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.
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.
SLAC, Menlo Park, California
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
KEK, Ibaraki
LAL, Orsay
UMAN, Manchester
CERN, Geneva
Funding: Work supported in part by Department of Energy Contract DE-AC02-76SF00515
Using a new extraction line currently being commissioned, the ATF2 experiment plans to test a novel compact final focus optics design using a local chromaticity correction scheme, such as could be used in future linear colliders*. Using a 1.3 GeV beam of ~30nm normalised vertical emittance extracted from the ATF damping ring, the primary goal is to achieve a vertical IP waist of 35nm. We discuss our planned strategy, implementation details and early experimental results for tuning the ATF2 beam to meet the primary goal. These optics require uniquely tight tolerances on some magnet strengths and positions, we discuss efforts to re-match the optics to meet these requirements using high-precision measurements of key magnet elements. We simulated in detail the tuning procedure using several algorithms and different code implementations for comparison from initial orbit establishment to final IP spot-size tuning. Through a Monte Carlo study of 100's of simulation seeds we find we can achieve a spot-size within 10% of the design optics value in at least 90% of cases. We also ran a simulation to study the long-term performance with the use of beam-based feedbacks.
*"ATF2 Proposal", ATF2 Collaboration (Boris Ivanovich Grishanov et al.)., KEK-REPORT-2005-2, Aug 23, 2005.
SLAC, Menlo Park, California
LAL, Orsay
The Flight Simulator is a tool used for international collaboration in the writing and deployment of online beam dynamics algorithms. Written as an add-on to the Lucretia tracking software, it allows simulation of a beamline in a control system environment identical to that in the control room. This allows the testing and development of monitoring and correction tools by an international collaboration by making the control system transparent to the user. The native beamline representation are those adopted by Lucretia, so, in order to allow third party software, to interface with this system, it was necessary to develop functionality to convert the lattice to a universal representation. Accelerator Markup Language (AML), and its associated Universal Accelerator Parser (UAP), were used for this purpose. This paper describes the use of the UAP to convert the internal beamline representation to AML, and the testing of this conversion routine using the lattice description of the ATF2 final focus experiment at KEK, Japan. Also described are the inclusion of PLACET and SAD based algorithms using appropriate converters, and tests of these on the ATF2 extraction line.
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.
