Measurements, ideas, curiosities

1
Measurements, ideas, curiosities

• Possible scenarios and milestones for the LHC
  luminosity upgrade

Complement to the presentation on LHC performance
upgrade
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
NbDtsep 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

4
LHC arc heat load vs. intensity, 25 ns spacing
R0.5
calculation for 1 bunch train
(F. Zimmermann, 2005)
heat load for quadrupoles higher in 2nd batch
5
LHC arc heat load vs. spacing, Nb1.15x1011
(F. Zimmermann, 2005)
6
Beam-Beam tune spread for round beams
tune shift from head-on collisions (primary IPs)
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 IPs 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 3 0.01
conservative value for total tune spread based on
SPS collider experience
high-lumi in IP1 and IP5 (ATLAS and CMS), halo
collisions in IP2 (ALICE) and low-lumi in IP8
(LHC-b)
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)

8
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

9
RHIC Beam-Beam Long Range compensation test
design locations
10
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-h
hh.web.cern.ch/CARE-HHH/LUMI-05/ CARE-HHH
Workshop (LHC-LUMI-05) on Scenarios for the LHC
Luminosity Upgrade, Arcidosso, 30 Aug3 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, 38 March 2003 (CERN AB-2003-008 ADM,
2003), pp. 260267