Some Aspects of FELWI
  A threshold condition for amplification without inversion in a free-electron laser without inversion (FELWI) is determined. This condition is found to be too severe for the effect to be observed in an earlier suggested scheme because a threshold intensity of the field to be amplified appears to be too high. This indicates that alternative schemes have to be found for making the creation of an FELWI realistic. 
Karen Badikyan
physics.acc-ph