CERN, Geneva
The Compact Linear Collider (CLIC) is studied by a growing international collaboration. Main feasibility issues should be demonstrated until 2010 with the CLIC Test Facility (CTF3) constructed at CERN. The CLIC design parameters have recently been changed significantly. The rf frequency has been reduced from 30 GHz to 12 GHz and the loaded accelerating gradient from 150 MV/m to 100 MV/m. The consequences and logic of these changes will be reviewed and coherent parameter sets for a 3 TeV and a 500 GeV machine will be presented. The status and perspectives of the CLIC feasibility study will be presented with a special emphasis on experimental results obtained with CTF3 towards drive beam generation as well as progress on the high gradient accelerating structure development. The frequency change allows using high power X band test facilities at SLAC and KEK for accelerating structure testing at 11.4 GHz. The design gradient of 100 MV/m has been achieved in a recent test at SLAC with a very low breakdown-rate.
CERN, Geneva
Recently the CLIC study has changed the operating frequency and accelerating gradient of the main linac from 30 GHz and 150 MV/m to 12 GHz and 100 MV/m, respectively. This major change of parameters has been driven by the results from a novel main linac optimization procedure. The procedure allows simultaneous optimization of operating frequency, accelerating gradient, and many other parameters of CLIC main linac. It takes into account both beam dynamics (BD) and high power rf constraints. BD constraints are related to emittance growth due to short- and long-range transverse wakefields. Rf constraints are related to rf breakdown and pulsed surface heating of the accelerating structure. The optimization figure of merit includes the power efficiency, measured as a ratio of luminosity to the input power as well as a quantity proportional to investment cost.
Fermilab, Batavia
Northern Illinois University, DeKalb, Illinois
Euclid TechLabs, LLC, Solon, Ohio
ANL, Argonne
Funding: Work supported by US. Department of Energy, under Contract No. DE-FG02-06ER41435 with Northern Illinois University.
We present a diagnostics suite and analyze techniques for setting up the longitudinal beam dynamics in ILC electron injectors and bunch compressors. Techniques to measure first order moment and recover the first order longitudinal transfer map of the injector intricate bunching scheme are presented. Coherent transition radiation diagnotics needed to measure and monitor the bunch length downstream of the ~5 GeV bunch compressor are investigated using a vector diffraction model. We finally introduce a new diagnostics capable of measuring time-transverse correlation along a single bunch. Such a diagnostics should be valuable for controlling emittance dilution via transverse wakefield and for properly setting the crab cavities needed for maximizing luminosity for non-zero crossing angle at the interaction point.
KEK, Ibaraki
Higher-order-mode (HOM) free superconducting (SC) single cell cavities were developed for the rf system of high luminosity storage ring colliders. Because of the successful results of these cavities under ampere-class beams, the components and technology of the SC cavities have immediately been applied to the middle sized storage rings upgrading the beam intensity by using a few SC cavities. Beside the storage ring rf, a SC based high intensity proton linac was commissioned for neutron physics. Recently, the feasibility study of energy recovery linacs has been carried at various laboratories aiming for the 4th generation light source. Status of these developments will be described.
CERN, Geneva
SLAC, Menlo Park, California
KEK, Ibaraki
In recent years evidence has been found that the maximum sustainable gradient in an accelerating structure depends on the rf power flow through the structure. The CLIC study group consequently designed a new prototype structure for CLIC with a very low group velocity, input power and average aperture (a/λ = 0.12). The 18 cell structure has a group velocity of 2.4% at the entrance and 1% at the last cell. Several of these structures have been made in collaboration between KEK, SLAC and CERN. A total of five brazed-disk structures and two quadrant structures have been made. The high power results of some of these structures are presented. The first KEK/SLAC built structure reached an unloaded gradient in excess of 100 MV/m at a pulse length of 230 ns with a breakdown rate below 10-6. The high-power testing was done using the NLCTA facility at SLAC.