Giant high-peak power pulses in the UV OK-4/Duke storage ring FEL using the gain modulator

We use the gain modulation technique to generate giant pulses in the OK-4/Duke storage ring FEL for applications requiring high peak power. This technique provides the increase of the peak power by several orders of magnitude. It is also very reliable, predictable and reproducible. The design, the parameters and the gain modulator performance are described. Comparison of expected and measured pulse forms is presented. Application of gain modulator for future harmonic generation experiments is also discussed.