IN2P3-LAPP, Annecy-le-Vieux
KEK, Ibaraki
LAL, Orsay
SLAC, Menlo Park, California
Funding: Work supported by the Agence Nationale de la Recherche of the French Ministry of Research (Programme Blanc, Project ATF2-IN2P3-KEK, contract ANR-06-BLAN-0027).
CLIC is one of the current projects of linear colliders. Achieving a vertical beam size of 1 nm at the Interaction Point (IP) with several nanometers of fast ground motion imposes an active stabilization of final doublet magnets (FD) at a tenth of nm above 4Hz. ATF2 is a test facility for linear colliders whose first aim is to have a vertical beam size of 37nm. Relative motion tolerance between FD and the IP is of 7nm above 0.1Hz. Because ground motion is coherent between these two elements, they were fixed to the floor so that they move in a coherent way. Investigations are going on to have in 2011 a useful active stabilization for ATF2 in order to use it as a CLIC prototype. Parameters of a 2D ground motion generator were fitted on measurements to reproduce spatial and temporal spectra, so it can be used for ATF2 simulations. Thus, we evaluated the ideal response function that an active stabilization FD system would need to have to improve on the present ATF2 system. Because ground motion coherence is lost with upstream magnets, we simulated the integrated vibrations at the IP to evaluate the usefulness of their stabilization. These results were validated with measurements.
IHEP Beijing, Beijing
JAI, Egham, Surrey
KEK, Ibaraki
ICEPP, Tokyo
SLAC, Menlo Park, California
University of Tokyo, Tokyo
Funding: NSFC 10525525 and 10775154. CNRS-IN2P3 and ANR.
The ATF2 project is the final focus system prototype for ILC and CLIC linear collider projects, with a purpose to reach a 37nm vertical beam size at the interaction point. We report on techniques developed based on simulation studies to adjust the horizontal and vertical beam waists independently in the presence of errors, at two different IP locations where the beam size can be measured with different accuracies. During initial commissioning, we will start with larger than nominal β-functions at the IP, to reduce the effects from higher-order optical aberrations and thereby simplify the optical corrections needed. The first measurements in such intermediate β-configurations are reported.
CERN, Geneva
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
IHEP Beijing, Beijing
LAL, Orsay
KEK, Ibaraki
UMAN, Manchester
SLAC, Menlo Park, California
The CLIC Final Focus System has considerably larger chromaticity than those of ILC and its scaled test machine ATF2. We propose to reduce the IP betas of ATF2 to reach a CLIC-like chromaticity. This would also allow to study the FFS tuning difficulty as function of the IP beam spot size. Both the ILC and CLIC projects will largely benefit from the ATF2 experience at these ultra-low IP betas.
LAL, Orsay
IFIC, Valencia
KEK, Ibaraki
SLAC, Menlo Park, California
Since several years, the vertical beam emittance measured in the Extraction Line (EXT) of the Accelerator Test Facility (ATF) at KEK, has been significantly larger than that measured in the damping ring (DR) itself. The EXT line that transports the beam to the ATF2 Final Focus beam line has been rebuilt, but the extraction itself remains in most part unchanged, with the extracted beam transported off-axis horizontally in two of the quadrupoles, beyond the linear region for one of them. A few other nearby magnets have also modelled or measured non-linearity. In case of a residual vertical beam displacement, this can result in increased vertical emittance through coupling between the two transverse planes. Tracking studies as well as measurements have been carried out to study this effect and the induced sensitivity of beam optical parameters to the trajectory at injection, in view of deriving tolerances for reproducible and stable operation.
SLAC, Menlo Park, California
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
JAI, Oxford
KEK, Ibaraki
IHEP Beijing, Beijing
LAL, Orsay
Royal Holloway, University of London, Surrey
IN2P3-LAPP, Annecy-le-Vieux
OXFORDphysics, Oxford, Oxon
ATOMKI, Debrecen
CERN, Geneva
DESY, Hamburg
Fermilab, Batavia
Kyungpook National University, Daegu
PAL, Pohang, Kyungbuk
Kyoto ICR, Uji, Kyoto
ICEPP, Tokyo
University of Tokyo, Tokyo
UCL, London
BNL, Upton, Long Island, New York
Tohoku University, Graduate School of Science, Sendai
UMAN, Manchester
Hiroshima University, Graduate School of Science, Higashi-Hiroshima
Cockcroft Institute, Warrington, Cheshire
ATF2 is a final-focus test beam line that attempts to focus the low-emittance beam from the ATF damping ring to a beam size of about 37 nm, and at the same time to demonstrate nm beam stability, using numerous advanced beam diagnostics and feedback tools. The construction is well advanced and beam commissioning of ATF2 has started in the second half of 2008. ATF2 is constructed and commissioned by ATF international collaborations with strong US, Asian and European participation.
LAL, Orsay
IN2P3-LAPP, Annecy-le-Vieux
KEK, Ibaraki
UMAN, Manchester
SLAC, Menlo Park, California
Funding: CNRS/IN2P3 ANR (Programme Blanc, Project ATF2-IN2P3-KEK, contract ANR-06-BLAN-0027)
The orbit in the ATF2 extraction line has to be accurately controlled to allow orbit and optics corrections to work well downstream. The Final Focus section contains points with large beta function values which amplify incoming beam jitter, and few correctors since the steering is performed using quadrupole movers, and so good orbit stability is required. It is also essential because some magnets are non-linear and can introduce position-dependent coupling of the motion between the two transverse planes. First experience monitoring the orbit in the extraction line during the ATF2 commissioning is described, along with a simulation of the planned steering algorithm.
LAL, Orsay
KEK, Ibaraki
SLAC, Menlo Park, California
Funding: CNRS-IN2P3, ANR
The purpose of ATF2 is to deliver a beam with stable very small spotsizes as required for future linear colliders such as ILC or CLIC. To achieve that, precise controls of aberrations such as dispersion and coupling are necessary. Initially, coupling correction upstream of the final focus line of the ATF2 will be performed with only two skew quadrupoles (SQ) in the extraction line (EXT). We thus first examine the feasability of coupling correction in the EXT with those two SQ, considering several possible coupling error sources. The correction is first based on an algorithm of minimisation of vertical emittance with successive skew scans, implemented in the Flight Simulator code*. We will then investigate new methods to measure and extract the first order four coupling parameters of the beam matrix in order to perform a more direct and accurate coupling correction.
*G. White et al., "A flight simulator for ATF2…", TUPP016 EPAC08