WEOC3
FEL/Duke University, Durham, North Carolina, USA
PKU/IHIP, Beijing, People's Republic of China
It is well known that the optical power of a storage ring FEL (SRFEL) is limited by the FEL induced e-beam energy spread (the Renieri's limit). This power limit can be derived using a 1D model under certain assumptions. However, systematic, experimental studies of SRFEL power as a function of operation parameters are lacking. In fact, it is difficulty to directly measure the e-beam energy spread over a wide range. In this work, we report our work on measuring e-beam energy spread in a wide range using optical klystron radiation [1]. A novel numerical method has been developed to treat spectral broadening and modulation on an equal footing. Using this new technique, we have conducted a systematic study of the SRFEL power as a function of various parameters. Our results show for the first time that for in a wide range of operation conditions, the storage ring FEL power only directly depends on the induced electron beam energy spread. Means of tuning of the FEL power, including changing the synchronization between electron and FEL beams, RF voltage, FEL cavity loss, etc, are possible though a change of the induced energy spread.
[1] Phys. Rev. STAB, 13, 080702 (2010)
