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K. Hübner et al.
10.6.2.1 The Straight Sections
Each straight section is approximately 528 m long and can serve as an experimental
or utility insertion. The two high luminosity experimental insertions are located at
diametrically opposite straight sections: the ATLAS experiment is located at point 1
and the CMS experiment at point 5. Two more experimental insertions, for ALICE
and LHCb are located at point 2 and point 8 respectively. These insertion regions
also contain the injection systems, for Beam 1 arriving from the SPS through the
transfer line TI2, and for Beam 2 arriving from the SPS through the transfer line
TI8. The injection kick occurs in the vertical plane with the two beams arriving at the
LHC from below the LHC reference plane. The beams only cross from one magnet
bore to the other at these four locations. The remaining four straight sections do not
have beam crossings. Insertion 3 and 7 each contain two collimation systems, for
momentum cleaning and betatron cleaning respectively. Insertion 4 contains two RF
systems: one independent system for each LHC beam. The straight section at point 6
contains the beam dump insertion where the two beams are vertically extracted from
the machine using a combination of horizontally deflecting fast-pulsed (’kicker’)
magnets and vertically-deflecting double steel septum magnets. Each beam features
an independent abort system.
The two beams share an approximately 130 m long common beam pipe along
the interaction regions (IR). The exact length is 126 m in IR2 and IR8 which feature
superconducting separation dipole magnets next to the triplet assemblies and 140 m
in IR1 and IR5 which feature normal conducting and therefore longer separation
dipole magnets next to the triplet assemblies. Together with the large number of
bunches (2808 for each proton beam), and a nominal bunch spacing of 25 ns, the
long common beam pipe implies 34 parasitic collision points for each experimental
insertion region (for four experimental IR’s this implies a total of 136 unwanted
collision points). Dedicated crossing angle orbit bumps separate the two LHC beams
left and right from the central interaction point (IP) in order to avoid collisions at
these parasitic collision points.
10.6.2.2 The Arcs
The arcs of the LHC are each made of 23 regular arc cells. The arc cells are 106.9 m
long and are made out of two 53.45 m long half cells each of which contains one
5.355 m long cold mass (6.63 m long cryostat) short straight section (SSS) assembly
and three 14.3 m long dipole magnets. The two apertures for Ring 1 and Ring 2 are
separated by 194 mm. The two coils in the dipole magnets are powered in series
and all dipole magnets of one arc form one electrical circuit. The quadrupoles of
each arc form two electrical circuits: all focusing quadrupole magnets in Ring 1 and
Ring 2 are powered in series and all defocusing quadrupole magnets of Beam 1 and
Beam 2 are powered in series. The optics of Beam 1 and Beam 2 in the arc cells is
therefore strictly coupled via the powering of the main magnetic elements.
K. Hübner et al.
10.6.2.1 The Straight Sections
Each straight section is approximately 528 m long and can serve as an experimental
or utility insertion. The two high luminosity experimental insertions are located at
diametrically opposite straight sections: the ATLAS experiment is located at point 1
and the CMS experiment at point 5. Two more experimental insertions, for ALICE
and LHCb are located at point 2 and point 8 respectively. These insertion regions
also contain the injection systems, for Beam 1 arriving from the SPS through the
transfer line TI2, and for Beam 2 arriving from the SPS through the transfer line
TI8. The injection kick occurs in the vertical plane with the two beams arriving at the
LHC from below the LHC reference plane. The beams only cross from one magnet
bore to the other at these four locations. The remaining four straight sections do not
have beam crossings. Insertion 3 and 7 each contain two collimation systems, for
momentum cleaning and betatron cleaning respectively. Insertion 4 contains two RF
systems: one independent system for each LHC beam. The straight section at point 6
contains the beam dump insertion where the two beams are vertically extracted from
the machine using a combination of horizontally deflecting fast-pulsed (’kicker’)
magnets and vertically-deflecting double steel septum magnets. Each beam features
an independent abort system.
The two beams share an approximately 130 m long common beam pipe along
the interaction regions (IR). The exact length is 126 m in IR2 and IR8 which feature
superconducting separation dipole magnets next to the triplet assemblies and 140 m
in IR1 and IR5 which feature normal conducting and therefore longer separation
dipole magnets next to the triplet assemblies. Together with the large number of
bunches (2808 for each proton beam), and a nominal bunch spacing of 25 ns, the
long common beam pipe implies 34 parasitic collision points for each experimental
insertion region (for four experimental IR’s this implies a total of 136 unwanted
collision points). Dedicated crossing angle orbit bumps separate the two LHC beams
left and right from the central interaction point (IP) in order to avoid collisions at
these parasitic collision points.
10.6.2.2 The Arcs
The arcs of the LHC are each made of 23 regular arc cells. The arc cells are 106.9 m
long and are made out of two 53.45 m long half cells each of which contains one
5.355 m long cold mass (6.63 m long cryostat) short straight section (SSS) assembly
and three 14.3 m long dipole magnets. The two apertures for Ring 1 and Ring 2 are
separated by 194 mm. The two coils in the dipole magnets are powered in series
and all dipole magnets of one arc form one electrical circuit. The quadrupoles of
each arc form two electrical circuits: all focusing quadrupole magnets in Ring 1 and
Ring 2 are powered in series and all defocusing quadrupole magnets of Beam 1 and
Beam 2 are powered in series. The optics of Beam 1 and Beam 2 in the arc cells is
therefore strictly coupled via the powering of the main magnetic elements.