Single-Particle Beam Dynamics and Optics

Paper Title Page
WOAC001 Aberration Correction in Electron Microscopy 44
  • H.H. Rose, W. Wan
    LBNL, Berkeley, California
  The resolution of conventional electron microscopes is limited by spherical and chromatic aberrations. Both defects are unavoidable in the case of static rotationally symmetric electromagnetic fields (Scherzer theorem). Multipole correctors and electron mirrros have been designed and built, which compensate for these aberrations. The principles of correction will be demonstrated for the tetrode mirror, the quadrupole-octopole corrector and the hexapole corrector. Electron mirrors require a magnetic beam separator free of second-order aberrations. The multipole correctors are highly symmetric telescopic systems compensating for the defects of the objective lens. The hexapole corrector has the most simple structure yet eliminates only the spherical aberration, whereas the mirror and the quadrupole-octopole corrector are able to correct for both aberrations. Chromatic correction is achieved in the latter corrector by cossed electric and magnetic quadrupoles acting as first-order Wien filters. Micrographs obtained with aberration-corrected electron microscopes will be shown demonstrating the improvement in resolution to better than 1 Angstroem.  
WOAC002 Chromatically Corrected Imaging Systems for Charged-Particle Radiography 225
  • B. Blind, A.J. Jason
    LANL, Los Alamos, New Mexico
  In proton radiography, imaging with systems consisting of quadrupole magnets is an established technique for viewing the material distribution and composition of objects, either statically or during fast events such as explosions. With the most favorable magnet configuration, the –I lens, chromatic aberrations generally dominate the image blur. Image resolution can be improved, and largely decoupled from the input-beam parameters, by using a second-order achromatic bend with some additional higher-order aberration correction. The aberration-correction approach is discussed. For a given resolution, such a bend allows use of much lower-energy imaging particles than a –I lens. Each bend design represents a set of equivalent systems; an 800-MeV proton design and its equivalent 40-MeV electron system are presented. The electron system is useful for imaging small objects. Magnet errors in the achromatic bends must be tightly controlled to preserve image quality, but not beyond feasibility of present technology. System performance is verified by particle tracking. Configurations alternative to the canonical achromatic bend are also discussed.  
WOAC003 Effects of Fringe Fields and Insertion Devices Revealed Through Experimental Frequency Map Analysis 266
  • P. Kuske
    BESSY GmbH, Berlin
  Funding: This work was supported by the Bundesministerium für Bildung und Forschung and by the Land Berlin.

Following the pioneering work at the ALS* frequency map analysis was performed at the light source BESSY. With altogether 7 families of sextupole magnets available in the storage ring, amplitude dependent tune shifts can be made rather small. Therefore, the impact of fringe fields of dipole and quadrupole magnets as well as systematic octupole and decapole field components of the quadrupole and sextupole magnets used in addition as horizontal, vertical and skew gradient correctors are clearly visible in the measured maps. Insertion devices with their known systematic and usually unknown random non-linear field components impact the appearance of the frequency maps even more strongly. In the talk the current status of the experiments as well as the results of the theoretical modeling will be presented.

*"Global Dynamics of the Advanced Light Source Revealed through Experimental Frequency Map Analysis," D. Robin, et al., Phys. Rev. Lett. 85, 558 (2000).

WOAC005 Application of Independent Component Analysis for Beam Diagnosis 489
  • X. Huang, S.-Y. Lee
    IUCF, Bloomington, Indiana
  • E. Prebys, R.E. Tomlin
    Fermilab, Batavia, Illinois
  Funding: This work is supported in part by grants from DE-AC02-76CH03000, DOE DE-FG02-92ER40747 and NSF PHY-0244793.

The independent component analysis (ICA)* is applied to analyze simultaneous multiple turn-by-turn beam position monitor (BPM) data of synchrotrons. The sampled data are decomposed to physically independent source signals, such as betatron motion, synchrotron motion and other perturbation sources. The decomposition is based on simultaneous diagonalization of several unequal time covariance matrices, unlike the model independent analysis (MIA),** which uses equal-time covariance matrix only. Consequently the new method has advantage over MIA in isolating the independent modes and is more robust under the influence of contaminating signals of bad BPMs. The spatial pattern and temporal pattern of each resulting component (mode) can be used to identify and analyze the associated physical cause. Beam optics can be studied on the basis of the betatron modes. The method has been successfully applied to the Booster Synchrotron at Fermilab.

*A. Belouchrani et al., IEEE Trans. on Signal Processing, {\bf 45}, 434-444, (1997). **J. Irwin, et al., Phys. Rev. Lett. {\bf 82}, 1684 (1999); Chun-xi Wang, et al., Phys. Rev. ST Accel. Beams} {\bf 6}, 104001 (2003).

WOAC006 Design of Large Momentum Acceptance Transport Systems
  • D. Douglas
    Jefferson Lab, Newport News, Virginia
  Funding: This work supported by The Office of Naval Research the Joint Technology Office, NAVSEA PMS-405, the Air Force Research Laboratory, U.S. Army Night Vision Lab, the Commonwealth of Virginia, and by DOE Contract DE-AC05-84ER40150.

The use of energy recovery to enable high power linac operation often gives rise to an attendant challenge – the transport of high power beams subtending large phase space volumes. In particular applications – such as FEL driver accelerators – this manifests itself as a requirement for beam transport systems with large momentum acceptance. We will discuss the design, implementation, and operation of such systems. Though at times counterintuitive in behavior (perturbative descriptions may, for example, be misleading), large acceptance systems have been successfully utilized for generations as spectrometers and accelerator recirculators.* Such systems are in fact often readily designed using appropriate geometric descriptions of beam behavior; insight provided using such a perspective may in addition reveal inherent symmetries that simplify construction and improve operability. Our discussion will focus on two examples: the Bates-clone recirculator used in the Jefferson Lab 10 kW IR Upgrade FEL (which has an observed acceptance of 10% or more) and a compaction-managed mirror-bend achromat concept with potentially very large acceptance.

*J.B. Flanz and C.P. Sargent, "Operation of an Isochronous Beam Recirculation System," Nucl. Instrum. and Methods A 241 (1985) 325–333.

WOAC007 Beam-Based Nonlinear Optics Corrections in Colliders 601
  • F.C. Pilat, Y. Luo, N. Malitsky, V. Ptitsyn
    BNL, Upton, Long Island, New York
  Funding: Work performed under the auspices of the US Department of Energy

A method has been developed to measure and correct operationally the non-linear effects of the final focusing magnets in colliders, which gives access to the effects of multi-pole errors by applying closed orbit bumps, and analyzing the resulting tune and orbit shifts. This technique has been tested and used during 3 years of RHIC (the Relativistic Heavy Ion Collider at BNL) operations. I will discuss here the theoretical basis of the method, the experimental set-up, the correction results, the present understanding of the machine model, the potential and limitations of the method itself as compared with other non linear correction techniques.

WOAC008 Measuring and Understanding the Momentum Aperture in a Storage Ring 645
  • C. Steier, D. Robin
    LBNL, Berkeley, California
  • W. Decking
    DESY, Hamburg
  • J. Laskar
    IMCCE, Paris
  • L.S.N. Nadolski
    SOLEIL, Gif-sur-Yvette
  • Y.K. Wu
    DU/FEL, Durham, North Carolina
  Funding: This work was supported by the U.S. Department of Energy, under Contract No. DE-AC03-76SF00098.

The momentum aperture of a storage ring is a very important parameter that strongly influences the performance, especially the beam lifetime. For the special case of synchrotron light sources with small emittance like the Advanced Light Source (ALS), the momentum aperture depends strongly on the transverse dynamics. It is very sensitive to machine conditions such as the tunes, chromaticities, lattice symmetry, and spurious coupling, since depending on those conditions the Touschek scattered particles explore different resonance regions in the phase space. In light sources, the momentum aperture usually also depends strongly on the vertical physical aperture. Applying frequency analysis techniques in simulations and for turn-by-turn orbit measurement data provides a very powerful tool to measure and understand limitations of the dynamic momentum aperture. The techniques presented are applicable to other light sources, as well as damping rings and many types of colliders.

WOAC009 Techniques for Measurement and Correction of the SNS Accumulator Ring Optics 674
  • S. Henderson, P. Chu, S.M. Cousineau, V.V. Danilov, J.A. Holmes, T.A. Pelaia, M.A. Plum
    ORNL, Oak Ridge, Tennessee
  Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. SNS is a partnership of six national laboratories: Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los Alamos and Oak Ridge.

The Spallation Neutron Source (SNS) Accumulator Ring will reach peak intensities of 1.5x1014 protons/pulse through multi-turn charge-exchange injection. Accumulation of these unprecedented beam intensities must be accomplished while maintaining extremely low losses (less than 1 W/m). It is anticipated that the control of the ring optics will be important for achieving these low loss rates. We describe our plans for measuring and correcting the optical functions of the accumulator ring lattice.

WOAC010 Measurement of Linear Lattice Functions in the ESRF Storage Ring Using Turn-by-Turn Data 698
  • Y. Papaphilippou, L. Farvacque, J.-L. Revol, V. Serriere
    ESRF, Grenoble
  • S.-L. Bailey
    The College of William and Mary, Williamsburg
  A model-independent method to measure linear optics functions has been tested in turn-by-turn data from the ESRF storage ring. This method does not necessitate neither the knowledge of the model nor magnetic element manipulation. It uses only the positions measured in consecutive BPMs of betatron oscillations issued by small transverse kicks. The phase advances and tunes necessary to construct the transfer matrices are issued by refined Fourier analysis. The method's precision is compared with classical methods such as response matrix analysis and beam matrix construction.