An analytical model of the emittance of a field emission array cathode for high performance free electron lasers

摘要

Advanced particle accelerators and Free Electron Lasers (FEL's) require high brightness electron sources [1]. A practical figure of merit for beam “optical quality” is rms emittance, and it relates to the ability to focus the electron beam within the laser beam optical mode within the wiggler for the laser threshold to be reached. Emittance characterizes the tendency of the beam to diverge as a consequence of transverse velocity components amongst the constituents of the beam, and is defined by