A Global Design Effort befan in 2005 to study a TeV scale electron-positron linear accelerator based on superconducting radio-frequency (RF) technology, called the International Linear Collider (ILC). In early 2007, the design effort culminated in a reference design for the ILC, closely based on the earlier TESLA design. The ILC will consist
of two 250 GeV linacs, which provide positron-electron collisions for
high energy physics research. The particle beams will be accelerated
to their final energy in superconducting niobium RF cavities operating
at 2 Kelvin. At a length of about 12 km each, the main linacs will be
the largest cryogenic systems in the ILC. Positron and electron
sources, damping rings, and beam delivery systems will also have a
large number and variety of other superconducting RF cavities and
magnets, which require cooling at liquid helium temperatures. Ten
large cryogenic plants with 2 Kelvin refrigeration are envisioned to
cool the main linac and the electron and positron sources. Three
smaller cryogenic plants will cool the damping rings and beam
delivery system components predominately at 4.5 K. This paper
describes the cryogenic systems concepts for the ILC.