• G. Penn, A. Sessler, J. S. Wurtele
  LBNL, Berkeley, California

By "conditioning" an electron beam, through establishing a correlation between transverse action and energy within the beam, the performance of free electron lasers (FELs) can be dramatically improved. Under certain conditions, the FEL can perform as if the transverse emittances of the beam were substantially lower than the actual values. After a brief review of the benefits of beam conditioning, we present a method to generate this correlation through the use of a plasma channel. The strong transverse focusing produced by a dense plasma (near standard gas density) allows the optimal correlation to be achieved in a reasonable length channel, of order 1 m. This appears to be a convenient and practical method for achieving conditioned beams, especially in comparison with other methods which require either a long beamline or multiple passes through some type of ring.

• D. Trbojevic, R. C. Gupta, B. Parker
  BNL, Upton, Long Island, New York
• E. Keil
  CERN, Geneva
• A. Sessler
  LBNL, Berkeley, California

We report on improvements in the non-scaling Fixed Field Alternating Gradient (FFAG) gantry design. As we previously reported*, a major challenge of the carbon/proton cancer therapy facilities is isocentric gantry design. The weight of the isocentric gantry transport elements in the latest Heidelberg carbon/proton facility is 135 tons**. In this report we detail improvements to the previous non-scaling gantry design. We estimate that this non-scaling FFAG gantry would be almost hundred times lighter than traditional heavy ion gantries. Very strong focusing with small dispersion permits passage of different energies of carbon beams through the gantry's fixed magnetic field.*