CLIC study workshop focuses on feasibility

The annual workshop for the Compact Linear Collider (CLIC) study was held at CERN on 12–16 October 2009. The study is preparing a conceptual design report (CDR), for the end of 2010, for an electron–positron linear collider in the multi-tera-electron-volt collision-energy range (CERN Courier September 2008 p15). Such a machine is complementary to that under study for the International Linear Collider (ILC) in the tera-electron-volt energy range, and would allow further exploration of the physics that might be revealed by the LHC. The CLIC accelerator study is a global collaboration with 34 participating institutes from around the world. Daniel Schulte chaired the workshop, which attracted more than 250 participants from 62 institutes in 21 countries.

After a welcome by CERN's director-general, Rolf Heuer, the leaders of the CLIC study (Jean-Pierre Delahaye), of the ILC Global Design Effort (Barry Barish) and of the newly formed Linear Collider Detector project (Lucie Linssen) gave an overview of the progress and plans, which were followed by more detailed presentations. The workshop continued in working groups focusing on physics and detector issues as well as on accelerator issues that might arise at CLIC. The closing session presented the conclusions of the working groups, followed by a summary of the workshop by Ken Peach, the newly elected chair of the CLIC Collaboration Board.

In preparing the CDR, the CLIC study has identified a number of feasibility issues that must be addressed to establish that the concept is viable, and has launched R&D to address them. These issues include the novel scheme of the two-beam acceleration, the production of high-intensity drive beam, the generation of a large amount of RF power at high frequency, the development of RF structures with high accelerating fields and of components that are vital to achieving high target luminosity. In addition, the detectors have to be adapted to the specific CLIC technology and the large beam-induced background that is inherently present at high electron–positron collision energies.

The status of the R&D on feasibility issues was consequently the focus of the workshop. Among the highlights presented was the recent demonstration of the full drive-beam generation scheme in the CLIC test facility (CTF3). Progress was also reported in many other critical areas, such as in the understanding of the structure of RF breakdown – one of the main gradient limitations – and in emittance preservation.

The workshop benefited from the participation of a number of ILC experts. The CLIC and ILC studies are collaborating closely on technical issues with strong synergies, in preparation for the best possible facility adapted to the demands of physics based on discoveries at the LHC. This collaboration has already proved to be extremely beneficial for both studies and is still improving. Hence, the studies decided to unite their workshops later this year in the context of an ECFA Linear Collider Workshop covering CLIC and ILC accelerators and detectors to be held at CERN tentatively in September or October 2010.

Participants at the annual workshop of the CLIC study pose outside CERN's main building.