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 especially in the longer wavelength regime, where the laser power loss on the relatively narrow beam-duct wall is not expected to be small, and actually, the saturation of the laser power was not seen. In order to evaluate and to improve the effects due to the beam duct, we have modified our three-dimensional FEL code to accommodate the finite beam-duct size. It is predicted that more than three times as large as the output power is theoretically achieved at an 18 mu m wavelength with newly designed beam ducts. (C) 1998 Elsevier Science B.V. All rights reserved.