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Feldman, R.

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TUZBAB03 The University of Maryland Electron Ring (UMER) Enters a New Regime of High-Tune-Shift Rings 820
  • R. A. Kishek, G. Bai, B. L. Beaudoin, S. Bernal, D. W. Feldman, R. Feldman, R. B. Fiorito, T. F. Godlove, I. Haber, T. Langford, P. G. O'Shea, C. Papadopoulos, B. Quinn, M. Reiser, D. Stratakis, D. F. Sutter, J. C.T. Thangaraj, K. Tian, M. Walter, C. Wu
    UMD, College Park, Maryland
  Funding: This work is funded by US Dept. of Energy and by the US Dept. of Defense Office of Naval Research.

Circular accelerators and storage rings have traditionally been designed with limited intensity in order to avoid resonances and instabilities. The possibility of operating a ring beyond the Laslett tune shift limit has been suggested but little tested, apart from a pioneering experiment by Maschke at the BNL AGS in the early 1980s. We have recently circulated the highest-space-charge beam in a ring to date in the University of Maryland Electron Ring (UMER), achieving a breakthrough both in the number of turns and in the amount of current propagated. At undepressed tunes of up to 7.6, the space charge in UMER is sufficient to depress the tune by nearly a factor of 2, resulting in tune shifts up to 3.6. This makes the UMER beam the most intense beam that has been propagated to date in a circular lattice. This is an exciting and promising result for future circular accelerators, and the UMER beam can now be used as a platform to study intense space charge dynamics in rings.

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THPAS031 Measurement and Simulation of Source-Generated Halos in the University of Maryland Electron Ring (UMER) 3564
  • I. Haber, S. Bernal, R. Feldman, R. A. Kishek, P. G. O'Shea, C. Papadopoulos, M. Reiser, D. Stratakis, M. Walter
    UMD, College Park, Maryland
  • A. Friedman, D. P. Grote
    LLNL, Livermore, California
  • J.-L. Vay
    LBNL, Berkeley, California
  Funding: This work is supported by the US DOE under contract Nos. DE-FG02-02ER54672 and DE-FG02-94ER40855 (UMD), and DE-AC02-05CH11231 (LBNL) and W-7405-ENG-48 (LLNL)

One of the areas fundamental beam physics that serve as the rationale for recent research on UMER is the study of generation and evolution of beam halos. This physics can be accessed on a scaled basis in UMER at a small fraction of the cost of similar experiments on a much larger machine. Recent experiments and simulations have identified imperfections in the source geometry, particularly in the region near the emitter edge, as a potentially significant source of halo particles. The edge-generated halo particles, both in the experiments and the simulations are found to pass through the center of the beam in the vicinity of the anode plane. Understanding the detailed evolution of these particle orbits is therefore important to designing any aperture to remove the beam halo. Both experimental data and simulations will be presented to illustrate the details of this mechanism for halo formation.

THPAS046 Transverse-Longitudinal Coupling in an Intense Electron Beam 3597
  • J. R. Harris
    LLNL, Livermore, California
  • R. Feldman, P. G. O'Shea
    UMD, College Park, Maryland
  Funding: This paper was prepared under the auspices of the U. S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.

This paper describes the longitudinal expansion of a 10 keV, 100 mA electron beam in the University of Maryland Electron Ring. The expansion of the beam tail was found to be sensitive to the choice of transverse focusing settings due to the presence of an abnormality in the beam current profile. Expansion of the beam head, where no abnormality was observed, is in good agreement with the one-dimensional cold fluid model.