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Schwarz, S.

Paper Title Page
MOPAS041 Design of Superferric Magnet for the Cyclotron Gas Stopper Project at the NSCL 524
  • S. Chouhan, G. Bollen, C. Guenaut, D. Lawton, F. Marti, D. J. Morrissey, J. Ottarson, G. K. Pang, S. Schwarz, B. Sherrill, A. Zeller
    NSCL, East Lansing, Michigan
  • E. Barzi
    Fermilab, Batavia, Illinois
  Funding: Michigan State University, Cyclotron-1, East Lansing, MI-48824

We present the design of a superferric cyclotron gas stopper magnet that has been proposed for use at the NSCL/MSU to stop the radioactive ions produced by fragmentation at high energies (~140 MeV/u). The magnet is a gradient dipole with three sectors ( B~2.7 T at the center and 2 T at the pole-edge. The magnet outer diameter is 3.8 m, with a pole radius of 1.1 m and B*rho=1.7 T-m). The field shape is obtained by extensive profiles in the iron. The coil cross-section is 64 cm*cm and peak field on the conductor is about 1.6 T. The upper and lower coils are in separate cryostat and have warm electrical connections. We present the coil winding and protection schemes. The forces are large and the implication on the support structure is presented.

TUPAS053 Beam Dynamics Studies for the Reacceleration of Low Energy RIBs at the NSCL 1769
  • X. Wu, G. Bollen, M. Doleans, T. L. Grimm, F. Marti, S. Schwarz, R. C. York, Q. Zhao
    NSCL, East Lansing, Michigan
  Funding: This work is supported by the U. S. Department of Energy

Rare Isotope Beams (RIBs) are created at the National Superconducting Cyclotron Laboratory (NSCL) by the in-flight particle fragmentation method. A novel system is proposed to stop the RIBS in a helium filled gas system followed by reacceleration that will provide opportunities for an experimental program ranging from low-energy Coulomb excitation to transfer reaction studies of astrophysical reactions. The beam from the gas stopper will first be brought into a Electron Beam Ion Trap (EBIT) charge breeder on a high voltage platform to increase its charge state and then accelerated initially up to about 3 MeV/u by a system consisting of an external multi-harmonic buncher and a radio frequency quadrupole (RFQ) followed a superconducting linac. The superconducting linac will use quarter-wave resonators with bopt of 0.047 and 0.085 for acceleration and superconducting solenoid magnets for transverse focusing. The paper will discuss the accelerator system design and present the end-to-end beam dynamics simulations.

THPAS040 The Cyclotron Gas Stopper Project at the NSCL 3588
  • G. K. Pang, G. Bollen, S. Chouhan, C. Guenaut, D. Lawton, F. Marti, D. J. Morrissey, J. Ottarson, S. Schwarz, A. Zeller
    NSCL, East Lansing, Michigan
  • M. Wada
    RIKEN, Saitama
  Funding: Work supported by DOE Grant # DE-FG02-06ER41413

Gas stopping is the method of choice to convert high-energy beams of rare isotopes produced by projectile fragmentation into low-energy beams. Fast ions are slowed down in solid degraders and stopped in a buffer gas in a stopping cell, presently linear. They have been successfully used for first precision experiments with rare isotopes*,** but they have beam-rate limitations due to space charge effects. Their extraction time is about 100 ms inducing decay losses for short-lived isotopes. At the NSCL a new gas stopper concept*** is under development, which avoids these limitations and fulfills the needs of next-generation rare isotope beam facilities. It uses a gas-filled cyclotron magnet. The large volume, and a separation of the regions where the ions stop and where the maximum ionization is observed are the key to a higher beam-rate capability. The longer stopping path due to the magnetic field allows a lower pressure to be used, which decreases the extraction times. The concepts of the cyclotron gas stopper will be discussed and the results from detailed simulation and design work towards the realization of such a device at the NSCL will be summarized.

* G. Bollen et al., Phys. Rev. Lett. 96 (2006) 152501 ** R. Ringle Phys. Rev. C Submitted*** G. Bollen et al., Nucl. Instr. Meth. A550 (2005) 27