Superconducting technology selected for International Linear Collider
A key decision on the technology to be used for the future international particle accelerator has been made, clearing the way for work on the project to commence. An international panel of physicists recommended the use of superconducting accelerating structures that operate at 2 Kelvin for the International Linear Collider (ILC), rather than 'X-band' accelerating structures that operate at room temperature. The recommendation was accepted by the International Committee for Future Accelerators at a conference in Beijing, China, on 20 August. 'Both the 'warm' X-band technology and the 'cold' superconducting technology would work for a linear collider,' said the chair of the panel charged with making a recommendation, Barry Barish. 'Each offers its own advantages, and each represents many years of R&D [research and development] by teams of extremely talented and dedicated scientists and engineers. At this stage it would be too costly and time consuming to develop both technologies toward construction.' The 'winning' technology was developed by the TESLA consortium, which brings together researchers from Armenia, China, Finland, France, Germany, Italy, Poland, Russia, Spain, Switzerland, the UK and the US. As stated in the recommendation text, however, the selection of one technology over another is based entirely on the technology, and not on design. 'We expect the final design to be developed by a team drawn from the combined warm and cold linear collider communities, taking full advantage of the experience and expertise of both.' The superconducting technology uses L-band (1.3GHz) radio frequency power for accelerating the electron and positron beams in the two opposing linear accelerators that make up the collider. The advantages of this technology, outlined in the recommendation, include: a large cavity aperture and long bunch interval that simplify operations, reduce sensitivity to ground motion, permit inter-bunch feedback and may enable increased beam current; the largest technical cost elements - the main linac and rf systems - are of comparatively lower risk; and the use of superconducting cavities significantly reduces power consumption. The collider will first be used to find the Higgs boson - hypothetical elementary particles predicted by the Standard Model of particle physics - or any alternative mechanism that takes its place. If it exists, the Higgs boson should be discovered at the Large Hadron Collider (LHC) at CERN in Geneva, Switzerland, but measuring its properties with precision will require a TeV-scale electron-positron linear collider. But work on the Higgs particle will be 'just the beginning', according to Hirotaka Sugawara, also a member of the recommendation panel. 'We anticipate that some of the tantalising superparticles will be within the range of discovery, opening the door to an understanding of one of the great mysteries of the universe - dark matter. We may also be able to probe extra space-time dimensions, which have so far eluded us,' he said. Now that a decision has been made, the international particle physics community can begin work on a design for the linear collider. At the same time, science funding agencies from Europe and elsewhere must reach an agreement on the funding of the project.