10 The Largest Accelerators and Colliders of Their Time
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Fig. 10.17 The LHC arc cell layout
An LHC arc cell is also equipped with corrector magnets, which can be split into
two distinct categories (see Fig. 10.17).
• The lattice corrector magnets attached on both sides of the main quadrupole
magnets are installed in the Short Straight Section (SSS) cryostats.
• The spool-piece corrector magnets which are thin non-linear windings attached
directly on the extremities of the main dipoles.
Contrary to the main dipole circuits and the two families (QF and QD) of lattice
quadrupoles for which, in each sector, Ring 1 and Ring 2 are powered in series, the
arc corrector magnets can be adjusted independently for the two beams.
10.6.2.3 The Dispersion Suppressors
A dispersion suppressor is located at the transition between an LHC arc and a
straight section yielding a total of 16 dispersion suppressor sections. The aim of
the dispersion suppressors is threefold:
• adapt the LHC reference orbit to the geometry of the LEP tunnel;
• cancel the horizontal dispersion arising in the arc and generated by the separation/recombination dipole magnets and the crossing angle bumps;
• help in matching the insertion optics to the periodic solution of the arc.
A generic design of a dispersion suppressor uses standard arc cells with missing
dipole magnets. The LEP dispersion suppressor, which defines the geometry of the
tunnel, was made of 3.5 cells with a 90 o phase advance, optimized to suppress the
dispersion. With the 2.5 times longer LHC dipole and quadrupole magnets, only two
LHC cells can be fitted in the dispersion suppressor tunnel.
10.6.2.4 LSS1 and LSS5
IR1 and IR5 house the high luminosity experiments of the LHC and are identical
in terms of hardware and optics (except for the crossing-angle scheme: the crossing
645
Fig. 10.17 The LHC arc cell layout
An LHC arc cell is also equipped with corrector magnets, which can be split into
two distinct categories (see Fig. 10.17).
• The lattice corrector magnets attached on both sides of the main quadrupole
magnets are installed in the Short Straight Section (SSS) cryostats.
• The spool-piece corrector magnets which are thin non-linear windings attached
directly on the extremities of the main dipoles.
Contrary to the main dipole circuits and the two families (QF and QD) of lattice
quadrupoles for which, in each sector, Ring 1 and Ring 2 are powered in series, the
arc corrector magnets can be adjusted independently for the two beams.
10.6.2.3 The Dispersion Suppressors
A dispersion suppressor is located at the transition between an LHC arc and a
straight section yielding a total of 16 dispersion suppressor sections. The aim of
the dispersion suppressors is threefold:
• adapt the LHC reference orbit to the geometry of the LEP tunnel;
• cancel the horizontal dispersion arising in the arc and generated by the separation/recombination dipole magnets and the crossing angle bumps;
• help in matching the insertion optics to the periodic solution of the arc.
A generic design of a dispersion suppressor uses standard arc cells with missing
dipole magnets. The LEP dispersion suppressor, which defines the geometry of the
tunnel, was made of 3.5 cells with a 90 o phase advance, optimized to suppress the
dispersion. With the 2.5 times longer LHC dipole and quadrupole magnets, only two
LHC cells can be fitted in the dispersion suppressor tunnel.
10.6.2.4 LSS1 and LSS5
IR1 and IR5 house the high luminosity experiments of the LHC and are identical
in terms of hardware and optics (except for the crossing-angle scheme: the crossing