Week 21
Monday
13 x 2e10 per beam into physics for the first time
Tuesday
Stable beams (13 x 2e10 p per beam)
Energy matching beam 1.
Injection kicker studies beam 2.
Nominal bunch studies: RF
Ramp nominal bunch to 3.5 TeV & collide
Wednesday
Access
Ramp nominal bunches – beam 2 lost (vacuum interlock)
Nominal bunches to 3.5 TeV and collide/RF studies
18 kV glitch
Thursday
Sector 67 tripped again. Access. BLM problem.
Power glitch affecting various systems: Recovery.
Injection 7 x 1e11 per beam.
Stable beams (450 GeV collisions).
Sector 67 trip.
Transverse damper studies.
31-05-10
LHC status - week 21
Week 21
Friday
• BPMs versus intensity
• Impedance measurements
• Nominal intensity ramp & collide
• 66 kV drop
Saturday
66 kV drop recovery
Sunday
66 kV drop recovery - cryogenics
31-05-10
LHC status - week 21
High intensity
Single bunch ~1e11 per beam
3.5 TeV unsqueezed
Weds a.m. Single beam looked stable.
Collisions at injection tunes, no Q split.
Beam lost to strong coherent instability
Weds p.m. Collision tunes, tune split.
Stable after going into collision, rocky before collision with some
manual chromaticity and tune trims to keep the beam.
Fri p.m.
31-05-10
Looked good longitudinally
Transverse messy spectrum but OK
Horns noted
Single beam rocky – sensitive to tune, coupling
LHC status - week 21
1e11 Observations
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Over-injection well established
Emittance blow-up of B2V at 450 GeV well documented
Big emittance blow-up in ramp
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although last time better
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Octupoles used systematically
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up to 40 A after 1 TeV
Longitudinal “quadrupole” oscillations gone after use of
increase longitudinal emittance from SPS and rematched voltage
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31-05-10
transverse damper B2V
chromaticity trimmed down in ramp
~0.7 eVs, 1.7 – 1.8 ns
3.5 MV at 450 GeV coming up to 5 MV in ramp
4 klystons per beam
LHC status - week 21
1e11 Observations
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Chromaticity difficult to measure at flat top but around 6
Rocky before collision with some manual chromaticity,
coupling & tune trims to help improve lifetime
Tune split before going into collisions
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31-05-10
Put an extra +3e-3 on beam 2 H and V
Collisions at 10 m. looks OK with tune split and collision
tunes
LHC status - week 21
The horns at 450 GeV
31-05-10
LHC status - week 21
Emittance in ramp
Big B1H to start with but overall actually the best we’ve seen
31-05-10
LHC status - week 21
Bunch length in ramp
Ramp with larger longitudinal
emittance (from SPS) : 0.7 eVs
instead of 0.3 eVs
31-05-10
LHC status - week 21
Beam 1 at 3.5 TeV
Beam
intensity
31-05-10
Horizontal tune
amplitude
Collide
LHC status - week 21
Beam 1 - coupling
31-05-10
LHC status - week 21
Beam 2 in collision
Beam
intensity
31-05-10
Horizontal tune
amplitude
LHC status - week 21
Vertical tune
amplitude
Colliding 13*2e10
31-05-10
LHC status - week 21
Orbit Feedback
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Two main problems:
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31-05-10
Inappropriate behaviour on not receiving energy
Oscillatory correction behaviour
First problem solved by our man in Japan
Stable after FGC loop period was changed to 80 ms
(from 100) to be in phase with the FB.
The FB survived an event without energy (due to the fact
that the tune systems stopped for some time). It took
some time to catch up the energy, but it eventually
managed.
Declare operational with some potential tuning to be
performed
LHC status - week 21
B2 injection oscillation for bucket one
31-05-10
LHC status - week 21
Bucket 1 – vertical kick
... For the moment, I have no explanation on how this is possible within
our timing system as the bucket number is not taken into account at
all....In order to see if it is a re-phasing issue within our 1ns fine delay
module, I propose to reduce the kick delay by 20ns and see if it has an
effect.
31-05-10
LHC status - week 21
Transverse dampers
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H.B1:
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V.B1:
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31-05-10
All power amplifiers used with two pick-ups, works correctly :-)
V.B2:
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Gain of two power amplifier chains is not correct; needs an
intervention in UX45 (#5 and #6); problem most likely inUX45.
V.B1 used with two power amplifiers (#7, #8) and two pick-ups
works correctly in both modes (with and without FIR phase
shifter)
H.B2:
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A VME crate in SR4 needs a local intervention before further
commissioning
All power amplifiers used, but only with pick-up Q9; pick-up Q7
has a noisy electronics; intervention in SR4 required
Multi-bunch mode needs to be tested.
LHC status - week 21
Dampers on for Beam 2
Successfully used with 1*1e11 at injection and in ramp (and flat top)
31-05-10
LHC status - week 21
BPM Study – B2 (Ongoing)
Average Orbit
RMS Orbit
High I
High I
Low I
Low I
31-05-10
LHC status - week 21
BPM Study – B1 (Ongoing)
Average Orbit
RMS Orbit
High I
High I
Low I
31-05-10
LHC status - week 21
Low I
Power cut – late Friday evening
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23:20:43 Lose 66 kV – major power cut across site
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23:20:54 Fire alarm in building 958 (BE) where the
breaker is situated
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31-05-10
Circuit breaker trips, but fault also brings down 66kV transformer
EHT7
EHT7 feeds North zone loop, SPS, LHC point 1 and the LHC
loop
Power was reestablished in 28 seconds following a successful
auto-transfer
Fire service intervene
LHC status - week 21
Configuration
31-05-10
LHC status - week 21
Diagnosis
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The fault was on a cable terminal inside the 404 cabinet;
it connects the BE9 bus bars to the North Area loop.
An arc developed inside the cabinet and then a short
between phases. The circuit breaker did not open on the
short because of the arc; instead it opened on thermal
protection after 250 ms;
The 66 kV supply through cabinet 27 (which was saw the
fault in cabinet 404) triggered, shutting down the PS,
the SPS and the general services LHC loop.
All the machine, experiments and infrastructure systems
were affected.
Francois Duval, Roberto Saban
31-05-10
LHC status - week 21
Saturday 18:00
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After a long day…
Back to the nominal configuration having by-passed
cabinet 404 and the cable between it and BA80 (North
Area loop is not a loop anymore.)
EPC is switching on the SVCs.
Another occurrence of a cable terminal fault. We are
carefully analyzing these terminals and their screen
connections; we will bring systematic consolidation when
the findings are conclusive.
Francois Duval, Roberto Saban
31-05-10
LHC status - week 21
QPS view of cut
29-05-10
LHC status
Recovery - Saturday
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Major effort Saturday
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Booster back up early Saturday morning,
PS Saturday afternoon
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AD still does not have beam – cooling pump problem target
area – finally fixed Sunday evening
SPS late Saturday evening
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31-05-10
EL, SVC, Cooling, ventilation, vacuum, controls, BI, power
converters, cryogenics, RF
Access plus RP as required
North area & CNGS back in operation
LHC status - week 21
LHC recovery - Saturday
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Power cut caused 3 trips that required further
investigation
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All Switches now closed and QPS reset for all circuits
EPC had ~20 circuits that needed attention
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all fixed Saturday morning (Valerie Montabonnet)
Collimators OK
MKI8 power supply access required
Access system: LHC Access system operational

31-05-10
RB.A45 (MB.B21R4) : heater discharge
RB.A81(MB.C32L1) : heater discharge
MQ.25L1 : Only 1 of 2 heaters fired
has one 48V power supply warning
LHC status - week 21
Full machine checkout
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RF – problem with one cavity – He level monitoring
Transverse dampers
Injection kickers
Beam instrumentation
Vacuum
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31-05-10
All insulation vacuum equipment restarted and functioning.
All beam vacuum equipment restarted/repaired.
All beam vacuum sector valves reopened when the cryo
temperature < 5K.
SPS: All beam vacuum equipment functioning and sector valves
open.
Beam down transfer lines
LHC status - week 21
Cryogenics – summary 1/2
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P18
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P2
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QSCCA compressor station for 4.5K fridge and full stop on
whole installation
Full stop on cold compressor station
Effected sector 2-3
P4
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31-05-10
QSCB compressor station for 4.5 K and QSCCB upper
compressor station for cold compressors
Full stop on whole installation
Effected sector 12
QSCCA compressor station for upper compressor station for
cold compressors
Full stop on cold compressor station
Effected sector 3-4
LHC status - week 21
Cryogenics
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P4
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P6
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CS and CM for both sectors
P8
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31-05-10
QSCB compressor station for 4.5K fridge and QSCCB upper
compressor station for cold compressor station
Effect sector 4-5
QSCCB upper compressor station for cold compressor station
Full stop for cold compressor station
Effected sectors 7-8 and 8-1
LHC status - week 21
Status earlier this morning
Prepared for 3 day technical stop
31-05-10
LHC status - week 21