8 Accelerator Engineering and Technology: Accelerator Technology
491
impact parameters at the absorbing collimators. Research challenges include the
emittance preservation of the beam core.
– The concept of a rotatable collimator [283] uses a circular jaw with many
facets. Such a solution can be used for applications where occasional damage
to the jaw surface cannot be avoided. After a damaging beam impact, the jaw is
rotated and a fresh facet is presented to the beam. The collimator only needs to be
exchanged once all facets have been used up. The testing of this concept is well
advanced, thanks to beam tests carried out recently on a prototype developed
at SLAC for the LHC upgrade [284]. Another, even more advanced variant
of a circular jaw design uses liquid metal coating that is continually refreshed
[285].
8.9 Geodesy and Alignment for Particle Accelerators
D. Missiaen
8.9.1 Introduction
Particle accelerators require very tight tolerances for the positioning of their
components. These tolerances are coming mainly from optics requirements but can
also be triggered by aperture and mechanical considerations as is the case for the
LHC.
The task of the surveyors in this domain is to measure and align the position,
the orientation, the shape and the size of big objects, such as electro-magnets and
particle detectors with an accuracy never requested elsewhere. This activity is deeply
linked to the geodesy.
8.9.2 Alignment Tolerances
The alignment precision requirements are the key values that will drive any survey
study. The absolute accuracy in the vertical direction is the deviation to the
theoretical plane of the collider, while it is the variation of its radius R with respect to
the theoretical value in the transversal direction. The differential variations between
several consecutive magnets represent the relative accuracy. This latter type of error
has a more direct effect on the closed orbit of the particles.
491
impact parameters at the absorbing collimators. Research challenges include the
emittance preservation of the beam core.
– The concept of a rotatable collimator [283] uses a circular jaw with many
facets. Such a solution can be used for applications where occasional damage
to the jaw surface cannot be avoided. After a damaging beam impact, the jaw is
rotated and a fresh facet is presented to the beam. The collimator only needs to be
exchanged once all facets have been used up. The testing of this concept is well
advanced, thanks to beam tests carried out recently on a prototype developed
at SLAC for the LHC upgrade [284]. Another, even more advanced variant
of a circular jaw design uses liquid metal coating that is continually refreshed
[285].
8.9 Geodesy and Alignment for Particle Accelerators
D. Missiaen
8.9.1 Introduction
Particle accelerators require very tight tolerances for the positioning of their
components. These tolerances are coming mainly from optics requirements but can
also be triggered by aperture and mechanical considerations as is the case for the
LHC.
The task of the surveyors in this domain is to measure and align the position,
the orientation, the shape and the size of big objects, such as electro-magnets and
particle detectors with an accuracy never requested elsewhere. This activity is deeply
linked to the geodesy.
8.9.2 Alignment Tolerances
The alignment precision requirements are the key values that will drive any survey
study. The absolute accuracy in the vertical direction is the deviation to the
theoretical plane of the collider, while it is the variation of its radius R with respect to
the theoretical value in the transversal direction. The differential variations between
several consecutive magnets represent the relative accuracy. This latter type of error
has a more direct effect on the closed orbit of the particles.