CERN-THESIS-2012-153 26/07/2012 - CERN Document Server

tion at the collision point, and F the geometric luminosity reduction factor due to the crossing angle at the
interaction point. A simplified list of designed LHC beam parameters at the peak luminosity is given in
Table 3.1
injection collision
Proton energy [GeV] 450 7000
Relativistic gamma 479.6 7461
Number of particles per bunch 1.15 × 10 11
Number of bunches 2808
Bunch spacing [ns] 24.95
Longitudinal emittance (4σ) [eVs] 1.0 2.5
Transverse normalized emittance [µm rad] 3.5 3.75
Circulating beam current [A] 0.584
Stored energy per beam [MJ] 23.3 362
Geometric luminosity reduction factor - 0.836
Table 3.1: LHC beam parameters relevant to the peak luminosity of 10 34 cm −2 s −1 . The quoted geometric
reduction factor assumes a total crossing angle of 285 µrad at the interaction point [61].
The LHC is supplied with protons from the injector chain: Linac2 - Proton Synchrotron Booster (PSB)
- Proton Synchrotron (PS) - Super Proton Synchrotron (SPS), as shown in Figure 3.1. Each of these com-
ponents accelerate protons (stripping off electrons from hydrogen atoms) to 50 MeV, 1.4 GeV, 26 GeV, and
450 GeV, respectively, before injecting them into the following component, or the LHC in the case of the
SPS. These accelerators have been upgraded to meet the new challenging needs of the LHC: many high
intensity proton bunches with small transverse and well defined longitudinal emittances. The “end-point”
beam requirements are summarized by Equation 3.1, but they also imply several conditions to be satisfied.
Example of these conditions are: the space-charge limit in the injector, which scales with Nb/εn and the
total intensity Nb · nb which is limited by the thermal energy produced by the synchrotron radiation which
must be absorbed by the cryogenic system [60,62,63].
The LHC has two high luminosity detectors, ATLAS and CMS, aiming to operate at the peak luminosity
of 10 34 cm −2 s −1 in the LHC proton operation. In addition to these high luminosity experiments, the LHC
has two low luminosity experiments: LHCb for B-physics, aiming at a peak luminosity of 10 32 cm −2 s −1 and
TOTEM for the detection of protons from elastic scattering at small angles aiming at a peak luminosity of
2×10 29 cm −2 s −1 with 156 bunches. In addition to the proton beams the LHC will also be operated with ion
beams. The LHC has one dedicated ion experiment: ALICE, aiming at a peak luminosity of 10 27 cm −2 s −1
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