WOPA  —  DPB/IEEE Awards   (18-May-05   13:00—17:50)

Chair: G. Dugan, Cornell University, Laboratory for Elementary-Particle Physics, Ithaca, New York

Paper Title Page
WOPA001 Wilson Prize Talk
  • K.R. Symon
    UW-Madison/PD, Madison, Wisconsin
  The formula for the center-of-mass energy as a function of the energy of the incident particle in a collision with a stationary target shows that the required beam energy is greatly reduced if we collide incident and target particles with equal and opposite momenta. Unfortunately the cross sections for collisions of interest are so small that until the middle 1900's it was not possible to achieve colliding beams of sufficient intensities to reach needed collision rates. In 1954 fixed field alternating gradient (FFAG) accelerators were invented. With a fixed magnetic guide field, it was possible to consider stacking successively injected beams to achieve very high intensity circulating beams. Calculations using Liouville's theorem showed that colliding beam experiments were now practical. Circulating electron beams over 10 amperes were achieved in a model accelerator built by the Midwestern Universities Research Association (MURA). With the invention of storage rings, a much cheaper accelerator configuration than FFAG, and utilizing beam stacking, colliding beams are now utilized to study high energy interactions.  
WOPA002 Experimental Results from the Small Isochronous Ring 159
  • E.P. Pozdeyev
    Jefferson Lab, Newport News, Virginia
  • F. Marti, R.C. York
    NSCL, East Lansing, Michigan
  • J.A. Rodriguez
    CERN, Geneva
  Funding: Work supported by NSF Grant # PHY-0110253 and DOE Contract DE-AC05-84ER40150.

The Small Isochronous Ring (SIR) is a compact, low-energy storage ring designed to investigate the beam dynamics of high-intensity isochronous cyclotrons and synchrotrons at the transition energy. The ring was developed at Michigan State University and has been operational since December 2003. It stores 20 keV hydrogen beams with a peak current of 10-20 microamps for up to 200 turns. The transverse and longitudinal profiles of extracted bunches are measured with an accuracy of approximately 1 mm. The high accuracy of the measurements makes the experimental data attractive for validation of multi-particle space charge codes. The results obtained in the ring show a fast growth of the energy spread induced by the space charge forces. The energy spread growth is accompanied by a breakup of the beam bunches into separated clusters that are involved in the vortex motion specific to the isochronous regime. The experimental results presented in the paper show a remarkable agreement with simulations performed with the code CYCO. In this paper, we discuss specifics of space charge effects in the isochronous regime, present results of experiments in SIR, and conduct a detailed comparison of the experimental data with results of simulations.