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Nelson, S. D.

Paper Title Page
TUYC02 High Gradient Induction Accelerator 857
 
  • G. J. Caporaso, D. T. Blackfield, Y.-J. Chen, J. R. Harris, S. A. Hawkins, L. Holmes, S. D. Nelson, A. Paul, B. R. Poole, M. A. Rhodes, S. Sampayan, M. Sanders, S. Sullivan, L. Wang, J. A. Watson
    LLNL, Livermore, California
  • M. L. Krogh
    University of Missouri - Rolla, Rolla, Missouri
  • C. Nunnally
    University of Missouri, Columbia, Columbia, Missouri
  • K. Selenes
    TPL, Albuquerque, NM
  
  Funding: This work was performed under the auspices of the U. S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.

Progress in the development of compact induction accelerators employing advanced vacuum insulators and dielectrics will be described. These machines will have average accelerating gradients at least an order of magnitude higher than existing machines and can be used for a variety of applications including flash x-ray radiography and medical treatments. Research describing an extreme variant of this technology aimed at proton therapy for cancer will be described.

 
slides icon Slides  
TUPAS057 Injector Particle Simulation and Beam Transport in a Compact Linear Proton Accelerator 1781
 
  • D. T. Blackfield, Y.-J. Chen, J. R. Harris, S. D. Nelson, A. Paul, B. R. Poole
    LLNL, Livermore, California
  
  Funding: This work was performed under the auspices of the U. S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.

A compact Dielectric Wall Accelerator (DWA), with field gradient up to 100 MV/m, is being developed to accelerate proton bunches for use in cancer therapy treatment. The injector first generates a few nanosecond long and 40 pQ proton bunch, which is then compressed in the compression section at the end of the injector. Finally the bunch is accelerated in the high-gradient DWA accelerator to energy up to 70 - 250 MeV. The Particle-In-Cell (PIC) code LSP is used to model several aspects of this design. First, we use LSP to determine the needed voltage waveform in the A-K gap that will produce a proton bunch with the requisite charge. We then model pulse compression and shaping in the section between the A-K gap and the DWA. We finally use LSP to model the beam transport through the DWA.

 
TUPAS058 Electromagnetic Simulations of Linear Proton Accelerator Structures Using Dielectric Wall Accelerators 1784
 
  • S. D. Nelson, G. J. Caporaso, B. R. Poole
    LLNL, Livermore, California
  
  Funding: This work was performed under the auspices of the U. S. Department of Energy, the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.

Proton accelerator structures for medical applications using Dielectric Wall Accelerator (DWA) technology allows for the utilization of high field gradients on the order of 100 MV/m to accelerate the proton bunch. Medical applications involving cancer therapy treatment usually desire short bunch lengths on the order of hundreds of picoseconds in order to limit the extent of the energy deposited in the tumor site (in 3D space, time, and deposited proton charge). Electromagnetic simulations of the DWA structure, in combination with injections of proton bunches, have been performed using 3D finite difference codes in combination with particle pushing codes. Electromagnetic simulations of DWA structures includes these effects and also includes the details of the switch configuration and how that switch time affects the electric field pulse which accelerates the particle beam. Design trade-offs include the driving switch effects, layer-to-layer coupling analysis and its affect on the pulse rise time.

 
TUPAS060 Particle Simulations of a Linear Proton Dielectric Wall Accelerator 1790
 
  • B. R. Poole, D. T. Blackfield, S. D. Nelson
    LLNL, Livermore, California
  
  Funding: This work was performed under the auspices of the U. S. Department of Energy, the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.

The dielectric wall accelerator (DWA) is a compact induction accelerator structure that incorporates the accelerating mechanism, pulse forming structure, and switch structure into an integrated module. The DWA consists of stacked stripline Blumlein assemblies, which can provide accelerating gradients in excess of 100 MeV/meter. Blumleins are switched sequentially according to a prescribed acceleration schedule to maintain synchronism with the proton bunch as it accelerates. A finite difference time domain code (FDTD) is used to determine the applied acceleration field to the proton bunch. Particle simulations are used to model the injector as well as the accelerator stack to determine the proton bunch energy distribution, both longitudinal and transverse dynamic focusing, and emittance associated with various DWA configurations.