| Paper |
Title |
Page |
| MOPP003 |
Study of Abnormal Vertical Emittance Growth in ATF Extraction Line
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553 |
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- M. Alabau, A. Faus-Golfe
IFIC (CSIC-UV), Valencia
- M. Alabau, P. Bambade, J. Brossard, G. Le Meur, C. Rimbault, F. Touze
LAL, Orsay
- D. Angal-Kalinin, J. K. Jones
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
- R. Appleby, A. Scarfe
UMAN, Manchester
- S. Kuroda
KEK, Ibaraki
- G. R. White, M. Woodley
SLAC, Menlo Park, California
- F. Zimmermann
CERN, Geneva
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Since several years, the vertical emittance measured in the Extraction Line (EXT) of the Accelerator Test Facility (ATF) at KEK, that will transport the electron beam from the ATF Damping Ring (DR) to the future ATF2 Final Focus beam line, is significantly larger than the emittance measured in the DR itself, and there are indications that it grows rapidly with increasing beam intensity. This long-standing problem has motivated studies of possible sources of this anomalous emittance growth. One possible contribution is non-linear magnetic fields in the extraction region experienced by the beam while passing off-axis through magnets of the DR during the extraction process. In this paper, simulations of the emittance growth are presented and compared to observations. These simulations include the effects of predicted non-linear field errors in the shared DR magnets and orbit displacements from the reference orbit in the extraction region. Results of recent measurements using closed orbit bumps to probe the relation between the extraction trajectory and the anomalous emittance growth are also presented.
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| MOPP005 |
The 2 mrad Crossing Angle Scheme for the International Linear Collider
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556 |
| |
- R. Appleby
UMAN, Manchester
- D. Angal-Kalinin
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
- P. Bambade, S. Cavalier, G. Le Meur, F. Touze
LAL, Orsay
- Y. Iwashita
Kyoto ICR, Uji, Kyoto
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The present baseline configuration of the ILC has a 14 mrad crossing angle between the beams at the interaction point. This allows easier extraction of the beams after collisions, but imposes on the other hand more constraints on the control of the beams prior to colliding them. Moreover, some limitations to physics capabilities arise, in particular because of the degraded very forward electromagnetic detector hermeticity and because calibration procedures for (gaseous) tracking detectors become more complex. To mitigate these problems, alternative configurations with very small crossing angles are studied. A new version of the 2 mrad layout was designed last year, based on simpler concepts and assumptions. The emphasis of this new scheme was to satisfy specifications with as few and feasible magnets as possible, in order to reduce costs. Recent progress designing several of the magnets involved and the particular vacuum chamber needed in the shared part of the beam line is reported.
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| MOPP006 |
Machine Induced Backgrounds for FP420
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559 |
| |
- R. Appleby, K. M. Potter, F. Roncarolo, G. J. Sellers
UMAN, Manchester
- I. Azhgirey, I. Baishev, I. L. Kurochkin, V. Talanov
IHEP Protvino, Protvino, Moscow Region
- M. Ruspa
INFN-Torino, Torino
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The LHC FP420 collaboration is assessing the feasibility of installing forward proton detectors at 420m from the ATLAS and/or CMS interaction points. Such detectors aim at measuring diffracted protons, which lost less than 2% of their longitudinal momentum. The success of this measurement requires a very good understanding of the charged and neutral particle environment in the detector region in order to avoid the signal being swamped as well as for detector survivability. This background receives contributions from beam-gas interactions, halo particles surviving from the Betatron and momentum cleaning systems and secondary showers produced by particles from the 14TeV collision region striking the beampipe upstream of the FP420 detectors. In this paper, such background sources are reviewed, and the expected background rates calculated.
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| MOPP030 |
ATF2 Final Focus Orbit Correction and Tuning Optimisation
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613 |
| |
- A. Scarfe, R. Appleby
UMAN, Manchester
- D. Angal-Kalinin, J. K. Jones
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
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ATF2 is an upgrade to the ATF facility at KEK, Japan consisting of a replacement to the current ATF extraction line and the addition of a final focus section. The final focus system has been designed, and is aiming to test, the local chromaticity correction scheme as proposed for future linear colliders. The final focus system focuses the ultra-low emittance beams at the collision point in the linear collider. To provide the required small beam sizes and to maintain the beam sizes to nanometer level requires optimised orbit correction and tuning procedures. In this paper, the optimisation of the orbit correction using a global SVD method is discussed, along with the progress on final focus tuning knob analysis. The tuning algorithms used at ATF2 will provide an important feedback for future linear colliders (including the ILC and CLIC).
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| TUPP062 |
Beam Coupling Impedance Studies on LHC FP420 Multi-pocket Beam Pipe Prototype
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1682 |
| |
- F. Roncarolo, R. Appleby, R. M. Jones
UMAN, Manchester
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The LHC FP420 collaboration is assessing the feasibility of installing forward proton detectors 420m from the ATLAS and/or CMS interaction points. The latest prototype of a FP420 station consists of a modified LHC beam pipe in which two pockets hosting the detectors introduce an abrupt cross-section variation of the pipe. During the FP420 proposed operation, each station is moved towards the beam as close as 3 mm (~ 10 σx). The impact on the LHC beam coupling impedance has been evaluated with a laboratory wire measurement and a suite of numerical simulations. In addition, we describe a proposed modification of the beam pipe design which minimizes the impedance of the resonances without compromising the FP420 detector signal to background ratio.
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| TUPP085 |
Beam Dynamics Using Graphical Processing Units (GPUs)
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1727 |
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- R. Appleby, D. Bailey, M. D. Salt
UMAN, Manchester
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Simulation of particle beam dynamics in accelerators is computationally expensive, and requires very high particle statistics and accuracy. Conventional beam tracking tools operate sequentially on particle phase space to compute the trajectories of particles through many turns of circular, and linear, machines. Graphical Processing Units (GPUs) utilise stream processing techniques to dramatically speed up parallel computational tasks, and offer considerable performance benefits to particle beam dynamics processing. In this paper, the stream processing beam dynamics code GPMAD is presented, which exploits the NVidia GPU processor, and demonstrates the considerable performance benefits to particle tracking calculations. The accuracy and speed of GPMAD is benchmarked using the Diamond Light Source BTS lattice, and the collimation system is evaluated.
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