Recent Progress in High-gain Fel Theory

High-gain free electron lasers (FEL) are being developed as extremely bright x-ray sources of a next-generation radiation facility. In this paper, we review the basic theory and the recent progress in understanding the startup, the exponential growth and the saturation of the high-gain process, emphasizing the self-amplified spontaneous emission (SASE). We will also discuss how the FEL performance may be affected by various errors and wakefield effects in the undulator. Invited talk presented at the 27 International Free Electron Laser Conference Stanford, CA, USA August 21 26, 2005 ∗Work supported by Department of Energy contract DE–AC02–76SF00515. †Email: [email protected] RECENT PROGRESS IN HIGH-GAIN FEL THEORY Zhirong Huang∗ Stanford Linear Accelerator Center, Stanford, CA 94309, USA