The history of the free electron laser

Summary form only given. It is pointed out that most of the literature on the FEL identifies its times of origin as the mid-1970s, coinciding with the well-documented experiments at Stanford and the coining of the term free electron laser. In fact, the FEL has a history which dates back to at least 1947 and a patent by Elmer Gorn, in which he describes a family of amplification producing fast electromagnetic wave (periodic electron beam) interactions. In the 1950s, there followed a proliferation of proposed new fast wave interactions. Most do not appear to have made it through the experimental verification stage. There were two important exceptions. The first was the undulator work of Motz, who passed the beam from a 3-MeV accelerator through a wiggler to produce millimeter wave radiation. He later used a 100-MeV beam to produce visible light. The second was the development, by the author, of the Ubitron, a mildly relativistic microwave FEL. The power producing capability of this device was so much greater than that of conventional klystrons and magnetrons that records for peak power generation, which would stand for two decades, were established at both centimeter and millimeter wavelengths