• O.K. Kester, G. Bollen, M.J. Johnson, M. A. Kostin, J. Ottarson, M. Portillo, S. Schwarz, C. Wilson
  NSCL, East Lansing, Michigan

The National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU) is implementing a system to reaccelerate rare isotope beams from projectile fragmentation to energies of about 3 MeV/u. The reacceleration of stopped radioactive beams from projectile fragmentation at the NSCL/MSU makes use of charge state breeding in an Electron Beam Ion Trap (EBIT) to provide a compact and cost efficient system layout of MSU’s ReA3. The MSU EBIT breeder device will provide a high electron beam current density of about 10⁴ A/cm² making it well suited to rapidly increase the charge state of short-lived isotopes within tens of milliseconds or less. In addition, the breeder is optimized to provide a high storage capacity, a high beam acceptance and uses a continuous injection and beam accumulation scheme explicitly, which makes it unique. To match the beam of singly charged rare isotope ions into the acceptance of the EBIT and to analyze and purify the EBIT beams, a sophisticated beam line and diagnostic system is required. The present paper will present an overview and the status of the ReA3 EBIT.

• M. Portillo, G. Bollen, S. Chouhan, O.K. Kester, G. Machicoane, J. Ottarson, S. Schwarz, A. Zeller
  NSCL, East Lansing, Michigan

Funding: This work was supported by Michigan State University and the National Science Foundation under grant PHY-0110253.

The NSCL at Michigan State University (MSU) is implementing a system called the ReA3 to reaccelerate rare isotope beams from projectile fragmentation to energies of about 3 MeV/u. The re-acceleration system uses an Electron Beam Ion Trap (EBIT) to provide a compact and cost efficient system. We discuss the design parameters for a m/q separator that is to be used to separate highly charged ions from an EBIT type charge breeder. The separator is designed to accept ions at 12 keV/u with mass to charge ratios in the range of m/q = 2.5 to 5 amu. The goal is to separate selected rare isotope species from any residual ions before injecting them into the ReA3 linear accelerator system. Using ray tracing simulations with SIMION*, as well as higher order map calculations with COSY INFINITY**, the performance of the separator has been evaluated in terms of the expected mass resolution and overall acceptance. The separator consists of a magnetic sector and a series of electrostatic devices to obtain a first order achromatic tune. For comparison, similar performance values will be derived as those for a similar separator constructed at REX-ISOLDE***.

*D.A. Dahl, Int. J. Mass Spectrom. Ion Processes 200, 3 (2000) .
**K. Makino and M. Berz, Nucl. Instr. and Meth. A 558, 346 (2005)
***R. Rao et. al., EPAC-98, Stockholm, Sweden, 2132-2134 (1998).

• 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.