OK-4/Duke storage ring FEL lasing in the deep-UV

In this paper we present the result of the deep-UV lasing with the OK-4/Duk e storage ring FEL. The OK-4 FEL was initially commissioned at Duke Free El ectron Laboratory in November 1996 followed by a yearlong shutdown. After r e-establishing the storage ring operation in early 1998, the OK-4 FEL lasin g was demonstrated in the wavelength range of 226-256 nm in April 1998. The OK-4 FEL successfully lased from 217 nm to 235 nm in August 1998. A number of lasing modes with electron energies ranging from 300 to 750 MeV have be en established to accommodate application researches. Starting September 19 98, the coherent deep-UV radiation is used for applications in surgery, cel l biology, surface physics, and nuclear physics. (C) 1999 Published by Else vier Science B.V. All rights reserved.