498
F. Bordry et al.
Fig. 8.98 BCAM
Fig. 8.99 Fiducials in the CCS
8.9.8 Determination of the Co-ordinates of the Fiducials
The combination of the theoretical position of the “beam” points and the position
of the “fiducials” with respect to a reference axis provides the coordinates of the
fiducials in the CERN Co-ordinates System (CCS) XYZ. The H co-ordinate is also
generated (Fig. 8.99).
8.9.9 Alignment of Accelerator Components
The initial alignment is the phase during which the components are aligned at their
absolute position, therefore with respect to the underground geodetic network. As
the function of the quadrupoles magnets is to focus/defocus the particle beams,
these are the most critical components in terms of alignment and consequently
they are aligned first, followed by the dipole magnets. Optical or digital levels
are used for the vertical positioning while total stations and wire offset measuring
devices are used for the horizontal (Fig. 8.100). The roll angle is adjusted thanks to
accurate inclinometers which are installed on the magnet reference surface. The
adjustment of the components is realized thanks to three mechanical jacks, an
auxiliary hydraulic device is sometimes needed when the necessary force to move
the jack in the vertical direction is too important.
As the major requirement for the geometry of an accelerator is that the relative
errors must be very small, a compulsory step is to check the alignment by measuring
F. Bordry et al.
Fig. 8.98 BCAM
Fig. 8.99 Fiducials in the CCS
8.9.8 Determination of the Co-ordinates of the Fiducials
The combination of the theoretical position of the “beam” points and the position
of the “fiducials” with respect to a reference axis provides the coordinates of the
fiducials in the CERN Co-ordinates System (CCS) XYZ. The H co-ordinate is also
generated (Fig. 8.99).
8.9.9 Alignment of Accelerator Components
The initial alignment is the phase during which the components are aligned at their
absolute position, therefore with respect to the underground geodetic network. As
the function of the quadrupoles magnets is to focus/defocus the particle beams,
these are the most critical components in terms of alignment and consequently
they are aligned first, followed by the dipole magnets. Optical or digital levels
are used for the vertical positioning while total stations and wire offset measuring
devices are used for the horizontal (Fig. 8.100). The roll angle is adjusted thanks to
accurate inclinometers which are installed on the magnet reference surface. The
adjustment of the components is realized thanks to three mechanical jacks, an
auxiliary hydraulic device is sometimes needed when the necessary force to move
the jack in the vertical direction is too important.
As the major requirement for the geometry of an accelerator is that the relative
errors must be very small, a compulsory step is to check the alignment by measuring