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Status of LHC Performance. P erformance, problems, projection. Mike Lamont for the LHC team. Ramp-up of number of bunches. MD, technical stop. Intermediate energy, TS, scrubbing. 15 weeks. Ramp-up - p erformance. Reached 1380 ( maximum possible with 50 ns bunch spacing) on 27 th June. - PowerPoint PPT Presentation
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Status of LHC Performance
Mike Lamont for the LHC team
Performance, problems, projection
Ramp-up of number of bunches
22-8-2011
Intermediate energy, TS, scrubbing
MD, technical stop
15 weeksLHC status
LHC status 3
Ramp-up - performance
2-8-2011
Reached 1380 (maximum possible with 50 ns bunch spacing) on 27th June
Luminosity
LHC status2-8-2011 4
26 pb-1/day
LHCb
LHC status 52-8-2011
UFOs In particular at the injection kickers
Single Event Effects (SEE) QPS, Cryogenics, Collimators, Power converters…
RF Couplers – particularly on trips RF wave-guide arc detectors
Beam induced heating injection kickers, cryogenics, collimators..
Vacuum activity
Ramp-up: not all plain sailing
2-8-2011 6LHC status
From 3 to 1380 bunches with a previous maximum of 368 in 15 weeks elapsed (via MD, TS, scrubbing, intermediate energy) has to be regarded as pretty good, however…
Collimation always critical Good stability - regular loss maps performed
144 bunches from SPS Beam quality from injector important 144 bunches per injection from SPS - 1.2 MJ down the lines
High temperature superconducting current lead quenched (7th April) Invoked quench of 11 magnets
Injection Kicker Flashover (18th April) Not pretty, heavy beam loss
Injection kicker erratics (28th July) Two incidents – not pretty, heavy beam loss
Increasing intensity – machine protection
2-8-2011 7LHC status
Routinely dealing with 90 to 100 MJ per beam at 3.5 TeV
2011 parameters - end June
LHC status
Energy [TeV] 3.5
Beta* [m] 1.5, 10, 1.5, 3.0 m
Normalized emittance [microns] 2.5 – 3.1 start of fill
Bunch intensity 1.1 - 1.2e11
Number of bunches 13801318 collisions/IP1&5
Bunch spacing [ns] 50 – good choice
Stored energy [MJ] 90 to 100
Peak luminosity [cm-2s-1] 1.27e33
Beam-beam tune shift ~0.015 – 0.017
82-8-2011
LHC status 92-8-2011
Emittance
• As we move around the machine the shape of the ellipse will change as (s) changes with the varying quadrupole (de-)focusing
• However the area of the ellipse () does not change
• Emittance shrinks naturally as we go up in energy (pS increases, pT doesn’t)
• Define energy independent normalized emittance:
• Units are mm.mrad but normally use microns (and drop normalized)
• Handy – constant across complex (give or take some blow-up)
x’
x
x
Aim: maximize peak luminosity
LHC status 102-8-2011
N Number of particles per bunch
KbNumber of bunches
f Revolution frequency
Beam size at interaction point
F Reduction factor due to crossing angle
Emittance
Normalized emittance
Beta function at IP
Minimize (normalized) emittance (~2 microns) Adiabatically increase bunch intensity (to ~1.6e11 ppb)
Maximum from injectors with 50 ns Beta* = 1 m should be OK (collimation, beam-beam)
Prepare test and then possibly implement after next technical stop
Stick with 50 ns Test 25 ns in MD & trial stable beams with limited number of 25
ns trains
Conclusions from mini-Chamonix
2-8-2011 11LHC status
before after buys
Emittance 2.5 – 3.0 2.0 ~1.38
Bunch intensity 1.2 1.6 ~1.78
Beta* 1.5 1 ~1.5
Emittances – start of fill – from luminosity
LHC status 122-8-2011
Bunch intensities
LHC status2-8-2011 13
Emittances down, bunch intensity more-or-less constant
It wasn’t meant to be like this
LHC status 142-8-2011
20% of design luminosity: - half design energy - nominal bunch intensity- half nominal emittance- beta* = 1.5 m (design 0.55 m)
Up until a week ago we’d been working with emittance blow-up in the SPS to give around 2.0 microns injected into the LHC (having worked down from 2.5 - 3.0) This gave good luminosity but some issues with beam losses
when adjusting collisions before stable beams
When switching off the blow-up completely – emittance from SPS of 1.6 microns – miraculously everything cleaned up Assumption: non-Gaussian tails generated by the blow-up were
causing the problem…
Emittance reduction
2-8-2011 15LHC status
Beam-beam tune shift
LHC status 162-8-2011
Tatiana Pieloni
Design report Now
Working point optimization
Fill 1992 – Qh = 0.312 Qv = 0.322
Coupled with the removal of transverse blow-up, removal of lifetime dip on going into collisions
Slight shift of the horizontal and vertical tune before collisions
Positive effect on beam lifetime either by moving some of the tune footprint away a resonance, or perhaps, a 50 Hz harmonic
Gianluigi Arduini2-8-2011 LHC status 17
OPERATIONAL EFFICIENCY
LHC status 182-8-2011
Last week: fills above 450 GeV 1/2
LHC status2-8-2011
Fill Mode Stable [h]
Int. L (pb-1)
Dump cause
Mon 25 1975 STABLE 2.5 13 Cryo valve PROFIBUS (UJ76) (SEU?)
Mon 25 1976 ADJUST - - Losses 83s RS on TCSG.A6L7.B1
Mon 25 1977 SQUEEZE - - RF Module trip
Mon 25 1979 STABLE 6 23 QPS RCO/RCD/RCS cross-talk S56
Tue 26 1980 RAMP - - False trip of 600A QPS RQTL7.R7B1.
Wed 27 1982 STABLE 2.5 13 Electrical network perturbation
Wed 27 1984 SQUEEZE - - Vacuum spike R2
Wed 27 1985 STABLE 11h22m 50.4 Electrical network perturbation
19
Last week: fills above 450 GeV 2/2
LHC status 202-8-2011
Fill Mode Stable [h]
Int. L (pb-1)
Dump cause
Thu 28 1986 STABLE 2.5 14 RF klystron vacuum
Thu 28 1990 STABLE 7.5 41 QPS trigger RCBXV3.R1 (SEU?)
Fri 29 1991 STABLE 5 27 Cryo valve PROFIBUS (UJ16) (SEU?)
Sat 30 1992 STABLE 56m 6.1 Collimator crate UJ16 (SEU?)
Sat 30 1993 STABLE 56m 6.4 UFO 31L8 on B1
Sun 31 1994 STABLE 45m 5.2 RF interlock on HOM line 2 B2
Sun 31 1995 ADJUST - - Mini UFO in triplet R1 from B1
Sun 31 1996 STABLE 1h9m 6.9 Lost cryo compressors in Pt8PLC problem
The last one took the cryogenics out for ~36 hours
Dumps > 450 GeV since Monday 18th July
LHC status 212-8-2011
From Monday 18th July and the move back up to 1380 bunches
Around 15/33 down to high intensity or high luminosity
Short fills hurt
LHC status 222-8-2011
and in particular LHCb
Still managed ~210 pb-1 last week
LHC status2-8-2011 23
Peak Stable Luminosity Delivered
2.03x1033 Fill 1993 11/07/30, 22:53
Maximum Luminosity Delivered in one day
63.7 pb-1 Friday 29 July, 2011
Maximum Luminosity Delivered in 7 days
276.15 pb-1 Saturday 23 July, 2011 - Friday 29 July, 2011
PROBLEMS PROBLEMS PROBLEMS
Three recent headaches
LHC status 242-8-2011
Luminosity driven SEE
LHC status 252-8-2011
Markus Brugger
LHC status 262-8-2011
Markus Brugger for R2E at mini-Chamonix
Planned mitigation – UJ16
LHC status 272-8-2011
Shield and re-locate
Christmas technical stopIn the meantime – victims of our own success
Vacuum - right of IP2 – last week
LHC status2-8-2011 28
Possible explanation (V. Baglin) is the outgassing of an ion pump when the discharge is starting from time to time. Increase the interlock
level on the nearby vacuum gauge temporarily to allow cleaning
Vacuum spikes 4L8: 23-24 July
LHC status2-8-2011
Dump Dump29
Triplets warmed up during technical stop to flush and pump absorbed gas
During the “distillation process”, most of the gas desorbed during the scrubbing run was either pumped out or flushed to the cold bore : Hydrogen, methane and carbon monoxide were pumped out Carbon dioxide was flushed to the cold bore Water remained at its original location
During this process, gas was redistributed in all the vacuum sector
So, we could expect some minor reconditioning ….
Vacuum after technical stop
2-8-2011 30LHC status
Vincent Baglin
And indeed the spikes do appear to have calmed down
Injection kicker erratics
LHC status 312-8-2011
D1
Side view
TDIKicker1. Un-kicked injected beam to
upper TDI jaw
2. Kicked circulating beam to lower jaw
Injection kicker – PFN & switches
LHC status 322-8-2011
PFN
DS MS
Mike Barnes
MKI2 Erratic of MS3 at 18:03:09hrs ON 28/7/2011
0
5000
10000
15000
20000
25000
30000
35000
40000
45000
50000
55000A
ppro
x PF
N V
olta
ge
Sample Number
MKI2. 28 July 2011, 6:03:09 PM
7/28/2011 6:03:09 PM PFN1
7/28/2011 6:03:09 PM PFN2
7/28/2011 6:03:09 PM PFN3
7/28/2011 6:03:09 PM PFN4
Erratic (untriggered) turn-on of MKI2 MS3
At 18:03:09hrs an erratic (untriggered) turn-on of MKI2 MS3 occurred during resonant charging – sending current to one of the four kicker magnets;
Interlocks did NOT detect erratic of MS3 (at 33kV): hence no immediate action was taken to turn-on other thyratrons. PFNs discharged via the DS after 4ms (no further magnet current);
The failure occurred early in the charging process, and the extraction from the SPS was inhibited;
The circulating beam which was swept over the aperture and protection elements (~17% of normal kick) for ~9µs.
PFNs 1 & 2 at normal voltage (~50kV)
PFNs 4 at low voltage (~33kV) because of PFN3 switch erratic
Mike Barnes
2-8-2011 LHC status 33
MKI2 event no. 2 – dumped beam BTVDD and dump line BCTs indicate that ~ 200 bunches
of the circulating were not dumped to TDI.
2-8-2011 LHC status 34
NEXT THREE MONTHS
LHC status 352-8-2011
Schedule
LHC status2-8-2011 36
What are days for?
LHC status2-8-2011
Ah, solving that questionBrings the priest and the doctorIn their long coatsRunning over the fields.
Days
Calendar 89
Special runs 3 (say...)
Technical stop 5
TS recovery 1
Ramp-up 3
Machine development 5
Floating MD 2
Physics 70
Protons: 2nd August to 29th October inclusive
+25 ns studies to come during MDs (to sort out injection and beam stability issues) and possibly an operational development period to validate scrubbing and future operation
37
70 days at present performance, reasonable efficiency ~2 fb-1
Start August Excellent peak luminosity performance & production rates Very good through inject, ramp, squeeze, collide
Effective turn around time is long: problem resolution, accesses etc…cruising we are not
Short fills – exposed to the intersecting failure space of a number of complex systems with huge number of components. This failure space is inflated by high intensity and high luminosity
Holding is sometimes more effective than raising Although the effects of “conditioning” and mitigation (UFOS,
vacuum, RF, QPS, SEUs) is clear… Will not be pushing bunch intensity aggressively until things
settle down
Conclusions
2-8-2011 38LHC status
Curate’s egg
LHC status 392-8-2011
“parts of it are excellent”
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