Exploring Minimal Scenarios to Produce Transversely Bright Electron   Beams Using the Eigen-Emittance Concept
  Next generation hard X-ray free electron lasers require electron beams with low transverse emittance. One proposal to achieve these low emittances is to exploit the eigen-emittance values of the beam. The eigen-emittances are invariant under linear beam transport and equivalent to the emittances in an uncorrelated beam. If a correlated beam with two small eigen-emittances can be produced, removal of the correlations via appropriate optics will lead to two small emittance values, provided non-linear effects are not too large. We study how such a beam may be produced using minimal linear correlations. We find it is theoretically possible to produce such a beam, however it may be more difficult to realize in practice. We identify linear correlations that may lead to physically realizable emittance schemes and discuss promising future avenues. 
Leanne D. Duffy, Kip A. Bishofberger, Bruce C. Carlsten, Alex Dragt,   Quinn R. Marksteiner, Steven J. Russell, Robert D. Ry...
physics.acc-ph