Technological Challenges for the LHC Upgrade Ingrid-Maria Gregor, - PowerPoint PPT Presentation

Technological Challenges for the LHC Upgrade Ingrid-Maria Gregor, DESY … a detector physicists view …. LISHEP
2011 Interna0onal
School
of
HEP Rio
de
Janeiro,
Brazil July
9,
2011

100 Outline The LHC (current status) Apologies for the many interesting topics I didn’t cover! Future Plans Overview Beam parameters and what they mean Ingrid-Maria Gregor, DESY - Challenges at High Lumi LHC Beam Intensity Higher Field Magnets Luminosity Leveling Crab Cavities Conclusions Lately inside the LHC 2 protons 0.000000000000000000001 sec before collision 2

Ingrid-Maria Gregor, DESY: The EUDET Telescope - at DESY and CERN The LHC (current status) 3

The CERN accelerator complex LEP e+e- 100 (1989-2000) Switzerland 104 GeV/c per beam Lake Geneva LHC accelerator LHC pp and ions (100m below surface) 7 TeV/c per beam 26.8 km length Ingrid-Maria Gregor, DESY - Challenges at High Lumi LHC 8.3 Tesla LHCb CMS superconducting magnets ALICE SPS accelerator ATLAS France CERN 4

100 LHC Accelerator Last magnet: April 26th 2007 Ingrid-Maria Gregor, DESY - Challenges at High Lumi LHC 27 km circumference 8500 of 8.4T dipole magnets Cooled to 1.9K with 140 tons of liquid helium Energy of one beam = 362 MJ Kinetic energy of a 747 at take off 5

100 LHC challenges The LHC surpasses existing accelerators/colliders in many aspects : The energy of the beam of 7 TeV that is achieved within the size constraints of the existing 26.7 km LEP tunnel. Ingrid-Maria Gregor, DESY - Challenges at High Lumi LHC A factor 2 in field LHC dipole field 8.3 T HERA/Tevatron ~ 4 T A factor 4 in size The luminosity of the collider that will reach unprecedented values for a hadron machine: LHC pp ~ 10 34 cm -2 s -1 A factor 30 Tevatron pp 3x10 32 cm -2 s -1 in luminosity SppS pp 6x10 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. 6

100 Beam Power Livingston type plot: Energy stored magnets and beam Ingrid-Maria Gregor, DESY - Challenges at High Lumi LHC Potential equipment damage in case of failures during operation. based on graph from R.Assmann 7

100 CERN Accelerator Complex Ingrid-Maria Gregor, DESY - Challenges at High Lumi LHC Year Top energy Length [GeV] [m] Linac 1979 0.05 30 PSB 1972 1.4 157 PS 1959 26.0 628 SPS 1976 450.0 6911 LHC 2008 7000.0 26657 8

100 LHC Start Up O. Brüning et al. 2008 2010 Accelerator complete 19.03 Ramp to 3.5 TeV Ring cold and under vacuum Collisions at 3.5+3.5 TeV Ingrid-Maria Gregor, DESY - Challenges at High Lumi LHC 10.09: First beams around LHC Reaches target energy for 2010/2011 19.09: Accident 2011 2008 –2009 22.04: LHC sets world record beam intensity 14 months of major repairs and consolidation record broken almost on daily basis NewQuench Protection System for online more Tops recorded than Tevatron monitoring and protection of all inter-magnet ….. joints But: uncertainties about the splice quality (copper stabilizer) Risk of thermal runaway scenarios => decision to limit beam energy to 3.5 TeV for first operation 20.11. Restart LHC at 1.18TeV 29.11: Both beams accelerated to 1.18 TeV simultaneously -> LHC Highest Energy Accelerator 9

100 Current Status LHC July 2011 Design Ingrid-Maria Gregor, DESY - Challenges at High Lumi LHC Momentum at collision 7 3.5 [TeV/c] Luminosity 1.00E+34 1.26E+33 [cm-2s-1] Number of bunches per beam 2808 1380 Bunch intensity 1.15E+11 1.25E+11 The performance of LHC is excellent Within a few months the goal for the year 2011 was reached: 1fb -1 ! Hopes are up to reach 5 fb -1 in 2011... https://twiki.cern.ch/twiki/bin/view/AtlasPublic/ 10 LuminosityPublicResults#2011_pp_Collisions

Ingrid-Maria Gregor, DESY: The EUDET Telescope - at DESY and CERN Future Plans Overview 11

100 Physics reason for an upgrade L. Rossi Operation at even higher luminosity has three main purposes: Perform more accurate measurement on the new Ingrid-Maria Gregor, DESY - Challenges at High Lumi LHC particles discovered in the LHC Observe rare processes (predicted or newly discovered) with rates below the current sensitivity Extend the exploration of the energy frontier, extending the discovery reach by probing rare events. Besides the with to increase the luminosity there are some more technical reason: Radiation damage limit of IR quadrupoles ~400/fb ->~2020 this limit will be reached Hardware and shielding has not really been optimized for very high radiation Necessity to increase the heat removal capacity Restoring cooling capacity in IR5 left and decouple RF from magnets 12

100 How the luminosity might evolve Int. Lumi by end of 2020: Ingrid-Maria Gregor, DESY - Challenges at High Lumi LHC 220 fb -1 Or (positive assumption to reach L= 2·10 34 ) 300 fb -1 E. Todesco 13

100 How the luminosity might evolve Even with a terrific machine, at some point the time to accumulate enough Ingrid-Maria Gregor, DESY - Challenges at High Lumi LHC statistics to reduce the error Error halving time (years) bands is getting very high -> an upgrade is needed! E. Todesco 14

100 Future plans for LHC (“Chamonix 2011”) Run until end of 2012 constantly improvements of the beam parameters (i.e. bunch spacing) Shut down for ~15 month to fully repair all ~10000 joints (non superconducting Ingrid-Maria Gregor, DESY - Challenges at High Lumi LHC between SC magnets) Resolder, install clamps …. Tie in LINAC4 (high intensity) Shut down in 2018 collimation upgrade (dispersion suppressors) preparation for crab cavities & RF cryosystem detector upgrades Shut down in ~2021 Full luminosity: 5x10 34 leveled New inner triplets based on Nb 3 Sn Crab cavities 15

Ingrid-Maria Gregor, DESY: The EUDET Telescope - at DESY and CERN Understanding the Beam Parameters “So to achieve high luminosity, all one has to do is make 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 2010, chapter 25 16

100 Beam Parameter Overview ? Unit nominal upgrade Parameter Energy [TeV] 7 Protons/Bunch [10 11 ] 1.15 1.7 Bunch Spacing [ns] 50…25 50…25 Ingrid-Maria Gregor, DESY - Challenges at High Lumi LHC ε n ( x, y ) [μm] 3.75 3.75 σ z (rms) [cm] 7.55 7.55 Bunch Length (4 σ ) [ns] 1.0 1.0 Longitudinal Emittance [eVs] 2.5 2.5 β* at IP1, IP5 [m] 0.55 0.25…0.14 Betatron Tunes {64.31, 59.32} {64.31, 59.32} Piwinski parameter: 0.65 1.4…2.5 BB Parameter, ξ , per IP 0.003 0.005…0.008 Crossing‐angle: θ c [μrad] 285 315…509 Main RF [MHz] 400 400 Crab RF [MHz] 400 Peak luminosity w/o crab cavity 10 34 cm ‐2 s ‐1 1 3.3…3.8 Peak luminosity with crab cavity 10 34 cm ‐2 s ‐1 1.2 5.8…10.3 Pile up events per crossing 19 44…280 17

100 Understanding LHC Luminosity area A Interaction Region Ingrid-Maria Gregor, DESY - Challenges at High Lumi LHC n 1 n 2 n 1 n 2 for a bunched beam L = f rev “head on collision” luminosity 4 πσ x σ y 2 area A n 1 n 2 = n B N B � σ = β ⋆ ǫ with Beta function β ⋆ is the beam envelope at the IP; determined by the magnet arrangement and powering beam emittance (the extent occupied by the ǫ particles of the beam in space and momentum phase space as it travels) 18

100 Understanding LHC Luminosity B. Holzer Angle at IP to avoid that the bunches collide in other places that the IP Crossing angle reduces luminosity Ingrid-Maria Gregor, DESY - Challenges at High Lumi LHC � � �� �� γf rev n b N b N b L = R φ β ⋆ 4 π ǫ N 2 σ z Geometry factor 2 σ x θ c “Piwinski parameter” Piwinski parameter describes the effect that the crossing effective cross section effective cross section angle is affecting the beam dynamics The shorter the bunches ( ) the smaller is the effect σ z 19

100 Understanding Luminosity Total beam current. Brightness Ingrid-Maria Gregor, DESY - Challenges at High Lumi LHC Number of bunches Energy � � �� �� γ f rev n b N b N b L = R φ β ⋆ 4 π ǫ N Geometry Factor β * 20

Ingrid-Maria Gregor, DESY: The EUDET Telescope - at DESY and CERN Collimation 21

100 LHC Collimation Provide passive protection against irregular fast losses and failures. Provide cleaning for slow losses in the Ingrid-Maria Gregor, DESY - Challenges at High Lumi LHC super-conducting environment. Manage radiation impact of beam loss. Minimize background in the experiments. LHC has almost 100 collimators and absorbers. 1.2 Alignment tolerances < 0.1 mm to ensure that over 99.99% of the protons are intercepted. The presently installed LHC collimation system provides optimum robustness but its performance is limited to a beam intensity of 40% with respect to nominal. At higher energies collimation gets harder! 22 beam http://indico.cern.ch/conferenceDisplay.py?confId=139719