434
F. Bordry et al.
pumps, the major limitation of the sublimation pumps is that the pumping speed of
noble gasses and methane is very small.
NEG pumps are commercially available as different types: cartridges [113], strips
and coatings. Only the first type is used as discrete pumping, strips and coatings
are, by nature, used as distributed pumping. NEG cartridges offer a huge pumping
speed for hydrogen, carbon mono- and dioxide. Once the NEG material is saturated,
the pumping capacity can be recovered by heating via Joule effect, most of the
commercial products include this option in the body of the NEG cartridge.
Turbo-molecular pumps are widely used by the industries and this has resulted
in a significant decrease of prices and increase in reliability. Most vacuum suppliers
provide a large variety of turbo-molecular pumps off-the-shelf. The improvement in
performance and lifetime over the last decades has stimulated their use in particle
accelerators. The major limitation comes from the radiation inherent in particle
accelerators. Indeed, this requires decoupling the power supply and associated
electronics from the body of the pump, a technical solution contrary to the needs
of industry. Thus explaining why most of the suppliers are reluctant to develop and
maintain such products in their catalogues.
Cryogenic pumps are also widely used by industry and similarly to turbomolecular pumps, the prices have decreased. Cryogenic pumps are used in accelerators to cope with huge local outgassing, mainly on unbaked systems. Special
operating precautions have to be taken to limit the back streaming of condensed
gasses in case of power cuts or compressor failure.
8.5.4.1.2 Distributed Pumping
Distributed pumping has been used for decades in particle accelerators and is of
special interest for conductance limited beam pipes. The most commonly used
distributed pump was the ion pumps cells inserted in the dipole beampipes [114];
the dipole magnet field serving also for the ion pump cells. Later on and in particular
in the large electron-positron collider (LEP), NEG strips were used. The NEG strips
[115] were activated by the Joule effect.
More recently, the large hadron collider (LHC) could profit from the development of the NEG coatings [116], a technology developed and industrialized at
CERN. These coatings provide many advantages such as a huge pumping speed,
large pumping capacity for hydrogen and low yields for secondary electrons and
stimulated desorption by electrons, photons and ions. The activation temperature
has decreased; 180 ◦ C is enough to obtain nominal pumping speed and capacity.
F. Bordry et al.
pumps, the major limitation of the sublimation pumps is that the pumping speed of
noble gasses and methane is very small.
NEG pumps are commercially available as different types: cartridges [113], strips
and coatings. Only the first type is used as discrete pumping, strips and coatings
are, by nature, used as distributed pumping. NEG cartridges offer a huge pumping
speed for hydrogen, carbon mono- and dioxide. Once the NEG material is saturated,
the pumping capacity can be recovered by heating via Joule effect, most of the
commercial products include this option in the body of the NEG cartridge.
Turbo-molecular pumps are widely used by the industries and this has resulted
in a significant decrease of prices and increase in reliability. Most vacuum suppliers
provide a large variety of turbo-molecular pumps off-the-shelf. The improvement in
performance and lifetime over the last decades has stimulated their use in particle
accelerators. The major limitation comes from the radiation inherent in particle
accelerators. Indeed, this requires decoupling the power supply and associated
electronics from the body of the pump, a technical solution contrary to the needs
of industry. Thus explaining why most of the suppliers are reluctant to develop and
maintain such products in their catalogues.
Cryogenic pumps are also widely used by industry and similarly to turbomolecular pumps, the prices have decreased. Cryogenic pumps are used in accelerators to cope with huge local outgassing, mainly on unbaked systems. Special
operating precautions have to be taken to limit the back streaming of condensed
gasses in case of power cuts or compressor failure.
8.5.4.1.2 Distributed Pumping
Distributed pumping has been used for decades in particle accelerators and is of
special interest for conductance limited beam pipes. The most commonly used
distributed pump was the ion pumps cells inserted in the dipole beampipes [114];
the dipole magnet field serving also for the ion pump cells. Later on and in particular
in the large electron-positron collider (LEP), NEG strips were used. The NEG strips
[115] were activated by the Joule effect.
More recently, the large hadron collider (LHC) could profit from the development of the NEG coatings [116], a technology developed and industrialized at
CERN. These coatings provide many advantages such as a huge pumping speed,
large pumping capacity for hydrogen and low yields for secondary electrons and
stimulated desorption by electrons, photons and ions. The activation temperature
has decreased; 180 ◦ C is enough to obtain nominal pumping speed and capacity.