The deep-UV operation of the OK-4/Duke storage ring FEL
In this paper we present the result of the deep-UV lasing with the OK-4/Duke storage ring FEL. The OK-4 FEL was initially commissioned in the near-UV at Duke Free Electron Laboratory in November, 1996 followed by a year-long shutdown. After re-establishing the storage ring operation in early 1998, the OK-4 FEL lasing was demonstrated in the wavelength range of 217 to 256 nm in 1998. A number of lasing modes with electron energies ranging from 300 to 750 MeV have been established to accommodate application research. Starting September, 1998, the coherent deep-UV radiation is used for applications in cornea surgery, cell biology, surface physics, and nuclear physics. In this paper we report the results of the deep-UV lasing with the OK-4/Duke storage ring FEL as well as our plans to advance towards the VUV.