The International Committee for Future Accelerators (ICFA) has released the Reference Design Report (RDR) for a future International Linear Collider (ILC). The report provides the first detailed technical description of the machine, including a cost estimate, and is a major step towards the engineering design report that would underlie a formal project proposal.
The concept behind the ILC is a high-luminosity electron–positron collider, operating at centre-of-mass energies of 200–500 GeV, with a possible upgrade to 1 TeV. The first map of physics at the tera-electron-volt scale will come from CERN’s LHC; the ILC would expand on the discoveries made in this new energy region, investigating it with high precision.
ICFA established the basis for the design in August 2004 when it accepted the advice of the International Technology Recommendation Panel to opt for superconducting radio-frequency (SCRF) accelerating cavities operating at 1.3 GHz. A year later the Global Design Effort (GDE), a team of more than 60 scientists, was officially formed to define the basic parameters and layout and develop the reference design.
The RDR defines the technical specifications for a 31 km long machine, which would deliver a peak luminosity of about 2 × 1034 cm–2s–1, at a top centre-of-mass energy of 500 GeV. The basic design achieves this high luminosity through a combination of small emittance beams and high beam power, facilitated by the use of 1.3 GHz SCRF. The design also allows for an upgrade to a 50 km, 1 TeV machine during the second stage of the project.
The major components start with a polarized electron source based on a photocathode DC gun and an undulator-based positron source, driven by a 150 GeV electron beam. The particles produced will then pass to 5 GeV electron and positron damping rings at the centre of the ILC complex, before being transported to the main linacs, where each beam will enter a bunch-compressor system prior to injection. The two 11 km long main linacs will use the 1.3 GHz SCRF cavities operating at an average gradient of 31.5 MV/m, with a pulse length of 1.6 ms and a cycle rate of 5 Hz. Finally, a 4.5 km long beam-delivery system will bring the two beams into collision at a 14 mrad crossing angle. Two detectors in a “push–pull” configuration will share the luminosity at the single interaction point.
As part of the RDR, the GDE members also produced a preliminary value estimate of the cost for the ILC. This estimate contains three elements: €1480 million ($1800 million) for site-related costs, such as for tunnelling in a specific region; €4040 million ($4900 million) for the value of the high technology and conventional components; and approximately 2000 people a year, or 13,000 person years, for the supporting manpower. Some 43% of the total costs come from the SCRF technology for the main linacs.
The value cost estimate provides guidance for optimization of both the design and the R&D to be done during the engineering design phase, which will formally start in the autumn. The global R&D effort will continue to focus on the performance of the high-gradient accelerating cavities. These are key components as the gradient governs the lengths of the linacs. The goal of an average operational gradient of 31.5 MV/m translates to a minimum of 35 MV/m in acceptance tests during mass production of the cavities. The next major milestone for the GDE will then be to produce the engineering design report – the detailed blueprints for building the machine – by 2010.
• To download a summary or the full report see www.linearcollider.org.