Short summary of last weekend’s LHC and LHCb results, using slides of Richard Jacobbson and Olaf Behrendt from the Tuesday meeting of Aug 26
Beamline around IP8
IP8
TDI
TED
TED: • 28 tonne beam stopper• ~ 200 meter from LHCb
TDI: • Collimator with 5 meter long jaws• About 50 meters from LHCb• Cannot be fully closed!
What happened Friday
• 14.00: Machine closed-up• 16.00: Access to TI8 to unblock the dump at the end of
TI8 + access to solve cryogenics problems at point 2• 16.50 : CMS opens a ‘green door…• 17.50: Beam down to dump (TED) at the end of TID• VELO Tracks !!!• 19.00: TED taken out• Problem with LHC timing• 20.00 – 20.30: Beam down to TDI after some struggle• 20.38: First shot on TDI• 20.53: TDI open and first shot straight to point 7 (3km)!
<- Beam monitor near TDI
Beam screen near point 7(after LHCb!)
Saturday• Aperture measurements between point 7 and 8• LCHb was off (apart from beam conditions monitor)
Sunday• Beam on TED from ~10:30 to 12:30• Whole VELO on
Beam incidents on Saturday• LHCb BCM pulled beam dump at three dumps on TDI
– 11:22, 12:10, 12:47– BLMs on triplets and around TDI did not show ‘much’ higher losses– Loss appeared as a concentrated shower at ~9 o’clock in BCM as
seen along Beam 2• Hypothesis: Compatible with little or no kick and TDI open at top
• 7400 nA max (!) seen in sensor 2 as compared to <200 nA during TDI dumps on Friday night
• 36 pA/mips >105 particles per sensor >107 particles assuming an area of 10x10cm2
Beam 2
BCM Downstream station
8x8mm2
0
1
2
3
4
5
6
7
?
VELO results
• 5 modules on each side switched on• timing adjusted to expected SPD trigger signal
[from SPD and VELO signal propagation times]• data taking with 15 consecutive triggers
[window of 350 ns around the expected signal]• compensation for not optimal timing by
– lowering the cluster thresholds– enhancing the signal amplification
TED Run 1 (22.08.08)
A First Glimpse of Beam
First reconstructed tracks in VELO
run: 30764event: 156time: 17:56?
• linked hits
• not not linked hits
Timing
central trigger
TED Run 2 (24.08.08)
• all Si modules switched on• all but 10 sensors read out [TELL1 problems]
• timing window reduced to 5 consecutive triggers
run: 30933event: 1
run: 30933event: 12
Sunday’s runAlso other subdetector were onIT, PRS, SPD, Muon and PileUp
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