DYNAMICS OF A MONOENERGETIC POINT-LIKE ELECTRON FLOW IN A HELIX UNDULATOR

A self-consistent linear theory is developed to describe the motion of a monoenergetic nondivergent point charge flow in a helix undulator w here the resultant undulator radiation field is taken into account. On this basis, a boundary in the space of external parameters for the co nsidered nonequilibrium system (beam + undulator) is established that separates the modes of its operation as a source of stimulated radiati on (free electron laser) and of incoherent spontaneous radiation (conv entional source of undulator radiation). Physical mechanisms responsib le for transitions from one mode to another under the corresponding pa rameter changes are discussed.