A   B   C   D   E   F   G   H   I   J   K   L   M   N   O   P   Q   R   S   T   U   V   W   X   Y   Z  

Lawton, D.

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.

TUPAS051 Radiation Simulations for a Pre-Separator Area for Rare Isotope Production via Projectile Fragmentation 1763
  • I. Baek, G. Bollen, M. Hausmann, D. Lawton, R. M. Ronningen, A. Zeller
    NSCL, East Lansing, Michigan
  Funding: U. S. Department of Energy under Grant No. DE-FG02-04ER41313

To support pre-conceptual research and development for rare isotope beam production via projectile fragmentation at the Rare-Isotope Accelerator facility or similar next-generation exotic beam facilities, the interactions between primary beams and beryllium and liquid-lithium production targets in the fragment pre-separator area were simulated using the Monte-Carlo radiation transport code PHITS. The purpose of this simulation is to determine the magnitude of the radiation fields in the pre-separator area so that levels of hadron flux and energy deposition can be obtained. It was of particular interest to estimate the maximum radiation doses to magnet coils and other components such as the electromagnetic pump for a liquid-lithium loop, and to estimate component lifetimes. We will show a detailed geometry of the pre-separator area developed for these simulations. We will provide verification that trajectories of beams and fragments when transported in the PHITS simulations agree with results from standard ion-optics calculations. We will present estimates of radiation doses to pre-separator components and give estimates for component lifetimes.

TUPAS052 Radiation Environment at ISOL Target Station of Rare Isotope Facility 1766
  • M. A. Kostin, I. Baek, V. Blideanu, G. Bollen, D. Lawton, R. M. Ronningen
    NSCL, East Lansing, Michigan
  • L. Ahle, S. Reyes, K. L. Whittaker
    LLNL, Livermore, California
  • T. Burgess, D. L. Conner, T. A. Gabriel, R. Remec
    ORNL, Oak Ridge, Tennessee
  • D. J. Vieira
    LANL, Los Alamos, New Mexico
  Next-generation exotic beam facilities will offer a number of approaches to produce rare isotopes far from stability. One of the approaches is the Isotope Online (ISOL) separation concept, that is, the isotope production by interactions of light ion beams with heavy nuclei of targets. A pre-conceptual design of an ISOL target station was done as part of the research and development work for the Rare Isotope Accelerator (RIA). This report summarizes the results of radiation simulations for the RIA ISOL target station. The above includes radiation effects such as: prompt doses around the target station and from neutron sky-shine; residual activation effects such as ground water, air, and component activation; life-time of target station components; and heating and cooling for target, beam dumps, and shielding.  
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