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. Content. Content. UFO Dumps. 18 beam dumps due to UFOs in 2010. - PowerPoint PPT Presentation
Slide 1
UFOs in the LHCTobias BaerLBOCJune, 14th 2011
Acknowledgements: N. Garrel, B. Goddard, E.B. Holzer, S.
Jackson, M. Misiowiec, E. Nebot, A. Nordt, J. Uythoven, J.
Wenninger, C. Zamantzas
LHC Beam Operation CommitteeJune, 14th 2011#1Content#LHC Beam
Operation CommitteeJune, 14th 2011LHC Beam Operation CommitteeJune,
14th 2011#Content#LHC Beam Operation CommitteeJune, 14th 2011LHC
Beam Operation CommitteeJune, 14th 2011#UFO Dumps18 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 due to UFOs in 2011.8 in injection region
(2010: 2)1 dump at 450 GeV. (6.6.2011)
#LHC Beam Operation CommitteeJune, 14th 2011LHC Beam Operation
CommitteeJune, 14th 2011#Content#LHC Beam Operation CommitteeJune,
14th 2011LHC Beam Operation CommitteeJune, 14th 2011#UFOs Detection
in 20112010: 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 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.#LHC Beam Operation CommitteeJune, 14th 2011LHC
Beam Operation CommitteeJune, 14th 2011#Events Below
Thresholdthreshold = lowest threshold in standard arc cell.Most
events are much below threshold.
nominal threshold 7 TeV628 candidate UFOs at 3.5 TeV.Signal RS05
> 510-4 Gy/s.#LHC Beam Operation CommitteeJune, 14th 2011LHC
Beam Operation CommitteeJune, 14th 2011#
Spatial UFO Distribution3.5 TeV1096 candidate UFOs.Signal RS05
> 510-4 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 GeV591 candidate UFOs.Signal RS05 > 510-4 Gy/s.Mainly
UFOs around MKIs#LHC Beam Operation CommitteeJune, 14th 2011LHC
Beam Operation CommitteeJune, 14th 2011#significant increase at
MKI.R8
On average: 10 UFOs/hourUFO Rate in 20111904 candidate UFOs
during stable beams. Signal RS05 > 210-4 Gy/s. Data scaled with
1.76 (detection efficiency from reference data)228 b 36 bpi336b 36
bpi336b 72 bpi480b 36 bpi336b 72 bpi480b 36 bpi480b 72 bpi624b 72
bpi768b 72 bpi228 b 36 bpi480b 72 bpi768b 72 bpi768b 108 bpi912b
108 bpi1092b 108 bpi1092b 144 bpi#LHC Beam Operation CommitteeJune,
14th 2011LHC Beam Operation CommitteeJune, 14th 2011#Peak SignalNo
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 ofE. Nebot
#LHC Beam Operation CommitteeJune, 14th 2011LHC Beam Operation
CommitteeJune, 14th 2011#Loss DurationTloss: Given by fitting
single function (Gaussian up to t=Tloss, 1/t afterwards) to
data.
Loss duration: UFOs have the tendency to become faster with
increasing intensity. (cf. E.B. Holzer at Evian Dec. 2010)
courtesy ofE. Nebot
#LHC Beam Operation CommitteeJune, 14th 2011LHC Beam Operation
CommitteeJune, 14th 2011#Peak Signal vs Loss DurationTendency that
harder UFOs are faster.
courtesy ofE. Nebot#LHC Beam Operation CommitteeJune, 14th
2011LHC Beam Operation CommitteeJune, 14th 2011#Content#LHC Beam
Operation CommitteeJune, 14th 2011LHC Beam Operation CommitteeJune,
14th 2011#Beam dump on 6.6.2011UFO at MKI in Pt. 2, at 450 GeV.
MKIsTCT#LHC Beam Operation CommitteeJune, 14th 2011LHC Beam
Operation CommitteeJune, 14th 2011#Beam dump 06.06.2011From fit to
losses (BLMEI.05L2.B1E10_MKI.D5L2.B1):Amplitude: 7.73
Gy/s(Threshold: 2.3 Gy/s)Width: 0.77 msresulting speed of
transiting dust particle = 0.47 m/s.(assuming n=2.2mrad) (cf. T.
Baer 86th LMC)
#LHC Beam Operation CommitteeJune, 14th 2011LHC Beam Operation
CommitteeJune, 14th 2011#Peak LossesPeak loss for MKI UFOs at 450
GeV.Threshold (RS1 = 2.3 Gy/s)
336 candidate UFOs at 450 GeV. Signal RS01 > 210-4 Gy/s.+ 1
event with 3.5Gy/s (dump 06.06.2011)#LHC Beam Operation
CommitteeJune, 14th 2011LHC Beam Operation CommitteeJune, 14th
2011#UFOs around Injection Region679 UFOs around the MKIs caused 9
beam dumps.
Most of the UFOs around the MKIs occur before going tostable
beams.
#LHC Beam Operation CommitteeJune, 14th 2011LHC Beam Operation
CommitteeJune, 14th 2011#MKI UFOs During ScrubbingTypical scenario
for MKI UFOs during scrubbing: Loss spikes occur in first few
minutes after an injection and go away then.
2 hours#LHC Beam Operation CommitteeJune, 14th 2011LHC Beam
Operation CommitteeJune, 14th 2011#18UFOs at MKIs per fillFlashover
of MKI D Pt.8 before Fill 1721 (vacuum valves moved in).
Fill 1721:21 MKI UFOs in Pt.82 MKI UFOs in Pt.2Flashover#LHC
Beam Operation CommitteeJune, 14th 2011LHC Beam Operation
CommitteeJune, 14th 2011#Correlation with VacuumDespite a large
vacuum spike, there is no clear correlation with UFOs
#LHC Beam Operation CommitteeJune, 14th 2011LHC Beam Operation
CommitteeJune, 14th 2011#UFOs at MKIs08.04. 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 IP2Right of IP8Beam directionBeam direction
#LHC Beam Operation CommitteeJune, 14th 2011LHC Beam Operation
CommitteeJune, 14th 2011#Content#LHC Beam Operation CommitteeJune,
14th 2011LHC Beam Operation CommitteeJune, 14th 2011#Next
StepsImprove 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.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.
#LHC Beam Operation CommitteeJune, 14th 2011LHC Beam Operation
CommitteeJune, 14th 2011#Summary11 UFO related beam dumps in 2011
so far (18 in 2010).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
magnetsDuring scrubbing: increased UFO rate after each
injection.Increased UFO rate after MKI Flashover.Next steps: UFO
MD, Improve the diagnostics, better understanding of quench limits,
learn from simulations.#LHC Beam Operation CommitteeJune, 14th
2011LHC Beam Operation CommitteeJune, 14th 2011#Thank you for your
Attention
Tobias BaerCERN BE/[email protected]: +41 22 76
75379Further 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.#LHC
Beam Operation CommitteeJune, 14th 2011LHC Beam Operation
CommitteeJune, 14th 2011#Backup slides#LHC Beam Operation
CommitteeJune, 14th 2011LHC Beam Operation CommitteeJune, 14th
2011#
UFOs in 201018 beam dumps due to UFOs.(since 07.07.2010)113 UFOs
below threshold foundin 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#LHC Beam Operation CommitteeJune, 14th 2011LHC Beam
Operation CommitteeJune, 14th 2011#Event Rate113 events below
threshold found in 2010. (E. Nebot)
UFO rate: proportional tobeam intensity.
courtesy ofE. Nebot#LHC Beam Operation CommitteeJune, 14th
2011LHC Beam Operation CommitteeJune, 14th 2011#Calibration of
TlossCorrelation of Tloss and width of Gaussian fitted topost
mortem turn-by-turn data.
courtesy ofE. Nebot#LHC Beam Operation CommitteeJune, 14th
2011LHC Beam Operation CommitteeJune, 14th 2011#Fast Loss Event
RateAfter 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.
#LHC Beam Operation CommitteeJune, 14th 2011LHC Beam Operation
CommitteeJune, 14th 2011#UFO AlgorithmLosses (RS 4) of at least two
BLMs within 40m are above 1E-4 Gy/s.A BLM is not taken into account
ifIt is at a TCTIt is in IP3, IP6 or IP7RS 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.#LHC Beam Operation CommitteeJune,
14th 2011LHC Beam Operation CommitteeJune, 14th 2011#LHC UFO
BusterLHC Console Manager -> Fixed Displays -> BLM -> UFO
Buster
#LHC Beam Operation CommitteeJune, 14th 2011LHC Beam Operation
CommitteeJune, 14th 2011#UFO DetectionFor 2010: 113 UFOs below
threshold found in logging database. (E. Nebot)For 2011: Online UFO
detection by UFO Buster.Detects UFOs in BLM concentrator data
(1Hz).5000 UFOs below threshold foundso far.
Most events are much below threshold.
threshold = lowest threshold in standard arc cell.
nominal arc threshold 7 TeV4905 candidate UFOs at 3.5 TeV.#LHC
Beam Operation CommitteeJune, 14th 2011LHC Beam Operation
CommitteeJune, 14th 2011#Dump on 01.05.2011Dump of
BLMQI.04L2.B1E20_MQY on RS 3, 4 and 5
Dump of BLMQI.04L2.B1E20_MQY on 320s, 640s and 2.5ms integration
time
#LHC Beam Operation CommitteeJune, 14th 2011LHC Beam Operation
CommitteeJune, 14th 2011#Dump on 01.05.2011 From fit to losses
(BLMEI.05L2.B1E10_MKI.D5L2.B1):Amplitude: 0.63 Gy/sWidth: 0.29
ms
#LHC Beam Operation CommitteeJune, 14th 2011LHC Beam Operation
CommitteeJune, 14th 2011#Correlation with Vacuum
#LHC Beam Operation CommitteeJune, 14th 2011LHC Beam Operation
CommitteeJune, 14th 2011#Dynamics of Dust ParticlesFrom
simulations:
Dust particle will be positively ionized and be repelled from
the beam.Beam intensity: 2.31012 protons, Al object.
Loss duration of a few ms.Losses become shorter for larger beam
intensities.courtesy ofF. Zimmermann
#LHC Beam Operation CommitteeJune, 14th 2011LHC Beam Operation
CommitteeJune, 14th 2011#Correlation with Wire ScannerFrom wire
scans: linear dependency of BLM signal on beam energy
courtesy ofM. Sapinski (cf. Chamonix 2011)#LHC Beam Operation
CommitteeJune, 14th 2011LHC Beam Operation CommitteeJune, 14th
2011#
Layout of MKI Region
#LHC Beam Operation CommitteeJune, 14th 2011LHC Beam Operation
CommitteeJune, 14th 2011#UFO sizeTwo 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 ofJ. Wenninger(cf. MPP 25.03.2011)#LHC Beam Operation
CommitteeJune, 14th 2011LHC Beam Operation CommitteeJune, 14th
2011#UFO SpeedUFO speed:
From free fall:
The UFO speed corresponds to the expected speed for a free fall
from the aperture.
vu: UFO speed, b: transverse beam size, u: UFO size, T: temporal
width of loss.
22 mm free fallnorm = 2.5 mrad = 150 m
#LHC Beam Operation CommitteeJune, 14th 2011LHC Beam Operation
CommitteeJune, 14th 2011#Known Dust Particle SourcesDistributed ion
pumps (PF-AR, HERA).Electrical Discharges (PF-AR).Movable
Devices.Particles frozen or condensated at cold elements.
(ANKA)#LHC Beam Operation CommitteeJune, 14th 2011LHC Beam
Operation CommitteeJune, 14th 2011#
