Measurements, ideas, curiosities Possible scenarios and milestones for the LHC luminosity upgrade Complement to the presentation on LHC performance & upgrade F. Ruggiero Univ. “La Sapienza”, Rome, 20–24 March 2006

Scaling of electron cloud effects blue: e-cloud effect observed red: planned accelerators experience at several storage rings suggests that the e-cloud threshold scales as Nb~Dtsep possible LHC upgrades consider either smaller Dtsep with constant Nb, or they increase Dtsep in proportion to Nb longer fewer more intense bunches more ‘ultimate’ bunches

Electron-cloud build-up in the LHC Beam synchrotron radiation is important provides source of photo-electrons Secondary emission yield (SEY) d(E) is important characterized by peak value dmax determines overall e– density e– reflectivity d(0) is important determines survival time of e– Bunch intensity Nb and beam fill pattern are important Main concern: power deposition by electrons on the cold beam screen F. Ruggiero LHC beam performance and luminosity upgrade scenarios

LHC arc heat load vs. intensity, 25 ns spacing (F. Zimmermann, 2005) calculation for 1 bunch train heat load for quadrupoles higher in 2nd batch F. Ruggiero LHC beam performance and luminosity upgrade scenarios

LHC arc heat load vs. spacing, Nb=1.15x1011 (F. Zimmermann, 2005) F. Ruggiero LHC beam performance and luminosity upgrade scenarios

Beam-Beam tune spread for round beams tune shift from head-on collisions (primary IP’s) tune shift from long-range collisions npar parasitic collisions around each IP increases for closer bunches or reduced crossing angle limit on xHO limits Nb/(ge) relative beam-beam separation for full crossing angle qc xHO / IP no. of IP’s DQbb total SPS 0.005 3 0.015 Tevatron (pbar) 0.01-0.02 2 0.02-0.04 RHIC 0.002 4 ~0.008 LHC (nominal) 0.0034 ~0.01 high-lumi in IP1 and IP5 (ATLAS and CMS), halo collisions in IP2 (ALICE) and low-lumi in IP8 (LHC-b) conservative value for total tune spread based on SPS collider experience F. Ruggiero LHC beam performance and luminosity upgrade scenarios

Beam-Beam tune footprints Comparison of tune footprints, corresponding to betatron amplitudes extending from 0 to 6 s , for LHC nominal (red-dotted), ultimate (green-dashed), and “large Piwinski parameter” configuration (blue-solid) with alternating H-V crossing only in IP1 and IP5. (Courtesy H. Grote) F. Ruggiero LHC beam performance and luminosity upgrade scenarios

Proton beam lifetime versus separation in RHIC SPS : t » 5ms (d/s)5 [measured 11/09/04] Tevatron: t ~ d3 [reported on 11/24/04] RHIC : t ~ d4 or d2 [measured 04/28/05] F. Ruggiero LHC beam performance and luminosity upgrade scenarios

RHIC Beam-Beam Long Range compensation test: design – locations F. Ruggiero LHC beam performance and luminosity upgrade scenarios

LHC beam performance and luminosity upgrade scenarios LHC Upgrade: recent links & references http://cern.ch/lhc-proj-IR-upgrade LHC IR Upgrade collaboration meeting, CERN, 11-12 March 2002 http://care-hhh.web.cern.ch/care-hhh/ (web site of the CARE-HHH European Network on High Energy High Intensity Hadron Beams) http://care-hhh.web.cern.ch/CARE-HHH/LUMI-05/ CARE-HHH Workshop (LHC-LUMI-05) on “Scenarios for the LHC Luminosity Upgrade”, Arcidosso, 30 Aug–3 Sept 2005 “LHC Luminosity and Energy Upgrade: A Feasibility Study”, O. Bruning, R. Cappi, R. Garoby, O. Grobner, W. Herr, T. Linnecar, R. Ostojic, K. Potter, L. Rossi, F. Ruggiero (editor), K. Schindl, L. Tavian, T. Taylor, E. Tsesmelis, E. Weisse, and F. Zimmermann, CERN LHC Project Report 626 (December 2002) “Parameters for First Physics and for 1033”, F. Ruggiero, in Proc. Workshop on LHC Performance (Chamonix XII), Chamonix, 3–8 March 2003 (CERN AB-2003-008 ADM, 2003), pp. 260–267 F. Ruggiero LHC beam performance and luminosity upgrade scenarios