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Ottarson, J.

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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.

THPAS039 Status Report on the NSCL RF Fragment Separator 3585
  • M. Doleans, V. Andreev, B. Arend, D. Bazin, A. Becerril Reyes, R. Fontus, P. Glennon, D. Gorelov, P. F. Mantica, J. Ottarson, H. Schatz, B. Sherrill, J. Stoker, O. Tarasov, J. J. Vincent, J. Wagner, X. Wu, A. Zeller
    NSCL, East Lansing, Michigan
  The RF Fragment Separator (RFFS) proposed in* is now under construction and should be operational by May 2007. The RFFS is an additional purification system for secondary beams at the National Superconducting Cyclotron Laboratory after the existing A1900 fragment separator and will primarily be used to purify beams of rare neutron deficient isotopes. The RFFS uses a transverse electric field of an rf kicker to separate unwanted particles from the desired ion beam, a pi/2 phase advance cell to rotate the beam in phase space before the beam reaches a collimating aperture for purification and a final pi phase advance cell to transport the desired beam to the experiment. The final design for the rf kicker and the focusing system is presented and a status report on the building and commissioning effort is given.

* D. Gorelov, V. Andreev, D. Bazin, M. Doleans, T. Grimm, F. Marti, J. Vincent and X. Wu, "RF-Kicker System for Secondary Beams at NSCL/MSU" PAC2005, Knoxville, Tennessee, 16th-20th, May 2005

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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