• Y.K. Batygin
  NSCL, East Lansing, Michigan
• M. Woodley
  SLAC, Menlo Park, California

Determination of exact values of beam emittance is important for future linear collider. Beam emittance measurements technique is based on measurement of beam sizes at several beam profile stations in a quadrupole channel shifted between each other by a specific value of phase advance of betatron oscillations. Four-dimensional beam emittance measuremenst requires determination of ten values of the beam σ-matrix, while two-dimensional beam emittance measurements scheme requires determination of six values of σ-matrix. Measurement procedure is sensitive to variation of beam sizes at the beam profile stations, which might result in unstable determination of beam emittance. Paper discusses errors of beam emittance measurements as a function of errors in beam size measurement. Regions of stable and unstable beam emittance measurements are determined.

• Y.K. Batygin, F. Marti
  NSCL, East Lansing, Michigan

The Facility for Rare Isotope Beams (FRIB) will provide intense beams of short-lived isotopes for fundamental research in nuclear structure and nuclear astrophysics. Operation of the facility requires intense uranium primary beams. At the present time acceleration of two simultaneous charge states of uranium from a single ion source is needed to achieve the required intensity. Three schemes are considered for funneling the beams from two sources as an alternate solution. One is the traveling wave RF kicker for merging of bunched beams extracted from ECR ion sources. Another one implements the idea of utilizing an RFQ for beam merging*, which can be used after preliminary acceleration of both beams. The third approach assumes usage of a conventional standing-wave RF kicker. Parameters of all three schemes are compared and analyzed.

*R.H.Stokes and G.N.Minerbo, AIP Conference Proceedings 139 (1985), p.79.

• Y.K. Batygin, G. Bollen, C. Campbell, F. Marti, D.J. Morrissey, G.K. Pang, S. Schwarz
  NSCL, East Lansing, Michigan

Cyclotron gas stopper is a newly proposed device to stop energetic ions in a high pressure helium gas and to transport them in a singly charged state with a gas jet to a vacuum region. Radioactive ions are slowed down by gas collisions inside the field of a weakly focusing cyclotron-type magnet and extracted via interaction with the Radio Frequency field of sequence of concentric electrodes (RF carpet). The present study focuses on a detailed understanding of space charge effects in the central ion extraction region. Such space charge effects originate from the ionization of the helium gas during the stopping of the ions and are the cause for beam rate limitations. Particle-in-cell simulation of two-component (electron-helium) plasma interacting via Coulomb forces were performed in a field created by ionized ions. Simulation results indicate beam rate capabilities and efficiencies far beyond those achieved with linear gas cells presently used to stop projectile fragments.