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Marti, F.

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.

 
TUPAS054 Design Studies of the Reaccelerator RFQ at NSCL 1772
 
  • Q. Zhao, V. Andreev, F. Marti, S. O. Schriber, X. Wu, R. C. York
    NSCL, East Lansing, Michigan
 
  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 a reacceleration that will provide opportunities for an experimental program ranging from low-energy Coulomb excitation and 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 planned RFQ will operate in the cw mode at a frequency of 80.5MHz to accelerate ion beams from ~12 keV/u to ≥ 300keV/u. An external multi-harmonic buncher will be used to produce a small longitudinal emittance beam out of the RFQ. In this paper, we will describe the design of the RFQ, present the beam dynamics simulation results, and also discuss the impact of the external buncher harmonics on the output beam properties.  
TUPAS055 End-to-End Beam Dynamics Simulations of the ISF Driver Linac 1775
 
  • Q. Zhao, M. Doleans, T. L. Grimm, F. Marti, S. O. Schriber, X. Wu, R. C. York
    NSCL, East Lansing, Michigan
 
  A proposed Isotope Science Facility (ISF), a major upgrade from the Coupled Cyclotron Facility at the National Superconducting Cyclotron Laboratory (NSCL), will provide the nuclear science community with world-class beams of rare isotopes. The ISF driver linac will consist of a front-end and three acceleration segments of superconducting cavities separated by two charge-stripping sections, and will be capable of delivering primary beams ranging from protons to uranium with variable energies of ≥200 MeV/nucleon. The results of end-to-end beam simulation studies including physical misalignments, dynamic rf amplitude and phase errors, and variations in the stripping foil thickness, will be performed to evaluate the driver linac overall performances and beam loss, even for the challenging case of the uranium beam with multiple charge states using the newly-developed RIAPMTQ/IMPACT codes. The paper will discuss ISF beam dynamics issues and present the end-to-end beam simulation results.  
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

 
FRXAB03 Design, Construction and Commissioning of the SuSI ECR 3766
 
  • P. A. Zavodszky, B. Arend, D. Cole, J. DeKamp, G. Machicoane, F. Marti, P. S. Miller, J. Moskalik, W. Nurnberger, J. Ottarson, J. J. Vincent, X. Wu, A. Zeller
    NSCL, East Lansing, Michigan
 
  Funding: This work was supported by the National Science Foundation under grant PHY-0110253.

An ECR ion source was constructed at the NSCL/MSU to replace the existing SC-ECRIS. This ECRIS operates at 18+14.5 GHz microwave frequencies and it is planned an upgrade to 24-28 GHz in the second phase of commissioning. A superconducting hexapole coil produces the radial magnetic field; the axial trapping is produced with six superconducting solenoids enclosed in an iron yoke to allow tuning the distance between the plasma electrode and resonant zone in the plasma. The plasma chamber of the ion source can be biased at +30 kV, the beam line at -30 kV. The voltage of the beam line vacuum pipe must be kept constant from the ECRIS to the point of full separation of the beam charge states near the image plane of the analyzing magnet. At this point, an insulator is used to increase the voltage up to zero value. The kinetic energy of the beam is decreased to 30 kV per unit charge after this point, as required for the injection in the Coupled Cyclotron Facility. To decrease the beam divergence, a focusing solenoid is installed after the vacuum pipe break. We report the details of the design, construction and initial commissioning results of this new ECIS.

 
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