad = 150 m
Slide 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 > 110 -3 Gy/s. courtesy of J. M. Jimenez
Slide 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
Slide 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 4.610 13 protons 3.5 TeV 2.310 12 protons round Al
Object
Slide 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
Slide 32
LHC UFO Study Working GroupSeptember 15 th 201132 Content UFOs
around MKIs
Slide 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.
Slide 34
LHC UFO Study Working GroupSeptember 15 th 201134 Layout of MKI
Region MKI.D MKI.CMKI.BMKI.A
Slide 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 > 110 -3 Gy/s.
Right of IP8 Beam direction 270 candidate UFOs around MKI in Pt.8.
Signal RS01 > 110 -3 Gy/s.
Slide 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
Slide 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
Slide 38
LHC UFO Study Working GroupSeptember 15 th 201138 UFO Dynamics
From fit to losses (MKI-D): 1.810 -2 Gy/s Amplitude: 1.810 -2 Gy/s
(Threshold: 11.6 Gy/s) 160 s Temporal Width: 160 s 7.6 ms Time
delay to kicker pulse: 7.6 ms 658 m/s resulting acceleration
(constant particle acceleration): 658 m/s 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
Slide 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
Slide 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 n =2.2mrad) (Brennan Goddard)
Slide 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
Slide 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
Slide 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 > 110 -2
Gy/s.
Slide 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.
Slide 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 > 110 -2
Gy/s.
Slide 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 > 110 -2 Gy/s.
Slide 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
Slide 48
LHC UFO Study Working GroupSeptember 15 th 201148 Correlation
with Vacuum Despite a large vacuum spike, there is no clear
correlation with UFOs
Slide 49
LHC UFO Study Working GroupSeptember 15 th 201149 Correlation
with Vacuum
Slide 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
Slide 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.
Slide 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
Slide 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
Slide 54
LHC UFO Study Working GroupSeptember 15 th 201154 Content MKI
UFO MD
Slide 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)
Slide 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.
Slide 57
LHC UFO Study Working GroupSeptember 15 th 201157 MKI UFOs at
MKI pulse 1.410 -2 Gy/s The peak loss at the MKI D in the second of
the kicker pulse are 1.410 -2 Gy/s (40s running sum). TDI MKI
D
Slide 58
LHC UFO Study Working GroupSeptember 15 th 201158 1.410 -3 Gy/s
The peak loss at the MKI D at injection is one order of magnitude
smaller (1.410 -3 Gy/s). Losses at MKI Loss at Kicker pulse
Slide 59
LHC UFO Study Working GroupSeptember 15 th 201159 UFO Dynamics
From fit to losses (MKI-D): 3.710 -3 Gy/s Amplitude: 3.710 -3 Gy/s
(Threshold: 11.6 Gy/s) 218s Temporal Width: 218s 2.2 m/s resulting
speed of transiting dust particle = 2.2 m/s. (assuming n =2.5mrad)
4.3 ms 2055 m/s Time delay to kicker pulse: 4.3 ms resulting
acceleration (assuming constant particle acceleration): 2055 m/s
8.8 m/s resulting speed during interaction with beam: 8.8 m/s
Slide 60
LHC UFO Study Working GroupSeptember 15 th 201160 Content
Conclusion and Summary
Slide 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)
Slide 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.
Slide 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?
Slide 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.