8 Accelerator Engineering and Technology: Accelerator Technology
477
– The nuclear interaction length λ i is the mean path length that a relativistic
charged particle can traverse through matter before its energy is reduced to 1/e of
its initial value.
– The nuclear collision length λ T is the mean free path of a particle before nuclear
reaction.
Collimator technology has seen significant advances over the last 40 years,
driven by the requirements of more and more performing accelerators. The first
collimation systems were conceived in the 1970’s, see for example [210]. In the
1980’s more elaborate collimation systems were designed and constructed for the
e + e − colliders LEP [211] and SLC [212]. The 1990’s saw the development of
two-stage collimation theory [213–218], primarily for hadron beams with energies
in the 100 GeV–10 TeV regime. The first two-stage collimation systems were
constructed for HERA [219], Tevatron [220, 221] and RHIC [222]. The 2000’s
took modern collimator technology to linac-based, GeV range energy, high power
facilities [223–231], where multi-stage collimation is required for ensuring handson maintenance and reducing environmental impact of high power accelerators. At
the same time collimator technology was developed for linear collider concepts
[232]. A major effort in the 2000’s was spent at CERN to develop an ultra-efficient
and robust collimation system for the LHC, in the end consisting of four stages
and more than 100 fully movable collimators [213, 233, 234]. Recently, this design
effort was further extended to cope with the challenges of the High-Luminosity
upgrade of the LHC (HL-LHC) [235, 236], adding in-jaw orbit measurements [237]
and conceiving improved designs for local protection of cold magnets with warm
collimators [238, 239]. Recent R&D develops a new collimator design with low
desorption for cryogenic accelerator regions [240].
8.8.2 Requirements for Modern Collimators
Modern collimators must support operation of accelerators with high power loss
and beams that are often beyond the destruction limits of available materials [233].
At the same time collimators must be placed closer and closer to the beam and
allowable tolerances have reached the micron regime [241]. A collimating slit is
shown in Fig. 8.83 for the example of an LHC collimator. At the LHC, the closest
jaws sit at distances as small as 1 mm from the circulating beam. Collimators
become heavily cooled, high power devices, which are highly radioactive, must be
good absorbers, extremely robust and work as precision tools under heavy beam
loads. A few central requirements that drive the collimator design are introduced.
The adopted solution must be closely targeted to the foreseen use case and requires
a detailed analysis of accelerator physics and operational requirements before the
design work is started.
477
– The nuclear interaction length λ i is the mean path length that a relativistic
charged particle can traverse through matter before its energy is reduced to 1/e of
its initial value.
– The nuclear collision length λ T is the mean free path of a particle before nuclear
reaction.
Collimator technology has seen significant advances over the last 40 years,
driven by the requirements of more and more performing accelerators. The first
collimation systems were conceived in the 1970’s, see for example [210]. In the
1980’s more elaborate collimation systems were designed and constructed for the
e + e − colliders LEP [211] and SLC [212]. The 1990’s saw the development of
two-stage collimation theory [213–218], primarily for hadron beams with energies
in the 100 GeV–10 TeV regime. The first two-stage collimation systems were
constructed for HERA [219], Tevatron [220, 221] and RHIC [222]. The 2000’s
took modern collimator technology to linac-based, GeV range energy, high power
facilities [223–231], where multi-stage collimation is required for ensuring handson maintenance and reducing environmental impact of high power accelerators. At
the same time collimator technology was developed for linear collider concepts
[232]. A major effort in the 2000’s was spent at CERN to develop an ultra-efficient
and robust collimation system for the LHC, in the end consisting of four stages
and more than 100 fully movable collimators [213, 233, 234]. Recently, this design
effort was further extended to cope with the challenges of the High-Luminosity
upgrade of the LHC (HL-LHC) [235, 236], adding in-jaw orbit measurements [237]
and conceiving improved designs for local protection of cold magnets with warm
collimators [238, 239]. Recent R&D develops a new collimator design with low
desorption for cryogenic accelerator regions [240].
8.8.2 Requirements for Modern Collimators
Modern collimators must support operation of accelerators with high power loss
and beams that are often beyond the destruction limits of available materials [233].
At the same time collimators must be placed closer and closer to the beam and
allowable tolerances have reached the micron regime [241]. A collimating slit is
shown in Fig. 8.83 for the example of an LHC collimator. At the LHC, the closest
jaws sit at distances as small as 1 mm from the circulating beam. Collimators
become heavily cooled, high power devices, which are highly radioactive, must be
good absorbers, extremely robust and work as precision tools under heavy beam
loads. A few central requirements that drive the collimator design are introduced.
The adopted solution must be closely targeted to the foreseen use case and requires
a detailed analysis of accelerator physics and operational requirements before the
design work is started.