1. 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

2. 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

3. 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

4. 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

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

6. 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) 2
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

7. 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

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

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

10. LHC beam performance and luminosity upgrade scenarios
LHC Upgrade: recent links & references
LHC IR Upgrade collaboration meeting, CERN, March 2002
(web site of the CARE-HHH European Network on High Energy High Intensity Hadron Beams)
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 ADM, 2003), pp. 260–267
F. Ruggiero
LHC beam performance and luminosity upgrade scenarios