Author: Mayes, C.E.
Paper Title Page
WEPPC074 HOM Studies on the Cornell ERL Prototype Cavity in a Horizontal Test Cryomodule 2384
  • N.R.A. Valles, M.G. Billing, G.H. Hoffstaetter, M. Liepe, C.E. Mayes
    CLASSE, Ithaca, New York, USA
  The main linac 7-cell cavity for Cornell's Energy Recovery Linac was optimized to maximize threshold current through the ERL. This was achieved by designing center and end cells that reduce the strength of dipole higher-order modes. A prototype cavity was fabricated based on the optimized RF design and found to meet fundamental mode specifications in a vertical test. The higher-order-mode spectrum was measured when the cavity was installed in a horizontal test cryomodule and is compared to 2D and 3D EM simulations.  
WEPPR086 Computed Wake Field Effects from Measured Surface Roughness in the Walls of the Cornell ERL 3132
  • M.G. Billing, G.H. Hoffstaetter, C.E. Mayes, K.W. Smolenski, H.A. Williams
    CLASSE, Ithaca, New York, USA
  Funding: Work supported by the NSF ERL Phase 1B Cooperative Agreement (DMR-0807731)
Wake fields arise from the discontinuities in a smooth vacuum chamber and will cause energy spread in the passing bunch. In an energy recovery linac (ERL), the spent bunches are decelerated before they are dumped to reuse the beam’s energy for the acceleration of new bunches. While the energy spread accumulated from wakes before deceleration is small compared to the beam’s energy after full acceleration, it becomes more important relatively as the beam’s energy decreases.* Thus, in an ERL wake fields can produce very significant energy spread in the beam as it is decelerated to the energy of the beam dump. We report on calculations of wake fields due to the roughness of the surface of the vacuum chamber walls as it affects the Cornell ERL design. These calculations include the effects from the measured roughness for real vacuum chamber wall surfaces.
* M. Billing, “Effect of Wake Fields in an Energy Recovery Linac”, PAC’09, Vancouver, BC, Canada, 4-8 May 2009.