8 Accelerator Engineering and Technology: Accelerator Technology
495
Fig. 8.93 From surface to the underground network
8.9.6 Tunnel Preliminary Works
The geometrical checks of the civil engineering works is done by the firm itself,
often with the help of a consultant specialist in geodesy. They are done with respect
to the geodetic surface network provided by CERN.
Once the civil engineering works are delivered to CERN, the beam line is
marked on the tunnel floor, with respect to the underground network, as well as
the longitudinal and transversal position of the components and their supporting
systems. This information is also very useful for the installation of all the services
from this early stage of installation.
8.9.7 The Alignment References
The “beam” points, entering and exiting each magnet, provided by the physicists
are often not accessible in the tunnel at the time of the alignment. The surveyors,
therefore, recommend the installation of “fiducials” or alignment references directly
on the magnets. In order to align a component along its 6 degrees of freedom, at least
two “fiducials” are requested and a reference surface for the measurement of the
transverse inclination also called the roll (Fig. 8.94). At CERN, these “fiducials” are
495
Fig. 8.93 From surface to the underground network
8.9.6 Tunnel Preliminary Works
The geometrical checks of the civil engineering works is done by the firm itself,
often with the help of a consultant specialist in geodesy. They are done with respect
to the geodetic surface network provided by CERN.
Once the civil engineering works are delivered to CERN, the beam line is
marked on the tunnel floor, with respect to the underground network, as well as
the longitudinal and transversal position of the components and their supporting
systems. This information is also very useful for the installation of all the services
from this early stage of installation.
8.9.7 The Alignment References
The “beam” points, entering and exiting each magnet, provided by the physicists
are often not accessible in the tunnel at the time of the alignment. The surveyors,
therefore, recommend the installation of “fiducials” or alignment references directly
on the magnets. In order to align a component along its 6 degrees of freedom, at least
two “fiducials” are requested and a reference surface for the measurement of the
transverse inclination also called the roll (Fig. 8.94). At CERN, these “fiducials” are