Design Overview of a Highly Stable Infrared Free Electron Laser at LBL
Abstract
An infrared free electron laser (IRFEL) is being designed for the Chemical Dynamics
Research Laboratory (CDRL) at LBL. The FEL is based on a 50 MeV rf linac operating in
synchronization to the Advanced Light Source (ALS), and will produce intense (100 micro
Joule per micropulse), narrow bandwidth (narrower than 0.1%) radiation between 3 and 50
micrometers. In the design, we pay particular attention to the FEL stability issues and
require that the fluctuations in electron beam energy and in timing be less than 0.05%
and 0.1 picosec, respectively. The FEL spectrum can then be stabilized to about 0.001, or
if grating is used, 0.0001. We discuss various sources of fluctuations in the gun, the
bunchers and the accelerator sections, as well as the feedback and feedforward schemes to
reduce these fluctuations. The accelerator structure is chosen to be the side-coupled,
standing-wave type for easier control. The beam transport is made isochronous to avoid
the coupling between the energy and timing fluctuations.
K.J. Kim, M. Berz, S. Chattopadhyay, C. Kim, J. Edighofer, R. Gough, C. Kim, A.H. Kung, W. Stein, M. Xie,
Nuclear Instruments and Methods A304 (1991) 233-237
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