NUMERICAL STUDY ON IMPROVEMENTS OF BEIJING FEL LASING PERFORMANCES THROUGH MODIFICATIONS OF THE BEAM-DUCT GEOMETRY

In January 1997, the first lasing at 8-18 mu m was observed at Beijing FEL (BFEL). However, the output powers were found not large enough es pecially in the longer wavelength regime, where the laser power loss o n the relatively narrow beam-duct wall is not expected to be small, an d actually, the saturation of the laser power was not seen. In order t o evaluate and to improve the effects due to the beam duct, we have mo dified our three-dimensional FEL code to accommodate the finite beam-d uct size. It is predicted that more than three times as large as the o utput power is theoretically achieved at an 18 mu m wavelength with ne wly designed beam ducts. (C) 1998 Elsevier Science B.V. All rights res erved.