TH3  —  Thursday Oral Session TH3   (02-Oct-08   13:40—14:40)

Chair: G. Pei, IHEP Beijing, Beijing

Paper Title Page
TH301 Beam Dynamics Studies of the 8 GeV Linac at FNAL 760
 
  • P.N. Ostroumov, B. Mustapha
    ANL, Argonne
  • J.-P. Carneiro
    Fermilab, Batavia
 
 

Funding: This work was supported by the U.S. Department of Energy, Office of Scince, under contracts number DE-AC02-06CH11357 and No. W-31-109-ENG-38.
The proposed 8 GeV proton driver (PD) linac at FNAL includes a front end up to ~420 MeV and a high energy section operating at 325 MHz and 1300 MHz respectively. A normal conducting RFQ and short H-type resonators are being developed for the initial acceleration of the H-minus or proton beam up to 10 MeV. From 10 MeV to ~420 MeV the voltage gain is provided by SC spoke-loaded cavities. In the high-energy section, the acceleration will be provided by the International Linear Collider (ILC)-style SC elliptical cell cavities. To employ the existing readily available klystrons, an rf power fan out from high-power klystrons to multiple cavities is being developed. The beam dynamics simulation code TRACK available in both serial and parallel versions has been updated to include H-minus stripping due to all known mechanisms to predict the exact location of beam losses. An iterative procedure has been developed to interact with the transient beam loading model taking into account feedback and feedforward systems applied for the rf distribution from one klystron to multiple cavities.

 

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TH302 Transport Limits in Periodic Focusing Channels 765
 
  • S.M. Lund
    LLNL, Livermore, California
 
 

It has been empirically observed in both experiments and particle-in-cell simulations that space-charge-dominated beams suffer strong growth in emittance and particle losses in alternating gradient quadrupole transport channels when the undepressed phase advance increases beyond about 85 degrees per lattice period. Although this criterion has been used extensively in practical designs of strong focusing intense beam transport lattices, the origin of the limit has not been understood. We propose a mechanism for the transport limit resulting from strongly chaotic classes of halo particle resonances near the core of the beam that allow near-edge particles to rapidly increase in oscillation amplitude when the space-charge intensity and the flutter of the matched beam envelope are both sufficiently large. A core particle model is applied to parametrically analyze this process and the results are compared with extensive particle simulations.

 

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TH303 Towards a Model Driven Accelerator with Petascale Computing 766
 
  • B. Mustapha, P.N. Ostroumov, J. Xu
    ANL, Argonne
 
 

Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC-02-06CH11357.
Accelerator simulations still do not provide everything designers and operators need to deploy a new facility with confidence. This is mainly because of limitations preventing realistic, fast-turnaround, end-to-end simulations of the beam from the source all the way through to a final interaction point and because of limitations in on-line monitoring that prevent a full characterization of the actual beam line. As a result, once a machine is built there can be a gap between the expected behavior of the machine and the actual behavior. This gap often corresponds to enormous work and significant delays in commissioning a new machine. To address the shortcomings of the existing beam dynamics simulation codes, and to fulfill the requirements of future hadron and heavy-ion machines, a starting point for a realistic simulation tool is being developed at ANL that will support detailed design evaluation and also fast turnaround computation to support commissioning and operation of the facility. The proposed simulations will be performed on the fast growing computing facility at ANL with peta-scale capability.

 

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