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Grimm, T.L.

Paper Title Page
MPPE023 Improvement of the Longitudinal Beam Dynamics Tuning Procedure for the MSU RIA Driver Linac 1826
 
  • M. Doleans
    MSU, East Lansing, Michigan
  • D. Gorelov, T.L. Grimm, F. Marti, X. Wu, R.C. York
    NSCL, East Lansing, Michigan
 
  The Rare Isotope Accelerator (RIA) driver linac will use a superconducting, cw linac with independently phased superconducting radio frequency cavities for acceleration and, for the heavier ions, utilize beams of multiple-charge-states (multi-q). Given the acceleration of multi-q beams and a stringent beam loss requirement in the RIA driver linac, a new beam envelope code capable of simulating nonlinearities of the multi-q beam envelopes in the longitudinal phase space was developed. Using optimization routines, the code is able to maximize the linearity of the longitudinal phase space motion and thereby minimizing beam loss by finding values for the amplitude and phase of the cavities for a given accelerating lattice. Relative motion of the multi-q beams is also taken into account so that superposition of the beam centroids and matching of their Twiss parameters are automatically controlled. As a result, the linac tuning procedure has been simplified and the longitudinal lattice performance has been improved. In this paper, the general architecture of the code and the results of using it to determine tuning parameters for the RIA driver linac are presented.  
MPPE024 Failure Modes Analysis for the MSU-RIA Driver Linac 1868
 
  • X. Wu, M. Doleans, D. Gorelov, T.L. Grimm, F. Marti, R.C. York
    NSCL, East Lansing, Michigan
 
  Previous end-to-end beam dynamics simulation studies* using experimentally-based input beams including alignment and rf errors and variation in charge-stripping foil thickness have indicated that the Rare Isotope Accelerator (RIA) driver linac proposed by MSU has adequate transverse and longitudinal acceptances to accelerate light and heavy ions to final energies of at least 400 MeV/u with beam powers of 100 to 400 kW. During linac operation, equipment loss due to, for example, cavity contamination, availability of cryogens, or failure of rf or power supply systems, will lead to at least a temporary loss of some of the cavities and focusing elements. To achieve high facility availability, each segment of the linac should be capable of adequate performance even with failed elements. Beam dynamics studies were performed to evaluate the linac performance under various scenarios of failed cavities and focusing elements with proper correction schemes, in order to prove the flexibility and robustness of the driver linac lattice design. The result of these beam dynamics studies will be presented.

*X. Wu, "End-to-End Beam Simulations for the MSU RIA Driver Linac," Proceedings of the XXII Linac Conference, Lubeck, Germany, August 2004.

 
TPPT096 Cryomodule Design for a Superconducting Linac with Quarter-Wave, Half-Wave, and Focusing Elements 4317
 
  • M. J. Johnson, J. Bierwagen, S. Bricker, C. Compton, P. Glennon, T.L. Grimm, W. Hartung, D. Harvell, A. Moblo, J. Popielarski, L. Saxton, R.C. York, A. Zeller
    NSCL, East Lansing, Michigan
 
  The low-energy section of the driver linac for the proposed Rare Isotope Accelerator (RIA) incorporates the following superconducting elements: quarter-wave resonators, half-wave resonators, and 9 T solenoids. A prototype cryomodule has been designed to house all of these elements. A 31 T/m superferric quadrupole is also included as an alternative focusing element, since its stray magnetic field is more easily shielded. The cryomodule design is based on the RIA v/c=0.47 prototype cryomodule that was successfully tested in 2004.* The design uses a titanium rail structure to support the beam line elements. The beam line assembly is done in a class 100 clean room to maintain resonator cleanliness for optimal high-field performance. The cavities will be equipped with RF input couplers, tuners, and magnetic shields. High Tc current leads are used for both magnets. The cryomodule design takes into account static heat leak requirements and alignment tolerances for the beam line elements. A heat exchanger and J-T throttle valve will be used to provide a continuous supply of liquid helium for 2 K operation.

*T.L. Grimm et al., "Experimental Study of an 805 MHz Cryomodule for the Rare Isotope Accelerator", in Proceedings of the XXII International Linear Accelerator Conference, Lubeck, Germany (2004).

 
ROAC003 Superconducting RF for Low-Velocity and Intermediate-Velocity Beams
 
  • T.L. Grimm, W. Hartung
    NSCL, East Lansing, Michigan
 
  Existing superconducting radio frequency (SRF) linacs are used to accelerate ions (protons through uranium) with velocities less than about 15% the speed of light, or electrons with velocities approximately equal to the speed of light. In the last ten years, prototype SRF cavities have completely covered the remaining range of velocities. They have demonstrated that SRF linacs will be capable of accelerating electrons from rest up to the speed of light, and ions from less than 1% up to the speed of light. When the Spallation Neutron Source is operational, SRF ion linacs will have covered the full range of velocities except for v/c ~ 0.15 to v/c ~ 0.5. A number of proposed projects (RIA, EURISOL) would span the latter range of velocities. Future SRF developments will have to address the trade-offs associated with a number of issues, including high gradient operation, longitudinal and transverse acceptance, microphonics, Lorentz detuning, operating temperature, cryogenic load, number of gaps or cells per cavity, proximity of magnetostatic focussing elements, and higher-order-mode damping. An overview of recent developments and future areas of interest will be presented.  
FPAE072 RF-Kicker System for Secondary Beams at NSCL/MSU 3880
 
  • D. Gorelov, V. Andreev, D. Bazin, M. Doleans, T.L. Grimm, F. Marti, J. Vincent, X. Wu
    NSCL, East Lansing, Michigan
 
  The design and construction of a radio frequency (RF) kicker system at the National Superconducting Cyclotron Laboratory (NSCL), Michigan State University (MSU) has been proposed. This RF kicker system will be used to purify secondary beams of rare isotopes after the existing A1900 Fragment Separator and will open a wide range of possibilities for new experiments at the forefront of nuclear science. The proposed system is studied as an efficient alternative to the traditional approach using Wien Filter. Rare neutron deficient secondary beams are challenging to purify because of the presence of intense contaminants that cannot be removed by the traditional energy loss method. However, velocity differences resulting in time-of-flight differences can be used for the effective separation of the beams transversely using the time-varying electromagnetic fields of the RF kicker. Its technical design will be presented together with the beam dynamics analysis of a secondary beam in realistic 3D electromagnetic fields. The expected purification improvement of the exotic beams for the foreseen nuclear physics experiments will be shown in details.