Author: Lewellen, J.W.
Paper Title Page
THP023 Simulation of Alpha Magnet Elements in Dipole-only Tracking Codes 735
  • J.W. Lewellen, F.L. Krawczyk
    LANL, Los Alamos, New Mexico, USA
  Alpha magnets are used in a variety of ion-beam and low-energy (< 5 MeV) electron-beam transport systems as both “switchyard” elements and as bunch compressors. A unique feature of the alpha-magnet is its natively achromatic transport. Particles of different energies, injected at a specific location and angle, will exit at the same location and (symmetry-reflected) angle but with a different time-of-flight. Despite the general usefulness of alpha magnets in low-energy beam transport and compression schemes, few simulation codes support them as native elements. The (arguably) most-common codes used for injector design, PARMELA, ASTRA and GPT (listed in order of their release) do not support alpha magnets natively, but do support modeling of space-charge-dominated beams through dipole magnets. As a result, the most commonly used injector design codes are unable to incorporate one of the most useful and interesting beam transport devices. We present a method for simulating an alpha magnet in a tracking code using dipole elements. As elegant supports both dipoles and alpha magnets, it is used to provide a basic check of the approximation and a means of estimating the induced errors.  
THP024 High-gradient Cathode Testing for MaRIE 739
  • J.W. Lewellen, F.L. Krawczyk, N.A. Moody
    LANL, Los Alamos, New Mexico, USA
  X-ray free-electron lasers (X-FELs) provide unprecedented capabilities for characterizing and controlling matter at temporal, spatial and energetic regimes which have been previously inaccessible. The quality of the electron beam is critical to X-FEL performance; a degradation of beam quality by a factor of two, for instance, can prevent the X-FEL from lasing at all, rather than yielding a simple reduction in output power. While conceptual designs for new beam sources exist, they incorporate assumptions about the behavior of the photocathode, under extreme operating conditions. The combined requirements for high bunch charge, short bunch duration, and small emission area, dictate the use of high-efficiency photocathodes operating at electric field gradients of ~140 MV/m. No suitable cathode has been operated at these gradients, however, so the success of next-generation X-FELs rests on a series of untested assumptions. We present our plans to address these knowledge gaps, including the design of a high-gradient RF cavity specifically designed for testing cathodes under MaRIE-relevant conditions.