Current status of the VEPP-3 storage ring optical klystron

Lasing in a wide 2400-6900 Å spectral range was reached in the optical klystron OK-4 installed on the VEPP-3 storage ring. OK-4 is the first FEL operating in UV. In the recent experiments the Δλ/λ = 3·10
^-6
relative linewidth was obtained with the use of intracavity quartz plate.