ILC Reference Design Report: Accelerator Executive Summary

The International Linear Collider (ILC) is a 200-500 GeV center-of-mass high-luminosity linear electron-positron collider, based on 1.3 GHz superconducting radiofrequency (SCRF) accelerating cavities. The use of the SCRF technology was recommended by the International Technology Recommendation Panel (ITRP) in August 2004 [1], and shortly thereafter endorsed by the International Committee for Future Accelerators (ICFA). In an unprecedented milestone in high-energy physics, the many institutes around the world involved in linear collider R&D united in a common effort to produce a global design for the ILC. In November 2004, the 1st International Linear Collider Workshop was held at KEK, Tsukuba, Japan. The workshop was attended by some 200 accelerator physicists from around the world, and paved the way for the 2nd ILC Workshop in August 2005, held at Snowmass, Colorado, USA, where the ILC Global Design Effort (GDE) was officially formed. The GDE membership reflects the global nature of the collaboration, with accelerator experts from all three regions (Americas, Asia and Europe). The first major goal of the GDE was to define the basic parameters and layout of the machine--the Baseline Configuration. This was achieved at the first GDE meeting held at INFN, Frascati, Italy in December 2005 with the creation of the Baseline Configuration Document (BCD). During the next 14 months, the BCD was used as the basis for the detailed design work and value estimate (as described in section 1.6) culminating in the completion of the second major milestone, the publication of the draft ILC Reference Design Report (RDR). The technical design and cost estimate for the ILC is based on two decades of world-wide Linear Collider R&D, beginning with the construction and operation of the SLAC Linear Collider (SLC). The SLC is acknowledged as a proof-of-principle machine for the linear collider concept. The ILC SCRF linac technology was pioneered by the TESLA collaboration*, culminating in a proposal for a 500 GeV center-of-mass linear collider in 2001 [2]. The concurrent (competing) design work on a normal conducting collider (NLC with X-band [3] and GLC with X- or C-Band [4]), has advanced the design concepts for the ILC injectors, Damping Rings (DR) and Beam Delivery System (BDS), as well as addressing overall operations, machine protection and availability issues. The X- and C-band R&D has led to concepts for the RF power source that may eventually produce either cost and/or performance benefits. Finally, the European XFEL [5] to be constructed at DESY, Hamburg, Germany, will make use of the TESLA linac technology, and represents a significant on-going R&D effort which remains of great benefit for the ILC. The current ILC baseline assumes an accelerating gradient of 31.5 MV/m to achieve a centre-of-mass energy of 500 GeV. The high luminosity requires the use of high power and small emittance beams. The choice of 1.3 GHz SCRF is well suited to the requirements, primarily because the very low power loss in the SCRF cavity walls allows the use of long RF pulses, relaxing the requirements on the peak-power generation, and ultimately leading to high wall-plug to beam transfer efficiency. The primary cost drivers are the SCRF Main Linac technology and the Conventional Facilities (including civil engineering). The choice of gradient is a key cost and performance parameter, since it dictates the length of the linacs, while the cavity quality factor (Q{sub 0}) relates to the required cryogenic cooling power. The achievement of 31.5 MV/m as the baseline average operational accelerating gradient--requiring a minimum performance of 35 MV/m during cavity mass-production acceptance testing--represents the primary challenge to the global ILC R&D With the completion of the RDR, the GDE will shortly begin an engineering design study, closely coupled with a prioritized R&D program. The goal is to produce an Engineering Design Report (EDR) demonstrating readiness for construction by 2010, followed by start of construction in 2012. A seven-year construction phase is currently assumed, allowing operations to begin in 2019. This is consistent with a technically driven schedule for this international project