• R.J. England, E.R. Colby, C. McGuinness, R.J. Noble, R. Siemann, J.E. Spencer, D.R. Walz
  SLAC, Menlo Park, California
• R. Ischebeck
  PSI, Villigen
• T. Plettner
  Stanford University, Stanford, California
• C.M.S. Sears
  MPQ, Garching, Munich

Funding: DOE Grants DE-AC02-76SF00515, DE-FG06-97ER41276

An experimental effort is currently underway at the SLAC National Accelerator Laboratory to focus a 50pC, 60 MeV electron beam into the hollow core of a commercial photonic bandgap fiber. The wakefield radiation produced in the fiber will be spectrally analyzed using a spectrograph in order to detect the frequency signatures of fiber modes that could be used as accelerating modes in a laser-driven fiber-based accelerator scheme. We discuss the current status of the experiment, including efforts to successfully focus the electron beam through the fiber aperture and to collect the produced wakefield radiation.

• N.A. Kirby, I. Blumenfeld, M.J. Hogan, R. Siemann, D.R. Walz
  SLAC, Menlo Park, California
• A.W. Davidson, C. Huang
  UCLA, Los Angeles, California

The effect of ion motion and the need for practical positron propagation in a plasma wakefield accelerator (PWFA) have incited interest in hollow plasma channels. These channels are typically assumed to be cylindrically symmetric; however, a different geometry might be easier to achieve. The introduction of an obstruction into the outlet of a high Mach number gas jet can produce two parallel slabs of gas separated by a density depression. Here, there is a detailed simulation study of the density depression created in such a system. This investigation reveals that the density depression is insufficient at the desired plasma density. However, insights from the simulations suggest another avenue for the creation of the hollow slab geometry.

• I. Blumenfeld, F.-J. Decker, M.J. Hogan, R. Ischebeck, R.H. Iverson, N.A. Kirby, R. Siemann, D.R. Walz
  SLAC, Menlo Park, California
• C.E. Clayton, C. Huang, C. Joshi, W. Lu, K.A. Marsh, W.B. Mori, M. Zhou
  UCLA, Los Angeles, California
• T.C. Katsouleas, P. Muggli, E. Oz
  USC, Los Angeles, California

High gradient acceleration of electrons has recently been achieved in meter scale plasmas at SLAC. Results from these experiments show that the wakefield is sensitive to parameters in the electron beam which drives it. In the experiment the bunch lengths were varied systematically at constant charge. Here we investigate the correlation of peak beam current to the wake amplitude. The effect of beam head erosion will be discussed and an experimental limit on the transformer ratio set. The results are compared to simulation.