(n)QPS

(n)QPS

LHC status

LHC: past, present and futureMike Lamontfor the LHC team

121-3-2011

Clear priority to lay the foundations for 2011 and the delivery of 1 fb-1. Peak luminosity target 1x1032 cm-2s-1

Gain solid operational experience of injecting, ramping, squeezing and establishing stable beams

Steady running at or around 1 MJ for an extended period

Perform a safe, phased increase in intensity with validation and a running period at each step

2010 – main aims

LHC status 221-3-2011

Luminosity: 3 running periods

3

Bunch trains

Nominal bunch commissioning

Initial luminosity

run

Nominal bunch

operation(up to 48)

Performance ramp-up

(368 bunches)

Perform

ance

ramp-u

p mad

e pos

sible

by a

safe,

stag

ed co

mmission

ing.

Meticu

lous p

repara

tion f

or un

safe

beam

s!

21-3-2011 LHC status

2010 parameters

LHC status

2010 Nominal

Energy [TeV] 3.5 7

beta* [m] 3.5, 3.5, 3.5, 3.5 m 0.55, 10, 0.55, 10

Emittance [microns] 2.0 – 3.5 start of fill 3.75

Transverse beam size at IP [microns] around 60 16.7

Bunch current 1.2e11 1.15e11

Number of bunches 368348 collisions/IP 2808

Stored energy [MJ] 28 360

Peak luminosity[cm-2s-1] 2e32 1e34

421-3-2011

Overall LHC efficiency in 2010

5

W. Venturini

65%availability!

Great a

chiev

emen

t for th

e firs

t

year

of op

eratio

n!


Physics operations

~30%Stable beams!

W. Venturini

21-3-2011 LHC status 6

2010 - records

Peak stable luminosity delivered 2.07 x 1032 cm-2s-1

Maximum luminosity delivered in one fill 6.3 pb-1

Maximum luminosity delivered in one day 5.98 pb-1

Maximum luminosity delivered in 7 days 24.6 pb-1

Maximum colliding bunches 348Maximum average events per bunch crossing

3.78

Longest time in Stable Beams for one fill 30.3 hoursLongest time in Stable Beams for one day 22.8 hours (94.9%)Longest time in Stable Beams for 7 days 69.9 hours (41.6%)Fastest turnaround to Stable Beams 3.66 hours (protons)

Courtesy AtlasLHC status 721-3-2011

Status LHC Stored Energy

80 kg TNT

Stored energy reached at 3.5 TeV: 28.0 MJ

8LHC status Ralph Assmann21-3-2011

Ions

LHC status

Protonsagain

50 & 75 ns

921-3-2011

Excellent single beam before collisions ~200 - 300 hours

Luminosity lifetime ~15 - 20 hours Reasonably well given by emittance growth and intensity decay Minimal drifts in overlap – beams very stable

Intensity lifetime ~90 hours Luminosity burn, losses on collimators

Emittance growth (hor. ~ 30 hours, vert. ~ 20 to 40 hours) Intra Beam Scattering and something else – at least sometimes “the hump”

Lifetimes


Aperture


Optics & magnetic machine Optics stunningly stable

Machine magnetically and optically well understood Excellent agreement with model and machine

Magnetically reproducible Important because set-up remains valid from fill to fill


Measured Cleaning at 3.5 TeV

IR8IR1

IR2

IR5

Mom

entu

m

Cle

anin

g

Dum

p P

rote

ctio

n C

ol.

(beam1, vertical beam loss, intermediate settings)

LHC status

Making sure the hierarchy is respected

1321-3-2011

Excellent single beam lifetime Ramp & squeeze essentially without loss

No quenches with beam above 450 GeV Excellent performance of Machine Protection

Optics close to model (and correctable) Excellent reproducibility Aperture as expected Better than nominal from injectors

Emittances, bunch intensity Beam-beam: can collide nominal bunch currents

With smaller that nominal emittances

LHC 2010 - summary

14

And surprisingly good availability… 21-3-2011 LHC status

PROBLEMS – TWO OF THEM


Many sudden local losses have been recorded. No quench, but preventive dumps Rise time around of the order 1 ms. Potential explanation: dust particles falling into beam

creating scatter losses and showers propagating downstream

Distributed around the ring – arcs, inner triplets, IRs

UFOs – unidentified falling objects


● Revision of thresholds on superconducting magnets could make the UFO effects acceptable

● More detailed analysis needed to understand discrepancies with current simulations + additional quench tests to benchmark

UFOs – a possible solution?

● More events at higher intensities● Only 1? event observed at 450GeV● Signal shortens, i.e. the losses are faster with intensity● Signal amplitude does not increase with intensity

B.Dehning, E. Holzer, A.Nordt, M.Sapinski 21-3-2011 LHC status 17

Electron cloud

LHC status

Schematic of electron cloud build up in LHC arc beam pipe due to photoemission and secondary emission [F. Ruggiero] Reflection

Secondary emission yield [SEY]

18

Very much dependent on bunch spacing: - 150 ns. – local signs in common beam pipe- 75 ns. – some first signs- 50 ns. – vacuum valves in

21-3-2011

Vacuum pressure rise (background in experiments) Single-bunch instability Multi-bunch instability Incoherent emittance growth Heat load in cold arcs (quenches in the limit) Perturbation of beam diagnostics

Electron cloud effects

LHC status

Electron cloud effects occur both in the warm and cold regions.

19

Well understood, very well studied (other machines, simulations…)

21-3-2011

Vacuum activity started off in regions with common beam pipe at 450 GeV as we pushed up the number of bunches with 150 ns spacing Test solenoids cured problem – electron cloud

Tried 50 ns bunch spacing Things really kicked off High vacuum activity in warm regions (single beam pipe) Significant heat load in cold regions Instabilities and beam size growth observed Surface conditioning (‘scrubbing’) observed

Gas desorption rates and SEY drop Time constant < 1 day

Situation a lot cleaner with 75 ns incoherent effects seen – emittance blow-up 800+ bunches injected into both beams

Experience in 2010


2010 observations are certainly due to ~ 2 < SEY < 2.5, whereas 1.7 was usually the max value studied in the past

Expect to be able to reach 200-300 b with 75 ns without scrubbing

Scrubbing with large emittance (>3.5 mm), high intensity (>1.2e11), 4x36b of 50 ns beam

Time 2-3 days needed to setup 50 ns at injection 7 days of scrubbing 1 day for validation and scrubbing result evaluation

Lots of wire wrapped around warm bits during the technical stop (solenoids)

Scrubbing strategy for 2011

21LHC status21-3-2011

Solenoids between DFBX and D1 in IR1R


2011

LHC status 23

Energy – stick at 3.5 TeV – we still worry about the splices

21-3-2011

Motivation is clear!

1 fb-1 delivered to each of IP1, IP5 and IP8 at 3.5 TeV Can probably do better for IP1 and IP5

It will be a challenge to deliver 1 fb-1 to IP8 Maximum luminosity : from 2e32 to 3e32 cm-2 s-1

Luminosity leveling via separation required to get close Alice

pp run: 5e29 < L < 5e30 cm-2 s-1, µ < 0.05

2011: main goals


fast, secure and far-reaching

Decided on beta* = 1.5 m in Atlas, CMS; 3 m in LHCb; 10 m in Alice

Beam commissioning: 3 weeks Exit - stable beams with low number of bunches

Ramp-up to ~200 bunches (75 ns): 2 weeks Multi-bunch injection commissioning continued Stable beams

Technical Stop: 4+1 days Scrubbing run: 10 days including 50 ns injection comm. [Intermediate energy run – 5 days] Resume 75 ns operation and increase no. bunches: 3

weeks 300 – 400 – 600 – 800 – 930 - MPS and OP qualification

Physics operation 75 ns: ~930 bunches (50 ns. remains an option if things look good)

Baseline scenario


2011 LHC schedule Q1/Q2

26LHC status21-3-2011

2011 Q3/Q4


Estimated Peak and Integrated Luminosity


Energy 3.5 TeVBeta* 1.5 mBunch spacing 75 nsBunch intensity 1.2 x 1011

Stored beam energy 75 MJDays at peak luminosity 135Hübner factor 0.2

Emittance[mm.mrad]

Beam-beam parameter

Peak Luminosity

[cm-2 s-1]

Integrated Luminosity

[fb-1]

2.5 0.006 1.3 x 1033 ~2.72.0 0.007 1.6 x 1033 ~3.3

2011 – progress so far

LHC status 29

19th February First beam, circulating beams established.

3rd March First collisions at 3.5 TeV, beta*=1.5 m. with pilot beams

5th March Nominal bunches at 3.5 TeV, start collimator set-up, injection and beam dump set-up & validation

13th March First stable beams, 3 bunches per beam, initial luminosity 1.6e30 cm-2s-1

18th March 32 bunches per beam, initial luminosity ~3e31 cm-2s-1

19th March 64 bunches per beam, initial luminosity ~6e31 cm-2s-1

20th March 75ns_136b+4small_138_102_105_24bpi11inj 1.45e32 cm-2s-1

Impressive re-commissioning, improvements across the board.

Operation cycle now well optimized: faster ramp & squeeze, much fewer manual actions required by shift crews

21-3-2011

Machine still beautiful


Injection, ramp and squeeze fully operational LHC magnetic model & optics excellent Beam instrumentation in good shape. Beam cleaning and collimation works reliably

with predicted efficiency. Machine protection excellent performance Machine aperture looks good Performance with beam (losses, lifetimes,

luminosity, emittance growth etc.) is very encouraging

Conclusions 1/2

LHC status 32

We have a beautiful machine on our hands!21-3-2011

Machine availability is excellent – the hard work of numerous teams

There are problems UFOs somewhat worrying Electron cloud well understood – measures prepared

2011 – another long year ahead… 75 ns. bunch spacing – up to 930 bunches Nominal intensities, beta* 1.5 m in Atlas and CMS Should be good for 5 to 10 x 1032 cm-2s-1 and 1 to 3 fb-1

Progress so far is good…

Will run in 2012 Attempt to measure splice resistance in 2011/2012 might open

the way to 4 TeV or higher

Conclusions 2/2


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