The Status of the LHC machine L. Ponce CERN /Beams Department Operation group

Outline Introduction LHC energy in 2010/2011 LHC performances High intensity issues Outlook LHC status – Moriond 2011 14.03.2011

LHC layout and parameters 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 RF - β* = 0.55 m (beam size =17 μm) - Crossing angle = 285 μrad - L = 1034 cm-2 s-1 Nominal LHC parameters Beam energy (TeV) 7.0 No. of particles per bunch 1.15x1011 No. of bunches per beam 2808 Stored beam energy (MJ) 362 Transverse emittance (μm) 3.75 Bunch length (cm) 7.6

LHC challenges 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 field 8.3 T HERA/Tevatron ~ 4 T The luminosity of the collider that will reach unprecedented values for a hadron machine: LHC pp 1034 cm-2 s-1 Tevatron pp 3x1032 cm-2 s-1 SppS pp 6x1030 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 LHC status – Moriond 2011 A factor 30 in luminosity 14.03.2011

Stored energy The present beam intensity will slice open a vacuum chamber even at injection 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 80 kg TNT LHC status – Moriond 2011 14.03.2011

Outline Introduction LHC energy in 2010/2011 LHC performances High intensity issues Outlook LHC status – Moriond 2011 14.03.2011

LHC target energy: the way down When Why 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) 7 TeV 2002-2007 Design 12 kA 5 TeV Summer 2008 Detraining 9 kA LHC status – Moriond 2011 Late 2008 3.5 TeV Joints Spring 2009 6 kA 1.18 TeV Nov. 2009 nQPS 2 kA 14.03.2011 450 GeV 7

LHC target energy: the way up When What Train magnets 6.5 TeV is in reach 7 TeV will take time Repair joints Complete pressure relief system Commission nQPS system 7 TeV 2015 ? Training 6 TeV 2014 Stabilizers LHC status – Moriond 2011 2011 3.5 TeV nQPS 2010 1.18 TeV 2009 14.03.2011 450 GeV 8

(Probability) Maximum Safe Energy Probability per Year of burning an interconnect Going to 4TeV, 50s implies a significant increase in the risk of burning an interconnect LHC Status – Moriond 2011 Remaining choice 14.03.2011 Presented in Chamonix 2011 by A. Verweij

Outline Introduction LHC energy in 2010/2011 LHC performances High intensity issues Outlook LHC status – Moriond 2011 14.03.2011

Luminosity : collider figure-of-merit The event rate N for a physics process with cross-section s is proprotional to the collider Luminosity L: “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 LHC status – Moriond 2011 High beam “brillance” N/e (particles per phase space volume)  Injector chain performance ! To maximize L: Many bunches (k) Many protons per bunch (N) Small beam sizes s*x,y= (b *e)1/2 b * : beam envelope (optics) e : beam emittance, the phase space volume occupied by the beam (constant along the ring) Small envelope  Strong focusing ! Optics property Beam property 14.03.2011 11

Peak luminosity performance Peak luminosity > 21032 cm-2s-1 (368 bunches/beam, 348 colliding bunches) LHC status – Moriond 2011 14.03.2011 Integrated proton luminosity 2010 ~48 pb-1 12

Associated LHC parameters 2010 Nominal Limited by Energy 3.5 TeV 7 TeV Hardware N (p/bunch) 1.11011 1.151011 kb (no. bunches) 368 (348 coll/IP) 2808 Machine protection e (mm rad) 2.5-5 3.75 b* (m) 3.5 (3.5) 0.55 (10) Aperture, tolerances Stored energy (MJ) 28 360 L (cm-2s-1) 21032 1034 LHC status – Moriond 2011 Squeezing at the IP (b*) is limited by aperture and tolerances. Beams are larger at 3.5 TeV ~ 1/g. sx = sy = ~45-60 mm - nominal value is 15 mm at 7 TeV. 14.03.2011 13

Outline Introduction LHC energy in 2010/2011 LHC performances High intensity issues Outlook LHC status – Moriond 2011 14.03.2011

SEUs QPS crate SEU count (RADMON) during off momentum loss map LHC status – Moriond 2011 Thijs Wijnands Not a problem at the moment but being monitored carefully 14.03.2011

Unidentified Flying Objects - UFOs As the beam intensity was increased unexpected fast beam loss events were observed in the super-conducting regions of the ring: Fast loss over ~0.5-2 ms, leading to a dump of the beam. Most events occurred during ‘rock’ stable periods. Losses in regions of very large aperture. The hypothesis quickly emerged that it is not the beam that moves to the aperture, but rather the opposite ! ‘Dust’ particles ‘falling’ into the beam, estimated size ~100 mm thick Carbon-equivalent object. We do not understand the mechanism that triggers such events. It is clearly induced by (presence of) beam – electromagnetic fields at the surface of the vacuum chamber. Sparking ??? Good news: signal amplitude seems to not depend on beam intensity Strategy for 2011: increase the BLM thresholds LHC status – Moriond 2011 14.03.2011 16

Intensity and vacuum (150 ns) Vacuum pressure increases were observed around the 4 experiments from the moment LHC switched to 150 ns train operation Intensity 2·1013 p+ LHC status – Moriond 2011 3·10-7 mbar Pressure 10-7 mbar 14.03.2011 17

Vacuum effects It was not possible to operate the LHC with bunch spacing of 50 ns for experiments data taking because the vacuum pressure increases were already too large at injection. Pressures easily exceeded 4x10-7 mbar (normal is 10-9 or less) leading to closure of the vacuum valves. Signs of cleaning by beam, with strong dependence on bunch intensity and bunch spacing. Consistent with the signature of electron clouds. e- cloud drive pressure rise, beam unstabilities and possibly overload the cryogenic system by the heat deposited on the chamber walls ! LHC status – Moriond 2011  The cloud can ‘cure itself’: the impact of the electrons cleans the surface (Carbon migration), reduces the electron emission probability and eventually the cloud disappears – ‘beam scrubbing’ Inject as much beam as you can (run at the limit of the vacuum / beam stability), operate for some time and Iterate until conditions are acceptable / good ( several days) – experience from the SPS. 14.03.2011 18

Outline Introduction LHC energy in 2010/2011 LHC performances High intensity issues Outlook LHC status – Moriond 2011 14.03.2011

Present LHC proton parameters End 2010 Nominal N (p/bunch) 1.21011 1.151011 kb (no. bunches) 368 2808 e (mm rad) 2.4-4 3.75 b* (m) 3.5 0.55 s* (mm) 45-60 16 L (cm-2s-1) 21032 1034 LHC status – Moriond 2011 Improvements for 2011: Reduction of b* to 1.5 m (measured aperture larger than design). Increase of N to 1.41011 or higher if possible. Increasing number of bunches using 50 ns or 75 ns spacing. Must overcome e-clouds effects. 14.03.2011 20

Days for Luminosity operation Item Days Total proton operation 264 5 MDs (4 days) - 20 6 TS (4+1 days) - 30 Special requests - 10 Commissioning - 20 to -30 Intensity ramp up - 30 to -40 Scrubbing run Total High intensity 124 to 144 (135 days for integrated L) LHC status – Moriond 2011 Assume 135 days at peak luminosity Stable period shrinks quickly if there are many exotic requests ! 14.03.2011

Estimated peak and integrated luminosity Baseline for 2011 is 2e32 Peak and 1fb-1 (integrated) But following 2010, we are confident we will do better value for b* = 1.5m in IP1/ 5 days HubnerFactor Fills with kb Nb e11 e mm L Hz/cm2 Stored energy MJ L Int fb-1 160 0.3 150 ns 368 1.2 2.5 ~5.2e32 ~30 ~1.9 135 0.2 75 ns 936 2 1.8 ~1.3e33 ~1.6e33 ~1.8e33 ~75 ~2.7 ~3.3 ~3.7 125 0.15 50 ns 1404 ~2e33 ~110 ~2.8 LHC status – Moriond 2011 14.03.2011 Possible integrated Luminosity of 2-3 fb-1

Conclusions Beam energy will stay at 3.5 TeV for 2011 run For 2012 run, can be revisited based on 2011 run experience Estimated no. of days at high luminosity ~135 days (for a total time of 260 days !) – 50% !! In order not to waste time we must have a good plan and not let ourselves be diverted from the target of stable high intensity running. Luminosity of 1033 cm-2s-1 could be reached with 75 ns beams. Integrated L ~1-3 fb-1. Optimum parameters to be selected carefully taken into account all parameters – for example injection efficiency may favor low e over high bunch charge. Efficiency, efficiency, efficiency. Not given yet… (UFOs, e-cloud, SEU)…but on the good way LHC status – Moriond 2011 14.03.2011

LHC status – Moriond 2011 14.03.2011