LHC Status - SUSY Bonn 1 Drawing by Sergio Cittolin Status of the LHC 6 months of beam operation in 2010 J. Wenninger CERN

Outline LHC Status - SUSY Bonn 2 Introduction LHC energy 2010/11 LHC performance targets and achievements LHC beam operation Outlook for 2010/11 and conclusions

LHC Status - SUSY Bonn The Large Hadron Collider LHC 3 CMS, Totem ATLAS, LHCf LHCbLHCb ALICEALICE Lake of Geneva Installed in 26.7 km LEP tunnel Depth of m Control Room LHC ring SPS ring

LHC layout and parameters 4  8 arcs (sectors), ~3 km each  8 long straight sections (700 m each)  beams cross in 4 points  2-in-1 magnet design with separate vacuum chambers → p-p collisions - - β * = 0.55 m (beam size =17 μm) - Crossing angle = 285 μrad - L = cm -2 s -1 RF Nominal LHC parameters Beam energy (TeV)7.0 No. of particles per bunch1.15x10 11 No. of bunches per beam2808 Stored beam energy (MJ)362 Transverse emittance (μm)3.75 Bunch length (cm)7.55

LHC accelerator complex 5 Beam 1 TI2 Beam 2 TI8 LHC proton path The LHC needs most of the CERN accelerators... ≥ 7 seconds from source to LHC

LHC challenges LHC Status - SUSY Bonn 6 The LHC surpasses existing accelerators/colliders in 2 aspects :  The energy of the beam of 7 TeV that is achieved within the size constraints of the existing 26.7 km LEP tunnel. LHC dipole field8.3 T HERA/Tevatron ~ 4 T  The luminosity of the collider that will reach unprecedented values for a hadron machine: LHC pp ~ cm -2 s -1 Tevatron pp3x10 32 cm -2 s -1 SppSpp6x10 30 cm -2 s -1 Very high field magnets and very high beam intensities:  Operating the LHC is a great challenge.  There is a significant risk to the equipment and experiments. A factor 2 in field A factor 4 in size A factor 30 in luminosity

LHC dipole magnet LHC Status - SUSY Bonn 7  1232 dipole magnets.  B field 8.3 T ( K (super-fluid Helium)  2 magnets-in-one design : two beam tubes with an opening of 56 mm.  Operating challenges: o Dynamic field changes at injection. o Very low quench levels (~ mJ/cm 3 )

Stored energy LHC Status - SUSY Bonn 8 Increase with respect to existing accelerators : A factor 2 in magnetic field A factor 7 in beam energy A factor 200 in stored beam energy Damage threshold

Collimation LHC Status - SUSY Bonn 9 beam 1.2 m  To operate at nominal performance the LHC requires a large and complex collimation system o Previous colliders used collimators mostly for experimental background conditions.  Ensure ‘cohabitation’ of: o 360 MJ of stored beam energy, o super-conducting magnets with quench limits of few mJ/cm 3  Almost 100 collimators and absorbers.  Alignment tolerances < 0.1 mm to ensure that over 99.99% of the protons are intercepted.  Primary and secondary collimators are made of Carbon to survive large beam loss.

Outline LHC Status - SUSY Bonn 10 Introduction LHC energy 2010/11 LHC performance targets and achievements LHC beam operation Outlook for 2010/11 and conclusions

LHC target energy: the way down LHC Status - SUSY Bonn TeV Summer TeV Spring TeV Nov GeV Detraining nQPS 2 kA 6 kA 9 kA WhenWhy 12 kA Late 2008 Joints 1.18 TeV Design  All main magnets commissioned for 7TeV operation before installation  Detraining found when hardware commissioning sectors in 2008 –5 TeV poses no problem –Difficult to exceed 6 TeV  Machine wide investigations following S34 incident showed problem with joints  Commissioning of new Quench Protection System (nQPS)

LHC target energy: the way up LHC Status - SUSY Bonn 12  Train magnets –6.5 TeV is in reach –7 TeV will take time  Repair joints  Complete pressure relief system  Commission nQPS system 2014 ? 2010 Training Stabilizers nQPS WhenWhat 7 TeV 3.5 TeV 1.18 TeV 450 GeV TeV

Ramp rate LHC Status - SUSY Bonn 13  At the start of the run the ramp rate had to be limited to 2 A/s (1.2 GeV/s) for magnet protection reasons. o Ramp duration TeV: 46 minutes  Since mid-July the rate for down-ramps and magnet pre-cycles (magnetic history reset) were increased to nominal value of 10 A/s (6 GeV/s).  Ramp speed with beam will be increased to 10 A/s (6 GeV/s) in September. o Ramp duration TeV: 16 minutes 2 A/s10 A/s 450 GeV 3500 GeV

Outline LHC Status - SUSY Bonn 14 Introduction LHC energy 2010/11 LHC performance targets and achievements LHC beam operation Outlook for 2011 and conclusions

Collider luminosity LHC Status - SUSY Bonn 15 “Thus, to achieve high luminosity, all one has to do is make (lots of) high population bunches of low emittance to collide at high frequency at locations where the beam optics provides as low values of the amplitude functions as possible.” PDG 2005, chapter 25  Parameters: –Number of particles per bunch  –Number of bunches per beamk b –Beam sizes at the collision point  –Betatron function (focusing) at IP  * –Normalized transverse emittance  –Revolution frequencyf –Crossing angle factor F ~ 1 Collision rate is proportional to luminosity Interaction Region Beam quality (emittance) Intensity

Collimation performance LHC Status - SUSY Bonn 16  I max ~6  protons per beam at 3.5TeV with intermediate collimator settings  (about 20% nominal intensity) 30 MJ stored beam energy Present stage collimation system sets limit to total intensity.  Assumptions: o Max. loss rate of 0.1%/s assumed (0.2h lifetime). o Ideal cleaning.  Performance degradation: o Deformed jaws. o Tilt & offset & gap errors. o Machine alignment.  Machine stability o Tight coll. settings are a challenge at early stage. o Intermediate coll. settings make use of aperture to relax tolerances. Collimator settings

Goals for Repair of Sector TeV nQPS 6kA 3.5 TeV I safe < I < 0.2 I nom β* ~ 3.5 m Ions 3.5 TeV ~ 0.2 I nom β* ~ 3.5 m Ions No BeamBBeam Goal for the run: Collect 1 fm -1 of data/exp at 3.5 TeV/beam. To achieve this goal the LHC must operate in 2011 with L ~ 2×10 32 cm -2 s -1 ~ Tevatron Luminosity which requires ~700 bunches of p each ~ 7x10 13 p (stored energy of ~30 MJ – 10% of nominal) Implications: Strict and clean machine setup. Machine protection systems at near nominal performance.

Commissioning phases LHC Status - SUSY Bonn 18  Phase 1: low intensity commissioning of the LHC. o Low intensity single bunches. No/very limited risk of damage. o Commissioning of the protection systems.  Phase 2: operation without crossing angle. o Bunches with large spacing (>  s). o Up to around k b =50 bunches. o Simplified operation in the interaction regions. o Machine protection system running in.  Phase 3: operation with crossing angle. o Bunches with close spacing (≤ 150 ns). o Aim for ~400 bunches in We are at end of phase 2

Commissioning steps in LHC Status - SUSY Bonn 19  Restart with beam.  Commissioning to 3.5 TeV. o Low intensity beams.  First collisions at 3.5 TeV.  Squeeze (  * reduction) commissioning. o  * = 2 m for collisions (injection 10 /11 m).  Increase number of bunches to 13 per beam. o Bunch population N = 3  p ~ 30% of nominal.  Switch to nominal bunch intensity. o Luminosity ~N 2 Gain ~ 10 o Back off in  * to 3.5 m. Loss ~ 0.6  Increase number of bunches up to 49 per beam. o Bunch population N = 9-10  p. o Stability run in August with 25 bunches/beam. Feb. 28th March March 30 th Mid April Mid-April – mid-May June July - August

Peak luminosity performance LHC Status - SUSY Bonn 20 8 colliding pairs/IR 36 colliding pairs Peak luminosity = 9.5  cm -2 s -1 (48 bunches/beam, 36 colliding bunches)

Integrated luminosity LHC Status - SUSY Bonn 21 Integrated luminosity ~ 2.2 pb -1 ( ) Figures : status 16 th Aug 2010

Availability LHC Status - SUSY Bonn 22  About 30% of time in physics data-taking. o A lot commissioning still on-going ! o Min. turn-around time collisions to collisions ~4 hours. 3.5 TeV 6.5  cm -2 s -1 Energy Lumi 01 – 21 August 2010

Outline LHC Status - SUSY Bonn 23 Introduction LHC energy 2010/11 LHC performance targets and achievements LHC beam operation Outlook for 2010/11 and conslusions

Machine Protection LHC Status - SUSY Bonn 24  Extensive testing of the machine protection system was performed, mostly in March/April o  20’000 signal enter the beam abort system.  Only about 10% of the beams above injection energy are dumped by the operators ! Beam dumps > 450 GeV

Beam dump LHC Status - SUSY Bonn 25 Extraction kickers Dilution kickers Extraction septum magnets Dump block  Complex beam dumping system commissioned. Beam swept over dump surface (power load)

Aperture and collimation LHC Status - SUSY Bonn 26 Primary 6 σ Secondary 8.8 σ Dump Protection 10.5 σ Tertiary 15 σ Triplet 18 σ  With collisions the aperture limit of the LHC is in the strong focusing quadrupoles (triplets) that are installed just next to the experiments. o Hierarchy of collimators must be preserved in all phases to avoid quenching super-conducting magnets and for damage protection. o  * is presently limited to 3.5 m by aperture and tolerances. Collimation hierarchy Exp.

Collimation LHC Status - SUSY Bonn 27  Collimator alignment is made with beam and then monitored from the loss distribution around ring.  Beam cleaning efficiencies ≥ 99.98% ~ as designed TCT = tertiary coll.

Magnet quenches LHC Status - SUSY Bonn 28  A local loss of some ~10 7 protons/s may lead to a quench at 3.5 TeV. o Compared to 5  stored protons.  So far no quench was observed at 3.5 TeV thanks to the excellent performance of the collimation system for absorbing lost protons and to the fast reaction of the loss monitors.  In only 5 occasions did some beam escape and was lost locally around super-conducting elements. o Beam loss detection system dumped the beams in time before a magnet could quench. o Events are under investigation... Possible cause are dust particles! The absence of problems with beam loss and quenches is good news for increasing the beam intensity !

Beam Optics LHC Status - SUSY Bonn 29  Beam optics is within specifications and reproducible over 3 months. o A stable machine is essential to reach high intensity and minimize frequent setup overhead, in particular for collimation. Relative beam size error   (  Specification:  0.2

Beam Emittance LHC Status - SUSY Bonn 30 Momentum and magnetic fields at the LHC are sufficiently strong for the protons to emit visible light that can be used to image the beams in real-time. The energy loss per turn is 7 keV at 7 TeV, 0.4 keV at 3.5 TeV.  Beam emittances below nominal can be produced and injected into the LHC (  = 2  m rad as compared to 3.5  m rad design).  This provides margin for emittance blow-up due to various noise sources – great value for a machine in early phase of operation.  Beam emittances in collisions are now mostly at design or below – the only exception being beam 2 in the vertical plane.

Noise on the beam LHC Status - SUSY Bonn 31  The beams are periodically excited by an unknown noise source (‘hump’) of varying frequency – affects mostly beam2 in vertical plane. o Amplitude ~  m.  When the frequency coincides with the beam eigen-modes (‘tunes’) it leads to emittance blow-up. Beam 1 Beam 2 Horizontal plane Vertical plane Frequency/Rev. frequency Time  1 hour Noise hump Tune

Beam-beam interaction LHC Status - SUSY Bonn 32 - blackwitness bunches (zero collisions); - red bunches colliding in IP 1 5 and 2 (3 collisions); - blue bunches colliding in IP 1 5 and 8 (3 collisions); - green bunches colliding in IP 2 and 8 (2 collisions).  Effects of the beam-beam force are visible on the lifetime of the various bunches. o Also sensitive to tune working point. o This will become even more complicated with trains of bunches. Beams in collision Beam1 Beam2 Intensity loss (%)

Lifetimes LHC Status - SUSY Bonn 33  Beam intensity lifetimes with colliding beams: o Dip to 2-5 hours in first minutes. o Progressive increase to ~100 hours.  Luminosity lifetimes: o Around hours due to emittance growth. Beams in collision Lifetime (h)

Present LHC parameters LHC Status - SUSY Bonn 34 ParameterPresentNominalLimited by N (p/bunch) 1   k b (no. bunches)482808Machine protection  (  m rad)  * (m) Aperture, tolerances L (cm -2 s -1 ) 6.5   Squeezing at the IP (  *) is limited by aperture and tolerances. o Beams are larger at 3.5 TeV ~ 1/ . o  x =  y = ~45-60  m - nominal value is 15  m at 7 TeV.  The number of bunches is limited by machine protection and by the fact that LHC is not yet operated with bunch trains. o Bunch separation is large (>1  s), no crossing angle at the IR.

Outline LHC Status - SUSY Bonn 35 Introduction LHC energy 2010/11 LHC performance targets and achievements LHC beam operation Outlook for 2010/11 and conclusions

Fall LHC Status - SUSY Bonn Switch to bunch trains Switch to bunch trains  To reach the target of cm -2 s -1 an intensity increase of factor 10 is required until end of October (start of Pb ion run). o But the most important is the slope of the increase!

Fall LHC Status - SUSY Bonn 37  To reach the target of cm -2 s -1, o the intensity must be increased very rapidly, o bunch train operation must be commissioned (1-2 weeks). >> Achievable integrated L is ~ pb -1 in  The goal is quite ambitious given the time left before the Pb ion run, but the main point is not the exact final luminosity, but rather that no problems or show-stoppers are encountered on the way. o So far there are no limitations.  The prospects for a very good run in 2011, 1 fm -1 of data, will be very high with a problem-free intensity (luminosity) increase in o But the most important is the slope of the increase!

Summary and outlook LHC Status - SUSY Bonn 38  Main beam commissioning phase of the LHC ended in June when operation with ~ nominal bunch intensities was established.  The LHC is now operating for physics data taking, with some interleaved commissioning activities in view of higher intensity. Efficiency for physics data taking ~30% with peak luminosities of 9.5x10 30 cm -2 s -1  Machine protection and collimation systems perform well, and one can anticipate a luminosity increase towards few to cm -2 s -1 in Final value for 2010 will depend on machine availability and length of commissioning bunch train operation.  A long run at cm -2 s -1 or above is in sight for fm -1 of integrated data is in reach.